Acrylonitrile Butadiene Styrene (ABS) is a common, opaque engineering thermoplastic. It is a terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene rubber. The proportions can vary from 15% to 35% acrylonitrile, 5% to 30% butadiene and 40% to 60% styrene, giving a wide range of grades.
SAN copolymers have been available since the 1940s and while their increased toughness over styrene made them suitable for many applications, their limitations led to the introduction of the rubber butadiene as a third monomer producing the range of materials popularly referred to as ABS plastics. These became available in the 1950s and the availability of these plastics and ease of processing led ABS to become one of the most popular of the engineering polymers.
The nitrile groups make ABS stronger than pure polystyrene and also contribute chemical resistance, fatigue resistance, hardness, and rigidity, while increasing the heat deflection temperature. The styrene gives the plastic a shiny, impervious surface, as well as hardness, rigidity, and improved processing ease.
The characteristic properties of ABS are created by fine particles of polybutadiene elastomer distributed throughout the rigid matrix, providing toughness and ductility at low temperatures.
ABS falls between standard resins (PVC, polyethylene, polystyrene, and so on) and engineering resins (acrylic, nylon, acetal) and often meets satisfactory engineering properties at a reasonable cost. It offers greater impact properties and slightly higher heat distortion temperature than High Impact Polystyrene (HIPS).
Increasing the proportions of polybutadiene in relation to styrene and acrylonitrile increases impact resistance but at the expense of heat resistance and rigidity. Ageing is also influenced by the polybutadiene content.
ABS is amorphous and therefore has no true melting point. Its glass transition temperature is approximately 105°C. In general, ABS can be used between −20 and 80°C.
Advantages
- High rigidity
- Impact resistance, even at low temperatures
- Insulating properties
- Weldability
- Abrasion and strain resistance
- Dimensional stability
- Surface brightness
- Very good resistance to dilute acid and alkalis
Limitations
- Low continuous service temperature.
- Low dielectric strength.
- ABS is soluble in polar solvents, such as esters, ketones (such as acetone), chloroform, and ethylene dichloride. It also offers poor resistance to chlorinated solvents and aldehydes.
- Can suffer from stress cracking in the presence of some greases.
- ABS is damaged by sunlight.
- ABS is flammable when exposed to high temperatures; it will melt and then boil, at which point the vapors burst into intense, hot flames.
- ABS can be recycled, although it is not accepted by all recycling facilities. Recycled ABS can be blended with virgin material to produce cheaper products while preserving the quality.
Processing
Selected ABS grades are designed for extrusion and injection moulding.
Moulding at high temperature improves gloss and heat resistance, whereas the highest impact resistance and strength are obtained by moulding at low temperature.
Grades containing glass and other fibers make the final product strong and raise the maximum operating temperature. Pigments can also be added, as the natural color is translucent ivory to white.
Machine grade ABS can be precision machined into structural parts.
Due to its high stability and various post-processing options, ABS is suitable for prototyping. When extruded into a filament, ABS plastic is a common material used in 3D printers using the fused deposition modeling (FDM) method. Particular forms of ABS filaments are ABS-ESD (electrostatic discharge) and ABS-FR (fire-resistant), which are used in particular for the production of electrostatically sensitive components and refractory prefabricated parts.
In medicine and surgery, ABS filament has proven to be the most popular 3D printing material for generating 3D medical models. It has been used commonly over the past 10 years for FDM printing due to its high-quality surface properties. It is resistant to damage, can be drilled, and used to manufacture surgical tools and guides and practice models. It is strong and slightly flexible, which makes it a good material for 3D printing. In addition, ABS filament has a 32MPa of tensile strength and can be easily extruded using a wide range of 3D printers.
Applications
Household and consumer goods comprise the major applications of ABS. It is widely used in electronic housings, auto parts, consumer products, pipe fittings and Lego toys. It is also used to make woodwind instruments. Golf club heads are often made from ABS, utilizing its shock resistance.
Even though ABS plastics are used largely for mechanical purposes, they also have electrical properties that are constant over a wide range of frequencies and little affected by temperature and atmospheric humidity.
ABS can be used in biomedical applications, with injection-moulded components being easy to manufacture for single-use. It can be sterilized by gamma radiation or ethylene oxide.
Alloys and Blends
ABS can be readily blended or alloyed with other polymers such as PA, PBT, PC etc. This blending with polymers further increases the range of properties available.
Acrylonitrile butadiene styrene/polycarbonate blend (ABS/PC) is a thermoplastic alloy that combines the toughness and high heat resistance of polycarbonate with the ductility and processability of ABS. Both of these polymers are widely used on their own and have very specific properties and also drawbacks of their own.
Methacrylate Acrylonitrile Butadiene Styrene (MABS) is a clear, transparent material with thermal and mechanical properties equivalent to ABS. The transparency is achieved by matching the refractive indices of the matrix resin (the transparent acrylate-acrylonitrile-styrene polymer) with the polybutadiene rubber impact modifier. MABS has the highest impact resistance of all the styrenics.
MABS is an amorphous thermoplastic with the same shrinkage as ABS and polycarbonate. It can be used in the same moulds. MABS adheres easily to PVC by solvent bonding.
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Thank you Andy for this plainly written, easy to understand and informative article on ABS. While I have worked in the polymer compounding business in a capacity other than as a polymer engineer, I have always had some questions regarding ABS, MABS, SAN and so forth that you have clarified for me.
Best regards,
Leon Richardson
TMC Plastic Coloring and Compounding, Inc.
Hello Sir,
I am Avinash and I am from India. I wants to start ABS granule manufacturing unit. Can you please help me for my start-up. Please reply me on my email or whatsapp. We can discuss more on this. I am looking forward for your precious reply..
Hi Avinash
I’m sorry, but my expertise is as a materials engineer, in the use of polymeric and other materials. I do not have any expertise in how to set up manufacturing plants for polymers. Maybe you could speak to the manufacturers of ABS (who you can find via the Materials Selector) and then find out if they are interested in licensing you? I’m afraid I have no better ideas, but maybe someone in the thread may be able to help more. Thank you for your enquiry.