ABS: Acrylonitrile Butadiene Styrene
Acrylonitrile butadiene styrene (ABS) is a plastic that is a terpolymer, a polymer consisting of three different monomers. ABS is made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. Acrylonitrile is a synthetic monomer made up of propylene and ammonia while butadiene is a petroleum hydrocarbon, and the styrene monomer is made by the dehydrogeneration of ethyl benzene. Dehydrogenation is a chemical reaction that involves the removal of hydrogen from an organic molecule and is the reverse of hydrogenation. Dehydrogenation converts alkanes, which are relatively inert and thus low-valued, to olefins (including alkenes), which are reactive and thus more valuable. Dehydrogeneration processes are used extensively to produce aromatics and styrene in the petrochemical industry. There are two types: One is for the extrusion of shapes and the other is a thermoplastic used for molded products. ABS composites are usually half styrene with the rest balanced between butadiene and acrylonitrile. ABS blends well with other materials such as polyvinylchloride, polycarbonate, and polysulphones. These blends allow for a wide range of features and applications.
Historically, ABS was first developed during WWII as a replacement for rubber. Although it was not useful in that application, it did become widely available for commercial applications in the 1950s. Today ABS is used in a diverse group of applications including toys. For example, LEGO® blocks are made from it because it is lightweight and very durable. Also molding at high temperatures improves the gloss and heat-resistance of the material while molding at low temperatures results in high impact resistance and strength.
ABS is amorphous, which means it has no true melting temperature but rather a glass transition temperature that is roughly 105◦C or 221◦F. It does have a recommended continuous service temperature of from -20◦C to 80◦C (-4◦F to 176◦ F). It is flammable when exposed to high temperatures such as those produced by an open flame. First it will melt, then boil, then burst into intense hot flames as the plastic vaporizes. Its advantages are that it has high dimensional stability and exhibits toughness even at low temperatures. Another disadvantage is that when burning ABS will result in high smoke generation.
ABS is widely chemical resistant. It resists aqueous acids, alkalis, and phosphoric acids, concentrated hydrochloric alcohols and animal, vegetable and mineral oils. But ABS is severely attacked by some solvents. Prolonged contact with aromatic solvents, ketones and esters does not yield good results. It has limited weather resistance. When ABS burns, it generates a high amount of smoke. Sunlight also degrades ABS. Its application in the seatbelt release button of automobiles caused the largest and most costly recalls in US history. ABS is resistant to a wide variety of substances including concentrated acids, dilute acids and alkalis. It performs poorly with aromatic and halogenated hydrocarbons.
The most important characteristics of ABS are impact-resistance and toughness. Also ABS can be processed so the surface is glossy. Toymakers use it because of these qualities. Of course, as mentioned, one of the best known users of ABS is LEGO® for their colorful, shiny toy building blocks. It is also used to make musical instruments, golf clubs heads, medical devices for blood access, protective headgear, white water canoes, luggage, and carrying cases.
CRAFTECH INDUSTRIES manufactures parts using ABS as well as 100 other different plastics. For more information about Craftech, visit www.craftechind.com.