Effect of polymeric matrix melt flow index in reprocessing extruded wood–plastic composites

Abstract

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.

Utilization of Recycled Material Sources for Wood-Polypropylene Composites: Effect on Internal Composite Structure, Particle Characteristics and Physico-Mechanical Properties

“…Even so that reprocessing or recyclability of WPC is still a minor subject in research [21], hitherto, several studies revealed that the issues has gained more interest in terms of scarcity of resources, mechanical and thermal degradation and particle degradation within lignocellulosic particle/fibre composites [32,33,[69][70][71][72][73][74][75][76][77][78]. Repeated reprocessing usually results in reduced mechanical properties [32,70,71], several studies revealed initially increased mechanical properties after reprocessing wood/polypropylene composites [32,34,76,79].…”

Effects of foaming through leaching on the electrical behavior of polystyrene/carbon nanotube composites

“…This can be attributed to the encapsulation of NaCl crystals using a thermoplastic similar to other fillers: composites such as NaCl/PS/CNT possess less than the minimum NaCl content to form a continuous network throughout the composite to leach NaCl using water. 31,43 Water penetration into the composites and the dissolution of the NaCl crystals, that is, leaching of NaCl, were easier in composites with higher NaCl contents, because there were more possible paths for the solvent to seep through the NaCl network. This is why voids were not only observable on the surface of the samples but also in the crosssections of the samples.…”

Polypropylene/wood powder/ethylene propylene diene monomer rubber‐maleic anhydride composites: Effect of PP melt flow index on the thermal, mechanical, thermomechanical, water absorption, and morphological parameters

“…Additionally, it has been reported that melt flow index (MFI) of WPCs shows great importance for the relationship between structure‐property. Sarabi et al 25 investigated the effect of reprocessing and MFI of high density polyethylene (HDPE) on the mechanical and physical properties of WPC. Composites with low‐MFI HDPE indicated the lowest water absorption and higher flexural and tensile properties among virgin composites, whereas for the reprocessed ones, higher water absorption was verified for composites with low MFI; upon increasing MFI composites became weaker under flexural and tensile loads.…”