Composites of Durian seed starch (DSS)/low-density polyethylene (LDPE) and durian seed starch (DSS)/poly(E-caprolactone) (PCL) were investigated. The study is divided into three parts. The first part involves the preparation and characterization of the filler, second part is to study the effect of filler content on the DSSILDPE and DSS/PCL composites, while the last part is to study the effect of blend ratio on the PCLILDPE/DSS composites. Glycerol was used as the plasticizer agent to modify the DSS at 20 wt. % of the DSS. Particle size analysis revealed that average size of DSS used in this research is 1 0 J.lm. Scanning electron microscopy (SEM) of both native and modified DSS was found to be in irregular shape particles and shows agglomeration.
The Fourier Transform Infra-Red (FTIR) analysis of native and modified DSS indicates that the modification is not easily detected because the positions of absorbance peaks are similar. The melting temperatures (T m) of the modified DSS were observed to be shifted to higher temperature compared to the native DSS shown by the differential scanning calorimetry (DSC) analysis. Three-stage degradation of the modified DSS was observed by thermogravimetric analysis (TGA) attributed to the volatilization of water and glycerol, and the decomposition of the starch. A series of DSSILDPE, DSS/PCL, and DSS/PCLILDPE composites with 5, 10, and 15 wt. % of filler content were prepared using Brabender Plastograph EC internal mixer at temperature at 150 °C for 6 minutes. The blend ratio used for PCL/LDPE hybrid composites was 25175 ratio. Studies on their properties were carried out by FTIR, tensile test, melt flow index (MFI), TGA, DSC and simple biodegradability test. Tensile strength and elongation at break (Es) decreased as DSS was added into LDPE and PCL due to the agglomeration of the DSS and poor interfacial adhesion between the filler and LDPE and PCL matrix. Elastic modulus was increased as DSS was added into LDPE and PCL. DSS/PCL composites were found to have better tensile properties than DSSILDPE composites. TGA analysis shows that the addition of the DSS has improved the thermal stability of LDPE and PCL. Furthermore, DSS/LDPE composites show higher onset degradation temperature (To) and weight loss indicate that DSSILDPE have better thermal stability compared to DSS/PCL composites. The Tm of the DSS/LDPE and DSS/PCL composites
has reduced as filler content was increased as shown by the DSC results. In the same ftller content, the LDPE/DSS composites give a higher T m values than the PCLIDSS composites. The incorporation of DSS into the PCLILDPE hybrid composites however has reduced its tensile properties as well as the thermal degradation properties of the composites. There is no significant change of the T m values in the PCLILDPE/DSS hybrid composites shown in DSC analysis indicate that LDPE/PCL hybrid composite is hardly miscible or incompatible at the molecular scale with the DSS. Scanning electron microscopy (SEM) shows that higher filler content caused poor bonding at the interfacial area between filler and matrix polymer which lead to the brittle deformation of the composite. However, SEM of PCLILDPE/DSS composites show poorer morphology than DSSILDPE and DSS/PCL composites which more filler pulled-out, de-wetting of the filler by matrix and poor filler dispersion in polymer matrix were observed. Simple biodegradability test was conducted on each series of the composites, where FTIR analysis was done to determine the degradability of the composites. Results showed that all composites are subjected to degradation.
