I noticed in an add that “foaming epoxy” was used in the construction of a board. What the heck is that, and how does it differ from the more standard epoxies?
it works well for sandwich construction and difficult mould shapes , helps get a board lighter , perfect for vacumn moulding …
its an epoxy that has a 3rd additive , that makes the resin foam , in the end left under sea level atmosphere not in a mould it resembles hard crunchy foam , restricting the area it has to expand will give it different properties , plus when mixed with different laminates the foam takes on different properties as well …
great for filling voids in hard to reach spots where strength and bond are still important …
regards
BERT
How about epoxies with rubber added (saw an ad the other day) any uses? Ad said that rubber made it tough and with increased peel strength and flexibility.
wells
Wells, that would be neat to see/test… increased elongation and impact resistance perhaps?
…it seems you’d need more than standard s-glass to get the full potential out of such a composite since it’s key to match the fiber’s elongation % to the matrix elongation %.
Does anybody know if foaming additives are usually low viscosity/low melting point waxes or something of that nature -essentially lightweight, liquid thixotropeners?
Bert, can you get similiar effects from simply “whipping” air bubbles into your batch of epoxy?
cheers,
Brennan
Quote:
Does anybody know if foaming additives are usually low viscosity/low melting point waxes or something of that nature -essentially lightweight, liquid thixotropeners?
Bert, can you get similiar effects from simply “whipping” air bubbles into your batch of epoxy?
i dont know exactly what the foaming agent is , its part of a 3 way system , the 2 part epoxy is just normal epoxy when you dont add the foaming agent , what i havent done yet is see if the foaming agent will get another brand of epoxy to react to it …
the stuff actualy forms quite a consistent foam with a density of about 150kg per m 3 at sea level …
ive got it down to about 70 or 80 under vacumn …
you can almost get similar results by allowing air to leak into a vacumn system in controlled places and amounts , but that tends to be inconsistent , this product is alot more consistent if you want bubbles in your resin …
seems weird to suggest air bubbles in your laminate , but when you cant see it you might as well get your lams as light as possible , what better way than heaps of air bubbles in your glass job …
i have to laugh …
trying to teach one guy in one side of the factory , to get more bubbles in his glass job , then walking into another section and grilling a guy and giving him a lecture for having a few tiny bubbles in his visable glass job …
hm maybe i should have swapped them around ,doh …
regards
BERT
Some of the Urethane adhesives (Gorilla Glue, etc) also foam up quite a bit. Has anybody tried it as a composite glue?
There are also thin foaming epoxy adhesive films that foam when heated.
I can envision them being used to fill out certain parts of a boards shape with a mold under vacuum much like Bert’s contour mats shape his bottoms.
the stuff actualy forms quite a consistent foam with a density of about 150kg per m 3 at sea level …
ive got it down to about 70 or 80 under vacumn …
ahhh…I get it…that better explains the mystery pic you posted on saturday…personally not going there tho
The foaming additives were used quite a bit in early molded sailboard development before they got the coring down. Since the cores were inexact the foaming epoxy was used to fill gaps. There was one technology used by F2 which used a very loose fitting core with glass pinned to it. The foaming epoxy would then be shot in and shortly thereafter a board would pop out. I don’t know anyone presently using foaming epoxy anymore. The coring technology has eliminated the need and today the boards come out much better, lighter, without voids.
As for rubber co-polymers, I’ve played with the stuff a bit. It was originally developed at Goodrich Chemical and from what was advertised sounded like good stuff. Promised was an increase in impact strength without effecting stiffness. In application though it didn’t quite work as advertised. I don’t think this is applicable to surfboards although for some other uses it could work… funny, that same chemical is now used as a food additive. Many of the urethane co-polymers are similar in their use in epoxy formulas as plastisizers. In our formulations we do include some plastisizers but we don’t use either of these. Again, really not applicable to our product (composites). More for coatings, anti grafitti paints.
An old trick I learned from a wise old Dow epoxy chemist since the '60’s… spit in the epoxy bucket and then jiffy mix it! You can vary the foam by varying the loogy amount hocked. Try to use pure H20…minimize mucus. It will react even more with heat or exotherm. This actually works.
If anyone wants any rubber or urethane epoxy additives, I think I have over a hundred gallons of each that have been sitting since 1990. Greg’s right on, elastomeric additives seem like a great idea, but they wipe out many of the important physical properties that you need in epoxy, mainly compression strength. It’s kind of like putting Kevlar in compression.
Del P.
I don’t know if that is such a good idea. Questions and replies from System Three Resins, Inc.(makers of SB 112 surfboard epoxy resin), Technical Support:
- Would rubbing alcohol be good to use as solvent in
thinning mixed epoxy?
Answer: Rubbing alcohol contains 30% water. Using this will cause
the resin to turn cloudy. Stick with lacquer thinner, xylene, etc.
- Is it necessary or desirable to put the SB 112 through a post cure heat cycle, such as described on the System Three web site?
Answer: It is not necessary to post cure SB-112.
Foam is by nature, cloudiness. The System Three duders just verified my tip. I use over 450 gallons of epoxy on a daily basis and thus have learned a few tricks over the years. Sweat drips will also create foaming. All my epoxy is run through static mixers so no air or moisture is induced in the mixing process. I try not to foam!
Heat must be applied during cure, not postcure, to create foam.
Love, Delbert Pumpernickel
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Rubbing alcohol isn’t the right stuff, denatured alcohol is. Also be careful with alcohol around water. They LOVE each other and are drawn to one another. Additive F keeps water away from the surface of your laminate, hot coat or gloss which is important if your using an alcohol based diluent. If your using EPS or another polystyrene foam DO NOT use xylene, lacquer thinner, acetone or similar products for viscosity reduction. DO use denatured alcohol. It won’t effect the foam, the others will.
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Most of the surfboard epoxies are room temperature cure systems. Post curing does give some physical advantages but post curing isn’t a must.
Holly… water can be used in conjuction with some other chemicals to create accellerators for some amine systems. We used to make one and if done right it doesn’t foam. The foaming is the oxygen in the H20 reacting which has a push/pull effect on the reaction (exotherm). These accellerators tend to dramatically shorten pot life, somewhat shorten tack time and minimally shorten set times. We used our custom accellerator for almost 20 years until about 3-4 years ago when we came up with a better way to shorten production time which is our present fast hardener. By the way, did you get the PM?
hey holmeister , check your mrs inbox …
while im here , just like to say , you have a serious act on the manufacturing front …
love to have a surfboard factory like the set up you guys have for punching out all the composite performance gismos you do …
hope you didnt mind me cutting those boards in half you sent me !!!
only joking …
they are so dam nice all i wanna do is pick them up and hold them …
regards
BERT
while were on the subject of foam and epoxy …
check this pic taken tonight …
3 finished boards (almost , 2 still need a cut back and polish , so they will still get lighter ) all 3 weigh the same as one glass board …
these finished boards weigh the same as unglassed blanks …
surfing a board the weight of a blank, they all have set fins to …
all week ive kept picking these boards up just to make sure im not dreaming …
everyone who has come in the shop has been invited to try and pressure dent them …
no one has succeeded yet …
showtime …
Greg, are you saying you can thin epoxy with denatured alcohol? Maybe do this for a thin gloss coat?
bert, are saying that bubbles do not influence the tensile strength so the inner layer can have bubbles? if thats true would a “dry” laminate have a similar effect and be ok for me as a garage builder?
thanks
uzzi