Dissertations / Theses on the topic 'Propylene polymer'

Thesis (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Most polypropylene copolymers commercially available have ethylene, and to a lesser degree t-butene as comonomers. Commercially available higher a-olefins, mostly even-numbered, are seldom used for the production of pp copolymers, probably due to cost. Sasol's Fischer- Tropsch oil-from-coal process produces many linear and branched a-olefins as by-products that can be isolated and purified by a relatively cheap refinery process, including the odd-numbered 1- pentene olefin. Sasol's gas-phase Novolen pp plant at Secunda, South Africa is ideally suited to the manufacture of high quality pp random copolymers. As such an opportunity was identified to research the use of higher a-olefins, and more specifically 1-pentene, in the gas-phase production of pp random copolymers. Different methods to produce propylene / 1-pentene random copolymers in the slurry phase on bench-scale were investigated. A procedure was subsequently developed to produce propylene / 1-pentene random copolymers in the gas-phase in 10 litre autoclaves. It was found that commercially available fourth generation supported catalysts successfully incorporated the bulky 1-pentene monomer into the propylene backbone, both during slurry and gas-phase polymerisations. Software modelling was employed to determine the dew points of selected gas mixtures typically found during the production of pp random copolymers. The results indicated that typical process conditions could be employed during the gas-phase polymerisation of propylene and 1-pentene without the risk of condensation taking place inside the reactor. Propylene / 1-pentene random copolymers were subsequently successfully produced on the 800 litre BASF pilot plant in Germany followed by the first commercial production of the copolymer on Sasol's 50m3 Novolen gas-phase plant at Secunda. Using commercially available software the impact of introducing 1-pentene as comonomer during the production of random copolymers on the condenser cooling capacity was evaluated. Feasible and safe plant operating conditions were established for the production of propylene / 1-pentene random copolymers. The relationship between operating pressure and powder morphology was investigated to optimise process conditions. Operating at higher pressure in the gas-phase increases the monomer concentration in the reactor and as such improves the space/time/yield ratio of the 50m3 reactors. It was shown that higher operating pressures could be employed through the introduction of 1-pentene as comonomer during the production of PP random copolymer. The dramatic increase in catalyst productivity observed during the 800 litre pilot plant trials, up to a comonomer ratio of about 5%, supported the results obtained from a kinetic study carried out in bench-scale autoclaves. A comprehensive study was undertaken to compare the rheological, thermal, crystallisation, physical and mechanical properties of propylene / 1-pentene random copolymers with those of commercially available pp random copolymers. A series of propylene homo- and random copolymers with 1-pentene and ethylene as comonomers respectively, was prepared. NMR and IR techniques were developed to facilitate the determination of copolymer composition for the new family of 1-pentene random copolymers. The effect of comonomer content, molecular weight and temperature on the properties of the series of polymers was investigated. The propylene / 1-pentene random copolymers show unique rheological behaviour associated with the short propyl branches in the polymer backbone with minimum zero shear viscosity at about 2% 1-pentene content. The effect of molecular structure changes with comonomer content were analysed by the calculation of square average end-toend distance, packing length, tube diameter, molecular mass between entanglements and critical molecular mass. The viscosity of the 1-pentene random copolymers shows higher shear and temperature sensitivity compared to propylene homo- and ethylene random copolymers. The thermodynamic melting point of the propylene / 1-pentene random copolymers showed a significant decrease with increasing comonomer content in the 0 to 5% range. A wider melting range and higher peak melting point depression rate was observed compared to ethylene random copolymers at similar and increasing comonomer content measured on a weight % basis. It was found that the crystal structure of the propylene / 1-pentene random copolymers contains both the Q- and the y-modifications with the ratio of the respective crystal forms a function of both comonomer content and crystallisation temperature. The glass temperature decreased slightly with increasing comonomer (1-pentene) content. It is proposed that the short branch (propyl) "defects" in the polymer backbone are .incorporated into the crystal lattice resulting in increased rate of melting point depression with increasing (wt%) comonomer content compared to other random copolymers while maintaining relative high stiffness. The propylene / 1-pentene random copolymers exhibit the lowest haze values compared to all commercially available pp random copolymers at corresponding levels of comonomer content on a wt% basis. The stiffness to haze ratio of propylene / 1-pentene random copolymers are unique for all the members of the pp family. An inverse relationship between comonomer content and the measured tensile yield strength and modulus is observed. Application studies conducted on the propylene / 1-pentene random copolymers highlighted several interesting characteristics. Films produced from these copolymers exhibited very low haze and xylene soluble values while maintaining mechanical integrity. In the BOPP application the combination of processability and premium film properties presents a unique opportunity for the family of propylene / 1-pentene random copolymers. Blow moulding and injection moulding trials highlighted several advantages of product properties manufactured with propylene / 1-pentene random copolymers if compared to other commercially available random copolymers. The 1-pentene randoms presented lower in-mould as well as total shrinkage than ethylene based random copolymers. Stabilisation and nucleation studies conducted on the propylene / 1-pentene random copolymers showed that a typical combination antioxidant package and nucleating agent, at normal loading levels, could be used. In the larger pp random copolymer family 1-pentene imparts a better balance of properties than other comonomers. The combination of low melting point and xylene solubles with high stiffness and clarity is unique to propylene / 1-pentene random copolymers.
AFRIKAANSE OPSOMMING: Die oorgrote meerderheid van kommersieel beskikbare polipropileen (PP) kopolimere het etileen, en tot 'n mindere mate buteen, as komonomeer. Die relatief hoë koste van kommersieel beskikbare hoër alfa-olefiene is moontlik die rede waarom hulle selde gebruik word vir die vervaardiging van PP kopolimere. Die Sasol Fischer-Tropsch proses, waartydens olie uit steenkool vervaardig word, lewer verskeie liniêre en vertakte alfa-olefiene as neweprodukte wat geïsoleer en gesuiwer kan word in 'n relatiewe goedkoop rafineringsproses. Dit sluit ook die onewe-koolstofgetal 1-penteen-olefien in. Sasol se gasfase Novolen PP aanleg in Secunda, Suid-Afrika, is besonder geskik vir die vervaardiging van hoë standaard PP statistiese kopolimere. Voortvloeiend hieruit is die geleentheid geidentifiseer om die gebruik van hoër alfa-olefiene, en meer spesifiek 1-penteen, na te vors tydens die gasfaseproduksie van PP statistiese kopolimere. Verskeie metodes om propeleen / 1-penteen statistiese kopolimere in 'n koolwaterstofoplosmiddel op laboratoriumskaal te produseer, is ondersoek. 'n Prosedure is daarna ontwikkel om propileen / 1-penteen statistiese kopolimere ook in die gasfase te vervaardig in 10-liter drukvate. Die bevinding was dat kommersieel beskikbare vierde-generasie ondersteunde kataliste die swaarder 1-penteenmonomeer suksesvol geïnkorporeer het in die propileenketting tydens beide die koolwaterstof oplosmiddel- en gasfase polimerisasiereaksies. Rekenaargebaseerde modellering is gebruik om die kondensasiekondisies van tipiese gasmengsels, teenwoordig tydens die produksie van PP statistiese kopolimere, te bepaal. Die resultate het aangedui dat normale proseskondisies tydens die gasfasepolimerisasie van propileen en 1-penteengeen risiko van kondensasie in die reaktor inhou nie. Propileen / 1-penteen statistiese kopolimere is gevolglik met groot sukses vervaardig by die 800-liter BASF loodsaanleg in Duitsland, gevolg deur die eerste kommersiële vervaardiging van die kopolimeer op die Sasol50m3 Novolen gasfase-aanleg in Secunda. Deur gebruik te maak van kommersieel beskikbare sagteware, is die impak van 1-penteen as komonomeer tydens die vervaardiging van statistiese kopolimere op die verkoelingskapasiteit van die kondensator bepaal. Veilige en uitvoerbare aanlegkondisies is uitgestip vir die vervaardiging van propileen /1-penteen statistiese kopolimere. Die verhouding tussen die reaktordruk en poeiermorfologie is ondersoek om die prosestoestande te optimiseer. Vervaardiging van kopolimere in die gasfase by hoër drukke lei tot verhoogde monomeerkonsentrasie in die reaktor en gevolglik hoër produksiedeursette. Daar is bewys dat tydens die produksie van PP statistiese kopolimere, met 1-penteen as komonomeer, hoër reaktordruk ingespan kan word. Die dramatiese toename in katalisproduktiwiteit waargeneem tydens die 800- liter loodsaanleg proefloop, tot en met 'n komonomeer inhoud van ongeveer 5%, word ondersteun deur die resultate van 'n kinetiese studie uitgevoer in laboriumskaal drukvate. 'n Omvattende studie, om die reologiese, termiese, kristallyne, fisiese en meganiese eienskappe van propileen / 1-penteen statistiese kopolimere te vergelyk met kommersieel beskikbare PP statistiese kopolimere, is uitgevoer. 'n Reeks propileen homo- en statistiese kopolimere, met 1-penteen en etileen as komonomere onderskeidelik, is berei. KMR- en IR- tegnieke is ontwikkel om die bepaling van komonomeersamestelling vir die nuwe familie van 1- penteen statistiese kopolimere te fasiliteer. Die invloed van komonomeersamestelling, molekulere gewig en temperatuur op die eienskappe van die reeks polimere is ondersoek. Die propoleen / 1- penteen statistiese kopolimere toon unieke reologiese eienskappe wat geassosieer kan word met die propielsykettings in die polimeerruggraat. Die viskositeit van die propileen / 1-penteen statistiese kopolimere toon 'n hoër wrywings- en temperatuursensitiwiteit in vergelyking met propileen homo- en etileen statistiese kopolimere. 'n Drastiese verlaging in die termodinamiese smeltpunt van die propileen / 1- penteen statistiese kopolimere met 'n toename in komonomeerinhoud is waargeneem tot en met 'n 5% komonomeerinhoud. Die propileen / 1-penteen statistiese kopolimere toon 'n breër smeltgebied en 'n hoër tempo in die piek smeltpuntafname in vergelyking met etileen statistiese kopolimere met soortgelyke komonomeer inhoud, gemeet op 'n massabasis. Daar is bewys dat die kristalstruktuur van die propileen / 1-penteen statistiese kopolimere beide die alfa en gamma modifikasies bevat. Die verhouding van die onderskeie kristalvorms is 'n funksie van komonomeerinhoud en kristalisasietemperatuur. 'n Afname in die glastemperatuur met verhoogde komonomeer inhoud is waargeneem. Die aanname dat die kort propielsykettings in die polimeerruggraat in die kristalstruktuur geïnkorporeer word, is gemaak. Dit verklaar die hoë afname in die tempo van die smeltpunt met toenemende komonomeer inhoud relatief tot ander statistiese kopolimere, met die handhawing van hoë moduluswaardes. Die besondere deursigtigheid van die propileen / 1-penteen statistiese kopolimere tesame met relatief hoë modulus waardes is uniek. 'n Omgekeerde verhouding tussen komonomeer inhoud en treksterkte asook moduluswaardes is waargeneem. 'n Toepassingstudie uitgevoer met die propileen / 1-penteen statistiese kopolimere het verskeie interessante resultate gelewer. Films vervaardig van hierdie kopolimere toon besonderse deursigtigheid en lae waarde van xileenoplosbaarheid, terwyl meganiese integriteit gehandhaaf word. Voordele in die vervaardigingsproses van BOPP-films asook bogemiddelde filmeienskappe hou unieke moontlikhede vir propileen / 1-penteen statistiese kopolimere in. Verskeie voordele tydens blaas- en spuitvormingsprosesse is waargeneem relatief tot ander beskikbare statistiese kopolimere. Die 1-penteen statistiese kopolimere toon 'n laer in-vorm sowel as totale krimping relatief tot etileen- gebaseerde kopolimere. 'n Studie het aangetoon dat tipiese bymiddelpakette by normale toevoegingsvlakke geskik is vir propileen / 1-penteen statistiese kopolimere. Gesien in die groter pp statistiese kopolimeer familie toon 1-penteen 'n beter balans van eienskappe as ander komonomere. Die kombinasie van laer smeltpunt en xileen-oplosbares met hoë moduluswaardes en helderheid is uniek aan propileen /1-penteen statistiese kopolimere.

