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Polybutylene Terephthalate (PBT)/ 30% Glass Fibre Reinforced - Properties and Applications - Supplier Data by Goodfellow

Polybutylene Terephthalate (PBT) is a white or off-white semi-crystalline polyester similar in both properties and composition to polyethyleneterephthalate (PET). When compared to PET, it has somewhat lower stiffness and strength, is slightly softer but has very similar chemical resistance and higher impact strength. As it crystallizes more quickly than PET, it is usually favoured for industrial scale moulding.


The reinforcement of Polybutylene Terephthalate ( PBT ) with glass fibre results in large increases in strength, stiffness and heat distortion temperatures without loss of impact strength. The normal colour is off-white.


Applications of Polybutylene Terephthalate ( PBT )include those for unfilled polybutylene terphthalate (PBT) together with high power lighting components, ignition rotors, distributor caps etc.

Other applications include automotive and electrical components (including "under-bonnet") and power tool casings.

Key Properties

The key properties of Polybutylene Terephthalate ( PBT ) / 30% Glass Fibre Reinforced are tabulated below.

Table 1. Key properties

Chemical Resistance
Acids – concentrated Good
Acids – dilute Good
Alcohols Very Good
Alkalis Poor
Aromatic hydrocarbons Good
Greases and Oils Good
Halogens Good
Ketones Very Good
Electrical Properties
Dielectric constant @ 1 MHz 4
Dielectric strength ( ) 20
Dissipation factor @ 1 kHz 0.002
Volume resistivity ( ) 2x1014
Mechanical Properties
Elongation at break ( % ) 2
Hardness – Rockwell M93
Izod impact strength ( J.m-1 ) 70
Tensile modulus ( GPa ) 12
Tensile strength ( MPa ) 185
Physical Properties
Density ( ) 1.63
Flammability Self Extinguishing
Limiting oxygen index ( % ) 23
Water absorption - over 24 hours ( % ) 0.15 - 0.35
Thermal Properties
Coefficient of thermal expansion ( x10-6 K-1 ) 20 - 70
Heat-deflection temperature - 0.45 MPa (°C ) 220
Heat-deflection temperature - 1.8 MPa (°C ) 200
Thermal conductivity ( W.m-1.K-1 ) 0.24 @ 23
Upper working temperature ( °C ) 120 - 200


About Goodfellow

Goodfellow supplies metals, ceramics and other materials to meet the research, development and specialist production requirements of science and industry worldwide.

The Goodfellow group consists of four companies. The main administration, research laboratories and workshops are located at the Company's headquarters in Cambridge, England. The subsidiary offices in America, France and Germany provide an additional service.


  1. vijay adhali vijay adhali India says:

    what about the coefficient of friction

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