Studying crystallization kinetics using solution crystallization analysis by laser light scattering (Scalls)

Robertson, Divann (2012-03)

Thesis (MSc)--Stellenbosch University, 2012.


ENGLISH ABSTRACT: This study involved the analysis of crystallization kinetics by means of a unique and newly developed Solution crystallization analysis by laser light scattering (Scalls) technique. In the main study we compared two commercial linear low-density polyethylene (LLDPE) polymers (PE-1- octene and PE-1-hexene) and studied the effect of short-chain branching on the solution crystallization of these complex polymer systems. Characterization of the polymers was done by nuclear magnetic resonance spectroscopy (NMR) and high-temperature gel permeation chromatography (HT-GPC). The second study involved the fractionation of a PE-1-hexene copolymer by temperature rising elution fractionation (Tref) and analyzing the solution crystallization of the different temperature fractions. This resulted in important details on the different molecular regions present in the polymer. A third additional study was done on the compatibility in polyolefin blends. Two different blends were prepared: isotactic polypropylene (iPP) – low density polyethylene (LDPE) blend and iPP – polypropylene impact copolymer (PPIC) blend. It was found that co-crystallization only occurred for the iPP - PPIC blends. Phase separation occurred for the iPP – LDPE blends, resulting in the formation of two phases for all blend compositions. Solution crystallization analysis is usually measured by the conventional Crystallization Analysis Fractionation (Crystaf) technique. In this study all crystallization data were compared with Crystaf results and a good correlation was found between the results obtained by Crystaf and Scalls. The major advantages of the Scalls technique are that, results similar to that of Crystaf can be acquired with much shorter analysis times and Scalls also allows for the measurement of solution melting of the crystallized polymer solutions.

AFRIKAANSE OPSOMMING: Hierdie studie het die analise van kristallisasie kinetika behels met behulp van die unieke en nuut ontwikkelde oplossing kristallisasie analise deur laser lig verstrooiing (Scalls) tegniek. In die hoof studie het ons twee kommersïele liniêre lae-digtheid polietileen (LLDPE) polimere (PE-1-okteen en PE-1-hekseen) vergelyk en die effek van kort-ketting vertakking op kristallisasie in oplossing van hierdie komplekse polimeer sisteme bestudeer. Karakterisering van die polimere was gedoen met kern magnetiese resonans spektroskopie (KMR) en hoë-temperatuur gel permeasie kromatografie (HT-GPC). Die tweede studie het die fraksionering van ‘n PE-1-hekseen ko-polieer met behulp van temperatuurstyging eluering fraksionering (Tref) behels asook die analisering van kristallisasie in oplossing van die verskillende temperatuur fraksies. Belangrike informasie oor die verskillende molekulêre areas teenwoordig in die polimeer was verkry. ‘n Derde addisionele studie was gedoen op die versoenbaarheid in poliolefin mengsels. Twee verskillende mengsels was voorberei: isotaktiese polipropileen (iPP) – lae digtheid polietileen (LDPE) mengsel en iPP – polipropileen impak ko-polimeer (PPIC) mengsel. Daar was gevind dat ko-kristallisasie slegs in die iPP – PPIC mengsel plaasgevind het. Fase skeiding het plaasgevind in die iPP – LDPE mengsels wat tot twee fases gelei het vir alle mengsel komposisies. Kristallisasie in oplossing word gewoonlik gemeet met die konvensionele kristallisasie analise fraksionering (Crystaf) tegniek. In hierdie studie was al die kristallisasie data met Crystaf resultate vergelyk en ‘n goeie korrelasie was gevind tussen die resultate van Crystaf en Scalls. Die grootste voordele van die Scalls tegniek is dat resultate soortgelyk aan diè van Crystaf kan verkry word met baie korter analises en Scalls laat ook toe vir die meting van smeltpunt van die gekristalliseerde polimeer oplossings.

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