Acrylonitrile butadiene styrene

Acrylonitrile butadiene styrene

Monomers in ABS polymer

ABS polymer grains
Identifiers
9003-56-9 YesY
Properties
(C8H8·C4H6·C3H3N)n
Density 1.060-1.080 g·cm−3 [1]
Insoluble in water
Related compounds
Related compounds
 Acrylonitrile, butadiene and styrene (monomers)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x·​(C4H6)y·​(C3H3N)z) is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F).[2] ABS is amorphous and therefore has no true melting point.

ABS is a terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. The proportions can vary from 15 to 35% acrylonitrile, 5 to 30% butadiene and 40 to 60% styrene. The result is a long chain of polybutadiene criss-crossed with shorter chains of poly(styrene-co-acrylonitrile). The nitrile groups from neighboring chains, being polar, attract each other and bind the chains together, making ABS stronger than pure polystyrene. The styrene gives the plastic a shiny, impervious surface. The polybutadiene, a rubbery substance, provides toughness even at low temperatures. For the majority of applications, ABS can be used between −20 and 80 °C (−4 and 176 °F) as its mechanical properties vary with temperature.[3] The properties are created by rubber toughening, where fine particles of elastomer are distributed throughout the rigid matrix.

Properties

The most important mechanical properties of ABS are impact resistance and toughness. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance. The impact resistance can be amplified by increasing the proportions of polybutadiene in relation to styrene and also acrylonitrile, although this causes changes in other properties. Impact resistance does not fall off rapidly at lower temperatures. Stability under load is excellent with limited loads. Thus, by changing the proportions of its components, ABS can be prepared in different grades. Two major categories could be ABS for extrusion and ABS for injection moulding, then high and medium impact resistance. Generally ABS would have useful characteristics within a temperature range from −20 to 80 °C (−4 to 176 °F).[3]

Lego bricks are made from ABS.[4]

The final properties will be influenced to some extent by the conditions under which the material is processed to the final product. For example, molding at a high temperature improves the gloss and heat resistance of the product whereas the highest impact resistance and strength are obtained by molding at low temperature. Fibers (usually glass fibers) and additives can be mixed in the resin pellets to make the final product strong and raise the operating range to as high as 80 °C (176 °F). Pigments can also be added, as the raw material original color is translucent ivory to white. The aging characteristics of the polymers are largely influenced by the polybutadiene content, and it is normal to include antioxidants in the composition. Other factors include exposure to ultraviolet radiation, for which additives are also available to protect against.

ABS polymers are resistant to aqueous acids, alkalis, concentrated hydrochloric and phosphoric acids, alcohols and animal, vegetable and mineral oils, but they are swollen by glacial acetic acid, carbon tetrachloride and aromatic hydrocarbons and are attacked by concentrated sulfuric and nitric acids. They are soluble in esters, ketones, ethylene dichloride and acetone.[5]

Even though ABS plastics are used largely for mechanical purposes, they also have electrical properties that are fairly constant over a wide range of frequencies. These properties are little affected by temperature and atmospheric humidity in the acceptable operating range of temperatures.[6]

ABS is flammable when it is exposed to high temperatures, such as a wood fire. It will melt then boil, at which point the vapors burst into intense, hot flames. Since pure ABS contains no halogens, its combustion does not typically produce any persistent organic pollutants, and the most toxic products of its combustion or pyrolysis are carbon monoxide and hydrogen cyanide.[7] ABS is also damaged by sunlight. This caused one of the most widespread and expensive automobile recalls in US history due to the degradation of the seatbelt release buttons.[8][9]

ABS can be recycled, although it is not accepted by all recycling facilities.[10][11]

Production

ABS is derived from acrylonitrile, butadiene, and styrene. Acrylonitrile is a synthetic monomer produced from propylene and ammonia; butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking; styrene monomer is made by dehydrogenation of ethyl benzene — a hydrocarbon obtained in the reaction of ethylene and benzene.

ABS combines the strength and rigidity of acrylonitrile and styrene polymers with the toughness of polybutadiene rubber. While the cost of producing ABS is roughly twice the cost of producing polystyrene, it is considered superior for its hardness, gloss, toughness, and electrical insulation properties.

According to the European plastic trade association PlasticsEurope, industrial production of 1 kg (2.2 lb) of ABS resin in Europe uses an average of 95.34 MJ (26.48 kW·h) and is derived from natural gas and petroleum.[12]

Machining

ABS is easily machined. Common machining techniques include turning, drilling, milling, sawing, die-cutting and shearing. ABS can be cut with standard shop tools and line bent with standard heat strips. ABS can be chemically affixed to itself and other like-plastics.[13]

Applications

Natural colored ABS 3D Printed Bell on a 3D printer.

