Wood plastic composites from chopped and pelleted waste plastic bags: effect of concentrations and reprocessing on flexural modulus and strength

Abstract

The utilization of waste plastic bag, especially as a matrix for wood plastic composites, is expected to reduce the environmental problems throughout the world caused by its use. Wood plastic composites were manufactured via melt mixing of chopped or pelleted waste plastic bags, sawdust and polyethylene grafting maleic anhydrate (MAPE) according to Extreme Lattice Mixture - Design of Experiment (DoE). The effects of concentrations and reprocessing of waste plastic bags on flexural modulus of elasticity and strength of composites were analyzed. In general, flexural modulus of composites from chopped and pelleted waste are increased but still below the value of SNI 8154–2015. Moreover, the flexural strength of the resulted composites from chopped waste also increased than that of the pelleted one. Some of the formulas of composites from chopped waste met the value required by SNI 8154 – 2015. On the contrary, the flexural strengths of composites from pelleted waste are decreased than that of the virgin one. This is probably due to the existence of interaction between pelleted waste and sawdust that prevented the waste plastic to perfectly melted, hence acted as stress concentration sites. Furthermore, the resulted composites were optimized for flexural modulus using response optimizer plot in order to achieve modulus 2000 MPa that required by the standard. However, the optimized flexural modulus of composites from chopped and pelleted waste was in the range of 1500 MPa, which is far below the standard. Therefore, reprocessing of chopped waste into pellets is not necessary due to inferior properties of composites from pelleted waste than that of the chopped one.