This article presents an experimental investigation on developing wood plastic composites reinforced with continuous glass fibers in an extrusion process. The main role of wood component in wood plastic composite is mainly as a filler to reduce cost, and not reinforcing. Adding wood component causes a noticeable reduction in strength and toughness. This will hinder their usage in load-bearing applications. In this study, a novel method for production of hybrid wood plastic composites is introduced. This manufacturing process takes the advantages of a cost-effective and flexible production line. First, E-glass rovings were impregnated with a polymer in an especially designed (impregnating) die. Then, six melt impregnated glass rovings were integrated with wood plastic composites in a single step via an extrusion process. Another unique die was designed and manufactured to feed and position the impregnated glass rovings into a round shaped wood plastic composite profile. Wood content was changed in three levels to investigate its effect on the processability and the final properties of the hybrid composites. The experimentation on the extruded hybrid wood plastic composites proved the feasibility of the process and the relative uniformity of the roving positions in the extrudate. Three-point bending tests were conducted to evaluate the flexural properties. Improvements in strength, modulus, and toughness were dramatic.
This article presents an experimental study on the effect of polymeric matrix flow behavior on the properties of the reprocessed wood-plastic composites (WPC) of highdensity polyethylene (HDPE) and wood sawdust. WPCs are considered as sustainable materials due to their durability in the environmental conditions and recyclability. Three grades of HDPE were utilized as polymeric matrix with different melt flow indices (MFIs). Composites containing 60 wt% of sawdust were manufactured via a twin-screw extruder to produce 15 mm rod-shaped profiles (named here as virgin WPCs). In reprocessing, the produced WPC profiles were then ground to obtain WPC granules and then reprocessed (reextruded) via the same extruder. The mechanical properties of both the virgin and the reprocessed profiles were obtained from the bending tests and tensile tests, and the physical tests including water uptake and density measurements were also carried out. Interestingly, reprocessed composites produced with the low and middle MFI HDPE showed an increase in mechanical properties compared with the virgin ones, while for the composites with the high MFI HDPE, opposite result was observed. Water uptake measurement also indicated the best performance of the composites produced with the middle MFI HDPE.
The present study focuses on visualization analysis of foaming mechanisms in foam injection molding process. A novel approach in mold design is introduced to take advantages of concepts such as counter-pressure and mold opening to further extension of expansion range, a visual mold with a rectangular cavity was designed and manufactured to observe the effectiveness of this approach. The mold consists of a main cavity and an over-flow well connected together via a secondary gate of variable sizes. The selected processing parameters were gate width and part thickness. The observation clearly showed the development of melt frontier and gas escape, which were affected by varying the selected parameters. The results showed that the relative bulk density and cell diameter decreased and cell population density increased as the optimum gate width (7 mm) was employed.
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