Effects of LLDPE on Mechanical Properties, Degradation Performance, and Water Absorption of Thermoplastic Sago Starch Blends

Abstract

The purpose of this study was to improve the mechanical and physical properties, degradation performance, and water absorption of a thermoplastic mixture of sago starch with the addition of Linear Low-Density Polyethylene (LLDPE). The method used is the grafting method where polyethylene is grafted onto Maleic Anhydride (LLDPE-g-MA). In this research, Thermoplastics Sago Starch (TPSS) was made with a mixture of Sago Starch (65%) and Glycerol (35%), added with water as a solution. Compatibilizer (PE-g-MA) was made by reacting LLDPE (88%) and Maleate Anhydride (9%) with an additional initiator of Benzoyl Peroxide (3%). The concentration of LLDPE varied from 10,15, 20, 25, and 30%. Substances were mixed into an internal mixer Thermo Haake Polydrive with a speed of 100 mm/minute, for 15 minutes. The concentration of 30% LLDPE produced the highest tensile strength and elongation at a break of 4.30 N/mm2 and 2.15%, respectively. Simultaneously, as LLDPE concentration increased, Young's Modulus decreased. This was powered by the morphology of the sampling surface, with the occurred reaction of adhesion interface or dispersion of LLDPE toward the whole surface with the assistance of compatibilizer as connecting substance between hydrophilic polymer and a hydrophobic polymer, which could improve the properties of mechanical. The formation of ester groups from the reaction of inter groups of hydroxyls derived from the starch with the groups of anhydride derived from the mixture of compatibilizer was visibly seen at the peak of 1693 cm-1. The degradation performance of the TPSS: LLDPE mixture with a ratio of 70:30 showed good performance where the degradation continued to increase up to 42% on the 30th day of degradation in freshwater, 18% in seawater, and 17% in soil burial. While the water absorption test showed that the higher concentration of LLDPE, the lower speed of water absorption.

Keywords

• bioplastics
• compatibilizer, coupling agent, grafting, starch