Resin did not melt foam
 

This afternoon I worked on the tail of my Jetta, and accidentally/on purpose got some resin on the exposed expanding foam currently residing on said tail. I waited for the melting. I was really looking forward to it, quietly hoping that it would only be a little bit so I wouldn't have to do a lot of reworking. Nothing happened. The resin hardened and there was no melting. I was kind of relieved and disappointed at the same time.

For the record, the foam that I have on there now is the kind that comes out of a can that you get at Home Depot, Lowes, or any other hardware supply store.

Pics or it didn't happen.

http://i1201.photobucket.com/albums/...g?t=1335642064

http://i1201.photobucket.com/albums/...g?t=1335642076

http://i1201.photobucket.com/albums/...g?t=1335642090

http://i1201.photobucket.com/albums/...g?t=1335642103

What kind of resin did you use ? Polyester, epoxy.. ?

Jethro, how long had the foam been curing? I had a maybe similar experience, maybe. Overnight cured foam melted, but weeks-old foam did not. I also found that spray paint would melt overnight cured foam, and not weeks-old foam.

CigaR007- El cheapo polyester resin.

California98Civic- Time may be the answer. The foam has been on for a week. I was leaving it on for a while before covering because my previous experience has shown that the foam will move a bit for a couple days.

I love what you have done aerowise to the car, but GOWD !
It is starting to look like you covered the car in brain matter :)

Too expensive, brain matter that is:D. Kinda tough having a "work in progress" that you have to run everyday. Good thing I don't get embarrassed easily.:D

Jethro, the foam-in-a-can is urethane, which once cured does not dissolve in resin...or gasoline, or pretty much anything else.

I own a composite shop (Dauntless Racing Cars), so here's a short primer on common foams and resins:

Urethane Foam - doesn't dissolve in anything, but breaks down under vibration loading. Cheap at low densities(<2 pcf), but increasingly expensive at higher densities (>6 pcf). Sold as tan-colored closed-cell insulation at home improvement stores.

EPS Foam - white bead-foam insulation or pink/blue insulation/float foam. Cheap at all densities, but weak and dissolves in ANY organic solvent (which includes polyester and vinylester resins, but NOT epoxy).

PVC Foam - AKA "divinycell", medium priced at low densities, and increasingly expensive at higher densities. Like white pvc pipes, pvc foam is essentially inert to practically everything, and does not break down with vibration or other loading. (Crushing is not "breaking down"...breaking down is turning into dust.)

Polyester Resin - Dirt cheap resin that is weak and stinks to high heaven from the styrene in it. Flammable.

Vinylester Resin - Fairly cheap and stinks from styrene. Stronger than polyester, but not as strong nor high-temperature tolerant as epoxy. Somewhat flammable.

Epoxy Resin - There are several types, but all true epoxies are styrene-free and so do not interact with solvents. Epoxies are potentially allergenic, so caution must be used when handling them (wear protective gloves at a minimum, and take their health and safety warnings seriously). Not flammable. Low-to-no smell.

Hope that helps! :)

With as much foam as you are using I wonder why you don't just get the two part foam in cans. It cures a lot harder than the foam spray cans.

I'm glad you didn't take offense.
I wish I didn't get embarrassed easily.

I can't wait to see you make it out to Bonneville.

Good info Stan,
I was at Lowes and saw they had some Polyisocyanurate Foam board,
twice as expensive as EPS foam, but I took a tiny sample home and it didn't melt from polyester resin. It is apparantly a stronger type of polyurethane
from a what little wikipedia says Polyisocyanurate - Wikipedia, the free encyclopedia
Do you know much about this stuff? I'm going to use some of it in my car, but now I'm thinking maybe my sailboat project even though I will use epoxy on the boat, this foam seems a LOT cheaper than PVC foam.

Yes, I'm very familiar with this foam. There are several different formulations of urethane foams and this is one of them. And in fact, is exactly what I had in mind when I wrote under Urethane Foam, "Sold as tan-colored closed-cell insulation at home improvement stores."

The challenge with urethane foams is that at low densities and thin sheets they tend to break down over time into dust (literally) under repeated vibration and pounding loads, so I recommend not using them in boat hulls, homebuilt airplanes, car body parts, etc. You live in Sactown, and pvc foam is available at Interstate Plastics for $70 for a 4'x8'x1/4" sheet.

I realize that may give you a bit of sticker shock, but pvc foam is a MUCH better choice, and in the big scheme of things, isn't much compared to the price of a complete boat.

we are getting a little off-topic, but I see there are 4 and 6lb densities available from a manufacturer in Indiana, is this going to be good?
how long does it take to crumble? This is even when clad in glass?
I would not use it in a significant structural role. My hulls are epoxy coated plywood, the cabin structure is what I'm looking at building primarily,
and I need the insulation value as well.

Yeah, sorry about the topic drift... :)

Anyway, I don't have exact data, as it will depend on thickness, loading and the specific formulation. If the application is not in the hull and is not carrying primary loads, I don't see why you couldn't use any foam you like in that case.