Effect of thermoplastic starch/poly(lactic acid) weight fraction on phase morphology and performance of biodegradable blends and their jute fiber composites

The present work investigates the phase morphology and properties of biodegradable thermoplastic starch (TPS)-poly(lactic acid) (PLA) blends and their jute fiber (JF) biocomposites. The TPS/PLA blends and TPS/PLA/ JF composites were fabricated using a twin-screw extruder and then injection molded into the test specimens, varying the TPS/PLA weight fractions (80/20, 60/40, 40/60, and 20/80) while keeping the JF content constant (10 wt%). At 80 wt% TPS, the TPS/PLA blend showed a co-continuous structure, whereas the remaining blends (20, 40, and 60 wt% TPS) exhibited a TPS droplets-PLA matrix structure. The TPS/PLA/JF composites displayed a PLA droplets-TPS matrix structure at 80 wt% TPS, a co-continuous structure at 60 wt% TPS, and a TPS droplets-PLA matrix structure at 20 and 40 wt% TPS. Increasing the proportion of PLA increased the melt flow ability, tensile strength, Young's modulus, storage modulus, thermal stability, and water contact angle of the blends and composites. The addition of jute fibers altered the phase morphology of the blends, enhanced their strength and stiffness, increased PLA nucleation, and improved the TPS-PLA phase compatibility. The blends and composites herein exhibit great potential in developing environmentally friendly injection-molded products, such as stationery, toys, gardening supplies, etc.