Plasticized jackfruit seed starch: a viable alternative for the partial replacement of petroleum-based polymer blends

Blends based on recycled high-density polyethylene (rHDPE) and jackfruit seed starch were prepared using a melt blending method. A total of three blend systems was studied: rHDPE/native starch blends, rHDPE/thermoplastic starch (TPS) blends and rHDPE/citric acid-treated thermoplastic starch (TPSCA) blends at ratios of 90/10, 80/20, 70/30 and 60/40. Modifications were made to overcome the problems of dealing with starch based blends, due to the blends' compatibility with hydrophobic rHDPE and the hydrophilic nature of starch. For the rHDPE/starch blends, the tensile properties were poorer than those of neat rHDPE, with lower ultimate tensile strength and elongation at break, but higher Young's modulus. Upon the conversion of starch into thermoplastic starch, the ultimate tensile strength (UTS), dispersion and thermal stability slightly improved. A blend ratio of 90/10 exhibited the highest tensile strength, while the 60/40 ratio exhibited the highest Young's modulus and better thermal stability. Similar trends were observed in rHDPE blended with citric acid-treated thermoplastic starch, with much better interfacial bonding between the rHDPE matrix and the TPSCA phase, as observed by SEM, thus improving the thermal stability as well as the tensile properties.