May 26 2003
Background
Polybutylene Terephthalate (PBT) is a semi-crystalline, white or off-white polyester similar in both composition and properties to polyethylene terephthalate (PET).
It has somewhat lower strength and stiffness than polyethylene terephthalate, PET, is a little softer but has higher impact strength and very similar chemical resistance. As Polybutylene Terephthalate (PBT) crystallises more rapidly than PET, it tends to be preferred for industrial scale moulding.
Applications
Applications of Polybutylene Terephthalate (PBT) include electrical and automotive components (including “under-bonnet”) and power tool casings.
Key Properties
The key properties of Polybutylene Terephthalate ( PBT ) are tabulated below.
Table 1. Key properties
| Chemical Resistance |
| Acids - dilute |
Good |
| Alcohols |
Good |
| Alkalis |
Poor-Good |
| Aromatic hydrocarbons |
Good |
| Greases and Oils |
Good |
| Ketones |
Good |
| Electrical Properties |
| Dielectric constant @ 1 kHz |
3.2 |
| Dielectric strength ( kV.mm-1 ) |
20 |
| Dissipation factor @ 1 kHz |
0.002 |
| Volume resistivity ( Ohm.cm ) |
1015 |
| Mechanical Properties |
| Elongation at break ( % ) |
250 |
| Hardness – Rockwell |
M70 |
| Izod impact strength ( J.m-1 ) |
60 |
| Tensile modulus ( GPa ) |
2 |
| Tensile strength ( MPa ) |
50 |
| Physical Properties |
| Density ( g.cm-3 ) |
1.31 |
| Limiting oxygen index ( % ) |
25 |
| Water absorption - over 24 hours ( % ) |
0.1 |
| Thermal Properties |
| Heat-deflection temperature - 0.45 MPa ( °C ) |
150 |
| Heat-deflection temperature - 1.8 MPa ( °C ) |
60 |
| Upper working temperature ( °C ) |
120-? |
| Properties Polybutylene Terephthalate Monofilament |
| Property |
|
Value |
| Density |
g.cm-3 |
1.31 |
| Extension to break |
% |
26 |
| Shrinkage @ 100 °C |
% |
3 |
| Tensile strength |
GPa |
0.5 |
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