PP: The “Everyday Hero” of Plastics

If there were an award for the most versatile plastic in your daily life, Polypropylene (PP) would win by a landslide. From the microwaveable container in your kitchen to the heavy-duty bumper on your car, PP is everywhere because it is incredibly tough, chemically “bored” (it doesn’t react with much), and remarkably light—it’s one of the few plastics that actually floats in water.

Its most famous “superpower” is its resistance to fatigue. PP is the material behind the “living hinge”—that thin piece of plastic on a flip-top cap that can be opened and closed thousands of times without snapping.

Technical Specs at a Glance

Injection vs. Blow Molding

In injection molding, PP is prized for its low melt viscosity, meaning it flows easily into complex shapes like thin-walled containers or medical syringes. In blow molding, PP’s excellent moisture barrier makes it the standard for detergent bottles, chemical drums, and specialized labware.

The Reality Check: PP is fantastic, but it’s not perfect for every job. It has a high “shrink rate,” which means parts can change size significantly as they cool. It also tends to get brittle in freezing temperatures. If your product is headed for a sub-zero environment or needs aerospace-level precision, we usually recommend adding glass fibers or mineral fillers to stabilize it.

Is your product destined for the microwave or a lab bench? Let me know the environment, and I can help you decide between a Homopolymer (stiffer) or a Copolymer (more impact-resistant) PP.