Study on Starch-based Bio-degradable Plastic
|Course||Of Food Science|
|Keywords||Starch Graft copolymerization Biodegradable plastics Twin screw extruder Degradation rate|
The starch is fully biodegradable natural polymeric substance has can be reproduced, inexpensive, easy to store and easy to transport characteristics, various reactions can be carried out under certain conditions, to derive a number of derivatives with good accessibility and biological degradation, making the raw material of the biodegradable material. Paper, cerium ammonium nitrate initiator system, the use of different monomers, by changing the amount of monomer addition, the amount of initiator added, reaction time, etc. single factor, measuring the rate of the starch graft product graft, and ultimately determine the best of the graft reaction conditions are as follows: 1 starch / MMA graft reaction: initiator content is 2.8%, 7.5% of the monomer content, the nitrogen-sealed stirring After 3.3 hours of reaction, graft ratio of 65.9%, a graft product heat 275 ° C, at 335 ℃ weight loss of about 80%, after the gradual decomposition. Grafting reaction of the starch / MMA / VAc: monomer ratio (VAc: MMA) of 1:2, adding 3% of the initiator, 8% of the total monomer content, nitrogen-sealed stirring reacted for 3.5 hours, then sticks rate up to 67.4%, but the product of heat resistance is not very good weight loss rate of 5.63% before 241 ℃, and little heat range at 345.4 ℃, rapid weight loss of 35.8%, after declining in and even after nearly 400 ℃ weight loss rate of 60% -70%, the samples continue to heat up after the melting process of 182 ℃ -229 ℃ partial oxidation decompose completely. 3, Starch / MMA / St graft reaction: monomer ratio of 1:1, and 2.8% of the initiator, the total monomer addition amount of 8% when the nitrogen was stirred for 3.3 hours, the graft ratio of a maximum of 61.2%, and the product good heat resistance, before 276 ℃, good thermal stability, and the weight loss was only 10.6% at 333.4 ℃, can be quickly the weightlessness reached 66.7%, indicating that the graft product has good stability before 276 ℃ 333.4 ℃ degradation, suitable for ordinary plastic material. Compare three different monomer added graft reaction, the grafting rate or less, but with mixed reaction of two monomers, more expensive, and the reaction is complicated, and is not suitable for industrial production. Therefore, the starch 80 ° C gelatinized 2H, insulation 0.5H, 40 ° C add 2.8% of initiator, 7.5% of MMA monomer, a nitrogen-sealed stirred after the reaction for 3.3 hours graft product, the use of screw center distance of 32mm barrel diameter f300mm L / D ratio of 12.5 and a twin-screw extruder, a control screw speed 100rpm sample moisture content of 20% extrusion was measured to know the sample can be resistant to temperatures of less than 302 ℃ was 14.7%, water resistance, and buried in a simple soil the case, after about 180 days to reach the weight loss rate of nearly 60%, can say basically completely degraded.