Do biodegradable plastic polymers need to be dried?

Biodegradable plastic polymers usually require drying treatment, but the specific process, degree, and method of drying may vary depending on the type of plastic, production process, and final application environment.
For many biodegradable plastic polymers, such as PGA, PLA, PBAT, etc., they do not fully crystallize after cooling and cutting from the molten state, so a specialized crystallization process needs to be designed in the finished product section to complete the crystallization. This pre crystallization process not only increases the softening temperature of the polymer, but also enables the material to use higher drying temperatures in the subsequent drying process, thereby achieving better drying results. The main purpose of drying treatment is to remove moisture and residual monomers, solvent volatiles, etc. from the polymer, in order to improve the quality indicators of the product, such as crystallinity, impurity content, moisture content, etc., and ensure that these indicators are as uniform as possible.
The crystallization temperature and time of different types of biodegradable plastic polymers are different, so the specific conditions for drying treatment will also vary. The selection of drying temperature needs to take into account the softening point temperature of the resin, as well as the time required for moisture and residue to migrate from the inside of the slice to the surface during the drying process. The higher the drying temperature and the lower the moisture content of the drying medium, the faster the drying speed and the shorter the required drying time. However, a too fast cooling process may not be conducive to crystallization, so after the slices are dried in the drying tower, appropriate cooling methods such as low dew point air cooling need to be used to ensure that the slices can be cooled to a temperature suitable for packaging (usually below 60 ℃).
In addition, it is worth noting that the heat recovery and utilization during the drying process is also an important means to reduce energy consumption and improve production efficiency. For example, the air coming out of the cooling chamber can recover the heat released during the cooling of the slices, which can be used for the drying or pre crystallization process in the early stage, thereby significantly reducing the energy consumption of the entire drying and cooling process.