Characterization and Properties of Polylactic Acid/Cottonseed Protein Bioplastics

Abstract

In this study, polylactic acid (PLA) is compounded with cottonseed protein concentrate (CPC) by melt blending under the compatibilization of maleic anhydride (MA), and then hot-pressed to prepare PLA/CPC composite bioplastics. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy showed that high temperature and compatibilizer induced the protein secondary structure to transition. CPC can be used as a heterogeneous PLA nucleating agent, effectively accelerating PLA crystallization, which is characterized by polarization optical microscopy (POM), synchrotron radiation wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). The highest crystallinity of the PLA/CPC10 composite is 8.9% higher than that of neat PLA. The unfolding of the protein secondary structure is likely to promote an orderly arrangement of PLA crystals, showing strong binding forces between them. Moreover, the CPC/PLA interfacial compatibility is improved by the addition of a small amount of maleic anhydride. The increased crystallinity and interfacial compatibility contribute to the improved mechanical properties, water resistance, and thermal stability of the bioplastics. Environmentally friendly plastic handicrafts (e.g., commemorative emblems, flower pots, ornaments, etc.) can be fabricated using these biocomposites for future value-added applications.