ABS, commonly known as acrylonitrile butadiene styrene, is a copolymerization of acrylonitrile, butadiene and styrene. Because the share of the three monomers is different, they can have different functions and melting temperatures. If ABS with active function is blended with other plastic moulding machines or additives, it can be extended to ABS with different uses and functions, such as impact resistance, heat resistance, flame retardant, bright, enhanced and plating.

The activity of ABS is between PS and PC. Its activity is related to injection temperature and pressure. The influence of injection pressure is slightly greater. Therefore, higher injection pressure is often used to reduce the melt viscosity and advance the filling function.

1. Treatment of plastics

ABS absorbency is about 0.2%-0.8%. For general grade ABS, bake for 2-4 hours with oven at 80-85 C or with hopper at 80 C for 1-2 hours before processing. For heat-resistant ABS with PC components, the drying temperature should be properly raised to 100 C. The specific drying time can be recognized by air extrusion.

The proportion of batch can not exceed 30%, and the batch can not be used in electroplating ABS.

2. Selection of Injection Molding Machine

The standard injection moulding machine of Huameida (screw length-diameter ratio 20:1, shrinkage ratio more than 2, injection pressure greater than 1500bar) can be selected. Assuming that color masterbatch or product appearance requirements are high, screw with small first-order diameter can be selected. The clamping force is recognized as 4700-6200t/m2, depending on the plastics grade and product requirements.

3. Mold and gate planning

The temperature of the die can be set to 60-65 C. The diameter of the runner is 6-8 mm. The gate width is about 3mm, the thickness is the same as the product, and the gate length should be less than 1mm. The exhaust hole is 4-6 mm wide and 0.025-0.05 mm thick.

4. Melt temperature

It can be accurately judged by the method of air-to-air injection. The melt temperature varies with the grade. It is advocated that the melt temperature should be set as follows:

Anti-impact grade: 220-260 C, 250 C is the best.

Electroplating grade: 250 C-275 C, 270 C is the best.

Heat-resistant grade: 240 - 280 C, 265 - 270 C is the best.

Flame Retardant Grade: 200 - 240 C, 220 - 230 C is the best.

Tongming Class: 230 C-260 C, 245 C is the best.

Glass Fiber Reinforcement Grade: 230-270 C

For products with high exterior requirements, higher melt temperature and die temperature should be selected.

5. Injection speed

Fire-proof grade should be used slowly and heat-resistant grade should be used quickly. If the exterior requirement of the product is high, the injection speed control of high-speed and multi-stage injection moulding should be used.

6, back pressure

In general, the lower the back pressure, the better. The commonly used back pressure is 5bar. The dyeing material needs a higher back pressure to make the mixing uniform.

7. Stay Time

The residence time of ABS in the melt drum should not exceed 5-6 minutes at 265 C. Flame retardant time is shorter. If shutdown is needed, the setting temperature should be lowered to 100 C, and then the melt drum should be cleaned up with general-purpose ABS. After cleaning, the mixture should be put into cold water to avoid further differentiation. If ABS material needs to be changed from other plastics, PS, PMMA or PE should be used to clean up the melt rubber cylinder. Some ABS products have no problem when they are just demoulded. They will discolor after a period of time. This may be caused by overheating or plastic staying too long in the melt drum.

8. Post-treatment of products

Generally, ABS products do not need post-treatment, as long as electroplated products need to be baked (70-80 C, 2-4 hours) to passivate the appearance trace, and electroplated products can not use demoulding agent, products should be immediately packaged after removal.

9. Matters needing special attention in moulding

There are several grades of ABS (especially flame retardant grade), after plasticization, the melt has a great adhesion to the screw surface, and will differentiate over time. When the above situation occurs, it is necessary to pull out the screw homogenization section and tighten the screw, and clean the screw regularly with PS, etc.