Investigation on microstructure and properties of foamed (wood fiber)/(recycled polypropylene) composites

Microcellular foamed (wood fiber)-reinforced recycled polypropylene composites (MFWPCs) were prepared by an injection molding process where azodicarbonamide was used as a chemical foaming agent. The influence of injection parameters (injection temperature, dwell pressure) on the microcellular structure (cell diameter and cell density) and the mechanical properties of the MFWPCs were investigated. The results indicated that when the melting temperature was 180 degrees C and the dwell pressure was 12.5 MPa, a uniformly distributed microcellular structure of MFWPCs was obtained. Compared with solid wood plastic composites, the density of the MFWPCs decreased by 24.5%, and its impact strength of MFWPCs increased by 53%, because the propagation direction of the crack changed to the skip or bifurcation mechanism as a result of the microcellular structure, and the surrounding matrix of this structure made it easy to produce forced high-elastic deformation. The toughening mechanism of the microcellular structure was analyzed. J. VINYL ADDIT. TECHNOL., 2012. (C) 2012 Society of Plastics Engineers