POLYPROPYLENE (PP)
Polypropylene (PP) is a heavily used for injection molding and comes in the form of pellets. PP is a thermoplastic polymer made from the combination of propylene monomers. It is used in a variety of industries and applications such as household plastic items, living hinges, automotive parts, medical devices, plumbing, etc. Its extensive use has projected that demand will rise from 45 million to approximately 72 million metric tons by 2022.
Advantages of PP
- Inexpensive
- High manufacturability
- High flexural strength due to its semi-crystalline nature
- Great resistant to absorbing moisture
- Chemical resistance over a wide range of bases and acids
- High fatigue resistance
- High impact strength
- Polypropylene is a good electrical insulator
Disadvantages of PP
- High thermal expansion coefficient which limits its high temperature applications
- Susceptibility to UV degradation
- Poor resistance to chlorinated solvents and aromatics.
PP Specifications
| Melt Temperature | 160°C (320°F) |
| Typical Injection Mold Temperature | 32 – 66 °C (90 – 150 °F) * |
| Heat Deflection Temperature (HDT) | 100 °C (212 °F) at 0.46 MPa (66 PSI) * |
| Flexural Strength | 41 MPa (6000 PSI) * |
| Tensile Strength | 32 MPa (4700 PSI) * |
| Specific Gravity | 0.91 |
| Shrink Rate | 1.5 – 2.0 % (0.015 – 0.02 in/in) * |
*At standard State