An experimentai investigation on surface quality and water absorption of extruded wood-plastic composite

摘要

This article presents an experimental study on the relationship between surface quality (roughness) and water absorption for wood-plastic composites (WPCs) in an extrusion process. A problem that usually occurs in the production of extruded parts of polymeric materials, and in special case of WPC, is flow instabilities at the extrusion die exit. The instabilities lead to the production of profiles with unacceptable surface quality. In this article, the influences of the important material and process parameters on the surface quality and water absorption are Investigated. The attempt was made to find a relationship between surface roughness and water absorption of WPC extruded profiles. The variable parameters were selected as wood content, polymer melt flow Index (MFI), screw speed, melt temperature, die diameter, and finally length-to-dlameter ratio (LID) of the die land. The experiments specified that increasing die land LID, die temperature and wood content and decreasing screw speed and polymer MFI lead to improved surface quality. It was found that increasing die diameter and also decreasing die land UD, die temperature, speed, wood content, and polymer MFI lead to an improvement in water resistance. The results also showed that a rough surface quality could cause a low water resistance specification.