Polylactic acid (PLA) is a kind of completely biodegradable polymer. The degradation products are carbon dioxide and water, which will not pollute the environment. Its raw material lactic acid is fermented from renewable natural materials such as corn. Therefore, one of the biggest advantages of developing PLA plastics is that it does not use non renewable resources such as fossil.
However, due to the slow crystallization rate of PLA, it is almost amorphous polymer after processing, and its obvious disadvantage is poor high temperature stability. When the temperature exceeds 60 ℃, the product will deform and lose its function. Therefore, improving the heat resistance of PLA products is an important way to broaden its application range.
At present, the main methods to improve the heat resistance of PLA are as follows:
1. Composite with fiber;
2. Increase the glass transition temperature;
3. Improve the crystallinity.
The heat resistance of PLA blends can be effectively improved by isothermal crystallization, but the isothermal crystallization time is too long, it takes about 1 hour, and the production efficiency is low. And compounding PLA with fiber will affect its degradation performance.
Talc powder has three functions in the modification of PLA:
1. The preparation method of talc powder filled polylactic acid composite has the advantages of beautiful appearance, good rigidity, short molding cycle, light weight and low price.
2. Strength improvement: Natural talc powder is melt blended, and the composite is completely biodegradable; it has excellent mechanical properties, in which the tensile strength can reach 50 ~ 70MPa.
3. Polylactic acid has better heat resistance because of its own crystallization and the promotion of crystallization by nucleating agent talc.