Compatibilizing and toughening bamboo flour-filled HDPE composites: Mechanical properties and morphologies

Mechanical properties and morphologies of HDPE/bamboo flour (BF) composites modified with two maleated ethylene/propylene elastomers (EPR-g-MA) and one maleated polyethylene (PE-g-MA) were investigated. The concentration of each modifier varied between 0 and 8.3 wt% based on the total composite weight. The highest values in strengths and moduli were achieved for the composites containing PE-g-MA, whereas the use of semi-crystalline EPR-g-MA (sEPR-g-MA) led to the maximum impact strength. However, the presence of amorphous EPR-g-MA (aEPR-g-MA) reduced strengths of the resultant composites. The impact toughness of the aEPR-g-MA modified composites initially increased with aEPR-g-MA loading up to 2.9 wt%, and then gradually decreased beyond this level. By simultaneously incorporating both PE-g-MA and EPR-g-MA, the strength–toughness balance of the final composites was optimized. The optimal balance of composite properties was achieved at lower percentage of sEPR-g-MA and medium BF loading level. Dynamic mechanical analysis (DMA) and morphology observations well substantiated the above-mentioned mechanical results. It was found that suitable interfacial adhesion and easiness of interlayer cavitations between HDPE and BF is beneficial to initiate massive matrix yielding in the composites, thereby achieving satisfactory impact strength.