As a thermoplastic “addition polymer,” polypropylene plastic, also known as polypropene (PP), is produced from the combination of propylene monomers. Like all thermoplastics, PP can be heated to its melting point, cooled, and reheated again without significant degradation. During polypropylene injection molding, the ability to liquefy and reheat the material allows the material to be injection molded and then recycled. Injection molded polypropylene produces naturally strong and flexible material. Additives; such as talc, calcium carbonate, glass and others, can enhance PP’s characteristics for even more robust capabilities.
PP became very popular for a variety of applications after it was first polymerized in 1951. Injection molded polypropylene is the second most widely-used injection material today. As such, PP is often compared to polyethylene, the most widely-used plastic for plastic injection molding. Polypropylene vs. polyethylene shows that PP is slightly harder, more heat resistant and expands less than polyethylene.
PP’s low melt viscosity makes it a common choice for plastic injection molding. Injection molded polypropylene is a logical choice when the finished product requires lightweight, heat resistance and rugged mechanics. Widely available at lower-end pricing, PP’s popularity is due to the material’s:
Although many characteristics of polypropylene plastic make it a good choice, the material is difficult to paint or finish other than with the use of additives within the plastic.
PP is found in almost every segment of consumer and industrial applications. It is invaluable as a plastic material and a fiber. Industries and applications utilizing PP include:
Common applications include:
Because of polypropylene plastic’s enduring characteristics and wide applicability, when selecting this material, it’s important to understand its performance nuances in each environment. Selecting the best material requires a thorough understanding of the material properties, performance and cost.