Preparation, chemical modification and degradability of durian seed starch (DSS) based composites

Preparation, chemical modification and degradability of Durian Seed Starch (DSS)/low-density polyethylene (LDPE) composites were investigated. All of composites were prepared using Brabender Plastograph EC internal mixer at temperature of 150 ͦC and rotor speed of 50 rpm, and moulded using compression moulding at temperature of 150 ͦ C. Particle size analysis revealed that average size of DSS used in this research is 15 μm. Scanning electron microscopy (SEM) of unmodified and modified starch were found to be irregular shape particles and shows agglomeration pattern. The Fourier Transform Infra-Red (FTIR) analysis on modified DSS indicates that the modification is easily detected due to the new positions of absorbance peaks. The effect of filler loading and different types of chemical modifications on mechanical properties, morphology and thermal properties of LDPE/DSS composites were studied. The various types of chemical modifications via acetic acid (AAc), acrylic acid (AA) and lactic acid (LA) were chosen in this study. The results showed that the addition of starch into LDPE matrix reduced the tensile strength, elongation at break, degree of crystallinity (Xc), whereas the thermal stability, Young’s modulus and percent of degradability of composites increased. The chemical modification of DSS resulted positive effect on mechanical and thermal properties of LDPE/DSS composites. The modified LDPE/DSS composites with AAc and AA have higher tensile strength, Young’s modulus, thermal stability, degree of crystalinity (Xc) compared to unmodified LDPE/DSS composites. Improvement in interaction between modified DSS and LDPE matrix was proven by SEM study. The FTIR spectra of modified DSS showed the new functional group from the formation of chemical bonding between DSS and chemical modifying agent. The modified LDPE/DSS composites with LA had lower tensile strength and elongation at break, but higher Young’s modulus, thermal stability, Xc than modified LDPE/DSS composites with AAc and AA. The SEM micrographs of modified LDPE/DSS composites with LA exhibit a rough surface. The composites properties were further enhanced with incorporation of montmorilonite (MMT) and Kaolin, as hybrid filler into DSS. The DSS/MMT and DSS/K hybrid ratio is studied at 100/0/0, 94/5/1, 88/10/2, 82/15/3 and 76/20/4 weight percent (wt %). Both hybrid fillers were found to act as reinforcing fillers to the DSS, with for the MMT show better properties than Kaolin. Both additions of hybrid fillers also have improved the tensile properties as well as the thermal degradation properties of the composites. SEM was also done to investigate the fracture surface behavior. Simple biodegradability test was conducted on each series of the composites were taken for 9 month. Based on biodegradability test, the modified LDPE/DSS composites with AAc had higher rate of degradation compare to AA and LA. Meanwhile, hybrid filler of MMT give higher degradability compare hybrid filler of Kaolin. FTIR analysis and optical microscopy was done to determine the degradability of the composites.