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Strange resin sought
4

Strange resin sought

Strange resin sought

(OP)
I'm looking for a sort of thermoset, such as unfilled polyester casting resin.  At least that's what I think it is.  

A client of mine is getting some parts machined from what I believe is a pre-cast resin in rod form (from a vendor in England, I believe).  This seems to be because of the nature of the appearance and water resistance of the part.

I need a nice opaque white part, able to put a polished finish on it.  I've looked at the thermoplastics available and cannot seem to find quite the right look/feel.  (Tried Delrin--nice white, but somewhat translucent.)  Normally, injection molded high-volume production stuff is my niche, but this part cannot be feasibly molded while retaining the aesthetic characteristics I need (very thick sections--over 1" in areas--with thin sections in other areas, bad undercuts to be machined in, etc.)

This part will work as part of a premium-line bathing accessory, so it will get plenty of soap and hot water over time.  It doesn't need to be terribly accurate (+/-0.015" tolerance is fine) when machined, but needs to be able to sustain decent drops onto the floor without damage.

Can anyone recommend a resin that may work for this machining process, even if somewhat complicated?

One more thing--if it's a cast thermoset, we can cast the rods ourselves, but cannot use the material if there is a significant risk of air bubbles within the rod to be machined.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe trumps reason.

RE: Strange resin sought

It sounds like you are trying to make something like cultured marble, as used for sinks, countertops etc. I am no expert on that but I know someone who is. He said they are made from methylmethacrylate filled with ATH (aluminium trihydrtae or aluminium hyroxide). The methylmethacrylate is then cured to give PMMA. This gives the right look and enables you to polish out scratches during use with a mild abrasive. If you need to know more I can try to ask him directly as he spent years developing such formulations.

RE: Strange resin sought

Thermal sets do not normally have good drop resistance if they are not reinforced. The reinforcement usually means they can not achieve a high polish. Thermoplastic rods can be bought from many distributors like Caddilac Plastics. Try a Goggle search or Thomas register. Delrin is slightly translucent in its natural color but can easily obtained in white. It would be my choise.

RE: Strange resin sought

Filled thermoset methyl methacrylate or filled thermoset polyester can be used, I think the methyl methacrylate is superior.

Acetal, PET or PMMA rod coloured white could be used.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

(OP)
Wow--thanks for the quick tips.

I've checked into acetals (Delrin, POM [Acetron GP]) and PET, and those aren't quite what I need in this case (yeah, very picky about the final finish/aesthetic qualities).  However, methyl methacrylate I've not checked on (isn't that sort of a brittle acrylic?).  Corian I've heard of, but haven't checked that either--does it come in rods instead of only sheets?

I'll do some research in those areas and see how well they pan out for this application.  For the filled polyester, what would be the fill?  What I've got could be talc-filled, but nothing like glass fiber.  If I can polish the final part, I can put a gloss coat over it if necessary, but the surface finish does need to be extremely smooth when complete.

Thanks again!  I'll report back if I need some tweaked material suggestions.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

Methyl methacrylate is acrylic.

It actually has fairly high energy at break, but very low elongation.

Corian is filled methyl methacrylate.

The filler you need will depend on the appearance you want.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

(OP)
Thanks again.

I'd like a pure white, but if I could also get a very white pearlescent sort of color, that would be great to check out--maybe a Corian (or variant) would be available like that.  I imagine it would machine well, judging by the countertops I've seen.

By the way, this is an industrial design/product design project.  I'm creating a women's razor design and some other things that will use the same material I need for the razor handle.  Normally I wouldn't have something like this machined, but molded, but for technical reasons (like the huge, solid sections coupled with thin sections I mentioned) this really won't work out well while keeping a stellar aesthetic.  Plus, we'd like to keep up-front tooling costs to a minimum.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought


Jeff,

PMMA can be solvent polished to a very high gloss.

Not sure if it's still available, but Cellulose Acetate (Propionate or Butyrate - CAP or CAB) machines well, polishes excellently and easily - very tough (used to be used for screwdriver/chisel handles) - and self-polishes with handling.

Likley to be expensive if you can get it....

Cheers

Harry

RE: Strange resin sought

Yes you can still get those cellulosics from Eastman. As you mentioned the CAP is used for screwdriver handles due to a special feel it has. Also you can polish out scratches or anneal them out with a heat gun or hairdrier. CAP is around the 3 Euro per kilo mark or it was last time I checked. You can find the material properties and links to suppliers at www.matweb.com (free)

RE: Strange resin sought

(OP)
OK, I've contacted Eastman and DuPont for Corian samples.  The Corian rep says I can only get Corian 1/2" thick and will have to laminate to thickness (would like to start machining with 2" diameter rods) and then machine--we'll see if that works well--certainly will add to the cost.

Still waiting to hear back from Eastman.

Thanks, again, everyone for the input on this.  I'm hoping one of these materials will work out.

