Mechanical properties, morphology, and creep resistance of ultra-highly filled bamboo fiber/polypropylene composites: Effects of filler content and melt flow index of polypropylene

Simultaneous realization of high filler fraction and excellent comprehensive properties remains a great challenge for extruded wood plastic composites (WPCs). Herein, ultra-highly filled bamboo fiber/polypropylene composites (UH-BPCs) with total filler content varying from 75 wt% to 90 wt% were fabricated via profile extrusion. Six kinds of polypropylene (PP) with melt flow indices (MFIs) ranging from 0.165 to 24 g (10 min)(-1) were selected as the matrix. The tensile, flexural, impact strengths and dimensional stability of the UH-BPCs decreased with increasing filler content. However, a relatively high filler content (no more than 85 wt%) could improve the modulus and creep resistance of UH-BPCs. At 85 wt% filler content, the UH-BPCs with PP of moderate MFI exhibited the best mechanical properties with a tensile strength, tensile modulus, flexural strength, flexural modulus, and unnotched impact strength of 22.39 MPa, 6.05 GPa, 39.86 MPa, 7.19 GPa, and 4.22 kJ m(-2), respectively. The UH-BPCs with low MFI PP presented better dimensional stability and creep resistance, especially at high temperatures. This work can provide an important reference to prepare ultra-highly filled WPCs with high performance via profile extrusion.