3d Printing 101(b) - What is ABS?

by Astin Smith Article Writer

Intro

In our last article, we discussed Polylactic Acid ("PLA") and its use in 3d rapid prototyping. However, PLA is one of many types of plastic-y materials which can be used by inventors to quickly realize their inventions and products in three dimensions.

Body

A 3d printing material nearly equally as popular as PLA is Acrylonitrile Butadiene Styrene ("ABS"). Famous the world over for its use in Lego(r) blocks, ABS is, like PLA, a thermoplastic. A 3d printer which can utilize ABS material deposits it like it deposits PLA: the material is fed, as a filament, into the 3d printer's print head which heats the filament to an appropriate viscosity and injects the semi-liquid material in a predetermined pattern.

For some applications (e.g., rough dimensioning and/or ergonomic explorations), there may be little difference between 3d printing a part in PLA and ABS, but the compounds have distinct properties. Chemically, ABS is a polymerization of three monomers: acrylonitrile, styrene, and (poly) butadiene, each of which has its own chemical properties and together can be mixed in different ratios to produce ABSs of different properties. ABS and its constituent monomers are petroleum-derived and, upon 3d printing with ABS, you can immediately tell: molten ABS gives off fumes which should be ventilated. The extrusion temperature of ABS (~230°C) is higher than that of PLA, and thus the printing process can be trickier: if the material on which the molten ABS is deposited is too cool, too much heat is drawn out of the plastic too quickly resulting in warped features.

Mechanically, ABS is more flexible (~330ksi) than PLA and tolerates heat more easily (100°C Vicat softening point). Like PLA, ABS can be machined. Because petroleum-derived ABS is soluble in acetone, ABS surfaces can also be easily treated/brushed post-printing to give them glossy finishes. Both acetone and methyl ethyl ketone can be used to "melt" ABS surfaces and fuse individual ABS parts together.

ABS filaments come in an array of colors, although raw ABS has a translucent white color. Like PLA, ABS is recyclable (SPI Code 7), though not as readily-so as PLA. Raw ABS is somewhat susceptible to ultraviolet light, although this susceptibility can be minimized by pigments or other additives. While it goes without saying that ABS-printed prototype parts should generally not be used for high-temperature applications, ABS combusts into hydrogen cyanide and carbon monoxide, among other gases, albeit it ~400°C.

Conclusion

For a few very basic 3d printing applications, a customer will be indifferent to whether his part(s) is made from ABS or PLA. The most relevant difference between ABS and PLA is usually ABS' flexibility. A part made out of PLA and a part made out of ABS will sustain approximately the same handling and forces before breaking, though ABS' flexibility and temperature tolerance result in parts made out of ABS being a bit more durable than PLA-versions. The other differences are, frankly, the printer's problem.

Stay tuned to Au-LLC.com and its upcoming launch of Protolyze.com for more info about 3d rapid prototyping technology.

For more information about rapid prototyping or visit at www.au-llc.com