Thesis (PhD)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: From the Sasol Fischer- Tropsch process, a variety of different a-olefins are produced. Sasol recently started presenting these a-olefins to polymer producers. To demonstrate the application possibilities of these a-olefins as comonomers for ethylene and propylene polymerization, it was necessary to first synthesize catalysts having a combination of high activity and good comonomer incorporation, and in the case of propylene copolymers, also sufficient stereospecificities. Different methods to produce catalysts conforming to these requirements were investigated and it was found that catalysts produced from a MgCb-support activated by a combination of chemical and mechanical means produced suitable catalysts. The amount of alcohol used during the support activation step and the time allowed for alkylation of the active centers were important. No clear correlation between total titanium content and activity was observed. The degree to which active sites are protected was evaluated from the amount of comonomer present in the final copolymer based on the amount added to the reaction. Cyclopentadiene was used to selectively deactivate the unprotected active sites to determine the ratio between protected and "open" active sites. High activity catalysts are not suitable for gas-phase copolymerization and were consequently "diluted" by dispersion in a pre-formed polymer powder and by prepolymerization. Catalyst activity based on titanium content was substantially decreased, but comonomer incorporation was not. Catalysts for producing crystalline polypropylene require the presence of both an internal and external electron donor. It was shown that isotacticity increased linearly with an increase in external modifier at the expense of catalyst activity and that a double treatment of the support or catalyst before the final TiCl4 fixation was more effective at increasing stereospecificity. The less stereospecific sites are more capable of accepting bulky comonomers in the coordination complex and thus by decreasing the amount of less-stereospecific active sites, the overall capability of the catalyst to incorporate comonomer was decreased. Comonomer sequence distributions and average lamellar thicknesses of different ethylene / a-olefin copolymers were calculated from CH2 dyad concentrations determined by I3C NMR spectroscopy. Ethylene sequences in the I-butene containing copolymers are generally longer than those where a higher a-olefin was used as comonomer which indicates that a more random comonomer distribution is obtained when the higher u-olefins are used. It was shown that an inverse relationship exists between branch size and density. For density, no effect resulting from the comonomer type was observed. This same inverse relationship was also observed for tensile strength. Modulus, hardness and impact strength, on the other hand, did show an effect resulting from the comonomer type. Modulus and hardness were not depressed as much and impact strength improved more than what was expected from calculations based on branch size. Homogeneous copolymers have broad melting peaks. It was shown that at sufficiently high comonomer content, peak broadening occurs when the higher cc-olefins are used as comonomer, which also indicates that more random comonomer distributions are obtained with the higher aolefins. From the chain propagation probabilities calculated it was observed that two types of active sites are present. Those responsible for producing mainly polyethylene have an alternating character while the sites capable of incorporating comonomer have a blocky character. It was expected that the additional introduction of a third a-olefin during ethylene / 1- pentene copolymerization will produce a terpolymer with density and related properties similar to the mathematical average between those of the relevant copolymers. This was only observed for the terpolymers containing l-heptene, 1- octene and l-nonene. The I-butene containing terpolymers have densities well below the expected values while the I-hexene containing terpolymers have values very similar to that of the ethylene / l-hexene copolymer densities, but still below the expected values. Properties related to density, such as tensile strength and modulus, follow this same trend. It is believed that the presence of l-pentene breaks up the tendency of the lower c-olefins to cluster which results in improved randomness. Compared to the copolymers, I-butene and l-hexene containing terpolymers seem to reach the impact strength maximum at a lower total comonomer content than that of the I-pentene copolymers which also indicates an enhanced effect from the combined use of I-pentene with these o-olefins. No substantial difference between impact strengths of co- and terpolymers prepared with higher a-olefins was observed. In general, the melting temperatures of the terpolymers are slightly lower and spread over a wider temperature range than those of the copolymers which can be realized if the comonomer units are less clustered and thus more randomly distributed. Decrease in melting temperature was, however, not as much as for the metallocene catalyzed terpolymers. From sequence length calculations from l3C NMR spectroscopy it was found that the crystallizable ethylene sequences of l-butene containing terpolymers were shorter than those of the corresponding copolymers, which confirms the notion that the introduction of a third comonomer resulted in an increase in randomness. Crystallizable sequence lengths became gradually shorter when higher cc-olefins were used in co- and terpolymers and those of the terpolymers are generally shorter. From the different types of active centers present on a Ziegler-Natta catalyst, it was reasoned that three main types of polymer chains can be present in the terpolymers: (a) ethylene homopolymer, (b) ethylene / lower a-olefin copolymer and (c) ethylene / lower a-olefin / higher a-olefin terpolymer. The ratio between these components in the final terpolymer depends primarily on the size of the higher a-olefin. The larger the third a-olefin becomes, the more active sites will reject it, resulting in a higher amount of ethylene / lower a-olefin copolymer. It was thus suggested that the large decrease in density and the associated change in related properties observed for ethylene / l-pentene / l-butene terpolymers can be related to the combined result of improved random comonomer incorporation together with the decrease in the amount of ethylene homopolymer. The possibilities of using the higher a-olefins having uneven carbon numbers were investigated in random propylene copolymers. Similar to that observed for the ethylene copolymers, less of the higher a-olefins was necessary to achieve a certain level of crystallinity. A good agreement was observed between tensile properties and comonomer type and content and the size of the branch and the resulting defect it causes in the crystal structure is the primary factor affecting tensile strength. For impact strength a close correlation between the size of the comonomer side chain and comonomer content was observed. It was shown that the effect of the heptyl branch derived from a l-nonene unit was 2.3 times that of the propyl group derived from the I-pentene unit. Properties of block copolymers can not be related directly to l-pentene content as is the case with random copolymers, mainly due to the heterogeneity of the block copolymers. The activating effect of hydrogen on catalyst activity was observed. It was also observed that the amount of l-pentene incorporated in the copolymer as well as the copolymer yield were higher in the presence of hydrogen than when the reaction was carried out in the absence of hydrogen. By using DSC it was possible to identify different crystalline phases in the propylene / I-pentene block copolymers due to the differences in their crystallization kinetics. A connection between the low-temperature peak and impact strength was observed. It was found that the presence of the low-temperature peak resulting from thin lamellae formed by chain containing many defects was undesirable when high impact strength is required. It was not possible to quantify the extent to which the intensity of this peak affected mechanical properties of the block copolymers. However, from sequence length calculations it was found that the ratio between the propylene and 1- pentene sequence lengths could be related quantitatively to impact strength, modulus, hardness and tensile strength of the polymers investigated.
AFRIKAANSE OPSOMMING: 'n Verskeidenheid van verskillende «-olefiene word in die Sasol Fischer- Tropsch proses vervaardig. Sasol het onlangs begin om hierdie a-olefiene aan polimeervervaardigers te bied. Om die toepassingsmoontlikhede van hierdie aolefiene as komonomere vir etileen en propileen polimerisasie te demonstreer was dit nodig om eerstens 'n katalis met 'n kombinasie van hoë aktiwiteit en goeie komonomeer invoeging te sintetiseer. In die geval van propileen word voldoende stereospesifisiteit ook vereis. Verskillende metodes om kataliste wat aan hierdie vereistes voldoen te vervaardig is ondersoek. Daar is gevind dat kataliste waarvan die MgCb basis deur 'n kombinasie van chemiese- en meganiese metodes geaktiveer is, die vereiste eienskappe besit. Die hoeveelheid alkohol gebruik tydens die basis aktivering stap en die tyd toegelaat vir die alkilering van die aktiewe spesies was belangrik. Geen duidelike verband tussen totale titaan inhoud en aktiwiteit is waargeneem nie. Die mate waartoe aktiewe spesies beskerm is, is bepaal vanaf die hoeveelheid komonomeer teenwoordig in die finale kopolimeer in verhouding met die hoeveelheid bygevoeg tydens die reaksie. Siklopentadieen is gebruik om onbeskermde aktiewe spesies selektief te deaktiveer om die verhouding tussen beskermde en oop aktiewe spesies te bepaal. Hoëaktiwiteit kataliste is nie geskik vir gasfase kopolimerisasie nie en is gevolglik verdun deur dit te versprei in 'n voorafgevormde polimeer poeier en deur prepolimerisasie. Katalis aktiwiteit gebaseer op titaan inhoud was aansienlik laer maar komonomeer invoeging was nie merkbaar beinvloed nie. Kataliste VIr die vervaardiging van kristallyne polipropileen vereis die teenwoordigheid van beide interne- en eksterne elektron donors. Daar is gewys dat isotaktisiteit liniêr verhoog met 'n toename in eksterne modifiseerder ten koste van katalis aktiwiteit en dat 'n dubbele behandeling van die basis of katalis, voor die finale titaan fiksering, meer effektief was om stereospesifisiteit te verhoog. Die spesies met laer stereospesifisiteit is meer bevoeg om bonkige komonomere in die koërdinasie kompleks toe te laat en deur dus die konsentrasie van hierdie spesies te verlaag is die bevoegdheid van die katalis om bonkige komonomeer te inkorporeer, verlaag. Komonomeer reeksverspreiding en gemiddelde lamellêre dikte van verskillende etileen / o-olefien kopolimere is bereken vanaf CH2 diad konsentrasie bepaal deur KMR spektroskopie. Etileen reekse in die kopolimere wat l-buteen bevat is oor die algemeen langer as dié waarin 'n hoër a-olefien as komonomeer gebruik was, wat aandui dat 'n meer egalige komonomeer verspreiding verkry word as hoër «-olefiene gebruik word. Daar is getoon dat 'n inverse verhouding tussen die grootte van die vertakking en digtheid bestaan. Geen effek komende van die komonomeer tipe kon waargeneem word nie. Hierdie soortgelyke inverse verhouding was ook waargeneem vir treksterkte. Modulus, hardheid en impaksterkte aan die ander kant, hét 'n effek komende van die komonomeer tipe getoon. Modulus en hardheid was nie soveel verlaag, en impak sterkte soveel verhoog as wat verwag is vanaf berekeninge gebaseer op vertakking grootte nie. Homogene kopolimere toon breë smeltpieke. Daar is gewys dat by voldoende komonomeer inhoud 'n verbreding van die pieke voorgekom het wanneer hoër a-olefiene as komonomere gebruik is, wat ook aandui dat 'n meer egalige komonomeer verspreiding met hierdie c-olefiene verkry kan word. Vanaf berekening van die ketting voortplantingsmoontlikhede is waargeneem dat twee tipes aktiewe spesies teenwoordig is. Die verantwoordelik vir die vorming van polietileen het 'n alternerende karakter terwyl die sentra wat komonomeer kan inkorporeer 'n blokagtige karakter het. Daar is verwag dat die addisionele byvoeging van 'n derde o.-olefien tydens etileen / I-penteen kopolimerisasie, 'n terpolimeer met digtheid en verwante eienskappe soortgelyk aan die wiskundige gemiddelde tussen dié van die relevante kopolimere tot gevolg sal hê. Dit was egter slegs waargeneem vir terpolimere wat I-hepteen 1- okteen en l-noneen bevat. Die I-buteen bevattende terpolimere het digthede ver onder die verwagte waardes terwyl die I-hekseen bevattende terpolimere waardes soortgelyk aan die etileen / l-hekseen kopolimeer digthede het' wat steeds onder die verwagte waardes is. Eienskappe verwant aan digtheid, soos treksterkte en modulus, volg dieselfde neiging. Dit word geglo dat die teenwoordigheid van l-penteen die neiging van die laer a-olefiene om saam te bondelopbreek wat 'n verbeterde egaligheid in komonomeerverspreiding tot gevolg het. Vergeleke by die kopolimere blyk dit dat die terpolimere wat l-buteen en I-hekseen bevat, die impaksterkte maksimum by 'n laer totale komonomer inhoud bereik as dié van die 1-penteen polimere. Dit dui ook op 'n verbeterde effek as gevolg van die gekombineerde gebruik van l-penteen met ander a-olefiene. Geen duidelike verskil tussen die impaksterktes van ko- en terpolimere, wat met die hoër a-olefiene berei was, is waargeneem me. In die algemeen is die smeltingstemperature van die terpolimere effens laer, en versprei oor 'n wyer temperatuurgebied as dié van die kopolimere wat verklaar kan word as komonomere minder saamgebondel is en dus meer homogeen versprei is. Die afname in smelt temperatuur was egter nie soveel as dié van die metalloseengekataliseerde terpolimere nie. Vanaf reekslengte berekeninge met behulp van KMR spektroskopie is daar gevind dat die kristalliseerbare etileen reekse van die l-buteen bevattende terpolimere korter was as dié van die ooreenkomstige kopolimere, wat die gevoel dat die byvoeging van 'n derde komonomeer 'n verbeterde komonomeerverspreiding tot gevolg het, bevestig. Vanaf die verskillende aktiewe spesies teenwoordig in 'n Ziegler-Natta katalis is daar geredeneer dat drie hooftipes polimeerkettings in die terpolimere teenwoordig kan wees: (a) etileen hompolimeer, (b) etileen / laer a-olefien kopolimeer en (c) etileen / laer a-olefien / hoër a-olefien terpolimeer. Die verhouding tussen hierdie komponente in die finale terpolimeer hang primêr van die grootte van die hoër aolefien af. Hoe groter die derde a-olefien is, deur hoe meer van die aktiewe spesies sal dit verwerp word wat 'n groter hoeveelheid etileen / laer a-olefien kopolimeer tot gevolg sal hê. Daar word dus voorgestel dat die groot afname in digtheid en die geassosieerde veranderings in die toepaslike eiensappe waargeneem vir etileen / 1- penteen / I-buteen terpolimeere, herlei kan word na die gekombineerde effek van verbeterde komonomeerverspreiding tesame met die afname lil die hoeveelheid etileen homopolimeer. Die moontlikheid om hoër cc-olefiene met onewe koolstofgetalle te gebruik in homogene propileen kopolimere is ondersoek. Soortgelyk aan dit wat waargeneem is vir die etileen kopolimere, was minder van die hoër cc-olefiene nodig om 'n spesifieke vlak van kristalliniteit te bereik. 'n Goeie ooreenkoms tussen trek-eienskappe en . komonomeer tipe- en inhoud is waargeneem en die grootte van die vertakking en die gevolglike defek wat dit veroorsaak in die kristal struktuur is die primêre faktor wat treksterkte beinvloed. Vir impaksterkte is 'n noue verband tusssen die grootte van die vertakking en komonomeer inhoud waargeneem. Daar is aangetoon dat die effek van die heptiel vertakking vanf die l-noneen eenheid 2.3 keer dié van die propiel groep van die l-penteen eenheid is. Eienskappe van blok kopolimere kan nie direk na l-penteen inhoud herlei word soos die geval met die homogene kopolimere was nie, hoofsaaklik as gevolg van die heterogeniteit van die blok kopolimere. Die aktiverende effek van waterstof op katalis aktiwiteit is waargeneem. Daar is ook gesien dat die hoeveelheid l-penteen geïnkorporeer in die kopolimeer, sowel as die kopolimeer opbrengs, hoër was in die teenwoordigheid van waterstof as wanneer die reaksie sonder waterstof uitgevoer is. Deur DSC te gebruik was dit moontlik om verskillende kristallyne fases in die propileen / l-penteen blok kopolimere vanaf die verskille in hulle krisallisasie kinetika, te identifiseer. 'n Verbintenis tussen die lae-temperatuur piek en impaksterkte is waargeneem. Daar is gevind dat die teenwoordigheid van die laetemperatuur piek, komende van die dun lamellas gevorm, deur kettings wat baie defekte bevat, ongewens is wanneer hoë impaksterkte vereis word. Dit was nie moontlik om die bereik waartoe die intensiteit van hierdie piek die meganiese eienskappe van die blok kopolimere affekteer, te kwantifiseer nie. Vanaf reekslengte bepalings is daar gevind dat die verhouding tussen die propileen en I-penteen reekslengtes kwantitiatief herlei kan word na impaksterkte, modulus, hardheid en treksterkte van die ondersoekte polimere.

