Study On Hydrolytic Degradation Of Polylactic Acid Plastic At High Temperature

At present,plastic products are widely used in many fields.However,the commonly used petroleum-based plastics are all synthesized by fossil energy production,which greatly increases the consumption of fossil energy and greenhouse gas emissions,and because of their strong durability,they can cause pollution to ecosystems.Therefore,biodegradable polymers become more environmentally friendly and more promising future commercial plastics.Among them,polylactic acid(PLA)is a biodegradable bio-based aliphatic polyester,which is widely used in medical,plastic products and environmental repair membranes.PLA hydrolytic degradation is an efficient degradation method,and has good environmental benefits.In this paper,PLA tableware is used as the raw material.First,the hydrolysis and degradation process of PLA materials at high temperature is studied,and the changes of the hydrolysis process and the composition of the products are analyzed.The results show that,at a high temperature of 180?,the hydrothermal degradation process of PLA materials is completed within 60 minutes.In the process of hydrothermal degradation,the weightlessness of PLA materials and the formation of lactic acid have experienced the process of fast,then slow,and finally stabilized.From a microscopic point of view,the long-chain PLA macromolecule breaks the ester bond under the attack of water molecules violently vibrating at high temperature.The final product is only lactic acid and a small amount of oligomers.In order to investigate the influence of various factors in the laboratory environment on the hydrolysis and degradation of PLA,this paper compares the hydrolysis and degradation of PLA under various laboratory conditions.The results show that the specific surface area of PLA material has no effect on the hydrothermal degradation of PLA,and the hydrothermal degradation of PLA occurs through the overall erosion mechanism.The replacement of air with nitrogen as the filling gas has little effect on the degradation process of PLA materials.A higher PLA/water ratio will produce a higher concentration of lactic acid solution,but the actual production needs to comprehensively consider each energy ratio for comprehensive selection.In this study,the catalytic role of the solvent during the hydrolysis and degradation of PLA was also investigated to find a more suitable solvent.The results show that the use of hydrochloric acid solution instead of pure water for PLA hydrothermal degradation reaction has no obvious effect on the overall degradation process.Using lactic acid solution as a solvent has a certain catalytic effect.In practical applications,it is very economical and convenient to use lactic acid solution as a solvent select.In addition,in this study,the product lactic acid solution was further used as a solvent to perform the hydrothermal process,and the stability of the hydrothermal process was investigated.The results show that the cyclic hydrothermal process using the lactic acid solution of the PLA hydrolysis degradation process as a solvent has cyclic stability.The product solution increases the concentration of lactic acid under multiple cycles,reduces the energy load of the concentration step,and saves costs for the subsequent chemical cycle process.