The aim of this study was to fabricate highly filled wood plastic composite pallets with extrusion‐compression molding technique and investigate the effects of processing parameters on mechanical performance and production stability. The composites were blended in twin‐screw extruder and subsequently measured by weight with an electronic scale. Before compression, it was divided into pieces and rearranged in the cavities of compression mould according to the mass distribution. The effects of compression pressure and mould temperature on flexure strength, density, water absorption, and dimensional deviation were investigated. The results show that both the flexure strength and density of the pallets increased with compression pressure and remained higher than that of extruded deck when compression pressure exceeded 6.5 MPa. Water absorption and dimensional deviation decreased with compression pressure and remained lower than that of extruded deck after the compression pressure exceeded 6.0 MPa. Compression pressure could increase the final passed yield by improving the composite melt filling state and lowering the buckling deformation, but further increase above 6.7 MPa would result in a decline in final passed yield. Increase in mould temperature contributed to the production stability but an excessive value would extend the molding cycle. The insights gained from this study may be of assistance in optimizing extrusion‐compression processing parameters and expanding the application of highly filled wood plastic composites in complicated and irregular products.
Demand for natural fibers reinforced composites is growing as an alternative to synthetic fiber reinforced plastic composites. However, poor compatibility between natural fiber and matrix has limited its development. Therefore, it is necessary to improve their interfacial adhesion to improve the comprehensive properties of composites. In this work, sisal fibers were subjected to an alkali/polyvinyl alcohol coating treatment by an ultrasonic impregnation method, and the sisal/high-density polyethylene composite was prepared by a twin-screw extruder. The Fourier transform infrared spectroscopy was used to characterize the modification effect of sisal fiber. The surface morphology of sisal fiber and the interfacial morphology of sisal/high-density polyethylene composites were observed. The mechanical properties and water absorption of sisal/ high-density polyethylene composites were also studied. The results show that alkali/polyvinyl alcohol coating compound treatment can effectively improve the interfacial adhesion between sisal fiber and high-density polyethylene, improve the mechanical properties of composite, and reduce water absorption. Alkali/polyvinyl alcohol coating compound treatment is a very environment-friendly, cost-effective fiber modification method when compared with traditional modification methods. It is helpful for the development and application of natural fibers reinforced composites.
A self‐made thermal mechanical analyzer was manufactured to characterized the compression and bending stress relaxation behavior for bamboo fiber reinforced polypropylene composite with different bamboo fiber and coupling agent concentration. The effects of bamboo fiber concentration, interfacial strength, load controlling method, compression speed, and temperature on composite stress relaxation parameters were investigated. The obtained results show that two‐stage relaxation process could be observed for both compression and bending test while shearing relaxation process was a single exponential decay. The relaxation time for slow exponential relaxation process was two orders of magnitude to that for fast relaxation process and the force decay amplitude on the first linear stage was about 3.5 times as much as that on the second exponential decay stage. Both the filling of bamboo fiber and coupling agent could increase the stress relaxation time but higher temperature would promote the movement of polymer chains and lengthen the stress relaxation time. The insights obtained from the experiments and fitting results can offer valuable reference to precisely controlling of dimensional accuracy and production efficiency for the composite products of irregular structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.