Polypropylene
A versatile thermoplastic polymer, second only to polyethylene in production volume.
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer produced via chain-growth polymerization from the monomer propylene. It is the second-most widely produced commodity plastic after polyethylene, belonging to the group of polyolefins, and is partially crystalline and non-polar. Its properties are similar to polyethylene, but it is slightly harder and more heat-resistant, and it is a white, mechanically rugged material with high chemical resistance.
- field
- Polymer chemistry / Materials science
- known_for
- Second-most widely produced commodity plastic; discovery of propylene polymerization and stereoselective isotactic polypropylene
Lore & Background
Phillips Petroleum chemists J. Syndiotactic polypropylene was also first synthesized by Natta. Interest in polypropylene development is ongoing, including making polypropylene from bio-based resources in the 21st century.
Reader's Guide
Its mechanical and thermal properties depend on molecular weight, crystallinity, and tacticity. It competes with engineering plastics like ABS and is used in a wide variety of applications. The discovery of stereoselective polymerization by Natta and Rehn enabled large-scale production, and ongoing research includes bio-based production. Polypropylene's properties can be modified by copolymerization with ethylene, affecting crystallinity, melting point, and transparency.
Did You Know?
- Atactic polypropylene is amorphous and lacks crystal structure, making it soluble even at moderate temperatures.
- The melt flow rate (MFR) of polypropylene helps determine how easily the molten material flows during processing; higher MFR reduces impact strength.
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