Study On Interfacial Modification And Properties Of Wood-Plastic Composites

Adopted hot pressing molding, extruding and injection molding, a serials wood-plastic composites (WPCs) modified by varied interface modified method were prepared, and which were characterized by a variety of testing and analyzing methods. The objective of this study was to find a new method to improve the interface compatibility of WPCs, and through which a kind of WPC with outstanding combination properties could be prepated.In this paper, three parts were studied as follows:(1) Through double-roll blending and hot pressing molding, a serials high density polyethylene based WPCs with maleic anhydride (MAH) and (or) dicumyl peroxide (DCP) modified wood flour and the WPC used MAH grafted high density polyethylene (MAPE) as the coupling agent were prepared. The mechanical properties, dynamic thermo-mechanical properties and processing characteristic of the composites were investigated, and the interface of the composites was analysed by scanning electronic microscope (SEM). The result showed:compared with MAPE modified HDPE-WPC (in this composite, wood flour mass fraction is60wt%, HDPE add MAPE mass fraction is40wt%, MAPE mass fraction is5wt%relative to wood flour), the composite prepared with MAH add DCP modified wood flour (in this composites, wood mass fraction is60wt%, HDPE mass fraction is40wt%; relative to wood flour MAH and DCP mass fractions are1.5wt%and0.5wt%) have better mechanical properties, especially the impact strength up to1.5times of the former, and the processability was saved. But when the mass fraction of DCP (relative to HDPE) is greated than0.3wt%, the mechanical properties of the composites is essentially the same. The analysis results also indicated the mechanism of improving engineerin of WPC including MAH grafted HDPE by DCP initiating to improve interface compatibility and HDPE cross-linked by DCP initiating to improve the strength of matrix.(2) The hot pressing process had long cycle and low production efficiency, which were not suitable for large scale manufacture and general adoption of marketization. In this job, low density polyethylene (LDPE) based WPCs were prepared through mixing extruding and injection molding. The effects of interface modification method and the contents of MAH, DCP and wood flour to the mechanical properties, dynamic thermo-mechanical properties and processing characteristic of the composites were investigated comprehensively. The results indicated the tensile strength, flexural strength and storage modulus of the WPCs (in these composites, MAH mass fraction is1.5wt%relative to wood flour, and DCP mass fraction is0.5wt%relative to LDPE) improving and the impact strength and loss factor decreasing with the increasing of wood flour content. And In the composites as the mass fraction of wood flour is40wt%, when the mass fraction of MAH relative to wood flour is0.5wt%, and the mass fraction of DCP is0.3-0.5wt%relative to LDPE, the composite shows best comprehensive performance. And the study results also indicated the WPC prepared with MAH and DCP modified wood flour has better properties compared with the WPC prepared with the LDPE which melting extruded with MAH and DCP. There the two WPCs have the same component (LDPE mass fraction is60wt%, wood mass fraction is40wt%, mass fraction of MAH relative to wood flour is0.5wt%, and the mass fraction of DCP is0.3--0.5wt%relative to LDPE), the tensile and flexural strength increased about10%, and the impact strength increased up to40%. And the processabilty also improved obviously, the balance norque only one-third of the latter. The brittle broken interface SEM photos shows in the latter composit, the wood flour aggregated clearly.(3) In order to improve the properties of WPC furtherly. Glass fiber (GF), Calcium carbonate (CaCO3) and Talcum powder were introduced as the reinforced fillers to the WPCs. Which were prepared by extruding molding or injection molding. The effects of GF’s particle size and content to the mechanical properties, processability and dynamic thermo-mechanical properties were studied. And the effect of different rigid inorganic particles to the properties of WPC was investigated. The results showed:the rigid inorganic particles can improve the impact strength and processability of these WPCs, but the strength and storage modulus decreased. In these fillers, talc filled WPC with best performance, and CaCO3filled WPCs with best toughness and lowest strength.