Wood plastics composites: Bond formation mechanism and mechanical properties

Abstract

Wood fibers are increasingly being used as reinforcement in commercial thermoplastic composites due to their low cost, high specific strength properties and renewable nature. The ultimate goal of our research was to find the fundamental understanding of the mechanical behavior of poplar wood fiber/polypropylene (PP) composites. The effect of wood fiber concentrations and compounding temperature on the mechanical properties of composites, prepared using MAPP as the coupling agent, was investigated. In the sample preparation, four levels of fiber loading (10, 20, 30, and 40 w/w%) and three compounding temperatures (180, 190, and 200oC) were used. The results revealed that the major changes in composite properties occurred at fiber contents above 30%. The results clearly showed that the fiber loading of 30 and 40 w/w% at 190oC provided adequate reinforcement to increase the tensile and flexural strength of the composite. The modulus also increased with increasing fiber content, because poplar wood fibers are believed to be more rigid than polymer. However, the addition of wood fibers resulted in the reduction of both elongation and impact strength properties of the composites. The FTIR spectroscopy showed that the polymer was bonded to the fibers by ester linkages and hydrogen bonds at 1705–1735 cm-1.

Keywords

• COMPOSITES
• chemical bonding
• temperatures
• mechanical behavior
• FTIR spectroscopy