Introduction, characteristics, application, injection molding process of ABS plastic raw materials

Time:2023-08-29 19:18:23 / Popularity: / Source:

01 Introduction of ABS plastic raw materials

ABS resin is acrylonitrile-butadiene-styrene copolymer. ABS plastic raw material is light yellow granular or beaded opaque resin, which is a bulk general-purpose resin. ABS is an engineering plastic after being modified (adding additives or alloys) to improve its performance. ABS alloy has a large output, a variety of types and a wide range of applications, and is main modified plastic.

02 Characteristic

ABS plastic is synthesized from three chemical monomers, acrylonitrile, butadiene and styrene. Each monomer has different properties: acrylonitrile has high strength, thermal stability and chemical stability; butadiene has toughness and impact resistance; styrene has easy processing, high finish and high strength. From a morphological point of view, ABS is an amorphous material. Polymerization of three monomers produces a terpolymer with two phases, a continuous phase of styrene-acrylonitrile and a dispersed phase of polybutadiene rubber. Characteristics of ABS plastic raw materials mainly depend on the ratio of three monomers and molecular structure in two phases.
injection molding process 

03 Injection molding process

Fluidity of ABS is between PS and PC, its fluidity is related to injection temperature and pressure, of which injection pressure has a slightly greater influence, so 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, use an oven at 80-85℃ for 2-4 hours or use a drying hopper at 80℃ for 1-2 hours before processing. For heat-resistant grade ABS containing PC components, drying temperature should be appropriately increased to 100℃, and specific drying time can be determined by extruding in the air.
Proportion of recycled materials cannot exceed 30%, and use of recycled materials cannot be used in electroplating-grade ABS. Standard injection molding machine of Ramada can be selected as injection molding machine (screw length-diameter ratio is 20:1, compression ratio is greater than 2, and injection pressure is greater than 1500bar). If color masterbatch is used or appearance of product is required to be high, a screw with a smaller diameter can be used. Clamping force is determined according to 4700-6200t/m2, which depends on plastic grade and product requirements. Mold and gate design: mold temperature can be set to 60-65℃. Diameter of runner is 6-8mm. Gate width is about 3mm, thickness is same as product, and gate length is less than 1mm. Exhaust hole is 4-6mm wide and 0.025-0.05mm thick.
Mold temperature 40~80℃
Injection pressure 100~150MPa (1000~1500bar)
Holding pressure: Holding time is relatively short, 30%~60% of injection pressure.
Melt temperature 220~250℃
Back pressure 5~15MPa (50~150bar); if back pressure is too low, air wrapped in melt will cause coking (gray and black lines in product)
Injection speed: best to use graded injection; slow to fast; injection speed is required to achieve good surface gloss, minimum weld seam, and high weld seam strength; need to open a vent tunnel at the meeting of front runners
Screw speed: Maximum screw speed is 0.6m/s, but it is better to set screw speed a little lower, as long as plasticizing process can be completed before end of cooling time.
Measuring stroke: (0.5~4)D
Amount of residual material is 2~8mm, depending on metering stroke and screw diameter
In some cases, pre-drying ABS can be directly fed from raw material bag without pre-drying, otherwise it will be dried at 80℃ for 3 hours; wet particles will cause cracks, scratches or bubbles in product;
Recovery rate: 30% recycled material can be added, provided that material has not been thermally degraded before
Shrinkage 0.4%~0.7%
Gate system: point gate and hot runner can be used; minimum wall thickness should not be less than 0.7mm, because ABS has poor fluidity
Machine downtime: no need to clean with other materials
Barrel equipment: standard screw, non-return ring, straight nozzle

