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Melting point of polyester resin


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  #1 Konrad in Lincoln

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Posted 23 December 2003 - 09:08 PM

Anyone happen to know the melting point of polyester resin? I've laid up a few pieces of carbon fiber for various parts for my Honda CR 500, all have turned out quite well.

I'd like to do a nice guard for the pipe, but I have a feeling that the pipe will get too hot and melt the resin and make a mess. My plan was to use some felt cabinet door bumpers as nubs that would hold it away from the pipe by about 1/4" or more, and keep it a little cooler.

Anyone? (a pipe guard will be fairly involved for me, I ain't gonna do it if it's just going to melt into goo.)

  #2 MikeStevenson

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Posted 24 December 2003 - 12:42 PM

I don't know the melting point, but we usually look to have an inch or so space between glass and exhaust at least. David Mysona's Alfa P3 CycleKart has had some softening problems around the muffler, and I suspect it was after stopping (hot muffler, nowhere for the heat to go and no movement to blow air around). The pipe comes out of the boattail with about a 1/2" gap around it and not too much trouble.

Mike

  #3 Frank Hagan

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Posted 25 December 2003 - 11:35 PM

Vinylester is better than polyester at higher temps. 200F is the highest in the charts I've seen for polyester and the strength is about 52% of the part at room temp. Vinylester is shown with a similar strength de-rating up to 300F.

See http://www.endurocom...s_tech_data.htm for a bunch of charts on it.

  #4 Konrad in Lincoln

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Posted 26 December 2003 - 09:22 PM

Thanks Frank.
I was kind of expecting that vinylester would be the best choice.
(It's just that I happen to have 3/4 gallon of polyester on hand.)

I've been laying up plastic replacement parts for my dirt biking buddies and have managed to score a nice little pile of change for them.

I'll just break down and get the vinylester, even though I probably have to buy a whole danged gallon of the stuff.

I'm still considering what to do for offsets to hold the guard away from the expansion chamber, ideally 1/4" or so. Wondering about some kind of ceramic nub, or felt that you buy to put on the bottom of chair legs to keep them from scratching a wood floor.

Still mulling this over. That's half the fun, you know.

  #5 Frank Hagan

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Posted 26 December 2003 - 11:16 PM

Look for ceramics as standoffs ... you might be able to adapt the sleeves on old spark plugs, or you might find some ceramic sleeves in the specialty aisle in the hardware store (they are used sometimes around machine screws as "spacers" in high heat applications). The other alternative is the foil stuff they use as heat shields behind pipes when soldering (it can be rolled up, although it uses a carbon backing and foil in a kind of corrugated configuration to keep heat away from the wall, and I suspect if you scrunch the corrugations too much the foil will just transmit the heat.

The softer plastics used for chair legs melt at pretty low temps, and I think the felt would also.

  #6 MikeStevenson

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Posted 28 December 2003 - 10:47 AM

Frank's soldering heat sheild idea sounds great. I forgot all about that stuff. It really works: I would hold the torch right on it and you couldn't feel any heat on the other side. I don't know how it works in a heat-soak situation though. It may eventually transmit enough heat ove to bother the glass, but it's certainly worth a try.

Mike

  #7 Frank Hagan

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Posted 28 December 2003 - 01:34 PM

We use a spun ceramic material as refractory in boilers, and you can have a torch on one side of 1" of the material, and you can't feel the heat on the other. It comes in both "brick" and blanket form, but it is soft and porous; water infiltration degrades the performance and structure of the material, so you can't really use it in outdoor applications unless it is absolutely isolated from any water. I don't think it would be appropriate on a bike, but there might be a more rigid material out there somewhere.