Gather Terephthalic acid Butanediol Esters English name polybutylece terephthalate (referred to PBT ), Are polyester series, is from 1.4-butanediol (1.4-Butylene glycol) and terephthalic acid (PTA ) Or terephthalate (DMT ) Poly condensation, and formed by the mixing process of milky white translucent to opaque, crystalline Thermoplastic Polyester resin. Collectively together with the PET thermoplastic polyester, or polyester.
PBT physicochemical properties
PBT as a milky white translucent to opaque, crystalline thermoplastic polyester having high Heat resistance , Toughness, fatigue resistance, self-lubricating, low friction coefficient, Weatherability , Water absorption Low, only 0.1%, in wet conditions remain a variety of physical properties (including electrical properties), electrical insulation, but the volume resistivity, Dielectric loss Great. Heat water, alkali, acids, oils, halogenated hydrocarbons but are vulnerable to erosion, poor resistance to hydrolysis, low temperatures can be rapidly crystallized, forming good. The disadvantage is that the gap Impact strength Low molding Shrinkage Great. Therefore, most of the glass fiber reinforced or inorganic filler modified Tensile Strength , Bending strength Can more than double, Heat distortion temperature But also a substantial increase can be long-term work at 140 ℃, glass fiber reinforced products after the longitudinal and transverse shrinkage consistent, easy to make products warpage.
PBT thermoplastic polyester can be referred to a plastic, to apply to different processing industries, the general number of additives are added, or blended with other plastics, as additives in different proportions, can produce different specifications of the products. PBT has the heat resistance, weather resistance, chemical resistance, good electrical properties, low water absorption, good gloss, widely used in electronic appliances, auto parts, machinery, household goods, etc., and PBT products, but also with PPE , PC, POM, PA and so were called the five generic Engineering Plastics.
PBT crystallization speed, the most suitable processing method forInjection Other methods include extrusion, Blow , Coating, and various secondary processing molding, molding required before pre-drying, moisture content should be reduced to 0.02%.
PBT injection molding process characteristics and process parameters setting:
PBT polymerization process maturity, low cost, easy molding. Poor performance of unmodified PBT, the practical application of PBT to be modified, wherein the glass fiber reinforced modified grades accounted for more than 70% PBT's.
Technological Characteristics of PBT
PBT has a sharp melting point, the melting point is 225 ~ 235 ℃, is a crystalline material, crystallinity up to 40%.
PBT melt viscosity is affected by temperature as shear stress so much so, in injection molding, injection pressure of PBT melt flow impact is obvious.
PBT in the molten state, good fluidity, low viscosity, second only to nylon, in the shape prone to 'cast' phenomenon.
PBT molded article Anisotropy . PBT easily degradable water at high temperatures.