FDM Printing Materials
ABS plastic is part of our everyday lives, especially those of us in the 3D printing industry. ABS is a terpolymer formulated from a mixture of three different polymers. This terpolymer is synthesized 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 polar nitrile groups from neighboring chains attract each other and connect the chains together through chemical bonds, making ABS stronger than pure polystyrene.
The most important mechanical properties of ABS are impact resistance, toughness, heat resistance, and tensile strength. A variety of modifications can be made to the terpolymer in order to improve these properties.
For example, 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 typically fall off rapidly at lower temperatures, and 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 molding, then high and medium impact resistance. For most applications ABS is formulated to have useful characteristics within a temperature range of −20 to 80 °C.
The material properties of ABS that lend well to manipulating the bulk polymer in applications of injection molding and extrusion also make it useful in manufacturing commercial products such as rock climbing gear, 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, luggage and protective carrying cases, small kitchen appliances, toys, including Lego and Kre-O bricks, and bicycle components.Household and consumer goods are the major applications of ABS and, in fact, you were probably just typing on your keyboard keycaps which are commonly made out of ABS.
Support material, overlooked by most, is just as important a consideration as the model material for 3D printing applications.
We’ve been printing efficiently in two dimensions since Gutenberg. When working with a third dimension, however, we have to deal with something you are very familiar with, gravity. As a part is being printed one layer at a time, what will prevent material from falling to the ground, into the undercuts, or through hollow features? If you remember your physics classes, Isaac Newton's third law applies here; the model material needs something to hold it in place. Thus, support material is a keystone in 3D printing functional parts.
Dissovable and Breakaway Support Materials
On printers with two print heads, the support material can be printed with dissolvable or breakaway support materials. The difference is that dissolvable support material has enhanced adhesion to the model material and does not tear away from the part but instead, dissolves away in a chemical solution that does not affect the model material of the printed part. The breakaway support material needs to be formulated so that it has less adhesion to the model material and is brittle, so it can be physically removed with ease. This is where polymer formulation gets exciting because both dissolvable and breakaway support materials have completely different properties and are made of completely different components yet they need to extrude from the print head the same, not an easy task.