Hi all, can anyone tell me chemical used as flex additive for epoxy? Cheers Petey
For light flexibilization use propylene glycol. For big flexibization better to use active flexibilizer ,epoxy function linked to pp glycol. Then with epoxy elastane hybride you can go very far in flexibility.
Lemat- What would you condsider a good amount (percentage, range) of propylene glycol to add to an epoxy batch for some extra flex? Merci, -J
Max 6% (of resin). PPg increase elongation to break and tenacity, but reduce stiffness modulus, strengh modulus and Tg, can reduce durability too so be carrefull with those cheap plastizer. If you want something more serious look to specific active products.
How much extra flex are you looking for? Compared to polyester epoxy is terrific in flex? If it is board flexure, aren’t you looking at tension and compression properties?
I tried to fix a crack in a hummingbird feeder by using epoxy once. Everything seemed as it should… the epoxy went off and seemed plenty hard. I filled the feeder with red food coloring mixed with sugar water and set it outside. After awhile it was empty and I checked it out… the epoxy had turned red and rubbery. It felt almost like those fruit roll-ups - leathery but super hard to tear.
I never followed up on it but have often wondered if sugar water, or perhaps red food coloring, has any effect on curing epoxy.
The reason why im looking at a flex additive is because here in Bali we only have a few types of epoxy readily available. It cracks and shatters really easily even after post curing. Unlike epoxies I have tried in the U.S. which had great flex caracteristics as well as being super hard to shatter or crack glass even while i slam the board into the wall. So ya I guess tensil strength is also what I am trying to acheive but I think adding a flex additive will accomplish this … Any more additives or suggestions … ? thanks all for your input.
Tensil strengh is for nothing, it’s toughness you want. It’s elongation to break you need, and not so much more than your typical indus resin. Polypropylène glycol can work right for what you expected. With industrial epoxy curing at high T° is imperative for toughness, may be you can’t go up to this temp because of foam blank.
adding pigment to epoxy will make it more flexible. I’ve done this when you want a more flexible tail or rail line…you can do it like a resin color patch. But you need to be pretty generous with the colorant.
Works great, and looks good too.
Pigments, unless they are epoxy reactive which is rare, act the same way lemat describes. The carrier does not react into the epoxy so it acts as a plasticizer.
If the epoxy is formulated at the theoritical mix ratio, adding 10-15% extra hardener will also increase elongation to break in most room temp cure epoxies but that plays hell with color stability.
Lemat, Resinhead, RobW-
Thanks for sharing your knowledge with us. Extra pigment sounds like a winner if the epoxy is not a nice color to start.
So, pouring finboxes…all the pigments and fillers…helping the epoxy to flex a bit more before failure as well as making things pretty and reducing total exotherm?
-J
Through r and d flex has a lot to do with what type of foam you are glassing… in a quick comparison xps has much more flex and memory than eps. EPS seems to get quite rigid after glassing and I have played with 22 kilo density all the way to 40 kilo densities. Has anyone have any feedback on varial foam flex or the new marko foam closed cell blanks ? Im keen to learn…
Thanks Rob W. Think you pointed out something key to why I may be gettting brittle results. I have had long debates as I beleive most 2 to 1 ratio epoxies may be 2 to 1 by volume but 10 to 4 by weight… So lately without thinking to much i have been using 10% more hardener tham necessary. Im reverting back to 10 to 4 by weight , I will try adding 6% propylene glycol and am hoping for better results… cheers…
Thanks Rob W. Think you pointed out something key to why I may be gettting brittle results. I have had long debates as I beleive most 2 to 1 ratio epoxies may be 2 to 1 by volume but 10 to 4 by weight… So lately without thinking to much i have been using 10% more hardener tham necessary. Im reverting back to 10 to 4 by weight , I will try adding 6% propylene glycol and am hoping for better results… cheers…
DSD,
I don’t think you’ve mentioned what epoxy you have, but just to be sure you understood RobW’s point: with many polyamide hardeners (often used in older or cheaper epoxies), adding more hardener actually increases elongation (conversely, adding less makes the cured material more brittle - to a point of course) Such formulations are sometimes referred to as nylon hardeners (nylon is a form of polyamide).