Apr 11 2003
Background
Polyethylene Naphthalateis a polyester that is chemically quite similar to polyethylene terephthalate but which is more temperature resistant. So far available only as biaxially oriented and heat stabilised films, they are semi-crystalline and colourless, either crystal clear or slightly hazy (the latter are available from Goodfellow stock).
Compared to their polyethylene terephthalate equivalents, they start to shrink significantly at 190 °C rather than 150 C and are certified for long term electrical use at 155 °C rather than 105/130 °C. Their tensile strengths are similar, but the modulus of Polyethylene Naphthalate is higher - say 25% at ambient temperatures but several times higher in the 100-150 °C region.
They also have better UV resistance and barrier properties and are more resistant to hydrolysis in alkaline or very hot aqueous conditions. Polyethylene Naphthalate films are, however, more expensive and have a lower flex life.
Applications
Applications for the Polyethylene Naphthalate films are mainly in the electrical and electronic areas.
Properties
The key properties ofPolyethylene Naphthalateare tabulated below.
Table 1.Key properties
| Chemical Resistance |
| Acids - concentrated |
Poor - Good |
| Acids - dilute |
Good |
| Alcohols |
Good |
| Alkalis |
Poor - Good |
| Aromatic hydrocarbons |
Good |
| Greases and Oils |
Good |
| Ketones |
Good |
| Electrical Properties |
| Dielectric constant @ 1 MHz |
3.2 @ 10 kHz |
| Dielectric strength ( kV.mm-1) |
160 @ 0.075 mm |
| Dissipation factor @ 1 MHz |
0.0048 @ 10 kHz |
| Surface resistivity ( ohm/sq ) |
1014 |
| Volume resistivity ( ohm.cm ) |
1015 |
| Mechanical Properties |
| Coefficient of friction |
0.27 - biax film |
| Elongation at break ( % ) |
60 - biax film |
| Tensile modulus ( GPa ) |
5-5.5 - biax film |
| Tensile strength ( MPa ) |
200 - biax film |
| Physical Properties |
| Density ( g.cm-3) |
1.36 |
| Flammability |
VTM-2 - UL94, 0.075 mm |
| Optical transmission ( % ) |
84 @ 0.075 mm |
| Thermal Properties |
| Coefficient of thermal expansion ( x10-6K-1) |
20-21 - biax film |
| Upper working temperature ( °C ) |
155 |
| Properties Polyethylene naphthalate Film |
| Property |
|
Value |
| Shrinkage |
% |
0.8 – 5 min @ 190 °C |
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