Thermoplastic elastomer is one of the priority polymeric compound identified for promotion and further development, given the growing demand for a number of commercial industries such as automobile, construction, footwear, healthcare, medical and food packaging sectors. In this study polypropylene (PP)/ethylene propylene diene monomer (EPDM) based thermoplastic elastomers are preferred for improving their properties as it can serve as a good replacement for PP or EPDM material, bridging the gap between thermoset and thermoplastic materials. This study focuses to develop PP/EPDM which can resist changes or improve properties when exposed to E-beam radiation, as E-beam also offers sustainable sterilization at low cost. The PP/EPDM blends with mixing ratios of 80/20, 50/50 and 20/80 were melt blended with the process parameters optimized using Design of experiments (DOE). The effect of E-beam on mechanical properties, thermal stability, crystallization and dynamic mechanical properties over the dose of 0 to 100 kGy were studied. The blends with high EPDM content (20PP/80EPDM) showed improvement in tensile strength up to 36% (at 40kGy and 60kGy) and resistant to impact strength up to 100 kGy, at the expense of elongation at break. On the other hand, the blends with high PP content (80 PP/20 EPDM and 50 PP/50 EPDM) showed detrimental effects on mechanical properties at all radiation dose studied and found to be not compatible for E-beam sterilization. Further, ethylene vinyl acetate (EVA) was incorporated to PP/EPDM blends at 10EVA/40EPDM/50PP, 20EVA/30 EPDM/50PP, 30EVA/20 EPDM/50PP and 40EVA/10 EPDM/50PP ratios. The gel content analysis showed that the efficiency of crosslinking decreased with increase in EVA loading. However, the presence of EVA in ternary blend especially facilitated the induction of sufficient crosslinks leading to improvement in tensile strength (up to 29% at 60 kGy), impact strength (up to 15% at 80 kGy) and retention of stiffness and thermal properties under radiation at the expense of elongation at break. In order to develop antibacterial ternary blends, silver nanoparticles (AgNP) were added by varying the loading from 0.3wt% to 1wt%. The Ag-ternary blends showed enhancement in impact properties (up to 9%) at the expense of decrement in tensile properties due to the agglomeration of AgNP. When, exposed to E-beam radiation, the mechanical and thermal properties exhibited similar trend of increment and decrement across radiation dose similar to the blends without AgNP. While, 1% Ag blend composites showed bacteriostatic effect on Staphylococcus aureuson, no significant reduction of Pseudomonas aeruginosa bacteria was observed. All the blends, before and after sterilization showed no significant toxicity on HaCaT cells investigated using in vitro analysis. Thus, the blends showed an instinct that their application could be extended to manufacturing of healthcare products and food packaging sector, as they are biocompatible and can withstand E-beam sterilization as demanded by the respective application. Among all the blends ternary blends studied (that exhibited biocompatibility even after radiation), 20EVA/30EPDM/50PP without AgNP showed the highest tensile strength of 18.41 MPa and impact strength of 43.64 J/m. Only a slight increase in tensile and impact properties was witnessed upon addition of 20% EVA to PP/EPDM blend in comparison to the binary blend (50PP/50EPDM blend). However, unlike the binary blend (whose properties decreased upon radiation), the ternary blend (20EVA/30EPDM/50PP) showed improvement in tensile strength up to 29% at 60kGy and up to 15% increase in impact strength at 80kGy.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2006.
Propylene/1-pentene random copolymers are a relatively new family of random copolymers being prepared by Sasol Polymers and reveals high impact strength, good tensile properties, excellent optical properties, good rheological properties and a large pool of processing possibilities. These commercial copolymers are being prepared with stereospecific heterogeneous Ziegler-Natta catalytic systems containing multiple active sites and therefore producing copolymers with a varying degree of stereoregularity. Two different groups of propylene/1-pentene random copolymers were received by Sasol Polymers and investigated in this project. The first group (Group 1, Polymers A - F) consisted of six totally different batches of commercial propylene/1-pentene copolymers which were produced by different catalyst systems. All had different melt flow indices (MFIs) and different 1-pentene contents and all of the copolymers, except for one, were nucleated. The second group (Group 2, Polymers G - J) were produced by the same catalyst, but with varying donor:catalyst ratios and also differing in their 1-pentene content. Investigation of the Group 1 copolymers was used in order to construct a “molecular toolbox” which was then used to study the Group 2 copolymers. The original commercial copolymers were all studied by various analytical techniques: high-temperature carbon thirteen nuclear magnetic resonance spectroscopy (13C-NMR), high-temperature gel permeation chromatoghraphy (HT-GPC), crystallization analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and positron annihilation lifetime spectroscopy (PALS). The random copolymers were all fractionated by preparative TREF and the fractions analyzed utilizing the following analytical techniques: 13C-NMR, HT-GPC, CRYSTAF and DSC. The results of these analyses were used to investigate inter alia the distribution of 1-pentene in the copolymers. In order to investigate the low molecular weight material of the copolymers, which were part of the room temperature fraction during TREF, solvent extractions were carried out using different solvents and different extraction techniques. A complete structural analysis study was carried out on the extracts. The percentages of xylene-solubles were also determined during the quantitative xylene extraction study of the copolymers. Characterization of the xylene non-soluble material was carried out using 13C-NMR, HT-GPC, CRYSTAF, DSC and WAXD in order to compare the properties of the unextracted copolymers with the material after removal of the xylene soluble fraction. Positron annihilation lifetime spectroscopy (PALS) was used as an alternative investigation method for the Group 1 copolymers and their XNS fractions in order to determine what type of information this novel analytical method could generate and how the results compared with those of previous PALS studies on poly-olefins. A new fractionation technique, preparative solution fractionation (SF), was developed and evaluated. The commercial propylene/1-pentene copolymers were fractionated using this novel technique, the fractions were analyzed by 13C-NMR, HT-GPC, CRYSTAF and DSC and the results were compared with previously existing fractionation methods, namely TREF and CRYSTAF. A final study was done on the random copolymers by blending one of the commercial Ziegler-Natta catalyzed propylene/1-pentene copolymers with a tailored, low 1-pentene content, metallocene propylene/1-pentene copolymer in different ratios. The blends were analyzed by molecular weight, thermal and crystal phase analysis in order to investigate the effect of the tailored, highly isotactic propylene/1-pentene copolymer on the properties the commercial random copolymers. Throughout the project the influence of the 1-pentene as well as the donor:catalyst ratio on the copolymers was investigated. This study, in its entirety, therefore allow a better understanding of the effects that the commercial, heterogeneous, transition metal catalysts have on the make up of the copolymers and, by extension, the ultimate properties of the materials.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Impact polypropylene copolymers (IPPC) are important commercial materials, but their morphology and molecular architecture are not yet fully understood. In this study the focus was on selectively removing specific fractions from the original IPPC, recombining the remaining fractions, and studying the properties of these recombined polymers. It was found that some properties of the samples changed remarkably, depending on the fraction of material that was removed before recombination. For example, the degree of phase separation and the crystalline morphology of the recombined materials varied noticeably. During the study an effective way of staining samples for transmission electron microscopy (TEM) was developed. Furthermore, a comparison of fourier transform infrared spectroscopy (FTIR), with TEM and scanning electron microscopy (SEM) results, revealed a hitherto unreported relationship between phase separation. Absorption bands appeared at 1100 cm-1 and 1080 cm-1 in the FTIR spectra and appear to be an indication of phase separation. It was further established that specific copolymer fractions present in the original polymer affect not only the morphology of the final polymer, but also the hardness and impact resistance.
AFRIKAANSE OPSOMMING: Impak polipropileen kopolimere (IPPK) is belangrike kommersïele materiale, maar die kennis met betrekking tot die morfologie en molekulere argitektuur van die materiale is nog gebrekkig. Tydens hierdie studie was die fokus op die selektiewe verwydering van spesifieke fraksies van die oorspronklike IPPK, herkombinering van die oorblywende fraksies, en die studie van die eienskappe van hierdie herkombineerde polimeriese materiale. Daar is gevind dat sommige van die eienskappe van die herkombineerde materiale daadwerklik verskil van die oorspronklike materiaal, en dat die verskille direk verband hou met die spesifieke fraksie wat uit die oorspronklike materiaal verwyder is. Die mate van fase-skeiding asook die kristal-morfologie van die herkombineerde materiaal het opmerklik verskil van die oorspronklike. Tydens die studie is n effektiewe manier ontwikkel om die materiale te vlek vir transmissie elektron-mikroskopie (TEM). Verder is daar ‘n verband tussen die resultate verkry deur Fourier Transform infrarooi spektroskopie (FTIS) en die verkry met TEM en skandeer elektron mikroskopie (SEM) vasgestel. Die verwantskap tussen FTIS en fase-skeiding is tot dusver nie in die wetenskaplike literatuur vermeld nie. Meer spesifiek is daar gevind dat absorbsie-bande sigbaar by 1100 cm-1 en 1080 cm-1 in die FTIS spektra ‘n aanduiding van fase skeiding kan wees. Dit was verder vasgestel dat spesifieke kopolimeer fraksies wat teenwoordig is in die oorspronklike IPPK, nie alleen die morfologie van die materiaal beinvloed nie, maar ook die hardheid en impak-weerstand van die materiaal.

