What are the thermal expansion coefficients of polypropylene vs. PVC in joint design?

When designing joints in engineering applications, understanding the thermal expansion coefficients of materials like polypropylene and PVC is crucial. Polypropylene has a thermal expansion coefficient of approximately 100-150 × 10⁻⁶/°C, while PVC typically ranges between 50-80 × 10⁻⁶/°C. This means polypropylene expands nearly twice as much as PVC under the same temperature changes.

In joint design, these differences can significantly affect performance. For example, polypropylene's higher expansion may require additional allowances or flexible connectors to prevent stress buildup. Conversely, PVC's lower expansion makes it more stable in environments with temperature fluctuations.

Choosing between these materials depends on the application's thermal conditions and mechanical requirements. Engineers must balance cost, durability, and thermal behavior to ensure long-term reliability.