What are the key differences between HDPE and HDPP plastics and how do they impact their respective applications?

High-density polyethylene (HDPE) and high-density polypropylene (HDPP) are both types of plastic, but they have key differences. HDPE is more rigid and has a higher melting point than HDPP, making it better for applications requiring strength and durability. HDPP, on the other hand, is more flexible and has better chemical resistance, making it suitable for applications where chemical exposure is a concern. These differences impact their applications, with HDPE commonly used for containers, pipes, and packaging, while HDPP is often used for automotive parts, medical devices, and textiles.