Preparation and Performance Evaluation of LDPE/Rice Starch Blend Composites by Extrusion Method

Abstract

Discarding synthetic polymers such as low-density polyethylene (LDPE) used in food packaging ingredients is today considered a serious ecological threat because they are non-decomposable.  The goal of this article is to create a decomposable polymer by incorporating a bio-polymer (starch) into its polymeric matrix. This article focuses on the preparation and characterization of rice starch (RS)-mixed LDPE decomposable polymer. In the first study, the effect of variability of RS content on mechanical properties (elongation at break and tensile modulus) and biodegradability of polymers was studied. LDPE was combined with 10%, 20%, 30%, 40%, and 50% of RS for this study. Then the effects of chemical crosslinking on the melt flow behavior, mechanical, thermal properties and biodegradation of RS-based composites were investigated. Sodium trimetaphosphate (STP) was used as cross-linking agent. In the second study, LDPE polymers were included with only 50% RS to avoid data impedance. The results show that the melt flow index (MFI) of LDPE/RS composites decreased with increasing RS content. Cross-linked RS in LDPE/RS composites has been shown to have higher MFI than other composites. The cross-linked RS in LDPE/RS composites gives rise to excellent dispersion of RS and better properties than other composites which indicate uniformity. The RS content had a direct effect on the mechanical properties and biodegradability of the polymer. Elongation at break decreases as RS content increases, while tensile modulus and weight loss (i.e., decay) increase with increasing RS content. Cross-linked RS-LDPE composites exhibit better elongation at break and tensile modulus than non-cross-linked RS-LDPE composites. However, cross-linking processes reduce the melting temperature of the polymer. Also, biodegradability was performed for various LDPE/RS composites. Besides, water absorption of cross-linked LDPE-RS composites was reduced. In conclusion, RS content and modification processes play an important role in controlling the mechanical, thermal, and degradation properties of RS-blended LDPE synthetic polymers, thus providing an opportunity to modify polymer properties for suitable applications.