What are the differences in thermal expansion rates between PVC and polyethylene?

Thermal expansion is a critical property to consider when selecting materials for applications exposed to temperature variations. PVC (Polyvinyl Chloride) and polyethylene are two widely used plastics with distinct thermal expansion behaviors.

PVC has a linear thermal expansion coefficient of approximately 50-70 x 10^-6 /°C, meaning it expands significantly with temperature increases. In contrast, polyethylene exhibits a higher thermal expansion rate, ranging from 100-200 x 10^-6 /°C, depending on its density (LDPE vs. HDPE).

The differences arise from their molecular structures. PVC's rigid, polar structure resists expansion more than polyethylene's flexible, non-polar chains. This makes PVC more stable in high-temperature environments, while polyethylene is prone to greater dimensional changes.

Applications requiring minimal expansion, such as piping or construction, often favor PVC. Polyethylene, however, is preferred for flexible products like packaging or tubing where slight expansion is tolerable. Understanding these differences ensures optimal material selection for thermal performance.