Experimental Study on theEffect of Melt Flow Index on Properties of Virgin and Reprocessed Wood-HDPE Composites

Wood-Plastic Composites consist of wood particles and a thermoplastic matrix such as PE, PP and PVC. Among the thermoplastics,high density polyethylene (HDPE) is more favorable since the processing temperature can be maintained low enough to avoid wood burning. Various grades of HDPE with different melt flow indexes (MFI) are available by the suppliers to be used in WPC composition which may result differences in final product properties.The aim of this study was to understand the role of matrix MFI on the recycle ability of WPCs produced via the extrusion process. Three grades of HDPE with low, middle and high MFI, respectively named as LMFI, MMFI and HMFI (0.45, 7 and 20 gr/10min), were used as the polymeric matrixto produce rod shaped profiles of WPC with 60 %wt. wood content. For reprocessing, produced WPC profiles were ground andwood-plastic granules obtained. Mechanical properties were obtained from tensile test. In addition, water uptake measurements were also carried out. The results show thatreprocessed WPCs with HMFI HDPE showpoorer properties in comparison tothose of non-reprocessed ones. On the other hand, interestingly results showed that reprocessed profiles with LMFI and MMFI HDPE reveal improved properties from mechanical aspects.

Keywords:

Wood-Plastic Composite (WPC) , Reprocessing , Extrusion , HDPE