PR Heat Curing

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KDM

KDM

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Now, you'd have thought that someone who's spent the last 12 months casting his own pen blanks would have known the answer, or at least thought about this...

I know polyester resin us usually catalysed and that he reaction is exothermic and that heat plays a part in the curing....

Question: can PR be cured purely by heat, or must it have some MEKP in there, too?
 
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it CAN, but it won't be the same and it would take a while.
If you mean "can I just pop it in the toaster oven and have
it cure like normal in 8 hours?" the answer is 'no'.

But if you leave the can in a warm room or in the sun,
you'll likely have trouble pouring it in a short time..
 
I have done very little casting, but I can tell you that if you let PR sit around long enough, it will harden (I assume cure). Can you tell that I didn't finish my container of PR?

So, yes, I think, it will cure with heat. Will probably take a long time though! Months? Year+?
 
Usually most PR is "pre-catalyzed". Meaning that it has a small amount of catalyst in it when you buy it. If it didn't, the cure time would be much longer.

The down side is that this will cause the PR will set up over time, and/or with heat. Depending on the brand of resin and the mass of resin sometimes it doesn't take much - or very long. DAMHIKT!!:mad:

Anyone want to buy a 5 gallon doorstop???:rolleyes:
 
PR_Princess said:
Anyone want to buy a 5 gallon doorstop???:rolleyes:
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Sure, I'll take it:biggrin:! I'll even pay the shipping! Does fully cured PR ship as a hazardous material?:biggrin::biggrin::biggrin:

That way, I'll have a matched set! In South Georgia, never order PR right before you leave town on vacation! DAMHIKT
 
PR isn't "pre-catalyzed" and doesn't contain catalyst.

It is however "pre-promoted" and uses alkyl anilines (dimethylaniline, diethylaniline, dimethyl-para-toluidine) in conjunction with cobalts or most common... cobalt napthenate. It is an accelerator and when the catalyst is added, begins the chemical crosslink.
 
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KDM said:
PR_Princess said:
Anyone want to buy a 5 gallon doorstop???:rolleyes:
Click to expand...

Could you run it up the bandsaw and make a shedload of transparent pen display rests?
Click to expand...

Possibly, but I don't know that I would. Being "set up" is not the quite the same as being cured. Internally (as Charlie and James have said) it's different. The cross linking polymerization is not complete.

Still it makes a great door stop.....or in Andy's case tent hold down!:tongue::cool:
 
What if I just put a tiny fart of MEKP into 200g resin and left it on a domestic radiator overnight?

(PRP - you've lived here long enough to know - to they call them "radiators" in the US?)
 
KDM said:
What if I just put a tiny fart of MEKP into 200g resin and left it on a domestic radiator overnight?

(PRP - you've lived here long enough to know - to they call them "radiators" in the US?)
Click to expand...



These chemicals along with the monomers such as styrene are what make PR very toxic, not the resin itself.

As an example...

The catalyst (MEKP) is an explosive and becomes less stable as it ages. It can also cause instant blindness if it gets in the eyes.

Most fail to understand that casting is dangerous..... especially for their health. Look up any of these chemicals or even the PR MSDS and read it.

Casting or curing inside where you and your family breath the air...

isn't wise.

Cast SAFE!
 
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