ABS's light weight and ability to be injection molded and extruded make it useful in manufacturing products such as drain-waste-vent (DWV) pipe systems, musical instruments (recorders, plastic clarinets, and piano movements), golf club heads (because of its good shock absorbance), automotive trim components, automotive bumper bars, medical devices for blood access, enclosures for electrical and electronic assemblies, protective headgear, whitewater canoes, buffer edging for furniture and joinery panels, luggage and protective carrying cases, small kitchen appliances, and toys, including Lego and Kre-O bricks.[14] Household and consumer goods are the major applications of ABS.[15] Keyboard keycaps are commonly made out of ABS.[16]

ABS plastic ground down to an average diameter of less than 1 micrometer is used as the colorant in some tattoo inks.[17] Tattoo inks that use ABS are extremely vivid.

Hazard for humans

ABS is stable to decomposition under normal use and polymer processing conditions with exposure to carcinogens well below workplace exposure limits.[18] However, at higher temperatures (400 °C) ABS can decompose into its constituents: butadiene (carcinogenic to humans), acrylonitrile (possibly carcinogenic to humans), and styrene.[18]

Concerns have been raised regarding airborne ultrafine particle (UFP) concentrations generated while printing with ABS, as UFPs have been linked with adverse health effects.[19]

See also

References

  1. ↑ "Matbase". Retrieved 3 July 2014.
  2. ↑ ABS. Stratasys Inc. (2007).
  3. 1 2 Plastic Properties of Acrylonitrile Butadiene Styrene (ABS) Small table of ABS properties towards the bottom. Retrieved 7 May 2010
  4. ↑ May, James (2009) [2009]. James May's Toy Stories. London: Conway. ISBN 978-1-84486-107-1.
  5. ↑ Benj Edwards Vintage Computing and Gaming | Archive » Why Super Nintendos Lose Their Color: Plastic Discoloration in Classic Machines. Vintagecomputing. January 12, 2007
  6. ↑ Harper C.A. (1975) Handbook of plastic and elastomers, McGraw-Hill, New York, pp. 1–3,1–62, 2–42, 3–1, ISBN 0070266816
  7. ↑ Rutkowski, J. V.; Levin, B. C. (1986). "Acrylonitrile-butadiene-styrene copolymers (ABS): Pyrolysis and combustion products and their toxicity?a review of the literature". Fire and Materials 10 (3–4): 93. doi:10.1002/fam.810100303.
  8. ↑ Henshaw, J. M.; Wood, V.; Hall, A. C. (1999). "Failure of automobile seat belts caused by polymer degradation". Engineering Failure Analysis (abstract) 6: 13. doi:10.1016/S1350-6307(98)00026-0.
  9. ↑ "Belts recalled in 8.4 million vehicles". The Baltimore Sun. Knight-Ridder News Service. May 24, 1995. Retrieved November 16, 2015.
  10. ↑ "ABS Recycling". Heathland B.V. Retrieved 2013-12-31.
  11. ↑ "Recycling plastic". Brisbane City Council. Retrieved 2013-12-31.
  12. ↑ Boustead, I (March 2005). Acrylonitrile-Butadiene-Styrene Copolymer (ABS) (Technical report). Eco-profiles of the European Plastics Industry. PlasticsEurope. cited in Inventory of Carbon & Energy database (Hammond, G. P.; Jones, C. I. (2008). "Embodied energy and carbon in construction materials". Proceedings of the ICE - Energy 161 (2): 87. doi:10.1680/ener.2008.161.2.87.)
  13. ↑ "ABS Plastic Sheet, Rod, Tube and Accessories". Interstate Plastics. Interstate Plastics. Retrieved September 2015.
  14. ↑ ABS – acrylonitrile butadiene styrene On Designsite.dk, lists applications. Retrieved 27 October 2006.
  15. ↑ Market Study Engineering Plastics, Ceresana, September 2013
  16. ↑ "Keycap Construction: ABS". Deskthority. September 2014.
  17. ↑ Kennedy, C.T.C.; et al. (2010), "Mechanical and Thermal Injury", in Tony Burns; et al., Rook's Textbook of Dermatology 2 (8th ed.), Wiley-Blackwell, p. 28.48
  18. 1 2 Unwin, John (2013). "Airborne emissions of carcinogens and respiratory sensitizers during thermal processing of plastics.". Annals of Occupational Hygiene 57.3: 399–406. doi:10.1093/annhyg/mes078.
  19. ↑ Stephens, Brent (November 2013). "Ultrafine particle emissions from desktop 3D printers". Atmospheric Environment 79: 334–339. doi:10.1016/j.atmosenv.2013.06.050.

Further reading

External links

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