The Iso resin debate - rehashed

right, sorry for dredging this up again. But, I’ve come across a new resin from my local supplier that I’m curious to play with, but can’t find any technical data to compare it with the normal Silmar 249b that we get over here in the UK.

here’s the only debate i can find in the archives, and it’s not much:

here’s the data sheet from the resin I’m playing with now:

So, what I’m after is the same technical data for silmar to compare the tensile strength, and elongation to break characteristics.

I will say however, in a test panel- made from a rail off cut 1" thick sanded flat on both sides - it does seem to flex well without delamming compared to the silmar. Not quite as flexible as the epoxies I’ve used, but somewhere in between.

I can’t comment on UV stability just yet, but will let you know what I find out, if you’re interested. It isn’t totally clear either, more like a slight milky white when in bulk, but when in a thin lam over white foam, that hasn’t shown a problem yet. I’ll admit to not making a full board with the stuff yet, as I’ve got some foam samples on the roof to see how yellow it goes in the next month or so, but am leaning towards giving it a go if I can find some numbers to compare…



I wouldn’t know about your particular resin but isopthalics tend to turn amber after a relatively short time when exposed to uv. You probably shouldn’t do your exposure test on foam since it can change color and throw off your test results, IMHO

If the Isopthalic resin were available, I would switch to it instantly. I have had excellent experience with it in the past. (way past!)

thanks for both your comments.

Mahana, yeah, I guess you’re right about the foam, but since its an off cut of the blanks i normally use, i figured it would be best to test the whole lot vs a piece with silmar. And surely in the real world it is the closest, hey?


Yeah, I read that they were banned in the US mainland, does that mostly have to do with styrene content? This one is pretty low(?) in comparison to the Dion stuff…

What did you like about it? Better dent resistence and flex?

Seems to take all the same additives, even pigment. I’ll attach a picture of the results next week…

Impact resistance, and tensile strength, were primary consideration. The resin excelled at both, when compared to polyester resin layups.

In olden times, balsa and early foam, iso was what we used. It was tough and easy to work with. I bought some from Tap Plastics a couple of years ago.

Thanks Bill,

I was impressed with the samples I got, and the tech data sheets. I guess the only way to really know is to make a full board, so I’ll get busy…

Thanks again everyone