What are the differences in shrinkage rates between PVC and polyethylene during cooling?

When comparing the shrinkage rates of PVC (polyvinyl chloride) and polyethylene during cooling, several key differences emerge due to their distinct material properties. PVC typically exhibits a higher shrinkage rate, ranging from 1-5%, depending on the formulation and processing conditions. This is because PVC is an amorphous polymer, which tends to shrink more uniformly but significantly as it cools.

Polyethylene, on the other hand, is a semi-crystalline polymer with a lower shrinkage rate, usually between 1-3%. The crystalline regions in polyethylene restrict excessive contraction, resulting in more predictable and controlled shrinkage. High-density polyethylene (HDPE) shrinks less (1-2%) compared to low-density polyethylene (LDPE), which can shrink up to 3%.

Factors influencing shrinkage include cooling rate, part thickness, and processing methods. Understanding these differences is crucial for manufacturers and designers to ensure dimensional accuracy and performance in final products.