Guangzhou Donoyo Chemical Co., Ltd

  Injection molding PC/ABS blends can present specific challenges. Silver streaks or silver marks, appearing as silver-white lines along the flow direction, are primarily caused by trapped gases—often from moisture in the material, entrapped air, or pyrolysis gases from overheating. Solutions begin with thorough material drying, followed by process adjustments and ensuring adequate mold venting. Flow marks, surface patterns from a cooling melt front, are addressed by increasing melt temperature to improve fluidity, alongside adjustments to mold temperature and injection speed. Shrinkage and voids (sinks or dents) result from insufficient packing or cooling issues. Corrective measures include raising mold and melt temperatures, increasing holding pressure and time, and optimizing gate design. Warpage and deformation stem from internal stress or uneven cooling/shrinkage, remedied by process adjustments like longer cycles and lower melt temps, as well as design modifications such as adding ribs and uniform wall thickness. Jetting, caused by a fast-moving melt stream "shooting" into the cavity, is solved by increasing melt/nozzle temperature, reducing injection speed, raising mold temperature, or modifying gate design. Pitting or surface defects from poor additive dispersion require checking material batches, ensuring proper drying, and potentially adding a dispersant or back pressure. Delamination or peeling is often related to high shear stress causing flow separation, potentially exacerbated by compatibility issues between PC and ABS. Solutions involve verifying material formulation (compatibilizer use), increasing melt and mold temperatures to reduce shear, and avoiding restrictive gates or high-friction mold surfaces.

  Plastic alloys are high-performance, functional, or specialized materials created through the physical blending or chemical grafting of different polymers. These compounds enhance or modify the properties of base resins and can reduce costs, making them indispensable in automotive, electronics, precision instruments, and construction. They represent one of the most dynamic and rapidly growing sectors within the plastics industry. While general-purpose alloys based on PVC, PE, PP, and PS remain widely used, the focus in advanced markets has shifted towards higher-value engineering plastic alloys. These typically involve blends where key engineering resins like PC (Polycarbonate), PBT, PA (Nylon), POM (Acetal), PPO/PPE, and PTFE form the primary matrix, including modifications of ABS. Accelerating the development and application of these sophisticated materials is crucial for maintaining competitiveness in the global plastics sector.

  Processing PBT requires precise control. The melt temperature range is narrow, typically between 250-260°C; temperatures below 240°C can lead to freezing, while exceeding 270°C risks thermal degradation. A barrel temperature profile maintaining around 210°C is recommended, with a mold temperature of 60-80°C. Injection pressure should be set between 100-140 MPa, with holding pressure at 50-60% of the injection pressure. A back pressure of 5-10 MPa helps avoid excessive frictional heat. High injection speed is crucial due to PBT's rapid solidification and crystallization rates, preventing premature cooling in the flow path. Adequate mold venting is essential to avoid air traps and potential burning. Screw speed should correspond to a maximum linear speed of 0.5 m/s. The dosing stroke is recommended at (0.5-3.5)D, and the total residence time in the barrel should not exceed 5 minutes to prevent thermal degradation. Material must be pre-dried at 120°C for 4 hours. For regrind usage, flame-retardant grades allow up to 10% recycled content if properly dried, while non-FR grades can incorporate up to 20%. Shrinkage largely depends on mold temperature, ranging from 1.4%-2.0% for unfilled PBT. Adding 30% glass fiber reduces shrinkage to 0.4%-0.6%. Gate design should favor direct or pinpoint gates for glass-filled grades, ensuring balanced filling. Hot runner systems require closed-loop temperature control. Standard screws with non-return valves and open nozzles are suitable. For machine downtime, the heater should be switched off and the barrel purged.

  Selecting materials for charging gun connectors involves evaluating several options, including PET, PBT, and PA (nylon). While PA (polyamide) reinforced with glass fiber and flame retardant (PA+GF+FR) is often a primary choice for many customers, PBT+FR becomes a preferred alternative when dimensional stability and minimal shrinkage are critical. PET also serves as a viable material selection option. Charging gun materials must pass rigorous tests for mechanical performance, temperature resistance, flame retardancy (FR), and electrical properties. PBT (Polybutylene Terephthalate), a thermoplastic polyester, is particularly well-suited for plugs and sockets due to its excellent mechanical strength, high electrical insulation, good thermal properties, strong weather resistance, and cost-effectiveness. For the connection base, the primary material selection schemes are PA+GF+FR or PBT+FR. When enhanced strength and rigidity are needed, a composite like PBT with 15-30% glass fiber and flame retardant (PBT+GF+FR) is considered.