Typical applications of
PBT -polybutylene terephthalate: household appliances (food processing blades, vacuum cleaner components, electric fans), electrical components (switches, motor casings, mobile phone covers, fuse boxes, computer radiators, Computer keyboard keys, etc., automotive industry (heatsink windows, body panels, wheel covers, door and window components, etc.).
Mold temperature: 40 to 60 C for unreinforced materials. The cooling channels of the mold are well designed to reduce the bending of the plastic parts. The loss of heat must be fast and even. It is recommended that the mold cooling channel has a diameter of 12 mm. Injection pressure: medium (up to 1500 bar).
Injection speed: The injection speed should be as fast as possible (because PBT solidifies quickly). Runners and gates: Round runners are recommended to increase pressure transfer (empirical formula: runner diameter = plastic thickness + 1.5mm). Various types of gates can be used. Hot runners can also be used, but care should be taken to prevent leakage and degradation of the material. The gate diameter should be between 0.8 and 1.0*t, where t is the thickness of the plastic part. If it is a submerged gate, the recommended minimum diameter is 0.75mm.
Chemical and physical properties:
PBT is one of the toughest engineering thermoplastics. It is a semi-crystalline material with excellent chemical stability, mechanical strength, electrical insulation properties and thermal stability. These materials are very stable under a wide range of environmental conditions. PBT has a weak hygroscopic property.
The tensile strength of the non-reinforced PBT is 50 MPa, and the tensile strength of the PBT of the glass additive type is 170 MPa. Excessive glass additives will cause the material to become brittle. PBT; crystallization is very rapid, which will cause bending deformation due to uneven cooling. For materials with a glass additive type, the shrinkage in the process direction can be reduced, but the shrinkage in the vertical direction to the process is essentially indistinguishable from that of the conventional material.
Generally, the material shrinkage rate is between 1.5% and 2.8%. Materials containing 30% glass additives shrink between 0.3% and 1.6%. The melting point (225% C) and the high temperature deformation temperature are both lower than the PET material. The Vicat softening temperature is approximately 170C. The glass transition temperature (glasstrasitiotemperature) is between 22C and 43C. Due to the high crystallization rate of PBT, its viscosity is very low, and the cycle time of plastic parts processing is generally low.
Injection molding process conditions:
Drying treatment: This material is easily hydrolyzed at high temperatures, so drying treatment before processing is very important. It is recommended to dry in air at 120C, 6~8 hours, or 150C for 2~4 hours. The humidity must be less than 0.03%. If drying with a hygroscopic dryer, the recommended conditions are 150C, 2.5 hours?. Melting temperature: 225~275C, recommended temperature: 250C.
