Quote:
Originally Posted by RobertSmalls
I was on Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc. , and I noticed epoxy resin is $100/gal, whereas polyester resin is $35/gal at the auto parts store. I'm tempted to just use the polyester because I read on the internet it's easier for a beginner to work with. Downsides of polyester are that it eats styrofoam, it's heavier and thicker than an epoxy composite of the same strength, and it gives off more VOC's during curing. |
Robert,
You won't have any trouble with the epoxy resin. I've used both over the years, and West System makes a very good product.
I bought the mixing plungers with my order. The epoxy has it's own plunger/dispenser, and so does the hardener.
One pump from each container into a Glad-Wrap plastic cup, mix up for a minute, and you are set to go. I purposely mix bubbles into the mixing operation, and then smooth out to remove them when I wet out the cloth.
Make sure to wear a protective glove when handling, so as to make clean up much easier. Although the epoxy
is easier to clean up.
The West System epoxy will burn your eyes very slightly if you get too close, but certainly much less so than polyester.
Over the years, I've had way more trouble mixing polyester, because I can easily lose count of how many drops of hardener I put in when interrupted for some reason. To me it's much more tedious. Some of my mixes have turned out, well, let's just say, not too good!! Either it goes too quickly or takes days to set up properly.
The epoxy is a little thinner, and but wets out the cloth fine, and really is very easy to work with. Plus like you said, the smell is much better with epoxy.
I'm going to be putting in an order for another gallon of West System this week some time. I use the 105 epoxy with 206 hardener.
At room temperature it sets up over night. If you want it go to faster then heat to about 120F or so, and it will get hard in about two hours or so. Maybe faster. I run as high as 150F in the oven.
The foam starts to get affected above this temperature, so be careful with the heat lamps.
Too much heat and the epoxy will start to blister on the surface. And then too much heat beyond that and the foam will start to get soft are distort in shape. Sometimes the foam shape will come back after it cools down a little and other times, not.
I have noticed on sharp corners, the epoxy does not hold the cloth tightly around the bend like polyester does, or even Elmers Wood Glue for that matter, and that's where vacuum bagging comes in. But if I'm going to vacuum bag, I try to keep the vacuum down to just enough to hold the material tight.
Too much vacuum can distort the shape of the part, especially if it's relatively weak foam. Then a heat lamp comes out to accelerate the setup time.
I don't mind paying extra for the better quality product. And with the mixing plungers, every batch sets up just like it should.
Very consistent in my experience, and much better than my trials with polyester.
Hope this helps.
Jim.