Mechanical and physical properties of core–shell structured wood plastic composites: Effect of shells with hybrid mineral and wood fillers

Abstract

The effects of shells filled with silane treated precipitated calcium carbonate (TPCC) and wood fiber (WF) on properties of core–shell structured wood plastic composites (WPCs) were studied with two different core systems. In a weak core system made with recycled polypropylene (PP)/high density polyethylene (HDPE), coextruded WPCs with reinforced virgin HDPE shells showed significantly improved flexural strengths compared with their core-only controls. In a strong core system made of virgin HDPE, the composite flexural strengths were lowered in relation to their core-only controls. Impact strengths for both systems were noticeably improved with added shells. Specially, the impact strengths of the weak core coextruded WPCs showed up to 150% increases in relation to their core-only controls. Impact fracture types varied largely with core quality and filler composition in the shell. Water absorption of coextruded WPCs with high TPCC contents in the shell was lower than that of core-only controls and coextruded WPCs with high wood contents in the shell layer. The use of high percentage of plastic in the shell layer led to the increases of overall composite’s coefficient of thermal expansion (CTE). However, increased filler loadings in the shell helped reduce the CTE values, especially, for the weak core system.