04 Scope of application

ABS/PC alloy is to improve flame retardancy of ABS, with good mechanical strength, toughness and flame retardancy. In ABS/PC alloys, PC contributes to heat resistance, toughness, impact strength, strength and flame retardancy. Advantages of ABS are good processability, apparent quality and low density, with auto industry parts as application focus.
ABS/PA alloys are impact-resistant, chemical-resistant, good-flowing and heat-resistant materials for automotive interior trim, power tools, sports equipment, industrial components such as lawn mowers and snow blowers, office equipment housings, etc.;
ABS/PBT alloy has good heat resistance, strength, chemical resistance and fluidity, suitable for automotive interior parts, motorcycle outer cushion parts, etc.;
Permanent antistatic grades with added antistatic agents are used for: paper transfer mechanism for copiers, fax machines, etc., IC chip supports, video and advanced audio tapes, etc.; in addition, there are ABS/PSU, ABS/EVA, ABS/PVC/ PET, ABS/EPDM, ABS/CPE, ABS/PU and other alloys.
High-gloss ABS is used in household appliances such as vacuum cleaners, fans, air conditioners, and telephones. It is achieved by controlling rubber particle size R+ (smaller) in ABS. Low-gloss ABS is used in instrument panels, instrument covers, and pillars, surface is microscopically shrunk by filling and thickening fillers to reduce surface gloss.
Typical application areas: automobiles (dashboards, tool hatches, wheel covers, mirror boxes, etc.), refrigerators, heavy-duty tools (hair dryers, blenders, food processors, lawn mowers, etc.), phone cases body, typewriter keyboards, recreational vehicles such as golf carts and jets.
injection molding process 

05 ABS plastic status

China is the world's largest consumer of ABS resin. In 1999, my country's ABS output was about 150,000 t/a, and import volume was 1.33 million t. From January to September 2000, 950,000 t had been imported, and market potential was very large. However, my country's ABS self-sufficiency rate is very low, and it needs to rely on a large number of imported products to meet demand. Other countries and regions in the world are dumping products to us. Joint venture production plant in mainland plans to expand production capacity and form a supply base. At the same time, ABS manufacturers around the world have applied for patents in China to strengthen,expand their influence and share in Chinese market.

06 5 major properties of ABS plastic raw materials

Five properties of ABS plastic raw materials include general properties, mechanical properties, thermal properties, electrical properties, and electrical properties. What are characteristics of these five properties of ABS plastic?
Plastic performance testing technical services are all over chemical industry. From raw material identification, chemical product formulation analysis, to industrial problem diagnosis in product production, product application failure analysis, and product reliability testing, we can provide the most professional analytical technical services. ABS resin combines excellent properties of three monomers, namely: gloss, electrical properties and formability of styrene; heat resistance, rigidity and oil resistance of acrylonitrile; impact resistance of butadiene.
Performance testing of plastic ABS due to attention:

1. General performance:

Appearance of ABS is opaque and ivory-colored granules, which are non-toxic, odorless, and low in water absorption. Its products can be colored in various colors and have a high gloss of 90%. ABS has good bonding with other materials, and is easy to surface printing, coating and plating. Oxygen index of ABS is 18.2, it is a flammable polymer, flame is yellow, there is black smoke, it is burnt but not dripping, it emits a special cinnamon smell. ABS is a resin with very good comprehensive properties. It has high impact strength and surface hardness in a relatively wide temperature range. It has a higher thermal deformation temperature than PA and PVC, and has good dimensional stability.
Fluidity of ABS melt is better than PVC and PC, but worse than PE, PA and PS, and similar to POM and HIPS. Flow characteristics of ABS are non-Newtonian fluids, its melt viscosity is related to processing temperature and shear rate, but is more sensitive to shear rate.

2. Mechanical properties:

ABS has excellent mechanical properties, its impact strength is excellent, and it can be used at extremely low temperatures. Even if ABS product is damaged, it can only be tensile damage and not impact damage. ABS has excellent wear resistance, good dimensional stability, oil resistance, and can be used for bearings under moderate loads and speeds. Creep of ABS is larger than that of PSF and PC, but smaller than that of PA and POM. Bending strength and compressive strength of ABS are poor among plastics. Mechanical properties of ABS are greatly affected by temperature.

3. Thermal properties:

ABS is an amorphous polymer with no obvious melting point; high melt viscosity, poor fluidity, poor weather resistance, and ultraviolet rays can cause discoloration; Raised by about 10℃. It is sensitive to temperature and shear rate; ABS can still show certain toughness at -40℃, and can be used for a long time in temperature range of -40℃ to 85℃

4. Electrical properties:

ABS has good electrical insulation and is almost unaffected by temperature, humidity and frequency, and can be used in most environments.

5. Environmental performance:

ABS is not affected by water, inorganic salts, alkali alcohols, hydrocarbon solvents and various acids, but is soluble in ketones, aldehydes and chlorinated hydrocarbons, will cause stress cracking when eroded by glacial acetic acid and vegetable oil.
Performance testing is to test various performance indicators of system by simulating a variety of normal, peak and abnormal load conditions through automated testing tools.
Performance characteristics are processability, good, high fluidity.

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