Tailoring the crystallization and melting behavior of 3D protein-polymer biocomposite materials: A study of pressure-induced silk fibroin/poly(L-lactic acid) foams

Abstract

Crystallization and melting behavior of 3-D composite materials is critical in the field of biopolymer materials, because the crystal structure and crystallization kinetics of the materials will affect the performance of the biocomposite materials and their fabrication process. In this study, thermal analysis combined with structural analysis such as X-ray diffraction (XRD) were used to study the melting behavior of silk fibroin/polylactic acid (SF/PLA) composite foam materials prepared under a pressure of 0–6 MPa, and the mechanism of their isothermal crystallization kinetics was discussed. The results showed that both α and α'-type crystals exist in the composite material, and their contents can be tuned by isothermal crystallization temperature. When the isothermal crystallization temperature is around 105 °C, the crystallization time is the shortest and the crystallization rate is the fastest. Besides, silk fibroin can shorten the crystallization half-life of the composite foam and improve the crystallinity of the material. However, the high isothermal temperature will facilitate the interaction between SF and PLA segments to slow down the diffusion, folding and crystallization of the PLA segments. Using Avrami analysis, it is found that the crystal growth in 3-D composites follows a non-three-dimensional truncated spherical direction. This study provides a deeper understanding of the crystallization behavior of protein-synthetic polymer biocomposite materials and offers experimental and theoretical guideline for the regulation and utilization of their structure and properties for the design of new biocomposite materials.