Over the next few weeks we will explore “The science of” different issues related to 3D printing. This week we are exploring the magic of ABS filament!
We will explore these topics through a series of interviews with Colin Hindle, Lecturer in Polymer Technology at Edinburgh Napier University, who is developing materials alongside us at 3dprintworks. With over thirty years experience in the plastics and polymer industries, Colin has been a great asset to the company and so we decided to take this opportunity to pick his brain.
What is ABS?
ABS is short for acrylonitrile butadiene styrene – bet you wished you never asked!
What qualities are looking for in ABS in order to achieve good print outs?
You are looking for a good flow behavior for it to melt and obviously flow from the head. You might also be wanting it to be a very tough material. ABS combines reasonable toughness with rigidity, good surface gloss.
What makes the strands adhere together in ABS?
The styrene’s got an acrylonitrile phase, a rigid styrene acrylonitrile phase and a rubbery styrene rich phase. But it is styrene acrylonitrile that makes it easily mould together.
Why do you need to heat the bed if you are printing ABS?
Well again it comes back to glass transition. Glass transition of ABS is round about 100 so you want the bed to keep material above the 100 degree mark. So that’s why for ABS you would use a heated bed.
So will it stick better to the bed because of that?
It will stick better initially, yes.
How do you find out your TG? What is TG?
TG is the glass transition temperature. It’s the temperature above which large scale polymer chain rotation becomes possible. We usually measure it by measuring a physical property which changes markedly at TG. An example of that would be a specific volume, the volume occupied by the given mass of material. But an easier quantity to measure perhaps is a change in specific heat. Which is a measure using Differential Scanning Calorimetry, DSC for short. That’s quite a quick and easy automated test for most people to determine TG by DSC.
What is conductive ABS and what makes it conductive?
Well, you can make plastics like ABS conductive by incorporating into them a conductive additive. It could be particles of metal, you don’t need to have them actually touching but the particles need to be near to each other so the metal charge can be carried, like stepping stones if you like across a river jumping from one to the next. Or you can use intrinsically conductive polymers which are incredibly expensive, but you don’t need a great deal of it to make it conductive. If you’re only looking for a low level of conduction, that’s to say just dissipating static electricity rather than conducting a current, then you can get away with things like carbon black – although in that case you can only have one colour of course, black!