Study of the Effect of Compatibilisers on the Properties of High-Density Polyethylene/Starch Blends

The development of partially biodegradable polymer blends incorporating thermoplastic starch into polyethylene matrices represents a strategy for improving the environmental profile of plastic packaging materials. This study investigates the effect of maleic anhydride-grafted polyethylene as a compatibiliser on the mechanical, thermal, and morphological properties of high-density polyethylene and thermoplastic starch blends. Blends were prepared by melt compounding at HDPE:starch ratios of 80:20, 70:30, and 60:40 by weight, with compatibiliser additions of 0, 3, and 5 percent. Tensile strength, elongation at break, and notched impact strength were evaluated. Differential scanning calorimetry and thermogravimetric analysis characterised thermal transitions and degradation behaviour. Morphological analysis by scanning electron microscopy assessed phase distribution and interfacial adhesion quality. Results demonstrate that without compatibiliser, HDPE/starch blends exhibit coarse phase separation and poor interfacial adhesion, resulting in tensile strength reductions of up to 42 percent relative to neat HDPE. Addition of 5 percent maleic anhydride-grafted polyethylene dramatically improved interfacial compatibility, producing finer starch dispersion and recovering tensile strength to within 12 percent of neat HDPE values at 80:20 blend ratio. Elongation at break improved markedly with compatibiliser inclusion, from 18 to 73 percent at 80:20 ratio with 5 percent compatibiliser. Thermogravimetric analysis confirmed that starch addition reduced thermal stability, a partially mitigated effect with compatibiliser present. The study provides formulation guidelines for producing partially biodegradable polyethylene packaging materials with commercially acceptable mechanical performance for Nigerian packaging manufacturers. Keywords: HDPE/starch blend, compatibiliser, maleic anhydride, biodegradable, packaging