Thesis (DSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.
Commercial polyolefins degrade under the influence of light, heat, chemical and mechanical factors. They are therefore stabilised to ensure that they maintain performance characteristics during their service life. Degradation results in changes in the molar mass, molar mass distribution, chemical composition and chemical composition distribution. Classical analytical techniques only provide averaged values of these properties. Much information is available in the open literature on the changes in molar mass, molar mass distribution and chemical composition of polypropylene upon degradation, but no information was available on the changes in chemical composition distribution (CCD) during degradation. This study describes the use of the following analytical techniques to study this: temperature rising elution fractionation (TREF), crystallisation analysis fractionation (CRYSTAF) and coupled size exclusion chromatography-Fourier transform infrared analysis (SEC-FTIR). The CRYSTAF results complimented those obtained by classical techniques: there was a broadening of the crystallisation peak (CCD), an increase in the soluble fraction and a decrease in crystallisation temperatures. SEC-FTIR analysis showed that most of the degraded products were concentrated in the low molar mass regions. TREF analysis was used to separate a degraded sample into fractions of different degrees of degradation. It was then possible to study the spatial heterogeneity in a thick, degraded polypropylene sample using SEC, FTIR and CRYSTAF. The degradation behaviour of selected Sasol propylene-1-pentene random copolymers was investigated. CRYSTAF, SEC-FTIR and TREF analyses provided information on the thermo-oxidative degradation behaviour differences between unstabilised polypropylene homopolymers and these propylene-1-pentene copolymers. It was found that the pentene copolymers degraded significantly faster compared to the homopolymers, even at low levels of pentene (< 3%). The reduction in stability was virtually linear with an increase in pentene content (up to 8 mol% pentene), indicating that higher levels of primary stabilisers are needed to ensure similar life spans for the Sasol propylene-1-pentene copolymers. The extrusion stability of the propylene-1-pentene copolymers was, however, similar to that of the polypropylene homopolymers, indicating that similar processing stabiliser packages may be used.

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Heterophasic copolymers (also known as HECO polymers) or often referred to only as impact copolymers or block copolymers comprise a polymer matrix with a dispersed rubbery copolymer phase. The polymer under investigation in this study consists of a polypropylene homopolymer matrix and ethylene-propylene copolymers (EPCs). Due to its diverse range of applications and unique properties, polypropylene is the choice of polymer for a vast array of applications. This has led to the development of an entire class of polypropylene materials known as visbroken or controlled rheology polypropylene. By adding a suitable peroxide to the polymer in the presence of heat, radicals are formed which will attack the polymer chains in a random fashion. The resultant polymers generally have a higher melt flow rate (MFR), a narrower molecular weight distribution than the parent polymer, and good impact-stiffness balance. The main focus of this investigation was to determine if there exist any differences in the molecular structure and physical properties of controlled rheology HECO polymers and if differences do exist, how they influence the physical characteristics of the polymer. Eight HECO polymers with equal ethylene contents were visbroken to varying degrees by making use of two different types of organic peroxide. The effects of the amount of visbreaking on the molecular characteristics and physical properties were subsequently studied by making use various types of fractionation techniques, including preparative temperature rising elution fractionation (PTREF) and crystallisation analysis fractionation (CRYSTAF). Subsequent offline analysis was then done on the fractionated samples that included nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), high temperature size exclusion chromatography (HT-SEC), Fourier transform infrared spectroscopy (FTIR) and deposition of the SEC fractions via the LC Transform Interface (SEC-FTIR) as well as high temperature high performance liquid chromatography (HT-HPLC), a novel technique for the characterization of olefins according to their chemical composition.
AFRIKAANSE OPSOMMING: Heterofase kopolimere, ook bekend as HECO polimere, of dikwels na verwys net as impak kopolimere of blok kopolimere bestaan uit 'n polimeer matriks met 'n verspreide rubberagtige kopolimeer fase. Die polimeer wat in hierdie studie ondersoek was het bestaan uit 'n polipropileen homopolimeer matriks en etileen-propileen kopolimere (EPCs). As gevolg van sy veelseidigheid van toepassings en unieke eienskappe is polipropileen die keuse van polimeer vir 'n wye verskeidenheid van toepassings. Hierdie veelseidigheid het gelei tot die ontwikkeling van 'n hele klas van polipropileen materiaal bekend as gevisbreekte of beheerde reologie polipropileen. Deur die byvoeging van 'n geskikte peroksied tot die polimeer in die teenwoordigheid van hitte, word radikale gevorm wat die polimeerkettings in 'n ewekansige wyse sal aanval. Die gevolglike polimere in die algemeen het 'n hoë smelt vloeitempo (MFR), 'n smaller molekulêre gewig verspreiding as die moeder polimeer, en 'n goeie impak/styfheid balans. Agt HEKO polimere met gelyke etileen inhoude was gevisbreek in wisselende hoeveelhede deur gebruik te maak van twee verskillende tipes organiese peroksiedes. Die gevolge van die hoeveelheid van visbreeking op die molekulêre eienskappe en fisiese eienskappe was vervolgens gebestudeer deur gebruik te maak van verskillende fraksionasie tegnieke, insluitend preparatiewe TREF (P-TREF) en CRYSTAF. Daaropvolgende analiese is gedoen op die gefraktioneerde monsters en sluit in kernmagnetiese resonansie spektroskopie (KMR), differensiële skandeer kalorimetrie (DSC), 'n hoë temperatuur grootte uitsluitings chromatografie (HT-SEC), Fourier transform infrarooi spektroskopie (FTIR) met deponeering van die SEC fraksies via die LC transform koppelvlak (SEC-FTIR) sowel as 'n hoë temperatuur hoë werkverrigting vloeistof chromatografie (HT-HPLC), 'n nuwe tegniek vir die karakterisering van olefiene volgens hul chemiese samestelling.

Magnetic nanoparticles that display high saturation magnetization and high magnetic susceptibility are of great interest for medical applications. Nanomagnetite is particularly desirable because it displays strong ferrimagnetic behavior, and is less sensitive to oxidation than magnetic transition metals such as cobalt, iron, and nickel. Magnetite nanoparticles can be prepared by co-precipitating iron (II) and iron (III) chloride salts in the presence of ammonium hydroxide at pH 9-10. One goal of this work has been to develop a generalized methodology for stabilizing nanomagnetite dispersions using well-defined, non-toxic, block copolymers, so that the resultant magnetite-polymer complexes can be used in a range of biomedical materials. Hydrophilic triblock copolymers with controlled concentrations of pendent carboxylic acids were prepared. The triblock copolymers contain carboxylic acids in the central urethane segments and controlled molecular weight poly(ethylene oxide) tail blocks. They were utilized to prepare hydrophilic-coated iron oxide nanoparticles with biocompatible materials for utility in magnetic field guidable drug delivery vehicles. The triblock copolymers synthesized contain 3, 5, or 10 carboxylic acids in the central segments with Mn values of 2000, 5000 or 15000 g/mol poly(ethylene oxide) tail blocks. A method was developed for preparing ~10 nm diameter magnetite surfaces stabilized with the triblock polymers. The carboxylic acid is proposed to covalently bind to the surface of the magnetite and form stable dispersions at neutral pH. The polymer-nanomagnetite conjugates described in this thesis have a maximum of 35 wt. % magnetite and the nano-magnetite particles have an excellent saturation magnetization of ~66 - 78 emu/g Fe3O4. Powder X-ray diffraction (XRD) confirms the magnetite crystal structure, which appears to be approximately single crystalline structures via electron diffraction spectroscopy analysis (EDS). These materials form stable magnetic dispersions in both water and organic solvents.
Ph. D.

The objectives of this study are to synthesize poly(dimethylsilane) (PDMS) preceramic polymer and to investigate its effect on morphology, flame retardant and mechanical properties of polypropylene (PP) based composites. There are mainly two parts in this thesis. In the first part, PDMS was synthesized by electrochemical polymerization of dichlorodimethylsilane, which was dissolved in 1,2 dimethoxyethane (DME) solvent consisting of tetrabutyl ammonium perchlorate (TBAP), as supporting electrolyte. PDMS was obtained in powder form and characterized with Fourier transform infrared, ultraviolet-visible and proton nuclear magnetic resonance spectroscopic analyses, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Since PDMS has some impurities coming from TBAP and DME, alternatively, the PDMS synthesis was done by electrochemical reduction of dichlorodimethylsilane without using solvent and/or supporting electrolyte for seven days. PDMS was produced as pure and characterized with the same methods used for previous synthesis. In the second part of this thesis, PP based composites with additives were prepared by using a twin-screw extruder and injection molding machine and were characterized with limiting oxygen index (LOI), horizontal burning, TGA, differential scanning calorimetry (DSC), tensile and impact tests and SEM analysis. Triphenyl phosphate, boron phosphate, magnesium hydroxide, intumescent flame retardants (IFR) (melamine phosphate (MP) and pentaerythritol (PER)), antimony trioxide and poly(methylsilsesquioxane) were additives used in this study other than PDMS. According to LOI test results, the highest LOI value among the PDMS composites was obtained in 1% PDMS, 14.25% MP and 4.75% PER (w/w) containing composite as 24%, whereas the LOI value of neat PP was measured as 17.5%. It was determined that elastic moduli of all the composites studied were higher than neat PP.

