Poly Terephthalic acid Butanediol Ester, the English name polybutylece terephthalate (abbreviation PBT ), Belonging to the polyester series, by 1.4 - butanediol (1.4-Butylene glycol) and terephthalic acid (PTA ) Or terephthalate (DMT ), And made into milky white translucent to opaque, crystalline form by a kneading procedure Thermoplastic Polyester resins, together with PET, are referred to as thermoplastic polyesters, or saturated polyesters.
PBT physical and chemical properties
PBT is a milky white translucent to opaque, crystalline, thermoplastic polyester Heat resistance , Toughness, fatigue resistance, self-lubricating, low friction coefficient, Weather resistance , Water absorption Low, only 0.1%, in the wet environment still maintain a variety of physical properties (including electrical properties), electrical insulation, but the volume resistance, Dielectric loss Large. Heat-resistant water, alkali, acids, oils, but vulnerable to halogenated hydrocarbon erosion, poor hydrolysis resistance, low temperature crystallization can be quickly, good formability. Impact strength Low, forming Shrinkage So the majority of the use of glass fiber reinforced or inorganic filler modified its Tensile Strength , Bending strength Can be more than doubled, Heat distortion temperature Can be greatly improved at 140 ℃ under long-term work, glass fiber reinforced products after longitudinal and transverse shrinkage is inconsistent, easy to make products warping.
PBT processing technology
PBT can also be called thermoplastic polyester plastic, suitable for different processors to use, the general number of additives will be added, or mixed with other plastics, with the proportion of different additives can produce different specifications of the product.Because PBT has heat It is widely used in electronic appliances, auto parts, machinery, household products, etc., and PBT products with the same, with good electrical properties, water absorption, good gloss, good weather resistance, chemical resistance, PPE , PC, POM, PA, such as a total of five known as the Pan Engineering plastics.
PBT crystallization speed, the most suitable method for processingInjection molding , There are other methods of extrusion, Blow molding , Coating and a variety of secondary processing molding, pre-drying to be formed before the water content to 0.02%.
PBT injection molding process characteristics and process parameters:
PBT polymerization process is mature, low cost, easy molding process. Unmodified PBT poor performance, the practical application of PBT to be modified, of which, glass fiber reinforced modified grades account for more than 70% of PBT.
PBT process characteristics
PBT has obvious melting point, the melting point of 225 ~ 235 ℃, is a crystalline material, the crystallinity of up to 40%.
The viscosity of PBT melt is less affected by temperature than shear stress. Therefore, injection pressure has obvious effect on melt flow of PBT.
PBT in the molten state of good liquidity, low viscosity, second only to nylon, prone to forming in the 'casting' phenomenon.
PBT molding products Anisotropy PBT is easily degraded by water at high temperatures.