Preparation and characterization of polypropylene-wood powder composites
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Date
2005-02
Authors
Salemane, Makgadiete Grace
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
The preparation and characterization of modified and unmodified polypropylene – wood powder composites were done under fixed processing conditions (mixing temperature, rate of rotation and mixing time). The mixing of samples was done using a Brabender plastograph mixer and sheets were formed by melt pressing the samples. Different techniques were used to study the effect of both wood powder size and content, as well as compatibilizer content on the properties of the composites. The results point to the fact that wood powder, WP, is settled in the amorphous part of the matrix and create new crystalline phases/zones. Scanning electron microscopy, SEM, micrographs and polarized optical microscopy, POM, photos show an even distribution of WP in the polypropylene, PP, matrix, which contributed to improvements observed in the properties of the material. Hg-porosimetry results indicate that the PP matrix, which has a low pore volume, was incorporated into the WP structure and filled the pores in the WP particles. This reduced the total volume of pores in the PP/WP composites. This observation was also supported by a general decrease in gas permeability of the material. Thermal analysis results indicate that the presence of both WP and maleic anhydride grafted polypropylene, MAPP, lead to an increase in enthalpy values of the composites, but also to a decrease in lamellar thickness in the composites containing MAPP. The thermal stability of the composite materials was also improved to a certain oxtent. There were distinctive differences between the results for composites containing different WP particle sizes, as well as for composites prepared in the presence and absence of MAPP. It is clear from the results that the presence of MAPP generally improves the tensile properties of the composites, probably because of an interaction between the reactive groups in MAPP and WP. Generally the larger WP particles gave rise to better tensile properties, in the presence and absence of MAPP, probably because of better stress transfer between the WP particles and the PP and PP/MAPP matrices.
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Keywords
Dissertation (M.Sc. (Chemistry))--University of the Free State (Qwaqwa Campus), 2005, Polypropylene, Fillers (Materials) Research, Polymeric composites, Polymers