Does anyone have any other creative materials ideas?  I don't know about the CAB/CAP materials yet, but the Corian will probably fulfill the aesthetic requirements very well--but will be a bit of a bear to machine.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

Howmany do you intend to make per year? If it is alot then a molding operation will be cheaper. If it is less than 5,000 per year machining will be less since you will not have to pay for tools.

RE: Strange resin sought

(OP)
Since we're just launching this as a new product, we don't expect high sales from the start.  Maybe 10,000 units the first year, depending how well things take off.

I just received some samples of the butyrate (Tenite) from someone who uses this stuff to make--you guessed it--screwdrivers.  This stuff looks great for this purpose, and although most of the samples are clear, they sent a white chip that looks great--excellent finishing capabilities and good color and opacity.

We may still machine this stuff even if volumes get high because of some strange undercut features we need for assembly.  However, I could mold some solid plugs of inexpensive resin, let those plugs shrink/sink like crazy, and then mold a much thinner, even-walled coat of Tenite over the plug.  (The plug could even be machined to give me my undercuts, but that would still involve additional cost.)  The guys that sent the samples to me suggested this molding option, and it may prove to be the viable link we need.  This stuff vapor-polishes great, so we could probably erase the parting line for a perfect finish if we go that way.

At this point, starting with machining is probably the best idea, and we can transition to molding later if that becomes more feasible.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

I see that you are deliberating machining versus injection molding. You also mentioned that the appearance of the part is critical. It could be important to consider that a filled part will show flow lines if you injection mold it due to the way the filler / pigment flows. This is likely to detract significantly from the appearance. In contrast an extruded rod or thermoset part can be made without flow lines and give the natural marble appearance you seem to be looking for.

RE: Strange resin sought

(OP)
Good point.  Because this is a "premium" item, we're planning to stick with machining, at least through the launch and into production.  If we can get identical quality in molding, and if molding becomes more feasible otherwise, we'll consider doing that.

It's nice to have options.

Thanks everyone for all the input so far!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought


Theophilus:

Jeff, how is the project going? Much joy or gloom, doom and despondency?


Merry Christmas

Harry

RE: Strange resin sought

I'd like to bump this thread as i'm kinda in a similar situation, high end bathroom accessories requiring material with similar spec.

Thanks.

RE: Strange resin sought

Why not start your own thread instead of hijacking this one.

You could start it with a post that is a clear and concise question. That is normally the best way to encourage a positive response.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

I'd just be making a thread the same as this one, which i dont see the point of.

I was more interested in his outcome and not hijacking.

RE: Strange resin sought

(OP)
Just got back into the office after quite a while out (nice vacation).  It seems I wasn't the only one out, since my prime contact for the butyrate material hadn't responded for a while either.

So--I'm meeting with my client today on this to get a quantity estimate, to look over our rapid prototype, and to otherwise begin moving toward production.  My client likes the butyrate sample my source gave (found through Eastman--very helpful people there).

Everything is moving along about as fast as I can move things along, considering all my projects.  So the help you've provided has been extraordinary!  I really appreciate it.  A similar hardness to the samples I received will probably meet our needs exactly, though the material is entirely different in chemical make-up from my original search.  The properties, however, and not the chemical recipe, is what we need.

More to report after receiving a machined sample in the right material to run through paces.

Thanks again!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

Thanks for responding with your results It greatly increases the value of this thread. Most people fail to close the loop on this board.

RE: Strange resin sought

(OP)
Update:
I just picked up some machined samples today from our machinist--the rod was extruded Tenite (Butyrate, Eastman) from another vendor.  It machined great, and the machinist may be able to obtain a perfect (for our standards) finish right on the lathe without any post-process vapor polishing.  The first trial is looking promising.

Thanks again!  More to follow as things progress, but it looks like we're on the right track with this very versatile material.

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

Thanks for the update, great to hear how things are working out!


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Strange resin sought

Hi Jeff/All,

Just goes to show - all these fancy new materials and one of the original plastics did the job!!

We will be talking caesin or Bakelite next!!

btw - if you eventually go for injection moulding, one of the CA's (not sure if it's the butyrate or propionate, or even both!), smells like dog s**t when molten!! You might like to warn your moulder if you go that route...

Perhaps when in production and confidentiality no longer applies you could post a photo/rendered drg. of the part - be interested to see it.

Cheers

Harry





RE: Strange resin sought

Yes, the cellulosics are temperature sensitive and so not so easy to injection mold. Long residence time will burn the cellulose acetate proprionate and I assume the other cellulosics too. Also you need a certain screw type in your injection molding machine, not a standard PE/PP screw. Eastman can help with all the details. Don't worry though, it can be done even for large parts, you just need to be aware of the conditions needed.


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Strange resin sought

Cellulose Butyrate smells like rancid butter as both contain butyric acid.

Propionate is very transparent and easier to mould with no unpleasant side effects. It was traditionally used for spectacle frames and tooth brushes.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

I once did some experiments with a series of carboxylic acids, C2, C3, C4, C5, etc up to C12 and C18. We surface treated fillers with them.

The very short chain ones like formic acid smell sharp like vinegar. The long ones smell fresh like soap. But as Pat said C4 and those next to it smell hideous. Was a week before the smell left the lab.


