HC Plastics News: Sino-US scientists have jointly developed a new technology that can significantly improve the heat and water resistance of biodegradable bioplastics, polylactic acid, reduce commercial production costs and reduce pollution.
A press release issued by the University of Nebraska-Lincoln said that the technology was jointly developed by the school and researchers at Jiangnan University in China. The core step is to heat the polylactic acid fiber to about 200 degrees Celsius and then slowly cool it. The two kinds of polylactic acid molecules are interwoven and intertwined to obtain a product with higher heat resistance and water resistance.
The research team reported in the Swiss Journal of Chemical Engineering that this heat treatment method can make the performance of bioplastics comparable to that of petrochemical plastics, which is simpler and greener than the prior art.
Polylactic acid, also known as corn plastic, is a polymer compound made from corn-rich agricultural products such as corn, which can be naturally degraded and is a potential environmentally friendly plastic. However, due to poor heat resistance and water resistance, its application range is limited.
Polylactic acid molecules have two mirror images of each other. Previous studies have found that plastics composed mainly of one molecule have poor performance. If the two molecules are mixed and intertwined in a proper ratio, the performance can be improved. Some of the existing technologies can achieve this "stereocomplexation", but the process is complicated, costly, and requires the use of harmful solvents or additives. At present, the polylactic acid fiber obtained by interlacing two molecules by heat treatment has a melting point higher than 38 degrees Celsius of polylactic acid composed of one molecule, and can still be well maintained in an aqueous environment having a temperature exceeding 120 degrees Celsius. The structure and strength meet the application requirements of the textile industry.
Researchers say they have clarified the relationship between heat treatment temperature and stereocomplexation and the strength of finished plastic fibers. Small-scale continuous production has been achieved in the laboratory and is being sought for existing industrial processes. 
Editor in charge: Ye Dan
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