ABS, commonly known as acrylonitrile butadiene styrene, is a copolymer of three monomers: acrylonitrile-butadiene-styrene. Due to different proportions of the three monomers, different properties and melting temperatures can be achieved. If ABS with flow properties is blended with other plastics or additives, it can be expanded to ABS with different uses and properties, such as impact-resistant grade, heat-resistant grade, flame-retardant grade, transparent grade, reinforced grade, electroplating grade, etc.
Fluidity of ABS is between PS and PC. Its fluidity is related to injection temperature and pressure. Injection pressure has a slightly greater impact. Therefore, higher injection pressure is often used during molding to reduce melt viscosity and improve mold filling performance.

 

Water absorption rate of ABS is about 0.2%-0.8%. For general-grade ABS, dry it in an oven at 80-85℃ for 2-4 hours or in a drying hopper at 80℃ for 1-2 hours before processing. For heat-resistant ABS containing PC components, drying temperature should be appropriately increased to 100℃, and specific drying time can be determined by extruding it into air.
Proportion of recycled materials cannot exceed 30%, and recycled materials cannot be used in electroplating grade ABS.

Ramada's standard injection molding machine can be used (screw length-to-diameter ratio 20:1, compression ratio greater than 2, injection pressure greater than 1500bar). If masterbatch is used or product appearance requires high material, a screw with a smaller diameter can be selected. Clamping force is determined according to 4700-6200t/m2, which depends on plastic grade and product requirements.

Mold temperature can be set to 60-65℃. Flow channel diameter is 6-8mm. Gate width is about 3mm, thickness is same as product, and gate length should be less than 1mm. Exhaust hole is 4-6mm wide and 0.025-0.05mm thick.

It can be accurately determined by empty injection method. Different grades have different melt temperatures. Recommended settings are as follows:
Impact resistance grade: 220℃-260℃, preferably 250℃
Electroplating grade: 250℃-275℃, 270℃ is better
Heat resistance grade: 240℃-280℃, preferably 265℃-270℃
Flame retardant grade: 200℃-240℃, preferably 220℃-230℃
Transparency level: 230℃-260℃, preferably 245℃
Glass fiber reinforced grade: 230℃-270℃
For products with high surface requirements, use higher melt temperature and mold temperature.

Use slow speed for fire protection grade and fast speed for heat resistance grade. If product surface requirements are high, high-speed and multi-stage injection molding injection rate control should be used.

Generally speaking, the lower back pressure, the better. Commonly used back pressure is 5 bar. Dyeing materials need higher back pressure to make color mixture even.

At a temperature of 265℃, residence time of ABS in melt barrel cannot exceed 5-6 minutes at most. Flame retardant time is shorter. If machine needs to be shut down, set temperature should be lowered to 100℃ first, then melt barrel should be cleaned with general-grade ABS. Cleaned mixture should be placed in cold water to prevent further decomposition. If you need to change from other plastics to ABS materials, you must first clean melt barrel with PS, PMMA or PE. Some ABS products have no problem when they are first demoulded, but will change color after a period of time. This may be caused by overheating or plastic staying in melt barrel for too long.

Generally, ABS products do not require post-processing. Only electroplated grade products need to be baked (70-80℃, 2-4 hours) to passivate surface traces. Products that require electroplating cannot use release agents, and products must be packaged immediately after being taken out. .

There are several grades of ABS (especially flame retardant grade). After plasticization, melt has a strong adhesion to screw surface and will decompose after a long time. When above situation occurs, it is necessary to pull out and wipe homogenizing section and compression of screw, clean screw regularly with PS, etc.