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Title: The relationship between microstructure and macroscopic property changes in wood plastic composites
Author: Lun To, Ka
ISNI:       0000 0004 2702 6649
Awarding Body: The Manchester Metropolitan University
Current Institution: Manchester Metropolitan University
Date of Award: 2011
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Wood plastic composites (WPCs) have attracted a great deal of interest in recent years. Their mechanical properties are commonly weaker than unfilled polymers, due to the incompatibility between the polymer matrix and the fillers. Consequently, coupling agents have been widely used in WPCs. The aims of this work are to investigate the mechanical, morphological, and crystalline properties of WPCs using a variety of test methods including: Scanning electron microscopy (SEM), Wide angle Xray scattering (WAXS) and Differential Scanning Calorimetry (DSC). SEM inspection has revealed that Maleic anhydride grafted polypropylene (MAPP) can effectively bind the sawdust to the polypropylene (PP) matrix. Measurements from the isothermal analysis (DSC) have shown that the content of sawdust and MAPP can reduce the PP crystallisation time Significantly. In WAXS analysis, peaks representing a and B-crystals were observed in the PP - WPCs. Furthermore, this work also investigate the degradation behaviours of PP - WPCs, PP - WPCs which were subjected to thermal and photo accelerated degradation to evaluate the stability of PP- WPCs. The rates of oxidation were monitored by both hydroperoxide formation and functional groups changes by using Fourier transform infrared spectroscopy (FTIR). Decomposition of lignin compounds was also observed during the photo irradiation. Thermal analyses, such as oxidative induction time (OIT) and thermogravimetric analysis (TGA) , are also presented. The activation energy during decomposition, and lifetime estimation were calculated from the TGA data. The results indicate that sawdust accelerated the formation of carbonyl functional groups and hydroperoxides in the composites. A series of relatively low activation energy were observed during the TGA pyrolYSis, attributed to scission of weak bonds in the polymer. OIT results showed antioxidation effects attributed to natural phenolic compounds form the wood filler during the polymer melt state. The estimated lifetime showed that unfilled PP has the highest service lifetime, and the estimated lifetime is reduced as the quantity of sawdust in the WPCs is increased. A novel technique has been developed to achieve the coupling effect between polyvinylchloride (PVC) and the cellulose material (sawdust), by coating the surface of the sawdust with emulsion PVC. The effect of this coating is highlighted by improved impact and flexural performance. Mechanical tests showed that the emulsion PVC coated sawdust did significantly enhance the impact strength by as much as 83% compared to uncoated sawdust, 37.8% compared to triethoxy(octyl)silane and 52.8% compared to 3-aminopropyltriethoxysilane coupling agent.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available