Solid-state interactions of materials: Applications-based solid-state NMR spectroscopy

Date
2022-04
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The solid-state interactions of various polymeric materials were investigated in this study to determine how these interactions affect the macroscopic properties of the solid. The work presented in this dissertation was classified into three commercial problems which were solved using solid-state NMR and a variety of other solid-state techniques. First, vis- breaking was performed in-situ on heterophasic ethylene-propylene copolymers (HEPCs) to determine the effect on HEPCs of increasing ethylene contents. Solution 13C NMR and solid- state NMR was used to determine the effect of the peroxide on the structure and morphology of the HEPCs. The extent of vis-breaking was found to be dependent on the homogeneity of chain sequences. In all cases vis-breaking increased the mobility of the crystalline domains forming a disordered crystal phase within the polypropylene α-structure. Second, the possibility of using impact copolymers as the polymer component of hot-melt adhesives (HMAs) was investigated. A high ethylene-content impact copolymer was blended with three types of waxes and characterised by various solid-state techniques. It was found that the ethylene-rich regions of the impact copolymer displayed strong interactions with the waxes and the extent of the interaction was dependent on the composition of the wax. The bond strength results of the HMAs were found to be comparable to that of an industry standard HMA and the failure mechanism was dependent on the wax type and concentration. Finally, the mechanism of oil entrapment by Fischer-Tropsch (FT) waxes was explored to determine whether wideline NMR is an appropriate method for determination of oil content of waxes. Benchtop solid-state NMR instruments apply wideline methods to determine oil contents commercially in cases where vast differences in mobility exist between phases. Blends of a standard oil and waxes of various melting temperatures were prepared and characterised by various techniques. The higher melting FT waxes were found to trap oil in small pools and limit the mobility of the oil making it difficult to detect by solid-state NMR. Linear correlations could only be obtained by using variable temperature methods and by simplifying the oil composition, however, the accuracy of the correlations was not high. The focus of this study was, therefore, not on the properties of a specific material but on the development of solid-state NMR methods with unique applications to solve industrial problems.
AFRIKAANSE OPSOMMING: In die huidige studie is die soliedefase interaksies van verskillende polimeer materiale ondersoek om te bepaal watter uitwerking hierdie interaksies op die makroskopiese eienskappe van die vastestof het. Tweedens, is die moontlikheid om van impak kopolimere as die polimeer komponent van hoë -smeltpunt kleefmiddels (HMAs) gebruik te maak, ondersoek. ’n Hoë etileeninhoud impak kopolimeer is met drie wassoorte gemeng en deur verskillende soliedefase tegnieke gekarakteriseer. Die etileenryke gebiede van die impak kopolimeer is bevind om sterk interaksies met die wasse te vertoon. Die omvang van hierdie interaksie is afhanklik van die samestelling van die was. Die bindingssterkte resultate van die HMAs is vergelykbaar gevind met dié van ’n industrie standaard HMA en die mislukkingsmeganisme is van die wassoort en -konsentrasie afhanklik. Ten laaste, is die meganisme van olie-vaslegging in Fischer-Tropsch (FT)-wasse ondersoek om te bepaal of breëlyn KMR ’n gepaste metode is om die olie-inhoud van wasse te bepaal. ‘Benchtop’-soliedefase KMR-instrumente pas breëlyn-metodes toe om olie-inhoud kommersieel te bepaal, in gevalle waar oneindig groot mobiliteitsverskille tussen fases bestaan. Samestellings van ʼn standaard olie en drie wasse, met verskillende smelttemperature, is voorberei en deur middel van verskillende tegnieke gekarakteriseer. Daar is bevind dat die hoër smeltende FT-wasse olie in klein poele vasvang en die mobiliteit van die olie beperk wat dit moeilik maak om deur middel van soliedefase KMR op te spoor. Lineêre korrelasies kon slegs verkry word deur veranderlike temperatuurmetodes te gebruik en deur die olie-samestelling te simplifiseer, maar die bevinding dui aan dat die akkuraatheid van die korrelasies nie hoog is nie. Die fokus van die huidige studie was dus nie gemik op die eienskappe van ’n spesifieke materiaal nie maar op die ontwikkeling van soliedefase KMR-metodes met unieke toepassings om industriële probleme op te los. Die resultate wat in hierdie tesis aangebied word, is volgens drie kommersiële probleme geklassifiseer wat deur die gebruik van soliedefase kernmagnetieseresonansie (KMR) en ’n verskeidenheid ander soliedefase tegnieke opgelos is. Eerstens, is vis-breking in-situ op heterofase polipropileen-etileen-kopropileen kopolimere (HEPCs) uitgevoer om die effek van verhoodge etileeninhoud op HEPCs te bepaal. Vloeistof 13C NMR en soliedefase KMR is gebruik om die effek van die peroksied op die struktuur en morfologie van die HEPCs te bepaal. Daar is bevind dat die omvang van vis-breking van die homogeniteit van kettingvolgordes afhanklik is. In al die bestudeerde gevalle is die mobiliteit van die kristalvormige domeine deur vis-breking verhoog wat tot die vorming van ’n versteurde kristalfase binne die polipropileen α-struktuur lei.
Description
Thesis (PhD)--Stellenbosch University, 2022.
Keywords
UCTD, Nuclear magnetic resonance, Organic solid state chemistry, Hot-melt adhesive, Waxes
Citation