ABS (Acrylonitrile Butadiene Styrene)

ABS, which stands for acrylonitrile butadiene styrene, is a thermoplastic blend that has been the workhorse of consumer product design for more than 60 years. It was commercialised in the 1950s by chemists at Borg Warner in the United States, and went on to become the material that defines what most people think a tough, paintable plastic looks like. Lego bricks are ABS. Power tool casings are ABS. Most caravan and RV interior panels are ABS. The keyboard and mouse on your desk are almost certainly ABS.

The name describes the chemistry. ABS is a copolymer of three monomers: acrylonitrile, which contributes chemical resistance and rigidity, butadiene, which contributes the impact strength and toughness, and styrene, which contributes the smooth glossy surface and ease of processing. The proportions can be tuned by the manufacturer to favour one property over another, which is why ABS is sold in dozens of grades ranging from high impact for safety helmets to plating grade for chrome plated bathroom fittings to flame retardant for electrical enclosures. The base material is opaque and naturally a milky tan colour, but it pigments easily and is available in essentially any colour the customer wants.

Mechanically, ABS sits in a useful sweet spot. It is significantly tougher than polystyrene or acrylic, with the ability to absorb knocks and impacts without cracking. It is also stiffer than HDPE or polypropylene, so it holds its shape under load and gives that satisfying solid feel that consumer products need. The service temperature of around 80 to 90 C is high enough for most product applications but limits ABS in things like under bonnet automotive parts, where higher temperature plastics such as nylon take over. Tensile strength sits around 40 to 50 MPa depending on the grade, and impact strength is high enough that designers rarely worry about it failing in normal use.

Where ABS earns its place in fabrication shops is its workability. It machines on a CNC router as easily as a hardwood. It drills cleanly with standard bits at normal speeds. It glues with simple solvent cements (acetone, MEK or commercial ABS cement) to make joints that are stronger than the parent material. It paints with standard primers and topcoats. It can be thermoformed at around 130 to 150 C into trays, panels, signage faces and bath shells. And in pellet form it is the foundation material for injection moulded production parts and FDM 3D printing filaments. Few plastics give designers as many fabrication options.

The main weakness is outdoor performance. Standard ABS is not UV stable. Left in direct Australian sun for 6 to 12 months, unprotected ABS will start to yellow, chalk and become brittle. For anything outdoor, ABS needs to be either UV stabilised at the resin level, painted with a UV protective coating, or replaced with ASA, which is essentially ABS with the butadiene replaced by an acrylic ester for better weatherability. ABS is also flammable, with a flame that produces dense black smoke containing styrene and small amounts of hydrogen cyanide. For electrical and electronic enclosures, flame retardant ABS (V-0 rated under UL 94) is specified and looks identical to standard grades to the eye.

Chemically, ABS handles dilute acids, bases and most household chemicals without trouble. It is not resistant to ketones, aldehydes, esters and chlorinated solvents, all of which will craze, soften or dissolve the surface. For applications that see fuel, brake cleaner or solvent based cleaning, HDPE or polypropylene are better choices.

Pricing is in the mid range, comfortably below polycarbonate and above HDPE on a per kilogram basis. Sheet sizes are standard at 2440 x 1220 mm in most thicknesses, with smaller and larger formats available on order. The most common stock colours in Australia are white, black and grey, all with a smooth glossy face and an embossed or textured back. Custom colours are typically available with minimum order quantities.

ABS is fully recyclable as a thermoplastic, and clean offcuts are widely accepted by plastic recyclers. End of life consumer products containing ABS, such as old computer cases and small appliance housings, are now being processed in some facilities back into pellet stock. From a sustainability perspective, ABS is best chosen where its properties genuinely match the application. Specifying ABS for an outdoor sign when a small price premium would buy a properly weatherable material adds avoidable cost and environmental impact.

When not to use ABS: outdoor service in standard grades. Anywhere fuel or aggressive solvents are present. Anywhere temperatures regularly exceed 90 C. And in highly transparent applications, where acrylic, polycarbonate or PETG should be specified. For everything else, particularly visible product parts that need to be machined, painted or solvent bonded, ABS is hard to beat.