Isolation and characterization of chitin nanowhiskers from fermented prawn waste as fillers in polylactic acid composites

Abstract

This study focuses on the application of chitin nano whiskers (CHW) from different chitin sources to the development of CHW-reinforced poly(lactic acid)(PLA) nanocomposites. Chitin sources used in this study consisted of commercial chitin (CC), fermented chitin (FC) and treated fermented chitin (TFC) whereby FCand TFC were obtained from fermentation of prawn waste. PLA was chosen due to its advantages such as biodegradability and good mechanical strength. The CHWs produced by acid hydrolysis (CCHW, FCHW and TFCHW) were characterized using Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy(TEM), x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The FTIR analysis revealed that the acid hydrolysis process did not alter the chemical structure of chitin but changes its surface morphology. TEM images revealed that CHW particles obtained had rod-like shapes 10-20 nm in width and 300-500 nm in length.XRD analysis showed that CCHW has a higher crystallinity index (70%) compared to FCHW (46%) and TFCHW (68%). Thermal analysis indicated that CHW possess a good thermal stability. The effects of CHW on properties of PLA were investigate dand the PLA/CHW nanocomposites were examined by FTIR, tensile test, TGA, and biodegradability and water absorption tests. Tensile strength for PLA/FCHW,PLA/TFCHW and PLA/CCHW increased with increasing filler content until it reached optimum value at 1 phr, 2 phr and 3 phr, respectively. Young’s modulus for the nanocomposites increased with increasing filler content but elongation at break decreased significantly with increasing filler content for all types of nanocomposites.TGA results indicated that PLA/CHW nanocomposites displayed better thermal stability as compared to pure PLA. The biodegradability and water absorption of nanocomposites increased with increasing filler content.Polyethylene glycol (PEG)was used in view of improving ductility of PLA and PLA nanocomposites. The FTIR spectra of PLA/PEG and PLA/FCHW/PEG revealed that addition of PEG into PLA broaden the O-H peak significantly, indicating the formation of hydrogen bonds between PEG and PLA. PEG/PLA showed increment in tensile strength and elongation at break at optimum loading of 5 phr while Young’s modulus decreased.Meanwhile, PLA/FCHW/PEG nanocomposites showed increment in tensile streng that an optimum loading of 1 phr while Young’s modulus increased with increasing FCHW. The elongation at break decreased dramatically upon addition of FCHW.