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 PBT physical and chemical characteristics of PBT as a milky white translucent to opaque, crystalline thermoplastic polyester. With high heat resistance, toughness, fatigue resistance, self-lubricating, low friction coefficient, weather resistance, low water absorption of only 0.1% in wet conditions remain a variety of physical properties (including electrical properties), electrical insulation, volume resistivity, dielectric, dielectric loss. Heat water, alkali, acids, oils, but are vulnerable to erosion of halogenated hydrocarbons, poor resistance to hydrolysis, rapid crystallization at low temperatures, good formability. The disadvantage is that the notched impact strength, mold shrinkage. Therefore, most of the glass fiber reinforced or inorganic filler modified the tensile strength, bending strength can be increased more than doubled the thermal deformation temperature has significantly increased. At 140 ℃ for long glass fiber reinforced products, vertical and horizontal shrinkage inconsistent, easy to make products warpage. 
 PBT combustion identification is not easy to combustion, combustion of liquid shed, leaving the flames extinguished within 5 seconds, the PBT process PBT may be called a thermoplastic polyester plastic, used for different processing industry, generally somewhat additive, or blending with other plastics, with the proportion of different additives, can be manufactured to different specifications. PBT has a heat resistance, weather resistance, chemical resistance, good electrical characteristics, water absorption, good luster, widely used in electronic appliances, auto parts, machinery, household goods, PBT products with the PPE, the PC, POM, , PA, were called the five pan-engineering plastics. PBT crystallization speed, the most appropriate processing method for injection, other methods include extrusion, molding, blow molding, coating, and a variety of secondary processing, the need to pre-drying prior to molding, the moisture content dropped to 0.02 percent. PBT, injection molding process characteristics and process parameters setting: maturity of PBT polymerization process, low cost, easy molding. Unmodified PBT poor performance, the practical application of PBT modified, including, glass fiber reinforced modified grades accounted for 70% of PBT. Of PBT PBT of process characteristics with a sharp melting point, melting point 225 ~ 235 ° C, the crystalline material, degree of crystallinity of up to 40%. PBT melt viscosity of the influence of temperature as the shear stress is so great, in the injection molding, injection pressure of PBT melt flow is obvious. PBT good fluidity in the molten state, low viscosity, second only to nylon, and "cast" phenomenon occurs in the molding easy. PBT molding products anisotropic. PBT high temperature water easily degradable. 
 2 plastic injection 
 Selection of screw injection molding machine. Should consider the following points. ① Products with feeding amount should be controlled in the injection molding machines rated for a maximum injection amount of 30% to 80%. Should not use large injection molding machines for production of small products. ② should use a graded three-screw, the aspect ratio of 15 to 20, the compression ratio of 2.5 to 3.0. (3) should be used in self-locking nozzle, with the heating temperature control device. ④ in forming flame retardant PBT, injection molding machine parts anti-corrosion treated thickness of 3 products and mold design ① products should not be too thick, PBT, the gap is very sensitive, so the products at right angles to the transition at the arc joining . ② not modified PBT mold shrinkage of 1.7% to 2.3%, mold have Demoulding. The ③ mold need to set up to vent or exhaust ducts. The ④ gate of the caliber to be. The ⑤ mold need to set the temperature control device. The highest mold temperature must not exceed 100 ℃. ⑥ flame retardant PBT molding, the mold surface chrome-plated, to the anti-corrosion. Four raw materials to prepare the injection to be dried to moisture content control below 0.02%.