Performance and application of PBT

Performance and application of PBT

Polybutylene terephthalate (PBT) engineering plastics have excellent comprehensive properties, can still maintain its good electrical insulation properties in higher temperatures or humid environments, and has good molding processability, and has been increasingly widely used in many fields such as electronic appliances, mechanical equipment and automotive industry.

1.PBT

PBT is a crystalline linear saturated polyester with regular linear structure. The benzene ring in the repeating unit has a large steric hindrance, and the benzene ring and ester group have conjugation effect. The color of the material particles is translucent to opaque milky white, which is prepared by the reaction of terephthalic acid and butanediol ester, and the molecular formula is as follows.

Due to the existence of ether bonds in the chain segment, its compliance is increased to a certain extent. In addition, the chain segment rotates around the two ends of the single bond, which improves the solubility of PBT molecules to a certain extent.

2. PBT production process

2.1 Indirect transesterification

First, dimethyl terephthalate and 1, 4-BDO are used to produce dibutyl terephthalate by transesterification, and then PBT is produced by polycondensation. There are two kinds of indirect transesterification methods in industry: intermittent and continuous process.

2.2 Direct esterification method

Direct esterification method is the direct polycondensation reaction of terephthalic acid and 1, 4-BDO to produce PBT. The advantage of this method is that energy consumption and equipment investment are relatively low, but the reaction conditions of the production process are relatively harsh, and enterprises with certain chemical strength are required to achieve it.

Third, PBT modification technology

There are many types of PBT, including flame retardant type, blended alloy grade, glass fiber reinforced flame retardant type and glass fiber reinforced type.

3.1 Enhanced Modification

Adding glass fiber to PBT can not only maintain the inherent good processability and chemical resistance of PBT, but also improve the physical properties of PBT, and reduce the notch sensitivity of PBT, and improve the HDT.

3.2 Flame retardant modification

Generally, the commonly used flame retardants for PBT are bromine compounds, phosphide and Sb2O3. Most flame retardants use decabromodiphenyl ether and Sb2O3 system, the disadvantage is that the flame retardants are easy to precipitate on the surface, which not only has an adverse effect on its electrical characteristics, but also causes damage to the appearance of the product. At present, the application of halogen-free flame retardants in PBT is increasingly concerned.

3.3 PBT blend alloy

PBT blending alloy refers to the blending of PBT resin with other resins to achieve effective modification of PBT engineering plastics, effectively improve the notched impact strength, improve the warping deformation caused by forming shrinkage, and enhance the heat resistance water. Common PBT blend alloys are as follows: PBT/ABS, PBT/polyolefin, PBT/PET, etc.

4. PBT engineering plastics application field

4.1 Automobile Industry

PBT engineering plastics are mainly used in three types of parts: all kinds of automotive external parts; Various parts and components of automobile interior; Automotive electrical parts.

4.2 Energy-saving lamps

In this field, PBT engineering plastics are mainly used for the production of energy-saving lamp heads, which show application characteristics of aging resistance, heat resistance and flame retardant class up to UL 94 V-0.

4.3 Coil skeleton.

PBT engineering plastics are mainly used in the production of coil frames, which show the application characteristics of dielectric strength, heat resistance, toughness, strength and flame retardant.