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

Recently, the use of natural materials has grown in the plastics industry. In this study, novel bio-nanocomposites were developed from poly(lactic acid)/poly(epsilon-caprolactone) (PLA/PCL) blends and silk fibroin nanoparticles (SFNP). SFNP were successfully synthesized from silk fibroin (SF) and analyzed by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained results revealed that the well-ordered structures in SF were changed to the amorphous structures in SFNP. Then (PLA/PCL) blends containing 10-30% of PCL were prepared and characterized. According to the obtained results, the PLA/PCL (70/30) blend was selected as the optimized sample for further studies. The scanning electron microscopy results illustrated that the addition of 1% of SFNP into this blend improved the compatibility between PLA and PCL and reduced the PCL droplet sizes from 1.170 +/- 92 to 794 +/- 46 nm. The results from TGA analysis indicated that the presence of SFNP enhanced the thermal stability of materials at high temperatures. The crystallization kinetics results revealed that while SFNP promoted the crystallization of neat PLA, the crystallization rate of PLA/PCL blend was decreased upon the incorporation of nanofiller. Furthermore, the PLA/PCL/SFNP exhibited higher microhardness and barrier properties than the neat blend. The results suggest that the developed bio-nanocomposites are promising materials for demanding applications such as food packaging.