Sciencemadness Discussion Board

Fortifying UV curing 3d printer acrylic resin with polyester resin?

Junk_Enginerd - 4-2-2023 at 02:05

My limited understanding of how the UV curing resins that DLP 3d printers use work suggests that I should be able to mix the 3d printer resin with polyester resin to get a stronger part. The acrylic resin by itself is quite lacking in strength, and breaks easily. Polyester resin is much stronger. To clarify, I mean the standard resin one can buy for use with fiberglass mats.

However, polyester resin makes a right mess under the best of conditions, and I don't want to subject my 3d printer to it unless I have a little more faith in it working out.

May I expect the polyester resin to "play well" with the acrylic resin?

Will the photoactive curing catalyst work to cure the polyester resin as well as the acrylic?

Mateo_swe - 4-2-2023 at 15:12

I doubt it would cure the polyester resin because if it did you would have seen polyester based resins for sale.
If you try it you might damage the resin container part and the transparent film.
But maybe it works, but i would as you said also want a bit more info on it before trying and possible damaging my printer.

Junk_Enginerd - 5-2-2023 at 04:36

Seems like it's such a new industry that I wouldn't be surprised if it was uncharted territory. I also wouldn't be surprised if polyester resin actually is already used. The manufacturers of resins are extremely secretive about what's in them, so figuring it out wouldn't be easy.

But also, polyester resin has some undesirable properties in the application that might work against it being mainstream. The eternal oozing and stickiness unless surface finished comes to mind.

Twospoons - 5-2-2023 at 19:11

Resin based 3d printing is not new. Its been around for a very long time, probably at least 20 years. Its just that it has only recently made it to consumer grade printers. UV cured adhesives have been around just as long. I know from experience there are a great variety of light cured adhesives with quite a range of mechanical properties.
The key thing to remember with consumer grade resins is they are made as cheap as possible, since most people are not making structural parts with them ... if you want better strength there will be better resins out there, but its going to cost more.

Mateo_swe - 6-2-2023 at 03:05

Ok, but its quite cool to make a DIY resin and cheaper too.

Junk_Enginerd - 6-2-2023 at 03:58

Quote: Originally posted by Twospoons  
Resin based 3d printing is not new. Its been around for a very long time, probably at least 20 years. Its just that it has only recently made it to consumer grade printers. UV cured adhesives have been around just as long. I know from experience there are a great variety of light cured adhesives with quite a range of mechanical properties.
The key thing to remember with consumer grade resins is they are made as cheap as possible, since most people are not making structural parts with them ... if you want better strength there will be better resins out there, but its going to cost more.


Oh that I know. But that doesn't necessarily mean that the producers of the consumer grade stuff are quite caught up. If there's anything I've learned from 15 years of product research and development, it's that "the industry" isn't nearly as competent as one might think.

I know there are fancy resins, going for $400/liter. But that doesn't say much about whether the polymerization catalysts of acrylic resins also work on polyesters, which is what I'm curious about since I'm curious about the chemistry of plastics.

Twospoons - 6-2-2023 at 14:05

Quote: Originally posted by Mateo_swe  
Ok, but its quite cool to make a DIY resin and cheaper too.


Oh, I agree. But when I looked into it I quickly realised it was beyond my meagre chemistry skills and resources.

Didn't take long to find this:
UV catalyst for polyester

So definitely possible, but it will be specific to polyester.
As for mixing polyester and acrylic - thats where its going to get tricky, since the cure catalysts for each are probably quite different. Nothing to stop you trying it though.

[Edited on 6-2-2023 by Twospoons]

Junk_Enginerd - 6-2-2023 at 23:24

Hmm. I looked at some video a while ago that explained why acrylic is usually the base of these resins. It mentioned something along the lines of acrylic being very receptive to other monomers, and would gladly polymerize with others than acrylic. I guess that's what seeded the thought.

I guess it should work if I use say 6 parts acrylic resin to 4 parts polyester, and also mix in some traditional polyester catalyst. A normal 1-2% mix takes about 30-45 minutes before anything starts happening, which is often enough for most smaller prints. If the acrylic resin is enough to hold it together until then it should be fine.

Or, let's say you add 0.25-0.5 % catalyst. The typical behaviour of polyester afaik when you have too little catalyst is that it will require a "kick" to properly harden, typically heating, and once it gets that it will harden just fine in the end even if it takes a little longer. It seems reasonable that you should be able to balance this so that none of the polyester even starts curing while in the 3d printer, and when you're done you just throw it in a mildly heated oven. Probably would need to carefully clean out everything after each run though.

Twospoons - 7-2-2023 at 18:25

If you use the polyester specific UV activated catalyst then the working lifetime shouldn't be an issue.