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Injection process, plastic composition and application conditions (1)

Update:28 Mar 2020

Due to the wide variety of plastic products on the mark […]

Due to the wide variety of plastic products on the market today, different brands, but what are the truly safe and reliable food-grade plastics? Today's plastic knife and fork small braids take everyone to understand the injection molding process, plastic composition and application conditions.
PC / ABS polycarbonate and acrylonitrile-butadiene-styrene copolymers and mixtures
1. Typical applications: computer and commercial machine housings, electrical equipment, lawn and garden machinery, automotive parts dashboards, interior decoration, and wheel covers).
2. Injection mold process conditions: Drying: Drying before processing is necessary. The humidity should be less than 0.04%, and the recommended drying conditions are 90 to 110C for 2 to 4 hours. Melting temperature: 230 ~ 300C. Mold temperature: 50 ~ 100C. Injection pressure: depends on the plastic part. Injection speed: as high as possible.
3. Chemical and physical characteristics: PC / ABS has the comprehensive characteristics of both PC and ABS. For example, the easy processing characteristics of ABS and the excellent mechanical characteristics and thermal stability of PC. The ratio of the two will affect the thermal stability of the PC / ABS material. PC / ABS hybrid materials also show excellent flow characteristics. The shrinkage is about 0.5%.

Mixture of PC / PBT polycarbonate and polybutylene terephthalate
1. Typical applications: gearboxes, automotive bumpers, and products that require chemical resistance and corrosion resistance, thermal stability, impact resistance, and geometric stability. Injection mold process conditions: drying treatment: 110 ~ 135C, about 4 hours of drying treatment is recommended. Melting temperature: 235 ~ 300C. Mold temperature: 37 ~ 93C. Chemical and physical characteristics: PC / PBT has the comprehensive characteristics of both PC and PBT, such as the high toughness and geometric stability of PC, and the chemical, thermal and lubricating properties of PBT. The shrinkage is about 0.5%.
2. Typical applications of PE-HD high-density polyethylene: refrigerator containers, storage containers, household kitchen utensils, sealing covers, etc.
3, injection mold process conditions: dry: if stored properly, there is no need to dry. Melting temperature: 220 ~ 260C. For materials with larger molecules, it is recommended that the melting temperature range be between 200 and 250C. Mold temperature: 50 ~ 95C. Plastic parts with wall thicknesses below 6mm should use higher mold temperatures, and plastic parts with wall thicknesses above 6mm should use lower mold temperatures. The cooling temperature of the plastic parts should be uniform to reduce the difference in shrinkage. For the optimal processing cycle time, the diameter of the cooling cavity should be not less than 8mm, and the distance from the mold surface should be within 1.3d (here "d" is the diameter of the cooling cavity). Injection pressure: 700 ~ 1050bar. Injection speed: High-speed injection is recommended. Runner and gate: The runner diameter is between 4 and 7.5mm, and the runner length should be as short as possible. Various types of gates can be used, and the gate length should not exceed 0.75mm. Particularly suitable for using hot runner molds.
4. Chemical and physical properties: The high crystallinity of PE-HD leads to its high density, tensile strength, high temperature distortion temperature, viscosity and chemical stability. PE-HD is more resistant to penetration than PE-LD. PE-HD has low impact strength. The characteristics of PH-HD are mainly controlled by density and molecular weight distribution. PE-HD suitable for injection molding has a narrow molecular weight distribution. For the density of 0.91 to 0.925 g / cm3, we call it the first type of PE-HD; for the density of 0.926 to 0.94 g / cm3, we call it the second type of PE-HD; for the density of 0.94 to 0.965 g / cm3 , Called the third type of PE-HD. The material has good flow characteristics with MFR between 0.1 and 28. The higher the molecular weight, the worse the flow characteristics of PH-LD, but the better the impact strength. PE-LD is a semi-crystalline material with a high shrinkage after molding, ranging from 1.5% to 4%. PE-HD is prone to environmental stress cracking. Cracking can be reduced by using materials with very low flow characteristics to reduce internal stresses. PE-HD is easy to dissolve in hydrocarbon solvents when the temperature is higher than 60C, but its anti-solubility is better than PE-LD.

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