Thesis (PhD)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Impact copolymers or heterophasic polypropylene-ethylene-co-propylene copolymers (HEPCs) commonly produced in industry are valued for their good mechanical properties, combining the rigidity of the polypropylene matrix with the toughness of the dispersed ethylene-propylene copolymer. The potential for further optimisation and tailoring of product properties can be realised through an improved understanding of how the copolymer phase produced in the second reactor develops with increasing ethylene incorporation, providing an intermediate link between predicted physical behaviour and the process parameters required to achieve this. To this end, the morphological development of heterophasic or impact copolymers, has been a topic of interest of many studies to date, yet due to the complexity of these polymers, there is still some uncertainty with regards to the mechanism of copolymer growth as well as the structure-function relationships that exist. These studies were limited either due to the use of autoclave products or final impact copolymer products obtained from industry. The work presented in this study was aimed at understanding how the nascent copolymer phase develops during a transition from homopolymer to the final copolymer. This was done by selecting samples at certain intervals from two different commercial gas-phase processes, yielding two sets of four samples, each with a range of increasing ethylene contents. These samples provided the unique opportunity to study the early development of copolymer in a sequential manner (as each sample builds on the morphology of the previous one). The morphological development of copolymer in these samples was investigated by high resolution FE-SEM and it was observed that the copolymers showed different degrees of internal and external distribution as well as porosity for the different sets, determined by the initial porosity of the homopolymer. It was also found that the copolymer was radially distributed throughout the particle in all instances, suggesting that ethylene monomer diffusion limitations did not play a significant role in the copolymerization process. A further aim of the study was to determine the effect of ethylene incorporation on bulk sample crystallinity, microstructure and chemical composition. It was observed by SCALLS and TREF that increasing ethylene incorporation attenuated the crystallinity of the homopolymer, resulting in a distribution of components with different crystallinities within the samples, suggesting some interaction between the developing copolymer and existing homopolymer. During the microstructural development of these samples, longer or more blocky ethylene sequences seemed to be favoured above isolated ethylene sequences with increasing ethylene incorporation and it was shown by solid-state NMR that ethylene partitioning between both amorphous and rigid environments occurred. Detailed characterization (solution and solid-state 13C NMR, HT-SEC and HT-HPLC) of the semi-crystalline copolymer fractions provided some information on the development of microstructure and chemical composition in these fractions that are responsible for compatibilization between the homopolymer matrix and dispersed rubber phase. Based on the different observations from the investigations outlined above, a model for copolymer development in each set was proposed and related to the physical property development observed for these samples.
AFRIKAANSE OPSOMMING: Die impak-kopolimere – ook bekend as heterofase polipropileen-etileen-kopropileen kopolimere (HEPC’s) – wat tans in die bedryf vervaardig word, is bekend vir hul goeie meganiese eienskappe, naamlik om die styfheid van ’n polipropileenmatriks met die sterkte van ’n etileen-propileen kopolimeer, wat in die matriks versprei is, te kombineer. Die potensiaal vir die optimisering en pasmaak van produkeienskappe kan bewerkstellig word deur beter begrip ten opsigte van hoe die kopolimeerfase wat in die tweede reaktor vervaardig word, ontwikkel as gevolg van toenemende inkorporasie van etileen, en hoe dit ’n skakel skep tussen voorspelbare fisiese gedrag en die prosesparameters wat nodig is hiervoor. Tot datum het heelparty studies gefokus op die morfologiese ontwikkeling van heterofase of impak-kopolimere, maar as gevolg van die komplekse aard van hierdie polimere is daar nog steeds onsekerheid oor die meganisme van kopolimeerontwikkeling, asook die verwantskappe tussen die polimeerstruktuur en -funksie. Sodanige studies was beperk omdat óf outoklaafprodukte óf finale produkte van industriële prosesse gebruik is. Die doel van hierdie studie was om begrip te kry vir hoe die kopolimeerfase ontwikkel tydens ’n oorgang van homopolimeer tot die finale produk. Hiervoor is twee stelle van vier monsters met toenemende etileeninhoude tydens die oorgang in twee verskillende gasfaseprosesse verkry. Hierdie monsters het die unieke geleentheid gebied vir die opvolgende bestudering van die vroeë ontwikkeling van die kopolimeer, deurdat elke monster voortgebou het op die morfologie van die vorige monster. Die morfologiese ontwikkeling van die kopolimeer is ondersoek deur van hoëresolusie FE-SEM gebruik te maak. Verskillende wyses van interne en eksterne verspreiding, sowel as porositeit van die onderskeie stelle (soos bepaal deur die aanvanklike porositeit van die homopolimeer), is vir die verskillende prosesse waargeneem. Daar is ook waargeneem dat die kopolimeer in alle gevalle op verskeie straalposisies binne die partikel versprei is, waarvan afgelei kan word dat monomeerdiffusiebeperking nie ’n beduidende rol in die kopolimerisasieproses speel nie. ’n Verdere doel van hierdie studie was om die uitwerking van etileen-inkorporasie op die kristalliniteit, mikrostruktuur en chemiese samestelling van die polimeer te bepaal. Deur middel van SCALLS en TREF is bevind dat toenemende etileen-inkorporasie die kristalliniteit van die homopolimeer verswak het. Die gevolg was die vorming van ’n verskeidenheid komponente met verskillende kristalliniteite, wat dui op ’n interaksie tussen die groeiende kopolimeer en die bestaande homopolimeer. Tydens die ontwikkeling van die mikrostruktuur van die monsters het dit geblyk dat lang, opeenvolgende etileeneenhede tydens toenemende etileen-inkorporasie vinniger ontwikkel as afgesonderde etileen- en propileeneenhede. Deur middel van soliedefase-KMR is daar bewys dat die etileen in beide amorfe en kristalagtige areas versprei is. Die semi-kristallyne kopolimere wat deur TREF verkry is, is verder gekarakteriseer met behulp van KMR in oplossing sowel as die soliede fase, HT-SEC en HT-HPLC, wat meer inligting verskaf oor die ontwikkeling van die mikrostruktuur en chemiese samestelling van hierdie fraksies wat normaalweg verantwoordelik is vir die interaksies tussen die homopolimeermatriks en die verspreide rubberfase. Op grond van die waarnemings soos hierbo vermeld, word ’n model vir die kopolimeerfase-ontwikkeling van elke stel monsters in hierdie studie voorgestel en verbind met die ontwikkeling van die waargenome fisiese eienskappe.

The composition and stability of polymer-magnetite complexes is essential for their use as a treatment for retinal detachment, for drug targeting and delivery, and for use as a MRI contrast agent. This work outlines a general methodology to design well-defined, stable polymer-magnetite complexes. Colloidal modeling was developed and validated to describe polymer brush extension from the magnetite core. This allowed for the observation of deviations from expected behavior as well as the precise control of polymer-particle complex size. Application of the modified Derjaguin-Verwey-Landau-Overbeek (DLVO) theory allowed the determination of the polymer loading and molecular weight necessary to sterically stabilize primary magnetite particles. Anchoring of polyethers to the magnetite nanoparticle surface was examined using three different types of anchor groups: carboxylic acid, ammonium, and zwitterionic phosphonate. As assessed by dynamic light scattering (DLS), the zwitterionic phosphonate group provided far more robust anchoring than either the carboxylic acid or ammonium anchor groups, which was attributed to an extremely strong interaction between the phosphonate anchor and the magnetite surface. Coverage of the magnetite surface by the anchor group was found to be a critical design variable for the stability of the zwitterionic phosphonate groups, and the use of a tri-zwitterionic phosphonate anchor provided stability in phosphate buffered saline (PBS) for a large range of polymer loadings. Incorporation of an amphiphlic poly(propylene oxide)-b-poly(ethyelene oxide) (PPO-b-PEO) diblock copolymer attached to the magnetite surface was examined through colloidal modeling and DLS. The relaxivity of the complexes was related to aggregation behavior observed through DLS. This indicated the presence of a hydrophobic interaction between the PPO layers of neighboring complexes. When this interaction was large enough, the complexes exhibited an increased relaxivity and cellular uptake. Thus, we have developed a methodology that allows for design of polymer-magnetite complexes with controlled sizes (within 8% of predicted values). Application of this methodology incorporated with modified DLVO theory aids in the design of colloidally stable complexes with minimum polymer loading. Finally, determination of an anchor group stable in the presence of phosphate salts at all magnetite loadings allows for the design of materials with minimum polymer loadings in biological systems.
Ph. D.

Zinc xanthates are active catalysts in stereoregular polymerization of propylene oxide and markedly more stable than that of known classical stereoregular catalysts. But steric control of zinc xanthates is weaker. To find more effective catalyst systems the isopropyl xanthates of Cu, Pb, Ni, Fe, Al and Sn are investigated and only copper (Cu(isoPr)Xt) and tin (Sn(isoPr)Xt) isopropyl xanthates were appeared to be active, but Cu(isoPr)Xt yielded only low molecular weight product. Therefore Sn(isoPr)Xt system was investigated in detail in polymerization of propylene oxide (PO). Polymerization of PO with this catalyst produced two contrasting polymers
high molar mass, crystalline (K-polymer) and low molar mass (D-polymer). Formation of double bonds in D-polymer was thought to be due to as an anionic process. Polymerization reactions were studied by changing polymerization conditions and reacting catalyst with predetermined amount of water. It&
#8217
s found that Sn(isoPr)Xt have considerably low efficiency than that of Zn(isoPr)Xt catalyst. The yield linearly increases by increasing catalyst concentration. The propagation is competed by termination or transfer process hence overall activation energy is negative. Some mechanistic features of this system was also discussed. The catalytical activity of carbamates in this field has also been reported, without any information about catalytical efficiency and stereoregularity of the process. Therefore zinc diethyl dithiocarbamate was also studied and found as an active catalyst in stereoregular polymerization but it showed weaker efficiency in the PO polymerization than that of Zn(isoPr)Xt catalyst (about 12 times weaker).

