Morphological and Thermal Analysis of Poly(L-lactic acid)/ Carboxymethyl Cellulose Bio-composites

Abstract

Poly (L-lactic acid) (PLLA) and carboxymethyl cellulose (CMC) are derived from renewable resources and both have excellent properties such as biocompatibility and biodegradability. Applications of PLLA are restricted for some of its inadequate physical properties such as low glass transition temperature, relatively low melting point, high crystallization temperature, slow crystallization rate, and poor heat stability. This study aims to prepare and characterize a renewable bio-composite with more adequate properties for applications by solution casting of different PLLA, and CMC ratios. CMC was prepared from microcrystalline cellulose (MCC) of mustard stalks (agricultural wastes) and the yield was about 78%. The samples were analyzed via Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetric (DSC), wide-angle X-ray diffraction (WAXRD), and scanning electron microscopy (SEM) for spectroscopic and thermal properties characterization. The interaction between carboxylate groups of CMC surfaces and the terminal hydroxyl, terminal carboxyl, and carbonyl groups of PLLA through hydrogen bonds caused the shift and broadening of the band of FTIR spectra. The decomposition temperature of CMC was increased and formed excellent bio composites with PLLA. Composite crystallinity varied with the percentages of the CMC. The fibrous form of CMCs is present in the SEM micrograph indicating cellulose's fibrous structure was not affected by carboxymethylation. In composites, the surfaces of CMC fibers are layered and different from the reported results of SEM micrographs of PLLA/MCC composites. PLLA/CMC performs better in thermal properties but its mechanical characteristics cannot be determined owing to a limitation where the composite was too brittle and not able to undergo tensile testing.