The Effect of Chitosan and Glycerol Variations on Galactomannan Extract from Coconut Pulp as a Raw Material for Making Bioplastics

Abstract

This study aims to develop galactomannan-based bioplastics derived from coconut dregs with the addition of chitosan and glycerol and to evaluate their chemical structure, morphology, mechanical properties, water resistance, and biodegradability. Galactomannan extracts were synthesized into bioplastics with 3 composition variations (A–C), which were then characterized using FTIR, SEM, tensile elongation test, swelling, and soil burial method biodegradation test. The FTIR spectrum of chitosan showed typical absorption bands of O–H/N–H, C–H, N–H bending, and C–O–C/C–O, with a deacetylation degree of 81%, meeting SNI 7949:2013 for chitosan (DD ≥ 75%). The SEM image of formulation A showed a fairly impermeable surface using tiny pores, but there were still cavities due to air bubbles and cracks associated with insoluble chitosan agglomerates. Mechanically, formulation A delivered the highest tensile strength (0.2892 MPa), while formulation C provided the best elongation (46%) and water resistance (87%). All formulations were very simple and degraded in soil (≥90% in ≤7 days) and exceeded the SNI limit for biodegradation, although only elongation and biodegradation met SNI 7188.7:2016. These results indicate that coconut waste galactomannan combined with chitosan and glycerol has the potential to be a raw material for biodegradable bioplastics, although optimal improvement of the composition is still needed to increase tensile strength while maintaining good water resistance and biodegradation.