Safripol is a South African polymer company producing mainly high density polyethylene and polypropylene for the South African market. Safripol used to be part of a global chemical company Dow Chemicals. Dow Chemical's divested in South Africa in 2006 and Safripol lost all the advantages of being part of a global corporate enterprise. The company is faced with a unique situation in that it is receiving monomer from Sasol, which is also its main competitor in the polymer market. The price of monomer and its low availability is putting pressure on Safripol's product margins, with a negative effect on the company's sustainability. The above was also defined as the research problem that threatens to undermine the company's competitive edge in the polymer market. It was clear from this research study that monomer and specifically propylene was the biggest burning point for Safripol regarding the price and availability thereof. Research into the South African polymer market has shown that Safripol will lose significant market share if the company is not showing additional growth in the market. The research problem is investigated through interviews, monomer availability investigations, plant capacity increasing and potential technology partner's discussions. A specific scenario planning process was also followed to help Safripol identify potential present and future scenarios that the company can investigate. The research problem was addressed by developing a strategy for Safripol to address the research objectives. Recommendations were done regarding the following: 1) Recommendations for additional propylene supply. 2) Recommendations to increase the polypropylene plant capacity. 3) Recommendations with regards to technology partners. 4) Recommendations regarding the scenario planning process.
Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011. (Mag eers in 2014 gepubliseer word)

>Magister Scientiae - MSc
HIV and AIDS are among the world's pandemics that pose serious concern to almost every individual in the world. With the current level of availability of anti-retroviral (ARV) drugs and the ease of accessibility of treatment in many countries such as South Africa, the disease can be controlled by suppressing the viral load of an infected individual. These anti HIV drugs such as delavirdine are metabolised by enzymes which are found in the liver microsomes, particularly those of the cytochrome P450 family. Due to the fact that the metabolic rate of a patient determines the effect of the drug, the drug could either have a beneficial or an adverse effect once it is administered. It is therefore imperative that the metabolic profile of a patient is determined at point-of-care is necessary for proper dosing of the ARV drugs. In this project a nanobiosensor system was devised and used for the determination of the metabolism of delavirdine, a non-nucleoside reverse transcriptase inhibitor (NNRTI) ARV drug. The nanobiosensor was prepared by the entrapment of the isoenzyme CYP3A4 into a pre-formed electro active carrier matrice consisting of a dendrimeric copper generation-2 poly (propylene imine)-co-polypyrrole star copolymer (Cu(G2PPI)-co-PPy). The metallo-dendrimer was used as a host for the enzyme and provided thenecessary bio-compatible environment that allowed the direct transfer of electrons between the enzyme's active centres and platinum electrode surface. Copper was the choice of metal used in the study due to its properties. Copper is a malleable, ductile and a good conductor of both heat and electricity. It is a better conductor than most metals. Silver which also belongs to group 1b in the periodic table is a better electrical conductor than copper but copper has better corrosion resistance and is a more abundant and hence it is a cheaper material to use. Cu(G2PPI)-co-PPy was prepared by the incorporation of the copper metal into the G2PPI and the electropolymerization of pyrrole onto the Cu(G2PPI). The incorporation of Cu into G2PPI was determined by FTIR which did not show the presence of the Cu but showed an increase in the intensities of the peaks after the incorporation. The surface morphology of Cu (G2PPI) was confirmed by the use of HRSEM which showed a difference in the surface morphology of the dendrimer moiety with the addition of the copper metal. The HRSEM images after Cu incorporation resulted in the change from rough surface to smooth surface with open cavities which were essential for the entrapment of the biological systems (CYP3A4). Energy dispersive spectrometry (EDS) and HRTEM were used to confirm the presence of spherically shaped copper nanoparticles in the Cu (G2PPI) and were found to have a size distribution of 12-17 nm with an average particle size of 15nm. The star copolymer (Cu(G2PPI)-co-PPy) was characterised using cyclic voltammetrywhere it was confirmed that the material was electroactive and conducting due to electron movement along the polymer chain. A diffusion co-efficient (D₀) value of 8.64 x 10⁻⁵ cm²/s was determined for the material indicating a slow electron transfer kinetics within the diffusion layer. The constructed nanobiosensor was developed using copper poly (propylene imine) – polypyrrole star copolymer, bovine serum albumin and glutaraldehyde coupled to the enzyme CYP3A4. The resultant nanobiosensor parameters include a dynamic linear range (DLR) of 0.01-0.06 nM, a limit of detection (LOD) of 0.025 nM and a sensitivity value of0.379 μA/nM.

Le centre de recherche ArcelorMittal de Montataire développent de nouvelles solutions acier innovantes associant métal et polymère. Pour les ailes de voiture, le composite retenu est un matériau multicouche composé d’une lame d’acier sur laquelle est déposé un film mince de polypropylène choc chargé avec des particules minérales par l’intermédiaire d’une fine couche de polypropylène fonctionnalisé par le greffage d’anhydride maléique. Afin de prévoir et de connaitre le comportement de la partie organique du matériau lors de sa mise en forme par emboutissage et à posteriori de prédire l’état de ses propriétés mécaniques lors de son utilisation, la détermination des lois de comportement mécanique vrai et intrinsèque sur le modèle de la loi G’sell et Jonas est nécessaire. Ces lois sont définies selon trois chemins de déformation : la traction uniaxiale, le cisaillement simple et la traction plane. Les micromécanismes de déformation de la microstructure semi-cristalline des différentes formulations des matériaux selon leur mode de sollicitation mécanique ont été étudiés. Les résultats obtenus Post Mortem et In Situ ont permis la description qualitative et quantitative des évolutions des principales modifications microstructurales. Ces dernières diffèrent avec l’ajout de charges minérales. Deux nouvelles méthodes, la Tomographie X et la spectroscopie Raman permettent la détermination de la déformation volumique dans le cas de matériau de géométrie fine (300 µm). Le retrait lors d’un cycle thermique est étudié. Les influences du chauffage, de la formulation et de la microstructure (orientation des chaînes macromoléculaires et endommagement volumique) sont décrites
The ArcelorMittal research centre of Montataire elaborates innovative steel / polymer products. In the case of automotive fenders, the composite is a multilayered material. A thin impact polypropylene film is laminated on steel using a thin layer of a functionalized polypropylene. Mineral particles are added to improve stiffness. In order to predict and understand the behaviour of the organic layer all along its production process and finally to be able to characterize the state of its mechanical properties in use, the determination of the true and intrinsic mechanical behaviour laws according to the G’sell and Jonas model is necessary. These laws are obtained for three different mechanical paths: uniaxial tensile, simple shear and plane tensile. The deformation micromechanisms of the impact polypropylene semi-crystalline microstructure which depend on the materials formulations and on the mechanical path used are studied. Post Mortem and In Situ results give qualitative and quantitative description of the main microstructural modifications. Two new methods, X Tomography and Raman spectroscopy allow the quantification of the volume deformation which is developed during tensile tests. They are mainly available for very thin samples. X radiography and VideoTraction™ are not suitable anymore for this kind of geometry. Finally, the thermo-mechanical phenomenon of shrinkage which occurs during thermal treatment above the material melting point is analysed. Influences of the heating conditions, of the material formulations and of the material microstructure are described. Special overviews are done on the macromolecular chains orientation and on the volume damage influences

Les molecules de meso di(n-carbazolyl)-2,4 pentane et oxyde de bis(phenyl-10 anthryl-9 methyl) servent de sondes fluorescentes pour l'analyse de la mobilite des chaines macromoleculaires de: polyoxydes de propene, polysiloxane, polybutadiene, polyisopropene et polyisobutene. Influence de la nature du polymere sur le mouvement de la sonde

Etude des mouvements locaux dans le polyvinylmethylether, le polybutadiene-1,4cis et le polyisoprene-1,4cis, le polyisobutène, les polyéthers en masse; polyoxypropylène et réseaux de polyoxyéthylène, influence de la microstructure sur les mouvements moléculaires locaux. Etude de la transition vitreuse dans les polymères en masse par simulation de Monte-Carlo dynamique; simulation de systemes de polymères places dans le réseau tétraédrique et simulation de systemes de sphères libres et de systemes de polymères en milieu continu.

Influence de l'ionisation par irradiation electrons du polyethylene et du polypropylene sur la structure et les transferts de masse (permeabilite et migration). Etude des degagements de produits volatils

Předkládaná práce se zabývá výzkumem nových materiálů a metod přípravy gelových polymerních elektrolytů (GPE) na bázi methakrylátů, které lze zejména vzhledem k jejich mechanickým vlastnostem s výhodou využít při konstrukci elektrochromních (EC) prvků.

Afin de determiner s'il est possible d'impregner les condensateurs au polypropylene metallise, nous avons tout d'abord etudie les decharges se produisant au voisinage du bord de metallisation. Cette etude a montre que l'utilisation d'un liquide dielectrique tel que le m/dbt, l'huile de colza ou l'huile silicone, permet une elevation considerable de la tension d'apparition des decharges partielles par rapport aux condensateurs metallises secs. Nous avons mis en evidence l'existence de deux regimes de decharges : les decharges du 1#e#r regime sont dues a des avalanches electroniques dans le liquide, tandis les decharges du 2#n#d regime se produisent dans des bulles de gaz et conduisent tres rapidement au claquage. Nous avons egalement examine l'influence de l'epaisseur de l'isolant, de la pression d'appui et de la nature de l'impregnant. Nous avons ensuite mis au point un dispositif experimental permettant de mesurer l'impulsion de courant et la lumiere emise au cours de l'autocicatrisation. Ce dispositif a ete valide dans un premier temps par des mesures sur des films non impregnes et en etudiant l'influence de l'epaisseur du film de polypropylene, de la nature et de l'epaisseur de la metallisation ainsi que de la pression. Nous avons ensuite etudie comment la presence d'un impregnant modifie le deroulement de l'autocicatrisation. Ces mesures electriques et optiques ont ete completees par des observations au meb, par des analyses chimiques et par une etude thermodynamique visant a determiner la nature des depots formes au cours de l'autocicatrisation, en presence ou non d'un impregnant. Ces experiences ont montre que lors du claquage du polypropylene metallise impregne au m/dbt ou a l'huile de colza, il y a formation de ponts de graphite qui empechent l'isolement du defaut. En revanche, dans l'huile silicone l'autocicatrisation fonctionne parfaitement, grace a la formation d'un depot de sio#2 qui empeche la formation d'un depot conducteur.

Cette étude est une contribution à la valorisation du grignon d’olives (GO), sous produits oléicoles à caractère lignocellulosique. La voie proposée consiste à utiliser le GO comme charge dans des polymères de grande diffusion à savoir le poly (éthylène/propylène) [CEP] d’origine fossile et le poly (acide lactique) [PLA], issu des ressources renouvelables. Les différentes formulations, CEP/GO et PLA/GO, élaborées à l’état fondu dans une extrudeuse bivis ont été étudiés du point de vue des propriétés rhéologiques, thermique, mécanique et de la morphologie. Différents tiers-corps copolymères de structures diverses ont été utilisés dans le but de promouvoir l’adhésion à l’interface des composants et/ou de réduire la dégradation du polymère matrice et améliorer les performances des systèmes composites ainsi conçus. Les observations morphologiques ont corroboré parfaitement l’ensemble des propriétés étudiées
This study is a contribution to the valorization of Olive Solid Waste (OSW) which displays a Lignocellulosic nature. The proposed approach consists in using the OSW as a filler in commodity polymers namely the poly (ethylene/propylene) [CEP] of fossil origin and the poly (lactic acid), derived from renewable resources. The different formulations, CEP/GO and PLA/GO, processed in the molten state in a twin screw extruder were studied from the side of rheological, thermal, mechanical properties and morphology. Different copolymers of various structures were used in order to promote the adhesion in the interface of the components and/or to reduce the polymer matrix degradation and to improve the composite systems performances. Morphological observations corroborated perfectly the studied properties

The synthesis of molecularly designed poly(propylene oxide) was accomplished by using aluminum porphyrin initiator/catalysts to prepare controlled molecular weights, narrow molecular weight distributions, topologies, and functionalities. Poly(propylene oxide) has been an important intermediate in macromolecular synthesis. However, lack of control via the conventional potassium hydroxide initiated synthetic method limits the applications of this polymer. In the synthesis of poly(propylene oxide) by using aluminum porphyrin catalyst system, polymerization occurred by exclusive cleavage of the epoxide methylene oxygen bond via nucleophilic attack. This type of ring opening polymerization yields to head to tail configuration with asymmetric monomers. The aluminum porphyrin allowed the synthesis of poly(propylene oxide) with a high molecular weight of ca. 100,000 g/mole and narrow molecular weight distribution, indicating a living nature of this system. A variety of reactive functional end groups, including both primary and secondary hydroxyl and amine could be incorporated in the polymer chains through the modification of the original catalyst with chain transfer agents such as bisphenol A or p-nitro phenol. These reagents also permitted very significant reductions in the required concentration of the catalyst. The well defined poly(propylene oxide)s allowed the systematic study of effects of functional end groups on thermal degradation behavior. Interestingly, aromatic amine and aromatic nitro end groups significantly improved the thermal stability, whereas the presence of unsaturated end groups caused very adverse effects. Some of the functionally terminated poly(propylene oxide)s were utilized in the synthesis of block and segmented copolymers to examine the well defined structures as characterized by spectroscopic analysis. The aluminum porphyrin catalyst system was also used to produce statistical copolymers of propylene oxide and allyl glycidyl ether or caprolactone.
Ph. D.

