Improving the molecular compatibility and mechanical property of starch compounding plastics by adding lecithin

• Main Authors: Shou-Yi Yeh, 葉守儀
• Other Authors: C.Will Chen
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/27063579377916133366

碩士 === 大同大學 === 生物工程研究所 === 91 === In the research, the starch-compounding plastics were produced by mixing the starch-degrading enzymes, cassava starch, lecithin and various additives in the single-screw or twin-screw extruder. The 24 factorial design was used to study the effect of composition on the mechanical properties （tensile strength、 elongation at break and toughness）, and also effect on physical properties (melt flow index、 water absorption and water-soluble weight loss and melting point analyze). The surface structure of specimen has investigated by the scanning electronic microscope (SEM). Lecithin was found to promote the elongation of sample；by only adding 0.92% of total content, the elongation at break increased 1.6 fold. The FTIR spectrum reveals the possible linkage between the lecithin and polycaprolactone (PCL). The maximum elongation of samples can reach to 519 %. Lecithin will enhance the positive effect of PCL on the mechanical properties. Glycerol has a positive effect on the elongation but negative effect on the modulus. Water will increase the tensile strength of samples. The maximum of tensile strength of samples by single extruder reach to 8.5 MPa. Lecithin、PCL、Glycerol has a positive effect on the melting flow index, and the best sample of melting flow index can reach 23.3 g/10min. Samples prepared in this study will not have any weight loss when submerged into water for about 4 hours, and the samples will have slight water absorptivity in the range of 1 gram of water per gram of dry plastic material per hour. From the DSC analysis, it is found that most of the sample had one major melting point around 60 ~ 62 °C. From the SEM analysis, it is found that samples with lecithin had better compatibility between components. The sample of manufactured by twin-screw extruder had better mechanical properties than samples from single-screw extruder.