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Strange resin sought

(OP)
We've encountered a bit of a roadblock.  One of the post-processes we intend to do with this part is a dye sublimation process (image transfer) that uses heat (325F) to sublimate and transfer the dye to the part.  However, at that temperature, we're seeing the delivery mechanism for the dye stick to the part--because the surface of the part is melting.

So this is a deal-killer with this resin (for now).

Can anyone think of a way around this?  I love this material, but the low melting point is certainly a problem with this post-process surface treatment.  Is there perhaps a sister material with an increased melting point?  A filler or other additive?

Thanks,

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

Best to ask Eastman who make the materials. It's
well known that the surface softens when heated. Normally they have that as a selling point because a lightly scratched surface can be fixed by heat treatment where the scratch heals.

The material we had from them was available with differing amounts of plasticiser. You should check with them what grades they have. One with less plasticiser should resist the heat a bit better.

Adding filler could help a bit, for example fine silica to maintain transparency but that may change the feels (haptic) of the part.

What happens when you put the parts in a fridge or freezer before the dye sublimation? That way perhaps you can stick with the material as-is and avoid too much surface heating!


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Strange resin sought

(OP)
Thanks!  I've contacted Eastman, but my contact was out of the office last week.

From what I saw on their materials pages, the melting point with similar plasticizer levels were all near 219F--still far too low.

Decreasing the part temperature is a great idea--I don't know if the part surface itself has to be warm for the dye transfer, but I can find out.

Thanks!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

If you want to use the sublistatic dyeing process, polyester will work a lot better. The process was developed for polyester fibres which are thermoplastic PET. 2 pot polyester casting resins are thermoset PET and will have a similar dye affinity.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

(OP)
Thanks, Pat.  I've looked into PET (thermoplastic) and have difficulties with the white color and opacity.  Ironically, however, I think our existing material is a polyester thermoset (such as a casting resin), and it does pick up the dye transfer fairly well.  However, it has a lack-luster finish, so it gets tumbled in a pellet/wax treatment to gain gloss (as best we can tell).

I like the Tenite we found because it machines so beautifully and we have so many other options available for color, etc.  Just seems the dye transfer isn't working very well.

Eastman is now checking into some alternatives, so I should have word back from them by mid-week.

Thanks!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

You can dye cellulosics, just not reliably by the sublistatic process.

Dyes that work for acetate rayon should work. They tend to be  the same basic class as used for polyester (being dispersed dyes) but of a lower molecular weight so they can absorb into the polymer or fibre at lower temperatures.

The sublistatic process works by evaporating the dye, then allowing it to condense onto the substrate, so evaporating temp vs substrate melting point is critical.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

There are dye sublimation processes modified for plastics. KOLORFUSION INTERNATIONAL is an example in the US but there are others.

RE: Strange resin sought

(OP)
Eastman ended up falling through for an alternative resin that would work for our needs.  So we're now giving POM a more serious look, since it works great for the dye sublimation.

My client was already working with Kolorfusion--that's interesting you mentioned them.  I read an article a while back that discussed this whole process that listed several others as well:
http://urltea.com/ja8

I think our difficulties will be in finding a good adhesive/solvent for the POM material and getting that perfect opaque look from the resin.  I'm concerned about that, but we're working on some samples to see what we can get.

Thanks!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought


Jeff,

Colour/pigmentation will not be a problem - talk to your local masterbatch folk.

Bonding POM - serious stuff. Solvents very toxic/noxious etc. Suggest you look at mechanical fixings. POM v. good for snap fits etc.

Good luck.

Cheers

Harry

RE: Strange resin sought

(OP)
Thanks, Harry.  I've got some housings I think I'll need to bond together--small stuff where I cannot mold undercut prongs and cosmetic so I cannot use shut-offs.  I don't think a friction fit will work well enough either.

Maybe I need to bark up another tree in materials--something else that I can find a solvent/adhesive for that works with dye sublimation and delivers great molded and machined results.  (Any ideas?)

Thanks again,

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

RE: Strange resin sought

POM is almost impossible to bond by methods other than welding.

Having said that, if anyone can bond it, 3M can.

DuPont and Ticona also probably have some data.

Cellulosics can be dyed by selected dispersed. Low molecular weight dispersed dyes might work by the sublistatic method, but you would need to make your own sublistatic dye impregnated paper. This might not be viable due to scale or available resources for project.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Strange resin sought

(OP)
I'm considering this Rynite PET as a possibility (sorry--looks like we're going all the way round to where we started--ug), but I've not yet seen the material "in person" to see if it will work aesthetically for my client.

From the article I posted earlier, I see this chart:
http://www.appliancedesign.com/AM/Home/Images/Fig-1-DuPont_large.jpg

Since the ability to do the dye sublimation is critical with these parts, this looks like a new "anchor" from which to decide materials.  I'm also attempting to see if we can approach the other dye options you mentioned, Pat.  We'll see how it shakes out.

Thanks again for the great input!

Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all.  And awe transcends reason.

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