L'etude met en evidence que le comportement du ppi est lie a sa structure cristalline ; on constate que si la phase hexagonale est majoritaire, le materiau est plus ductile que celui constitue d'une phase monoclinique

Vieillissement de condensateurs moyenne tension dit "tout film" au polypropene impregne: influence d'epoxydes comme additif au liquide d'impregnation (ralentissement des mecanismes conduisant au vieillissement du film, inities dans une couche de liquide de quelques mu d'epaisseur entre le film et l'electrode). Etude sur des modeles de condensateurs a geometrie plane. Mesure de la rigidite dielectrique du film impregne

Ce travail concerne le mecanisme de degradation de condensateurs moyenne tension au polypropylene impregne en presence d'oxygene. Cette etude a ete realisee sur des modeles de condensateurs en geometrie plane, avec des conditions experimentales (champ electrique alternatif compris entre 66 v/m-200 v/m, atmosphere d'oxygene, temperature de 80c) qui nous ont permis d'obtenir des resultats proches de la realite industrielle. Le vieillissement des condensateurs est essentiellement evalue par leur duree de vie et l'evolution des caracteristiques physico-chimiques du polymere et de l'impregnant. Le polymere est caracterise par sa rigidite dielectrique, ses pertes en basse tension, sa masse macromoleculaire (determinee par chromatographie sur gel), son absorption infra-rouge, sa cristallinite (mesuree par diffraction x aux grands angles) et l'observation microscopique de sa surface. Le liquide est caracterise par ses pertes dielectriques, son indice d'acidite, son absorption ultra-violette et infra-rouge. Nous montrons que la degradation du film par un mecanisme radicalaire conduit a un abaissement de sa rigidite dielectrique qui est responsable du claquage du condensateur. La presence de tetrachlorure de carbone et d'eau dans l'impregnant accelere le mecanisme de degradation du polypropylene en creant aux electrodes des especes capables d'initier une reaction radicalaire. L'acceleration de la degradation en presence d'oxygene s'explique par le schema classique de l'oxydation du film. Nous attribuons l'abaissement de la tension de claquage a la mise en solution de fragments de bas poids moleculaires. L'analyse de l'action des epoxydes sur les differentes etapes du mecanisme de degradation que nous proposons, nous permet d'ecarter son action comme antioxydant, piegeur d'acide ou encore comme reticulant du polypropylene. Pour interpreter leur action stabilisatrice dans la degradation des condensateurs, nous suggerons que les epoxydes agissent sur les especes formees aux electrodes

Des films de polyfluorure de vinylidène et de polypropylène, chargés en titanate de baryum, sont réalisés par extrusion. Les propriétés diélectriques de ces films sont mesurées dans différentes conditions. Les films à matrice PVDF présentent les meilleures caractéristiques pour une application de stockage d'énergie. L'évolution de la permittivité relative et de la rigidité diélectrique en fonction du taux volumique de charge, sont modélisées respectivement par la théorie de la percolation et par un modèle semi-empirique. Les mélanges sont étudiés en rhéométrie dynamique et capillaire. Les interactions interparticules donnent naissance à un réseau dont la structure est dépendante de la sollicitation appliquée. En écoulement de poiseuille, des instabilités d'écoulement ainsi que des défauts d'écoulement sont observés pour des gradients de vitesse de cisaillement relativement faibles

The effect of silica on the crystallization and melting behavior of a highly isotactic, well characterized isotactic polystyrene (i-PS) have been investigated. The origins of the various endotherms obtained upon heating have been defined by partial scanning experiments and by a study of the effect of heating rate using differential scanning calorimetry (DSC). The presence of 1 part silica in 100 parts polymer (1 pph) decreases the maximum degree of crystallinity considerably but has a minimal effect on the rate of crystallization. Analysis by the Avrami method shows that the silica does not affect the overall rate of crystallization significantly. The decrease in the crystallinity indicates that silica affects the level of secondary crystallization, thus the crystal perfection.
The surface morphologies and growth rates of i-PS spherulites, as studied by photomicroscopy, were not affected by 1 pph of silica. The experimental data were fitted to a modified form of the Hoffman-Lauritzen equation.
The effect of silica on spherulite growth rates and surface morphologies of isotactic poly(propylene oxide) (i-PPO) have also been investigated by optical microscopy. Two distinct i-PPO samples of different molecular weights were used, each of which was highly isotactic. The addition of silica has a pronounced effect on the morphology of the spherulites, producing dendritic type morphology. Upon step-crystallization, the spherulites exhibited mixed morphologies, i.e., fibrillar and ringed. Silica depresses the spherulite growth rates throughout the entire temperature range. The effects were more profound as the quantity of filler increased. The growth rate-temperature behavior was analysed in terms of the classical Hoffman-Lauritzen equation and a modified version to take into account the polymer-filler interaction.

Les decharges partielles ont ete mesurees sur des modeles de condensateurs tout-film dont le dielectrique est du polypropylene (pp) impregne. Ces cellules ont ete alimentees en haute tension alternative. L'influence de l'epaisseur de dielectrique ou des armatures ainsi que les effets de la temperature et du vieillissement ont ete examines. Les representations n() et q#m#o#y() du nombre et de l'amplitude des decharges dans la phase de la tension alternative servent a caracteriser la source de ces decharges : decharges en bord d'armature dans un modele de condensateur sans defaut ou decharges generees par des defauts artificiellement introduits dans la cellule d'etude (defaut d'impregnation, defaut de contact, cavite dans un film de pp, film de pp plie). Le but de cette caracterisation est la constitution d'une base de donnees qui servira a la reconnaissance de la source des decharges sur des appareils industriels et permettra d'estimer la duree de vie de ces appareils. Les tensions d'apparition et d'extinction des decharges partielles (tadp et tedp), l'evolution des decharges en fonction du temps ou de la tension appliquee sont des elements qui servent a la caracterisation des decharges. Cette tache se fait egalement au moyen de parametres calcules a partir des distributions n() et q#m#o#y(). Ces parametres peuvent etre les moments d'ordre 3 et 4 ou bien les parametres que nous avons introduits dans cette etude et qui sont les parametres de position et le parametre d'efficacite energetique. Ces deux derniers parametres sont les plus efficaces car ils permettent a eux seuls de differencier la plupart des cas etudies.

Zinc xanthates polymerize propylene oxide into high polymer (PPO) with coordination mechanism. In order to identify structure and stereoisomerisms of this polymer, PPO was subjected to thermal and column fractionation. Obtained fractions were characterized by end-group analysis, cryoscopy, viscometry, IR and 13C-NMR spectroscopy, melting temperature. PPO is composed of a high molecular weight, stereoregular, crystallizable polymer (K-polymer) with low molecular weight (=500 g/mol) D-polymer. Presence of double bonds and hydroxyl terminals was interpreted as the product of an anionic mechanism. K-Polymers can be thermally fractionated on the basis of their melting temperature (Tm) rather than molecular weight (Mwt). It&
#8217
s found that higher Tm fractions have lower Mwt, but they precipitate at higher temperatures than higher Mwt but lower Tm fractions. In column fractionation, K-polymers were deposited on glass beads from isooctane solution in a narrow temperature interval. Then the precipitated samples were split into a number of fractions by using again isooctane but at a higher temperature than the precipitation temperature by increasing residence time from 5 minutes to several hours. It&
#8217
s found that rate of solubility is not controlled by molecular weight, but controlled by percentage crystallinity and Tm. Highest Tm polymers, with relatively higher Mwt showed faster rate of solution than that of lower Tm, lower Mwt but higher percent crystalline fractions. This discrepancy was accounted by suggesting a stereo-block structure where tactic blocks are bound each other with non-crystallizable atactic blocks. The mechanism of polymerization was also discussed in some detail.

Depuis le début des années 80, un nouveau type de système catalytique (métallocène/MAO) a relancé l'intérêt industriel pour la catalyse de polymérisation. La structure bien définie de son précurseur (de type l2MCl2 avec M = Ti, Zr) offre la possibilité de faire varier systématiquement la structure du site actif et permet donc d'utiliser des méthodes théoriques pour prédire l'activité des catalyseurs. L’objectif de notre travail est l'obtention de modèles permettant la sélection de nouvelles molécules comme catalyseurs de polymérisation. L’étude effectuée s'est articulée autour de deux approches complémentaires : la mécanique moléculaire et la mécanique quantique (DFT). Nous exposons en premier lieu les calculs effectués sur une série de molécules déjà décrites dans la littérature (brevet Hoechst). Ces travaux nous permettent de montrer l'intérêt de la mécanique moléculaire pour ce type de problème. Nous présentons ensuite une méthode de mise au point de paramètres pour la mécanique moléculaire et l'utilisation de ces paramètres pour l'étude d'une nouvelle famille de molécules pouvant être utilisées comme catalyseurs. Nous développons par la suite les résultats des calculs quantiques et l'étude des mécanismes de polymérisation, en commençant par la polymérisation de l'éthylène pour poursuivre avec la polymérisation du propylène. Nous montrons ainsi le parallèle entre les deux réactions de propagation. Nous nous intéressons enfin aux processus de terminaison de chaines : β-h élimination, transfert au monomère et hydrogénation. L’analyse des résultats nous permet d'identifier quelques facteurs moléculaires essentiels pour l'activité et la sélectivité des catalyseurs. La modélisation de nouveaux systèmes et la prédiction qualitative de leurs propriétés sont donc tout à fait envisageables et représentent une aide précieuse pour la recherche expérimentale.

