Tensile Strength and Hydrophobic Effect of Starch-Based Biodegradable Polymers

Abstract:

Modern consumer lifestyle requires an enormous amount of plastic packaging and shipping. This study shows that starch has great potential as environmentally friendly packaging. An important candidate for future development of Agro-based products, starch possesses a renewable and biodegradable character compared to petrochemical polymers. Starch is a mixture of two types of glucose polymers, amylose and amylopectin, and their ratio affects the structure and properties of different plant-based starches. The purpose of this study is to determine the effect of different types of starch on the tensile strength and water absorption of the resulting starch-based bioplastics. This study consists of two parts, tensile strength test conducted with a Vernier dual range force sensor, and hydrophobic effect test to measure water absorption. It was hypothesized that the tensile strength will be the highest and water absorption will be the lowest for cornstarch, compared to potato, tapioca, and glutinous rice starch-based biodegradable polymers. This is because cornstarch contains the highest percentage of amylose and has a compact molecular structure. The results of this study showed that potato starch had the highest tensile strength and the lowest water absorption on average. Since each type of plant-based starches has different length of amylopectin side chains, additional tests revealed that tensile strength increases with polymer chain length and strength of cross-linking of polymer. While potato has the second highest percentage of amylose content (15-18% vs. 19-55% for cornstarch), it has a higher range in length of amylopectin side chains (29-31 vs. 23-33 DP for cornstarch). Therefore this study demonstrates that there is stronger correlation between tensile strength and length of amylopectin side chains than between tensile strength and amylose content. Future research will use the substance to make packaging of conventional shapes and test their endurance and strength.