Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice husk and acetyl tributyl citrate

Abstract

Developing a stiffness-toughness balance, low-cost, and biodegradable PLA composite is an effective strategy for improving product market competitiveness, reducing dependence on petroleum-based resources and protecting the environment. Rice husk (RH) is extensively used as a filler in polymers, but the addition of too much rice husk into PLA has damaged the toughness of the composite. In this work, fully biodegradable composites with a stiffness-toughness balance and low cost are successfully fabricated through melt blending of PLA, RH and acetyl tributyl citrate (ATBC), named PLAC0, PLAC3, PLAC6, PLAC9, PLAC12, PLAC15, PLAC18, PLAC20 respectively according to amount of ATBC (0phr, 3phr, 6phr, 9phr, 12phr, 15phr, 18phr, 20phr). The results show that bio-based plasticizer ATBC can improve the flowability of PLA composites, further enhancing their processability, which promotes the dispersion of RH in PLA. The impact strength and elongation at break of PLAC20 reach the value of 100 J/m and 148%, achieving an increase of 4.3 and 60.1 times compared with PLAC0, respectively. The torque rheological test shows that the maximum torque and equilibrium torque of PLAC18 decrease by about 67.4% and 63.5% respectively compared to PLAC0. This suggests a decrease in friction between PLA molecular chains, thereby increasing the fluidity of PLA composites and indicating a significant improvement in processing performance. As the ATBC amount increases, the water absorption rate of the composite progressively rises, while the contact angle steadily diminishes, resulting in the improvement for hydrophilicity, thereby broadening its potential applications.