Straw Type Disposable Tableware

The degradation products of PLA can assist plants to become the raw materials of PLA through photosynthesis, so PLA is a "cradle-to-cradle" green material.  At present, PLA is the main raw material of disposable tableware in the market.  PLA is relatively stable at room temperature, but it is easy to degrade rapidly in slightly high temperature, acid-base environment or microbial environment, and has poor impact resistance, which often cannot meet the requirements of circulation in harsh environment.

PLA straws deform and soften when drinking hot drinks, damaging the drinking experience

Modified methods for improving thermal stability

The thermal stability of PLA material is similar to that of PVC, but lower than PP, PE and PS. The processing temperature is generally controlled between 170~230 ℃. It is suitable for injection, stretching, extrusion, blow molding and other common processes.  However, the crystallization rate of PLA is slow in the actual processing process, so it generally needs to be modified.  At the same time, due to the slow crystallization rate and low crystallinity, the thermal deformation temperature of PLA is low, which limits its application in hot filling or hot sterilization product packaging. 

In order to improve the crystallization rate and crystallinity of PLA, the optical purity of PLA can be improved as much as possible during production.  Contains a small amount of PLLA PDLA crystallinity will sell at a discount greatly, annealing treatment is also a way of improving PLA crystallinity, also can add nucleating agent to improve crystallization behavior, improve the degree of crystallinity, thus improve the thermal deformation temperature, improve its heat resistance, a study by PLLA and PDLA structure composite were also have special properties such as high temperature resistant products.  

At present, blending with inorganic fillers or natural fibers is the main modification method to improve the properties of PLA materials.  For example, LiWH et al. modified PLA with bamboo fiber, and the bending strength and elongation at break of the composite material obtained were increased by 19.3% and 30.1% respectively. Shyif et al. prepared PLA banana fiber composites by melt blending method. By using coupling agent and chemical modification to combine banana fiber to PLA chain, the thermal stability and mechanical properties of the composites obtained were significantly improved.