1 Topic by genesat1

  • genesat1
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Topic: Talc + ABS

I tried adding talc to ABS pellets at a 5% load, I was hoping to have a more warp resistant ABS (less shrinkage).  It didn't go exactly according to plan.

The first thing that happened was filament started coming out much faster than it had been.  Multiple times faster than the same plastic at the same temperature.  Also, at the same temperature the plastic went from being 1.73-1.75mm to being over 2mm.  Motor load also increased from .8A for the raw generic ABS to 1.1A when talc was added.  Where things went wrong was I tried first reducing the cooling (no effect), then I tried increasing the drop distance (still oversized at max range for Filawinder sensor), and finally I tried increasing the temperature.  Even at an increased temperature I continued to get vastly oversized filament with the talc, and the only apparent effect of increased temperature was even faster extrusion speed and higher motor load.

What I think is happening is the talc is conducting heat up the barrel more than plastic would.  Higher temperatures are simply causing more melt further up the barrel thereby putting extra load on the motor.  The plastic is cooling down faster after being extruded as well (giving off heat quicker) so I'm ending up with larger filament regardless of the higher temperature.

Perhaps if I tried with a nozzle that is even smaller than the default 1.6mm?  Also, I believe the powder wants to fall down faster than the pellets, it doesn't entirely stick to them, so it might have a higher loading of talc than 5% where powder falls down into the hopper faster than the pellets.  Any suggestions on how to make it stick/adhere to the pellets more?

2 Reply by coolio986 (edited by coolio986 2019-06-07 23:55:21)

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Re: Talc + ABS

The talc is trying to reduce sheer on the screw by pushing the solids mass more forward toward the heater.

This in turn is forcing the mass to heat unevenly causing a sort of "solids plug"

Talc is sometimes used as a clarifying agent, but not used much to reduce warping. You need to mix ABS with another polymer that has polymer chains that can link to ABS. Using a less warping polymer that blends well will reduce the warping all together.

To get the talc to stick better to the pellets, use white mineral oil. Put the pellets in a bag, add a few drops of oil and shake, then add the talc and shake again. Coat the pellets with the oil before adding talc.

When you push the solids mass more forward (using talc since its a slip modifier), increase the temp and increase your vertical distance and decrease cooling at the nozzle. The increase in temp will cause the motor to unload, the melt will be hotter which will cause it to droop more.

Important to mention that talc doesn't really conduct heat anymore than anything else would. Talc is however non newtonian.

my 2c

3 Reply by genesat1

  • genesat1
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Re: Talc + ABS

All good information.  I did end up getting some to extrude, but the toughness was reduced to such a degree I didn’t pursue it further.  If I wanted to try making my own wood powder filament (sawdust that makes it through a 250 micron filter BEFORE mixing with pellets) I will try a drop of white mineral oil for better adhesion to the pellets.

4 Reply by tonycstech

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Re: Talc + ABS

Besides, if you want mixing, you need second heater half way the barrel and another temp controller.

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