This article covers the topic of pre-drying polymers, which is a crucial process in plastic manufacturing. Moisture absorption is a common occurrence in materials, including plastic, and can cause various issues during the manufacturing process.

For instance, excess moisture can result in silver marks on plastic parts, especially in humid areas like Mumbai. Therefore, pre-drying plastic using a pre-dryer is essential to eliminate any moisture from the material before it goes into the machine.

Different polymers have varying saturation limits, with some absorbing more moisture than others. For example, polycarbonate can absorb up to 0.5%, while PPO only absorb 0.1%. To remove any moisture from the plastic molecules, pre-heating at specific temperatures and time is necessary. However, overheating should be avoided, as it can damage the material and cause it to undesired results.

The pre-drying process is also crucial because plastic raw materials contain various additives like flow agents, mold release additives, fire-retardant additives etc.. Overheating can cause these volatile additives to escape, leading to issues like mold sticking and ejector marks on the parts. The optimum heating time for pre-drying polymers depends on the type of polymer, with some requiring more time than others.

In conclusion, pre-drying polymers is a vital process in plastic manufacturing to prevent moisture-related issues and ensure high-quality parts. Overheating and exceeding cumulative drying time of specific polymer should be monitored to prevent damage to the material and its additives.