to put more particle volume in a paste, I suggest to mix particles of very different size
, like concrete is made: cement and water fill the voids in sand, sand fills the voids between stones, and you can still pour the mix with little cement and water in it. Just a continuous range of sizes isn't enough apparently: you need several classes of sizes, well separated, like 10* diameter ratio. I'd have more than two sizes. Not only should the melt flow better, the solidified plastic should also be less brittle.
Last time I put graphite or MoS2
in a thin liquid, the suspension already stopped flowing around 60% volume liquid, while in concrete the water and cement volume proportion is much smaller.
If you get useful results, tell us! It would be all-important to metal-matrix ceramic toohttps://www.chemicalforums.com/index.php?topic=100877.0
Brittleness limits the proportion of ceramic presently.
Non-newtonian liquids are known, for instance silicone oil is a catastrophic lubricant because its viscosity drops at high shear number. What compound can fit in a printable polymer, I dunno.
Or could you add a solvent that evaporates once the molten filament is deposited and still warm on the future part? Keeping in mind all the drawbacks of evaporating solvents: explosion, fire, toxicity, shrinkage...
Compressibility of cold and warm polymers is known from injection. Data is available in:
Kunststoff-Tabellen, by Carlowitz (in German and 89€, ouch)
typical moduli are like 5GPa, a bit less at warmth, so like I imagine 3D printing it shouldn't matter much.
I hate Ptfe against friction, as massive parts and as a plain coating. As a mechanical designer I had only trouble with it. It creeps endlessly, and already if it's lukewarm, its friction coefficient gets as bad as any other polymer. You get less problems from Pp and Pa.
The proper use against friction is to embed Ptfe powder in a resisting matrix
. Most companies that sell plain bearings offer also the bearing material: Pi+Ptfe (expensive), bronze+Ptfe, of which you might make your nozzles. I let also make a coating of Ni+Ptfe, it was excellent even at huge contact pressure, and can be done in a hole too. For reasons I ignore, these compounds glide well even when warm.
If possible, I'd try a cylindrical or even diverging nozzle.