General Properties
Short Name:
Name:
Chemical Formula:
PS
Polystyrene
(C8H8)n
Polystyrene (PS) can be amorphous or semi-crystalline. In its amorphous form, this thermoplastic is widely used in many areas of daily life. In its expanded (expanded polystyrene – EPS or PS-E) form, it serves as an insulating material. There is atactic, syndiotactic and isotactic polystyrene (more on the tacticity on page 64). Commercial amorphous PS is atactic. The isotactic and syndiotactic types are semi-crystalline and melt at 240°C and 270°C, respectively*. Isotactic polystyrene, however, crystallizes very slowly and therefore does not play a role in industrial processing. Syndiotactic PS crystallizes quickly enough and can be processed in injection molding.
Structural Formula
Properties
| Glass Transition Temperature | 80 to 105°C |
|---|---|
| Melting Temperature | - |
| Melting Enthalpy | - |
| Decomposition Temperature | 415 to 425°C |
| Young's Modulus | 3100 to 3300 MPa |
| Coefficient of Linear Thermal Expansion | 50 to 70 *10-6/K |
| Specific Heat Capacity | 1.3 J/(g*K) |
| Thermal Conductivity | 0.14 to 0.18 W/(m*K) |
| Density | 1.05 g/cm³ |
| Morphology | Amorphous or semi-cristalline thermoplastic |
| Identification | transparent |
| General properties | Crystal clear and hard, Well resistant to aqueous bases and mineral acids |
| Processing | Injection and blow molding, Extrusion |
| Applications | Electrical engineering, Building industry (e.g. expanded polystyrene), Food industry (e.g., packaging), Consumer products for everyday use (e.g., CD covers, cloth hangers) |
| Modifications | Co-Po with PE, colored, Polymerfoam (EPS) |
| Manufacturer | Styrolution, Styron, Sabic, Nova Chemicals |
NETZSCH Measurement
| Instrument | DSC 204 F1 Phoenix® |
| Sample Mass | 12.36 mg |
| Isothermal Phases | 5 min |
| Heating/Colling Rates | 10 K/min |
| Crucible | Al, pierced lid |
| Atmosphere | N2 (40 ml/min) |
Evaluation
This example shows amorphous PS. Glass transition temperatures at 84°C (1st heating, blue, midpoint) and 88°C (2nd heating, red, also midpoint) were observed, each overlapped by RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation peaks. The RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation peaks are more distinctive in the 1st heating than in the 2nd heating. The 1st heating shows another small wave after the RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation peak, indicating the elimination of additional stress. The step heights (Δcp) were at 0.32 J/(g·K) (1st heating) and 0.29 J/(g·K) (2nd heating).