May 11 2001
Polyethylene is a whitish, semi-crystalline, and effectively opaque engineering thermoplastic which, chemically, is a very high molecular weight (3-6 million) HDPE.
As a result, its melt viscosity is extremely high and normally can only be processed by powder sintering methods. Polyethylene has excellent toughness and cut and wear resistance, and also has very good chemical resistance, slightly better than that of HDPE.
Polymer Type
Thermoplastic
Advantages
Advantages of HDPE include good low temperature impact resistance and excellent chemical resistance.
Disadvantages
Disadvantages of HDPE:
- Susceptible to stress cracking
- Has lower stiffness compared to Polypropylene
- High mould shrinkage and poor UV resistance
Applications
Pipe and pipefittings for water transportation. Toys, bowls, buckets, milk bottles, crates, tanks, containers. Film for packaging. Blown bottles for food. MDPE (Medium Density Polyethylene) is used for gas pipes and fittings.
Applications include marine quay headings, artificial joints, bearings, gears, and many "wear parts" (eg bottle handling machine components).
Typical Properties
| Property |
Value |
| Density (g/cm3) |
0.96 |
| Surface Hardness |
SD68 |
| Tensile Strength (MPa) |
32 |
| Flexural Modulus (GPa) |
1.25 |
| Notched Izod (kJ/m) |
0.15 |
| Linear Expansion (/°C x 10-5) |
12 |
| Elongation at Break (%) |
150 |
| Strain at Yield (%) |
15 |
| Max. Operating Temp. (°C) |
55 |
| Water Absorption (%) |
0.02 |
| Oxygen Index (%) |
17 |
| Flammability UL94 |
HB |
| Volume Resistivity (log ohm.cm) |
17 |
| Dielectric Strength (MV/m) |
22 |
| Dissipation Factor 1 kHz |
0.0005 |
| Dielectric Constant 1 kHz |
2.3 |
| HDT @ 0.45 MPa (°C) |
75 |
| HDT @ 1.80 MPa (°C) |
46 |
| Material. Drying hrs @ (°C) |
NA |
| Melting Temp. Range (°C) |
120 - 180 |
| Mould Shrinkage (%) |
3 |
| Mould Temp. Range (°C) |
30 - 70 |
Source : Abstracted from Plascams
For more information on Plascams please visit RAPRA Technology Ltd.