What are the differences in shrinkage rates during cooling for polyethylene versus PVC?

When comparing the shrinkage rates of polyethylene (PE) and polyvinyl chloride (PVC) during cooling, several key differences emerge due to their distinct material properties. Polyethylene, a semi-crystalline thermoplastic, typically exhibits higher shrinkage rates (1.5–4%) compared to PVC, which is amorphous and shrinks less (0.1–0.6%).

The primary reason for this disparity lies in their molecular structures. PE's crystalline regions contract significantly as they cool, leading to greater overall shrinkage. In contrast, PVC's amorphous structure results in more uniform cooling with minimal dimensional changes. Additionally, factors like cooling speed, filler content, and processing conditions can influence these rates.

Understanding these differences is crucial for manufacturers to ensure proper mold design and product dimensional stability when working with these plastics.