Structural and free-hole volume characterization of high-density polyethylene-chitosan composites plasticized with palm oil

A series of high-density polyethylene (HDPE) - chitosan (CS) composites with varying concentrations of chitosan have been prepared using a peroxide-initiated melt mixing process with maleic anhydride as compatibilizer. Palm oil has been added as a plasticizer to the optimized HDPE/CS5 composite. The variation in the free hole volume, microstructure, and crystallinity of the prepared composites has been studied using Positron annihilation lifetime spectroscopy (PALS), dynamic mechanical analysis (DMA), and X-ray diffractometry (XRD) respectively. The interaction between HDPE and chitosan is evidenced from the FTIR spectroscopic studies. The addition of palm oil to optimized HDPE-CS composite increased the crystallinity upto 41.3%. A shift as well as a decrease in loss modulus was obtained for 5 wt% chitosan added HDPE sample which can be ascribed to the better crosslinking observed in the composite. The increased amorphization of HDPE-chitosan composites with a higher concentration of chitosan beyond the optimized concentration is observed from the tan delta values. Free-hole value is reduced by 20 angstrom(3) with the addition of 5 wt% palm oil to HDPE/CS5 composite system. The microstructural analysis shows evidence of efficient interaction of HDPE-chitosan system that can be used for further applications in medical field and food packaging industry.