General Properties
Short Name:
Name:
POM (homo)
Polyoxymethylene (Homopolymer)
Polyoxymethylene, also designated POM-H, belongs to the classical engineering plastics. It has a large linear structure and is mostly produced from formaldehyde by means of polmyerization. POM as a homopolymer is mostly highly crystalline; the degree of crystallinity is typically between approx. 64% and 77%.
Structural Formula
Properties
| Glass Transition Temperature | -85 to -75°C |
|---|---|
| Melting Temperature | 175 to 190°C |
| Melting Enthalpy | 316 to 335 J/g |
| Decomposition Temperature | 365 to 390°C |
| Young's Modulus | 2600 to 3200 MPa |
| Coefficient of Linear Thermal Expansion | 160 to 180 *10-6/K |
| Specific Heat Capacity | 1.48 to 1.50 J/(g*K) |
| Thermal Conductivity | 0.30 to 0.37 W/(m*K) |
| Density | 1.39 to 1.43 g/cm³ |
| Morphology | Semi-crystalline polymer |
| General properties | Good stiffness, toughness and strength. Low humidity absorption. Good resistance to creeping and fatigue. High recovery capability. Good sliding properties. Food-compatible |
| Processing | Injection molding, extrusion, blow molding |
| Applications | Automobile industry. Instrument and apparatus engineering. Electrical/electronics industry. Food industry. Household goods |
NETZSCH Measurement
| Instrument | DSC 204 F1 Phoenix® |
| Sample Mass | 10.88 mg |
| Isothermal Phase | 7 min |
| Heating/Colling Rates | 10 K/min |
| Crucible | Al, pierced lid |
| Atmosphere | N2 (40 ml/min) |
Evaluation
The high degree of crystallinity of POM-H is reflected in the above DSC curve. It is dominated by a distinctive melting effect at 183°C (1st heating, blue, peak temperature) and 181°C (2nd heating, red, also peak temperature) as well as a quite small glass transition step at -77°C (midpoint). The height of the glass transition step Δcp is a measure for the amorphous content in the material while the melting enthalpy (here 195 J/g in the 2nd heating) is related to the crystalline content (in this case 62% – based on a theoretical enthalpy of a 100% crystalline material of 316 J/g); the larger the melting enthalpy, the larger the crystalline content. For semi-crystalline polymers, the magnitude of the glass transition and the height of the melting enthalpy are inversely proportional (i.e., if the heat of fusion increases, the glass transition step gets smaller and vice versa).