Effect of poly lactic acid on morphological, mechanical, and optical properties of compatibilized polypropylene and high density polyethylene blend

Abstract

Blends of compatibilized polypropylene (PP) and high density polyethylene (HDPE) with or without polylactic acid (PLA) were investigated to determine the influence of the addition of PLA on blend properties. Ethylene vinyl acetate copolymer (EVA) was used as a compatibilizer for PP/HDPE (80/20) blends. The compositions were prepared by co-rotating a twin screw extruder with six zones of temperatures ranging from 160 to 200 °C along the barrel to dye. The screw speed of the extruder was maintained at 200 rpm. Mechanical properties like tensile strength, elongation at break, burst strength, tear strength, and coefficient of friction were determined. Optical properties like haze and transmittance were also reported. The morphology was studied by scanning electron microscopy (SEM). Tensile properties and burst strength of the film were found to be maximum at 4 wt.% of PLA incorporated into the compatibilized PP/HDPE blend. Tear strength showed decreasing order on the PLA loading of 4, 8, 12, and 16 wt.% when tested in both the machine and transverse directions. Coefficient of friction of the film was found to be the lowest at 4 wt.% PLA loading into the blend when compared with other compositions. Optical property such as haze was increased and the value of transmittance was decreased as the loading of PLA wt.% increased. SEM showed that the presence of 4 wt.% PLA and EVA improves the dispersion of HDPE into PP.