Influence of Plasticizers on Mechanical and Thermal Properties of Methyl Cellulose based Biodegradable Films

Abstract

Methyl cellulose (MC) is the most abundant cellulose ether and has the vast potential to be used in biopolymer food packaging films due to its superior film forming, moisture and gas barrier properties. However, the inherently attributed brittleness of MC due to hydrogen bonding restricts its applications in packaging industry; which can be overcome by the addition of a suitable plasticizer. MC films plasticized with malic acid and sorbitol were prepared via solution casting and the influence of plasticizers at various concentrations on the moisture uptake, crystallinity, mechanical (tensile strength and elongation) and thermal characteristics of the films was investigated. The films were characterized with XRD, SEM, FTIR and TGA. A decline in tensile strength of the all films plasticized with malic acid and sorbitol was observed that was proportional to the plasticizer concentration. On the contrary, increase in percentage elongation at break was noted that was more pronounced in sorbitol plasticized films. Sorbitol blend films had higher water affinity due to additional hydroxyl groups resulting in a higher moisture uptake and subsequently higher flexibility. TGA analysis showed that, thermal stability was reduced with the addition of plasticizers and the sorbitol film samples were more thermally resistant as compared to malic acid. FTIR was performed to investigate the better insight of the hydrogen bond formation between MC and both plasticizers. Hydrogen bonding shifted from among the MC chains to the MC-plasticizer chains. The SEM micrographs of the control (MC) and plasticized films showed a smooth and homogeneous surface morphology as expected for a compatible polymer blend. XRD diffractograms depicted a semi-crystalline structure for the both the plasticized films. It is believed that MC plasticized films with enhanced flexibility will be highly suitable as a biodegradable material for food packaging applications.