Which type of polyethylene is characterized as safe to use and somewhat rigid?

High-Density Polyethylene (HDPE) is a type of polyethylene that is known for its rigidity and strength. Its molecular structure is composed of tightly packed, linear chains, allowing for a denser material that is both strong and somewhat rigid compared to other polyethylene types. This rigidity makes HDPE suitable for applications requiring higher strength and stability, such as in the manufacture of containers, bottles, and piping.

HDPE is also considered safe for various uses, particularly in food packaging and storage. It has a good resistance to impact and can withstand higher temperatures than its lower-density counterparts. In contrast, Low-Density Polyethylene (LDPE) is more flexible and less rigid, making it unsuitable for applications requiring structural integrity. Polyethylene Terephthalate (PET) and Polypropylene (PP) have different chemical properties and applications, further distinguishing them from HDPE. Hence, the characteristics of HDPE align well with the qualities of being safe and somewhat rigid, confirming it as the correct choice.