Microcellular Injection Molded Wood Fiber-PP Composites: Part I - Effect of Chemical Foaming Agent Content on Cell Morphology and Physico-mechanical Properties

Microcellular wood fiber reinforced polymer materials have important applications because of their ability to reduce the density of automotive components due to their structure-property advantages. This research investigates the effects of chemical foaming agent content on cell morphology, density, and mechanical (tensile, flexural, and impact) properties of microcellular injection molded wood fiber reinforced polypropylene (PP) composites. The effects of various concentrations (2-5 wt% of the composites) of the exothermic chemical foaming agent on the properties of the composites was studied with a view of establishing the concentration-structure-property relationships for these materials. The results indicate that exothermic 2 wt% content shows finer microcellular structure than other contents, dependent on wood fiber content. Density was reduced with all foaming agent contents, to a maximum of 30%, and decreased up to 0.739 g/cm3 at wood fiber content of 30 wt% with coupling agent. Mechanical properties increased nearly 80% with the addition of coupling agent.