What are the differences in processing temperatures for polyethylene vs. polypropylene?

Polyethylene (PE) and polypropylene (PP) are two widely used thermoplastics, but they differ significantly in their processing temperatures. Polyethylene typically processes at temperatures between 130°C and 180°C, depending on the type (LDPE, HDPE, etc.). In contrast, polypropylene requires higher temperatures, usually ranging from 160°C to 240°C, due to its higher melting point (around 160°C for PP vs. 115-135°C for PE).

The optimal injection molding temperature for polyethylene falls between 180°C and 280°C, while polypropylene requires 200°C to 300°C. These differences stem from their molecular structures - PP's methyl group makes it more heat-resistant than PE. Understanding these temperature variations is crucial for proper plastic fabrication, as exceeding or underheating can affect material properties and product quality. Both materials cool at similar rates but require different mold temperatures (20-60°C for PE, 20-80°C for PP) for optimal crystallization.