Characteristics of bio-plastic composites from the modified cassava starch and konjac glucomannan

Abstract

The production of bio-plastics from modified cassava starch and konjac glucomannan had been widely and dependently developed but still demonstrated characteristics that do not meet international quality standards. Therefore the key question for further exploration was to improve the protocol so as to develop a composite bio-plastic using the aforementioned materials. This study aimed to determine the ratio of modified cassava starch and konjac glucomannan and the concentration of acetic acid solution required to produce bioplastic composites with the best characteristics. This study followed a Factorial Randomized Block Design with two factors. Factor I was the ratio of the modified cassava starch and konjac glucomannan, and consisted of 5 levels namely 100:0, 75:25, 50:50, 25:75 and 0: 100. The factor II was the concentration of acetic acid which consisted of 5 levels, viz., 0, 0.5, 1.0, 1.5 and 2.0 %. Each treatment combination was grouped into 4 blocks based on the processing time of making bio-plastic composites, resulting in an altogether 100 experimental units. The data obtained were subjected to analysis of variance followed by Duncan’s multiple comparison tests. The results showed that the ratio of the modified cassava starch and konjac glucomannan, the concentration of acetic acid and its interaction had a very significant effect on the tensile strength, elongation at break, Young’s modulus, swelling and the degradation time of bio-plastic composites. The ratio of the modified cassava starch:konjac glucomannan :: 75:25 with supplemented with 1 % acetic acid produced the best bio-plastic composites with the desired characteristics viz., tensile strength of 1997.40 MPa, elongation at break of 8.90 %, Young’s modulus of 22442.70 MPa, swelling of 10.40 % and the degradation time of 6.33 days. The surface profile of bio-plastic composites in longitudinal appearance displayed presence of regular waveforms along with air cavities or regular pores. Bio-plastic composite profile in transverse appearance revealed arrangement of fibers in the form of regular nets and smooth cross links. These bio-plastic composites contained -OH, -CH, -C-C, -C=C, -NH and -C=O functional groups.