Polybutylene terephthalate (PBT)-based engineering plastics have excellent complex properties, and they can still maintain their good electrical insulation properties in high temperature or humid environments, and also have good molding processability. They are widely used in many fields such as electronic appliances. , mechanical engineering and automotive industry.
PBT is a crystalline linear saturated polyester with a regular linear structure. The benzene ring in repeating unit has high steric hindrance, and a conjugation effect is observed between benzene ring and ester group. The particle color of material is translucent to opaque milky white, which is obtained by reaction of terephthalic acid and butylene glycol ether, and molecular formula is as follows.
PBT molecular formula
Due to presence of ester bonds in chain segment, its flexibility is increased to a certain extent. In addition, chain segment rotates around two ends of single bond, which somewhat improves solubility of PBT molecules. improve.
2. PBT production process
2.1 Indirect interesterification
Firstly, dimethyl terephthalate and 1,4-BDO produce dibutyl terephthalate through a transesterification reaction, and then produce PBT through a polycondensation reaction. There are two types of indirect interesterification methods in industry: batch and continuous.
Table 2-1 Comparison of interesterification processes
2.2 Direct esterification
The direct esterification method is a direct polycondensation reaction of terephthalic acid and 1,4-BDO to form PBT. The advantage of this method is that energy consumption and equipment investment are relatively low, but reaction conditions for manufacturing process are relatively harsh and demanding. This can only be done by enterprises with a certain chemical resistance.
3. PBT Modification Technology
There are many types of PBT, including flame retardant, mixed alloy, flame retardant, glass fiber reinforced, glass fiber reinforced, etc.
3.1 Extended modification
Adding glass fiber to PBT can not only maintain PBT's inherent good processability and chemical resistance, but also improve physical properties of PBT, reduce PBT's notch sensitivity, and improve HDT.
Improved PBT GF
3.2 Fireproof modification
Common flame retardants commonly used in PBT include bromine compounds, phosphides and Sb2O3. Most flame retardants use decabromodiphenyl ether and Sb2O3 systems. The disadvantage is that flame retardants are easily deposited on surface, which not only adversely affects its electrical properties, but also spoils appearance of product. .
3.3 PBT alloy
PBT-added alloy refers to mixing PBT resin with other resins to achieve effective modification of PBT engineering plastics, effectively improve notched toughness, improve warpage deformation caused by molding shrinkage, and can improve hot water resistance. Common PBT blend alloys: PBT/ABS, PBT/polyolefin, PBT/PET, etc.
Fourth. Scope of engineering plastics PBT
PBT engineering plastics are mainly used in three types of parts: various parts of car exterior, various parts of car interior, and electrical parts of car.
4.2 Energy saving lamps
In this field, PBT engineering plastics are mainly used to produce energy-saving lamp holders, and their application characteristics include aging resistance, heat resistance, and fire resistance up to UL 94 V-0 level.
4.3 Coil coil.
PBT engineering plastics are mainly used for production of coil spools, and their performance characteristics are dielectric strength, heat resistance, toughness, strength and fire resistance.
Disclaimer: All text/images and other manuscripts marked "Source: XXX" are intended to provide additional information and facilitate industry discussion under this heading and do not constitute agreement with them. The content of article is for reference only. If there is any infringement, please contact us to have it removed. All texts/figures and other manuscripts in which author is indicated at beginning of article are originals with this heading number, if necessary, it is necessary to obtain authorization with this heading number.