Toughening effect of bamboo flour /polypropylene foamed composite

Abstract: In order to make full use of bamboo resources in China and reduce white pollution, save fossil energy, the foamed composite of 54 wt% PP and 13 wt% HMSPP containing 33 wt% bamboo powder and 1% modified azodicarbonamide (AC) foaming agent blends was prepared by injection molding. Meanwhile, in order to substitute for polypropylene(PP) applied to automotive interior parts and thus broaden the application fields of wood-plastic composite, the bamboo powder/polypropylene foamed composites toughened by polyethylene octane elastomer (POE) and maleic anhydride grafted polyolefin elastomer (POE-g-MAH) were researched. Effects of the two toughen fillers on mechanical properties including bending, tensile and impact strengths were studied and the impact fractured surfaces of non-toughened and toughened composites were investigated by environmental scanning electronic microscopy micrograph (ESEM). The rheological behavior of composites with respect to frequency sweep ranging from 0.01 Hz to 100 Hz at 180℃ was carried out. The results showed that the tensile and bending strengths were reduced slightly and notched impact strength of composites was improved significantly with the increase of toughen fillers content. The optimum amounts of POE and POE-g-MAH were 15% and 8% respectively. The tensile strength of 15% POE toughening composite was unable to meet the standard of automotive interior parts, although its notched impact strength was increased from 6.30 kJ/m2 to 7.65 kJ/m2. The 8% POE-g-MAH toughening composite could well be applied to automotive interior parts and its bending strength, bending modulus and tensile strength of 37.5 MPa, 2.69 GPa and 21.02 MPa respectively, which was reduced by 1.2%~6.9%, while the notched impact strength was 8.55 kJ/m2, which was increased by 35.7% compared with the non-toughened composite. ESEM observation of the impact fracture morphology indicated that the fracture mode of toughened composite transited into ductile fracture. The frequency sweep results showed that the effect of POE on the rheological behavior was relatively smaller than that of POE-g-MAH. The storage modulus and complex viscosity of composite toughened by POE-g-MAH were increased and the "second platform" phenomenon was more evident.