Depuis quelques années, Elf Atochem essaie d'acquérir une connaissance plus approfondie du site actif de la catalyse Ziegler-Natta, par l'élaboration d'un modèle moléculaire permettant de comprendre l'influence de la structure de la base de Lewis dite externe (espèces devenues indispensables si l'on veut induire une forte isospécificité à la croissance de la chaîne de polymère) sur le contrôle de l'isotacticité. L’objectif de la première partie de ce mémoire a été de développer la synthèse de différentes bases de Lewis, dont les caractéristiques structurales correspondent aux impératifs établis à partir de la modélisation, puis tester en polymérisation l'influence de leur structure moléculaire sur la stéréorégulation de la polymérisation du propylène. L’élaboration et l'étude de nouvelles bases de Lewis externes en polymérisations de l'éthylène font l'objet de la seconde partie de ce mémoire. L’étude de bases de Lewis externes phosphorylées est réalisée pour la première fois ici. Une vaste gamme de composés phosphorés de structures très variées ont été synthétisés et engagés en polymérisation de l'éthylène. Cette deuxième partie se termine par un chapitre plus court relatif à des essais concernant l'élaboration de composés pouvant à la fois jouer le rôle de bases de Lewis externes et d'agents de contrôle de l'exothermicité en polymérisation de l'éthylène

The goal of this project was to develop a mixed matrix membrane with enhanced properties for propylene/propane separations. To start with the project, one of the high performance 6FDA based polyimides was identified as the polymer matrix for the rest of the project. The chosen polymer (6FDA-6FpDA) was successfully synthesized in the laboratory. During the synthesis process the key objectives for high molecular weight and low polydispersity index polymer were identified. High molecular weight 6FDA-6FpDA was achieved via laboratory synthesis and was tested successfully. After successful synthesis of the high performance polymer, pure polymer dense films were tested for transport properties. One problem identified with 6FDA-6FpDA polymer films for propylene/propane separations was plasticization. A major objective of this research was to develop a method for plasticization suppression. A carefully controlled annealing procedure with high temperature permeation experiments was used in this research to suppress plasticization in a mixed gas environment. To the best of our knowledge, this is for the first time plasticization suppression was achieved with pure polymeric membrane material for propylene/propane separations with pure and mixed gases. The observed mixed gas experimental selectivity was lower than the pure gas selectivity which was explained by the combination effect of dual mode and bulk flow effect. The last objective of this project was to successfully incorporate molecular sieve materials to form a mixed matrix membrane hybrid material with enhanced transport properties First, an ideal molecular sieve for propylene/propane separation was identified and characterized. AlPO-14 was chosen for this research following its success with propylene/propane pressure swing adsorption. Mixed matrix membranes were successfully produced and tested for enhanced transport properties. Both pure and mixed gas results showed promising results with enhanced propylene permeability and propylene/propane selectivity. The experimental results were modeled with the Cussler and Maxwell models. A modified Cussler model was presented in this work. This is the first time an enhancement in the transport properties with mixed matrix membrane for propylene/propane separations has been observed. This fundamental dense film work holds a bright future for the scale up of propylene/propane separations.

L'etude consiste essentiellement a definir le role des constituants du liquide d'impregnation et le mecanisme causant la degradation de l'isolant solide lors du vieillissement des condensateurs moyenne tension. L'objectif principal de cette etude est de comprendre l'efficacite d'un additif epoxy deja utilise industriellement. Le vieillissement accelere en presence d'oxygene des modeles de condensateurs est essentiellement caracterise par leur duree de vie et par l'evolution physico-chimique de l'isolant et du liquide d'impregnation. Le liquide est etudie principalement par chromatographie en phase gazeuse. L'isolant est evalue par la rigidite dielectrique, par cartographie irtf et par observation microscopique de sa surface. Nos resultats confirment que l'abaissement de la tension de claquage est plus importante dans la couronne et montrent que les liquides d'impregnation ont une influence importante sur le vieillissement des modeles de condensateurs. La degradation du polypropylene se traduit par son oxydation classique, entrainant la formation de produits de faibles masses solubles dans le liquide et joue un role important dans la diminution de la rigidite dielectrique de l'isolant. Nous montrons que l'effet benefique de l'epoxyde dgeba est attribue principalement a la formation d'une couche protectrice de l'additif polymerise qui se depose sur la surface de l'isolant et reagit avec les especes formees aux electrodes. En presence de decharges electriques, l'addition du dgeba a un effet nefaste sur le vieillissement des modeles de condensateurs. Le vieillissement accelere dans nos conditions operatoires et suivi de la mesure de la rigidite dielectrique des films constituent une methode rapide pour tester des nouveaux materiaux ou additifs avant leur utilisation dans les isolations au polypropylene impregnees

This work reports the elucidation of the structure of a copolymer generated by the cross- catalyzed reactions of PF and pMDI prepolymers.  The electronic behavior of phenolic monomers as perturbed by alkali metal hydroxides in an aqueous environment was studied with 1H and 13C NMR.  Changes in electronic structure and thus reactivity were related to solvated ionic radius, solvent dielectric constant, and their effect on ion generated electric field strength. NMR chemical shifts were used to predict order of reactivity for phenolic model compounds with phenyl isocyanate with good success.  As predicted, 2-HMP hydroxymethyl groups were more reactive than 4-HMP in forming urethane bonds under neutral conditions and 2-HMP hydroxymethyl groups were more reactive than 4-HMP in forming urethane bonds under alkaline conditions.
The structure of the reaction products of phenol, benzyl alcohol, 2-HMP, and 4-HMP with phenyl isocyanate were studied using 1H and 13C NMR under neutral organic and aqueous alkaline conditions.  Reactions in THF-d8 under neutral conditions, without catalyst, were relatively slow, resulting in residual monomer and the precipitation of 1,3-diphenyl urea from the carbamic acid reaction.  The reactions of phenol, 2-HMP, and 4-HMP in the presence of TEA catalyst favored the formation of phenyl urethanes (PU). Reactions with benzyl alcohol, 2-HMP, and 4-HMP in the presence of DBTL catalyst favored the formation of benzyl urethanes (BU).  Reactions of 2-HMP and 4-HMP led to formation of benzylphenyldiurethane (BPDU).  DBTL catalysts favored formation of BDPU strictly by a benzyl urethane pathway, while TEA favored its formation mostly via phenyl urethane, although some BU was also present.  Under aqueous alkaline conditions, 2-HMP was more reactive than 4-HMP, exhibiting an enhanced reactivity that was attributed to intramolecular hydrogen bonding and a resulting resonance stabilization of the phenolic aromatic ring.  
ATR-FTIR spectroscopic studies generated real time structural information for model compound reactions of the cross-catalyzed system, differentiating among reaction peaks generated by the carbamic acid reaction, PU and BU formation.  ATR-FTIR also permitted monitoring of propylene carbonate hydrolysis and accelerated alkaline PF resole condensation.  ATR-FTIR data also showed that the overall reaction stoichiometry between the PF and pMDI components drove copolymer formation.  Benzyl urethane formation predominated under balanced stoichiometric conditions in the presence of ammonium hydroxide, while phenyl urethane formation was favored in its absence.  Accelerated phenolic methylene bridge formation became more important when the PF component was in excess in the presence of sufficient accelerator.  A high percentage of free isocyanate was present in solid copolymer formed at ambient temperature. The combination of ammonium hydroxide and tin (II) chloride synergistically enhanced the reactivity of the materials, reducing the residual isocyanate.
From 13C CP/MAS NMR of the copolymer, the presence of ammonium hydroxide and tin (II) chloride and the higher PF concentration resulted in substantial urethane formation.  Ammonium hydroxide favored formation of benzyl urethane from the 2-hydroxymethyl groups, while phenyl urethane formed in its absence.  The low alkalinity PF resole with ammonium hydroxide favored benzyl urethane formation.  Comparison of these results with the 13C NMR model compound reactions with phenyl isocyanate under alkaline conditions confirmed high and low alkalinity should favor phenyl and benzyl urethane formation respectively.  These cross catalyzed systems are tunable by formulation for type of co-polymer linkages, reactivity, and cost.

Ph. D.

L’objectif de ce travail est d'envisager les modifications de formulation ou de procédé dans la technologie de geltrusion développée par Batscap pour augmenter la fiabilité des supercondensateurs en limitant l'autodécharge. La technologie repose sur l’extrusion simultanée de polymères (PVDF, PVDF-HFP), d’un solvant (PC) et de charges (CA, NC). Le mélange réalisé en extrusion bivis est ensuite filmé et laminé sur le collecteur en aluminium. Dès lors, il a été fondamental de chercher à comprendre les interactions entre les différents composants de l’électrode, avec l’étude de la miscibilité du système ternaire polymère/polymère/solvant puis l’étude de l’adsorption du solvant sur les charges. Cette démarche a permis une meilleure compréhension des phénomènes impliqués en passant par une caractérisation approfondie du complexe, dans sa formulation actuelle aux différentes étapes du procédé. Ensuite, des modifications de formulations ont été envisagées. En particulier, l'effet de la structure et de la masse molaire des polymères sur l’adhésion a été étudié. Dans tous les cas, il a été envisagé de tester les possibilités offertes par l'utilisation d'un solvant différent (DMSO). Ce dernier étant un meilleur solvant du PVDF est plus facile à éliminer que le PC. Enfin, à partir des données rhéologiques du mélange, une modélisation mécanique, en utilisant le modèle de Maxwell à plusieurs temps de relaxation, a été menée dans l'opération de laminage du mélange en prenant en compte un comportement viscoélastique du gel. Toutes ces études ont permis de conclure sur les modifications pertinentes de la formulation ainsi que des conditions du procédé
The objective of this work is to consider changes in formulation or process of the geltrusion technology developed by Batscap to increase the reliability of supercapacitors by limiting self-discharge. The technology is based on the simultaneous extrusion of polymers (PVDF, PVDF-HFP), solvent (propylene carbonate) and fillers (activated carbon, carbon black). The mixture carried out in a twin-screw extrusion is then filmed and laminated on the aluminium collector. Therefore, it was important to understand the interactions between the different components of the electrode, and especially to study the miscibility of the ternary system polymer/polymer/solvent and also the adsorption of solvent on fillers. This approach has allowed a better understanding of the phenomena involved through a characterization of the complex, in its current form at different stages of the process. Then, changes in formulations were considered. In particular, the effect of the structure and molecular weight of the polymers on adhesion was studied. In all cases, it was envisaged to test the possibilities offered by the use of a different solvent (dimethyl sulfoxide). The latter being a better solvent for the PVDF, is also easier to remove than propylene carbonate. Finally, from the rheological data of the mixture, a mechanical modeling, using the multimodal Maxwell model, was conducted in the lamination step taking into account of the viscoelastic behavior of the gel. All these studies allow us to conclude on the relevant changes in the formulation and process conditions

Depuis les années 50, la polymérisation par catalyse Ziegler-Natta a suscité de nombreuses études. Ainsi, Atofina essaie d'acquérir une connaissance plus approfondie du site catalytique par l'élaboration d'un modèle moléculaire afin de comprendre l'influence de la base de Lewis "externe"sur le contrôle de l'isotacticité. La première partie décrit la synthèse de différentes bases de Lewis, dont les caractéristiques structurales correspondent aux impératifs établis par la modélisation. De nouveaux donneurs d'électrons silylés ou en série [gamma]-diéther très difficiles à préparer ont été synthétisés puis testés en polymérisation du propylène au Groupement de Recherche de Lacq. Deux composés inédits ont montré des performances tout à fait remarquables puisqu'ils permettent d'obtenir des résultats supérieurs à ceux des meilleures références actuelles. La deuxième partie concerne l'étude au laboratoire du comportement des réactifs dans des conditions expérimentales aussi proches que possible de celles du réacteur en continu à l'échelle industrielle. Une étude de l'évolution des systèmes catalytiques dans des conditions voisines de celles adoptées en polymérisation est présentée afin de comprendre 'le comportement variable des meilleurs catalyseurs en fonction de leur mode de préparation et d'utilisation. Une troisième partie est consacrée à la synthèse de métallocènes. Atofina, un des plus grands producteurs européens de polyaléfines, s'intéresse de très près au développement spectaculaire de ces composés. La synthèse de zirconocènes haute performance a été réalisée, afin de vérifier ou d'améliorer la faisabilité des meilleurs catalyseurs décrits. Ces nouveaux systèmes ont été testés en polymérisation du propylène. Cette étude a permis de réaliser deux objectifs importants : cerner les possibilités de ces systèmes et apprécier les difficultés de mise en oeuvre des réactions de polymérisation.