Help! Resin separated from painted tube

[Sawdust46]

I just finished two pens and they both have the same issue. I painted the tubes with powder coat which cured a couple of days. I cast the tubes in simlar 41 with 5 drops of activator per ounce. The castings cured over night. I turned and polished them and they were fine. When I pressed the components on (they pressed on with normal pressure) the resin separated from the painted tube at the end of the tubes!

Any suggestions or recommendations?

 

[Russianwolf]

The PR didn't bond well with the powder coating. One solution is to sand out the tubes and use loctite to hold the parts in.

 

[Sawdust46]

I'm afraid if the resin separated that easily it might separate under normal use. I guess the iossue is how to make the resin bond to the powder coat?

 

[Seer]

Isn't powder coating supposed to be baked on not just painted. It would seem to me that the problem is the powder coat is not sealed to the tube.

 

[Sawdust46]

The powder coat was baked and was in very good condition before the casting.

 

[mikespenturningz]

Since I found out I was allergic to CA I have been using Titebond Poly glue for my pens. This stuff really fills and may be just the trick for you. When it cures some of it squeezes out the ends. You would have to be very careful cleaning up but I bet it would hold! You could try putting something on the ends of the blank like Vaseline to keep it from sticking to your blank?

 

[frank123]

Why type of powder coat paint are you using? Polyester, epoxy, or one of the hybrid ones? (This is all there were available back when I did a fair amount of powder coat on various metal parts, there may be newer types now)

Maybe testing different ones to see which has the best bonding to the resin would be of value.

 

[PenMan1]

I think Frank is on to something! I used to have issues with HF powder paint doing exactly the same thing. I switched to Eastwood Powder and haven't had a problem since. I did notice that the Eastwood powder was advertised as working with Polyester. I never checked the HF powder, as it was advertised as a "do all".

 

[PenMan1]

One other thing.... I never use 5 drops of catylist for casting over paint. I noticed a long time ago that PR over Powder paint GIVES OFF A TREMENDOUS amount of heat when curing. When casting over powder, I usually use about 2 or no more than 3 drops per ounce.

Maybe the heat from curing so quickly is causing the seperation?

 

[Sawdust46]

I appreciate everyones comments. I used Eastman powders. I am using silmar 41 polyester resin. The powder coat is heat resistant and the separation did not appear until I pressed on the components. But perhaps the extra heat weakened the bond so it appeared under pressure. The only thing I can see as a potential cause so far is the amount of catalyst. I will try 2 drops per ounce as soon as I have time.

 

[OOPS]

I watched the Barry Gross video on making acrylic pens. He highly recommended that people use a chamfering tool on the brass tubes before assembling acrylic pens. This video was for first-time acrylic turners, so it didn't cover a subject as advanced as the problem you pose. However, he did say that the ends of the acrylic tubes are fragile, and you don't appreciate just how much pressure is placed on the parts during assembly. So you might consider this to be one of the possibilities, even though you stated the parts went together normally. I purchased one of the chamfering tools from Arizona Silhouette (apparently Gross liked the tool so much that he bought the company!) and it certainly makes pen assembly less stressful. It eliminates or reduces the pressure needed to force unwilling parts into alignment.

 

[mikespenturningz]

Was the pressure of putting on the fittings enough to change the tension of the metal and make is move ever so slightly?

 

[firewhatfire]

Disassemble and turn that off and cut a nice contrasting segment for the end. Can't help with seperation. I had 1 of 4 do it with what I was working on.

 

[mikespenturningz]

I didn't see the image. I had that happen when I used to use CA when after finishing the pen I didn't clean the end well enough after removing it from the finishing bushings. When I applied pressure to the blank pressing in the parts it really put pressure on the glue instead of the tube. Maybe something like that happened to you here? It doesn't take much when you are applying that much pressure to a very small area! If you had something get in between your blank and the hardware it would be a pressure overload for sure!

 

[PenMan1]

If the blank won't withstand the slight pressure of press fitting hardware to the blank without "jury rigging" the ends, is that really a product that you want out in the marketplace WITH YOUR NAME ON IT?

IMHO, it's far better to eliminate the "disease" that to treat the symptoms.

Respectfully submitted

 

[Sawdust46]

PenMan1, I'm with you on this. I want to find out the cause but I will not sell the pens. I have already disassembled them. I wouldn't want someone to buy it and have the separation to grow.

I think Seamus7727 may have identified the cause as we were trading emails. I was measuring the resin by weight and because of the density of the resin, I was getting a lot less resin that I thought. So when I added the catalyst, it was at a much higher concentration than I thought. I will attempt to verify this as soon as I can. I'm watching my grandson today.
Thans again for everyone's responses!

 

[bruce119]

I've see this a LOT a couple things contribute to it. Over tightening the bushings wile turning even a catch is bad news. Pressing in parts if they feel a little tight or go askew if you stretch the brass you are asking for trouble.

Now as was discussed too much MEKP is BAD it causes more than too much heat. Too much heat causes PR to be stiff and brittle. Cut your drops down to 2 no more then 3 drops your PR will take longer to cure maybe 12 hours and will still be sticky on the outside just put it in sun for a few hours. Now the PR will be a little more flexible and have the time to adhere to the surface.

Good Luck

 

[joefyffe]

I purchased from "Powder Buy the Pound" I had the same thing upon pressing parts. On clear Pr I could see the open space (air pocket) forming as I pressed. I have noticed this powder, in the toaster oven at 400 degrees, recommended, cures in 10 minutes to a gloss finish. I haven't had a chance to check it out yet, but should I have sanded the gloss finish off? Could that be Sawdust46 s problem? Apparently this is a much needed thread to more than one of us. Thanks for starting!

 

[bruce119]

I purchased from "Powder Buy the Pound" I had the same thing upon pressing parts. On clear Pr I could see the open space (air pocket) forming as I pressed. I have noticed this powder, in the toaster oven at 400 degrees, recommended, cures in 10 minutes to a gloss finish. I haven't had a chance to check it out yet, but should I have sanded the gloss finish off? Could that be Sawdust46 s problem? Apparently this is a much needed thread to more than one of us. Thanks for starting!

I would think that sanding off the gloss would help. I would use something like 1800-2000 micro mesh and wet sand. That should scuff it just a bit and I would bet that it would gloss rite back up after casting. This is all a guess so give it a try and let us know how it goes. :wink:
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