Polybutylene Terephthalate

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Polybutylene Terephthalate (PBT)

Polybutylene terephthalate (PBT), a strong and highly crystalline synthetic resin, produced by the polymerization of butanediol and terephthalic acid. PBT is similar in structure to polyethylene terephthalate (PET) – the difference being in the number of methylene (CH2) groups present in the repeating units of the polymer molecules. The mechanical properties of the two materials are also similar.

However, PBT has a lower melting point (223 °C [433 °F]) than PET (255 °C [491 °F]), so it can be processed at lower temperatures. This property, combined with its excellent flow when molten and its rapid crystallization upon cooling, makes PBT highly suitable for injection-molding into solid parts. Either unmodified or reinforced with glass fibers or mineral fillers, it is used in numerous applications, especially electrical and small machine parts, owing to its excellent electrical resistance, surface finish, and toughness.

PBT lends rigidity and thermoplastic properties to a synthetic rubber known as copolyester elastomer.

Chemical Resistance
Acids – dilute	Good
Alcohols	Good
Alkalis	Poor-Good
Aromatic Hydrocarbons	Good
Greases and Oils	Good
Ketones	Good

Electrical Properties
Dielectric constant @1kHz	3.2
Dielectric strength ( kV.mm-1)	20
Dissipation factor @ 1kHz	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 – 0.45MPa (°C )	150
Heat-deflection temperature – 1.8MPa (°C )	60
Upper working temperature (°C )	120

Member Testimonials

"ONGC - Oil and Natural Gas Corporation Limited" - Our complex drilling application where Shaft was eccentric and application was robust & muddy. Replacement was never easy. Mech Spares designed Oil seals resolved difficulty. This gave a complete joy to my maintenance team.

ONGC – Oil and Natural Gas Corporation Limited

"Mr Mohammed Al Duaigy" of (Kuwait National Petroleum Company) : We tried several diaphragms from renown worldwide Rubber manufacturing companies. We found Mech Spares technical know how and product to be of great durability and lasted 3 times more then anticipated. They have accurate understanding of there products.

Kuwait National Petroleum Company

"McCafferty BM Design Ltd, KENT United Kingdom" - Most of the O rings manufacturing company suggested to use larger diameter and expensive elastomers. We learnt with Mech Spares that elastomer being weaker compare to metal and alloys and needs appropriate back up for high pressure or high vacuum applications. Further not necessary the most expensive elastomer is the best for all applications. We trust Mr Nilesh chodhari completely for all our O rings designing applications.

McCafferty BM Design Ltd, KENT United Kingdom

"Dr. A. Singh" of BARC: The electric Insulation mat manufactured by MECH SPARES as per IS 15624 tested at ERTL and found to withstand 40 Kv and still didn't tear. We have been using since 5 years and still didn't generate any fatigue. They arranged bulk delivery in short period.

Bhabha Atomic Research Centre ( BARC )

"Tata Steel" - One of our old machines started making loud noise and disturbed the entire village. We were compelled to stop the machines which lead to huge production loss. With the help of Mech Spares designed bellows in two part we could retain the lubrication and eliminate the noise.

Tata Steel

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