How does the hardness of polyethylene compare to polypropylene?

Polyethylene (PE) and polypropylene (PP) are two widely used polymers with distinct properties, including hardness. Polyethylene is generally softer and more flexible compared to polypropylene. This difference arises from their molecular structures: PE has a simpler, more linear chain, while PP features a more rigid structure due to its methyl group side chains.

The hardness of polyethylene typically ranges between 40-70 on the Shore D scale, depending on its density (LDPE, HDPE, etc.). In contrast, polypropylene is harder, with a Shore D hardness of around 70-90. This makes PP more resistant to wear and deformation, ideal for applications requiring durability, such as automotive parts and industrial containers.

However, polyethylene's lower hardness provides advantages in applications needing flexibility, like packaging films and tubing. Understanding these differences helps in selecting the right material for specific uses, balancing hardness with other properties like impact resistance and chemical stability.