The biodegradable material PLA is a semi-crystalline polymer with a melting temperature of 180°C. Then why is the heat resistance of the material so poor after the product is made?

The main reason is that the crystallization rate of PLA is slow during ordinary processing and molding, and the final crystallinity of the product is low. In terms of chemical structure, the chiral carbon atom in the molecular chain of PLA contains a -CH3, the molecular chain forms a typical helical structure, and the mobility of the chain segment is low. The crystallization ability of polymer materials is closely related to the activity and nucleation ability of molecular chains. In the cooling process of ordinary processing and forming, the temperature window suitable for crystallization is very small, so that the crystallinity of the final product is small and the heat distortion temperature is low.

Nucleation modification is an effective method to increase the crystallinity of PLA, accelerate the crystallization rate to improve the crystallization performance and thus improve the heat resistance of PLA. Therefore, research on the modification of PLA materials such as nucleation, heat treatment, and crosslinking, to increase its heat distortion temperature and improve heat resistance performance, play an important role in broadening the application range of PLA products.

Nucleating agents are divided into inorganic nucleating agents and organic nucleating agents. Inorganic nucleating agents mainly include: layered silicate, hydroxyapatite and its derivatives, carbon materials and other inorganic nanoparticles. Clay is another type of layered silicate mineral material commonly used in polylactic acid modification, among which montmorillonite is the most representative. Organic nucleating agents mainly include: amides, dihydrazides and diureas, small biomass molecules, organometallic phosphorus/phosphonates, and polyhedral oligomeric silsesquioxanes.

Adding composite nucleating additives to improve its thermal stability is more effective than adding a single additive. The main degradation form of PLA is hydrolysis after moisture absorption, so melt blending method can also be used, adding hydrophobic additive simethicone to reduce hygroscopicity, adding alkaline additives to reduce the degradation rate of PLA by changing the pH value of PLA.

Henan Techuang Biotechnology Co., Ltd. is a modern green and environmental protection enterprise integrating R&D, production, sales and technical services, providing services for biodegradable plastic bags and products. For more information, please visit the official website of Baydeebio: www.baydeebio.com