Polypropylene

Polypropylene is an opaque, semi-crystalline plastic. It's commonly used plastic utensils and Tupperware. In packaging, it's often used for labels, stickers, and tape.

It's a thermoplastic which means it melts when heated to a certain temperature. This makes it a viable option for injection molding. On its own, it has very low density. To improve its strength, it can be combined with other plastics (or even fiberglass) to improve its strength and durability.