Effect of particle size on physical properties and biodegradability of cassava starch/polymer blend
2000
Chawalit Petnamsin | Niti Termvejsayanon | Klanarong Sriroth (Kasetsart Univ., Bangkok (Thailand). Faculty of Agro-Industry. Dept. of Biotechnology)
Blending starch with a biodegradable polymer is one method to produce a bioplastic. Due to the high cost of biopolymers, techniques have been developed to enable a high concentration of starch in the blend. The study was conducted in order to determine the effect of particle size (9 to 15 micro m) of cassava starch on the physical and biodegradable properties of polycaprolactone (PCL)/cassava starch blend. Particles of cassava starch, after ball milling (0, 60, 90 and 120 minutes), lost their crystallinity as observed by DSC and birefringency. With less crystallinity, particles observed by SEM, easily formed clumps during the blending process. The tensile strength and percent elongation decreased from 12.21 MPa and 302.89 of PCL/native starch to 4.48 MPa and 25.63 for the 120 minutes ball milled starch/PCL blend (15:85 w/w). Addition of glycerol (25 percent w/w) into the blend could support only percent elongation but not tensile strength. Excellent susceptibility to alpha-amylase and glucoamylase hydrolysis were evident when small particles were incorporated in the blend, compared to native starch. Blends with 60, 90, 120 minutes ball milled (both with and without addition of glycerol) showed very high biodegradability as determined by total organic carbon (TOC) released after subject to amylase digestion.
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