Biodegradable Nanocomposites Developed from PLA/PCL Blends and Silk Fibroin Nanoparticles: Study on the Microstructure, Thermal Behavior, Crystallinity and Performance

Abstract

Recently, the use of natural materials has grown in the plastics industry. In this study, silk fibroin nanoparticle (SFNP) was successfully synthesized from silk fibroin (SF) and analyzed by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained results revealed that the well-ordered domains in SF were changed to an amorphous structure in SFNP and it was attributed to the cleavage of SF polypeptide chains upon acid hydrolysis. Then several blends of poly(lactic acid)/poly(Ԑ-caprolactone) (PLA/PCL) containing different amounts of PCL were prepared and characterized. Based on the test results the best properties were achieved in the blend with 30% of PCL. The addition of 1% of SFNP into this blend enhanced the compatibility between PLA and PCL and reduced the PCL droplet size from 1.170±92 μm to 794±46 nm, this was observed by scanning electron microscopy (SEM). Thermal analysis indicated that the presence of SFNP caused an improvement of thermal degradation stability of the PLA/PCL blend in the end set temperature range. The crystallization process also slowed and the crystal growth rate decreased from 0.34 to 0.31 min-1. Additionally, the use of SFNP increased (9.7%) the hardness value and reduced (15.7%) the water vapor permeability value of the PLA/PCL blend. The results of these experiments demonstrated that the prepared PLA/PCL/SFNP green nanocomposites have good potential for the food packaging applications.