Characterization and properties of recycled polypropylene (rPP)/ recycled high density polythylene (rHDPE) blends and its composites

Abstract

The thermoplastic blends of recycled polypropylene (rPP) and recycled high density polyethylene (rHDPE) was studied. The rPP/rHDPE blends were prepared by using twin screw extruder at temperature 190⁰C and rotor speed of 180 rpm. The effect of blend ratio on tensile properties, morphology and thermal properties were investigated. It was found that the increasing in rHDPE content of rPP/rHDPE blends have decreased the tensile strength, modulus of elasticity but increased in the elongation at break. The crystallinity and thermal stability of blends increased with increasing rHDPE content. The morphology of rPP/rHDPE blends showed rHDPE was dispersed in the rPP continuous phase with increasing rHDPE content. The compatibilizer, maleic anhydride grafted polypropylene (MAPP) was used to enhance tensile properties of the blends. The addition of MAPP has improved the tensile strength, modulus of elasticity, crystallinity of blends and thermal stability but lower the elongation at break. The micrograph SEM of tensile fracture surface of rPP/rHDPE blends with MAPP showed enhanced interfacial interaction and adhesion between rPP and rHDPE due to the reduction of rHDE dispersed phase. The addition of kaolin as filler has led to significant changes to the rPP/rHDPE blends properties. At 10 php of kaolin content, the tensile strength and modulus of elasticity showed optimum values. The incorporation of kaolin has increased the thermal stability of rPP/rHDPE/kaolin composites and the crystallinity of rPP, and rHDPE components was reduced. The water absorption of rPP/rHDPE/kaolin increased with increasing kaolin content. The presence of MAPP in rPP/rHDPE/kaolin composites exhibit higher tensile properties of the composites compared to composites without MAPP. The composites with MAPP have better water resistance compared to composites without MAPP. The crystallinity and thermal stability of composites with MAPP were higher than composites without MAPP. The improvement of interfacial-interaction with rPP/rHDPE and kaolin with the presence of MAPP was proven by SEM studied.