General Properties
Short Name:
Name:
Chemical Formula:
PP (isotactic)
Polypropylene
(C3H6)n
Polyproyplene (PP) belongs to the polyolefin group. It has an approx. 20% share in plastic production worldwide and is therefore the second most important polymer after PE. Its tacticity (isotactic, syndiotactic and atactic) is dependent on the polymerization conditions employed.
Polypropylene is nonpolar and cannot be bonded or painted without pre-treatment (activation). A lot of derivatives of the classical PP homopolymer exist. The majority of PP types available are copolymerized with PE in order to reduce their glass transition temperature and to improve their impact strength in the low-temperature range. PP is processed with additives, fillers or other polymers to a variety of PP compounds, which cover a broad range of properties.
Structural Formula
Properties
| Glass Transition Temperature | -20 to 20°C |
|---|---|
| Melting Temperature | 160 to 165°C |
| Melting Enthalpy | 207 to 209 J/g |
| Decomposition Temperature | 450 to 470°C |
| Young's Modulus | 1300 to 1800 MPa |
| Coefficient of Linear Thermal Expansion | 130 to 180 *10-6/K |
| Specific Heat Capacity | 1.8 J/(g*K) |
| Thermal Conductivity | 0.17 to 0.25 W/(m*K) |
| Density | 0.90 to 0.91 g/cm³ |
| Morphology | Semi-crystalline thermoplastic |
| Identification | White granule |
| General properties | Easy to process, Good combination of stiffness and toughness, Good chemical resistance, High stress corrosion resistance, High electrical resistance, Better stability, hardness and stiffness than PE |
| Processing | Injection molding, extrusion, deep drawing |
| Applications | Food containers, packaging, Automotive engineering, Sports equipment, textiles, toys, Building industry |
| Modifications | Co-Po with PE, Compounds with rubber, minerals, reinforcement, colored |
| Manufacturer | Lyondellbaseel, Borealis, DOW, Exxon, Sabic |
NETZSCH Measurement
| Instrument | DSC 204 F1 Phoenix® |
| Sample Mass | 5.67 mg |
| Isothermal Phases | 10 min/3 min/10 min |
| Heating/Colling Rates | 10 K/min |
| Crucible | Al, pierced lid |
| Atmosphere | N2 (40 ml/min) |
Evaluation
For commercial semi-crystalline PP types, a melting temperature (represented by the peak temperature) of approx. 160°C to 165°C is typical. This correlates well with the present case, in which peak temperatures of 168°C and164°C were observed in the 1st heating (blue) and the 2nd heating (red), respectively, with corresponding melting enthalpies of 94 J/g (1st heating) and 112 J/g (2nd heating). The lower melting temperature in the 2nd heating can be attributed to better contact between the sample and crucible bottom after the first melting (in the 1st heating). The difference in the heat of fusion results from the different cooling conditions used during production or processing of the polymer and during the measurement (cooling rate: 10 K/min). The glass transition step for PP can usually be found between -20°C and +20°C. In the present example, it was at -8°C (2nd heating). In the 1st heating, the glass transition was barely detected.