When you seal an EPS blank with spackel are you changing the bonding properties of the epoxy to the EPS? How does this work without causing delaminations down the road? If you were to seal an expanded polyethelene foam with spackle would you be able to use epoxy for laminating? http://www.specialchem4adhesives.com/…p;log=epoxy_adhesive this link explains why you can’t bond certain polymers. But it seems that EPS and EPE are very similar, so could you use epoxy with EPE using heat and vacuum? I guess I could seal the EPE with something like this http://www.stealth316.com/2-dp8005.htm, Im just worried about adding weight and involving another time consuming process.
What’re you makin Turbo???
Kind of surprised and disapointed I got no real answer, I guess Im just going to try out what I was going to do anyway. Worse comes to worse I’ll try sealing or using a heat activated laminating film. I’m looking into a new type of foam, you’ve probably never heard of it before…I’m trying to get a block to sample and if it easy to shape and glass, surfs well, and is cost effective I’ll let you guys know whats up… I’ve been testing out a whole bunch of shit lately, feel kind of dickey I haven’t posted any pictures yet, nothing completely new and finished yet. Had some good experience with a new composite , it only dented with a hammer and I did the horse saw jump test with it only laminated on one side of foam. I’ll be ordering a whole bunch of good stuff soon and hopefully some RR epoxy which would help alot with the composite, the epoxy is providing the structure and flex characterisitics…
hey turbo , when i saw the names of the links , i thought ,looks like hes onto something that requires a little more thought …
so i havent had time to check the links and get an insight into what your were thinking , its on my list , but both greg and myself have been hell busy at the moment …
i will check those links , i was going to do it tonight but ran out of time , have to go now …
will get back with at least some thoughts once ive been through the links …
regards
BERT
hey bert,
I know you’re busy so when you get to it, you get to it…I’ve contacted the manufacturer and hopefully I’ll be getting samples to play with soon, so I hope I can answer my own questions and get back to guys with some real feedback.
If you go to forum archives and look up “peel strength” you will find a post by Greg Loehr (March 29 2004- the Great Epoxy Escapade) in which he states that spackle is every bit as strong if not stronger than microbaloons and epoxy. I trust his expertise and that’s why I went with spackle rather than epoxy for the seal. Plus it costs less.
I’ve used spackle to seal EPS many times, however, I don’t think I’m completely understanding the actual chemistry behind it. I’m also asking this question becasue I’m looking into a new foam alternative that is not polysterene.
On the link to the site you posted is your clue to understanding the physics of adhesion, you really don’t need to get into the chemistry, starting with the first word. “LOW”; EPE has a low energy surface.
That link has a good discussion of low energy surfaces.
The opposite is a high energy surface, which describes the adhesive holding energy of a material that things like to stick to.
You really don’t have to go much further than that. That is the chemists job.
So if I understand your situation correctly you need a primer for EPE foam. For that I would probably try or lean towards a primer paint of some kind first. Perhaps a 100% acrylic primer like Pro Block by SW. They have several formulas of Pro Block primer, and they may have one that will bond good enough with EPE.
Then you can epoxy directly to that.
Look at it this way if you are already spackling EPS, why not painting EPE? There is more structure to the paint than the spackle, but I think the spackle is applied so thin that it probably absorbs the epoxy, and in effect does the same as epoxy and micro balloons. Because, if you read the container of the spackle, number one ingredient is, you guessed it, micro balloons.
I almost forgot mechanical bond. The rougher the surface the better. You will need to experiment with how rough you can go without going too rough.
I went through all these adhesion problems when searching adhesives for MVGs. The technical support people at 3M were great. Simple accurate answers to a myriad of questions.
with surfboards , foam cored surfboards , the problem isnt with the bond strength of a polymer to the substrate …
its the substrate it self which is the weak link …
ive used the foam your talking about and the bond you get is insane , better than eps ,xps , or p/u , its the best of any foam ive used because the foam itself is more structural …
on the lighter epe and epp you start to get the same problems of losing peel strength , again , nothing to do with the bond of polymer to the foam , but the foam it self will pull appart …
i would be real interested in what you come with using epe or epp , ive been to busy to chase it down …
another interesting thing with epe is you can use polyester resin over it …
i think it has promise , but its yet to be produced in any practical sizes for surfboards , but when you get some you will be amazed at the peel strength …
better give us a progress report …
you wont need the bonder or primer listed on the second site …
the use of spackle on eps is to hide blemishes and to stop the blank drinking the resin …
if you laminate 1# foam with an epoxy that is highly viscous with a long pot life , it can drain right through the core and drip out the other side , even with 2# foam , not sealing and using a longer pot life resin will still allow the resin to penatrate up to 15mm , that is weight , so sealing keeps resin usage down , and adds performance by not locking up the foam allowing better flex …
but for the p/u guys making the transition …
i would say let the baby drink it , then youll have dead flex and extra weight , if your gonna make the change to better materials then might as well do what you can to make them perform as bad as what your used to …
regards
BERT
So it seems to me maybe the actual bond between the resin and the foam isn’t that strong in the first place. I’m not sure how it differs from EPS/epoxy to poly/poly. I guess you’re thermoforming the resin/fiberglass anyway, plus the resin filling in gaps in the foam would create a sort of mechanical hold. The spackle is great for fixing blemishes, UV protection, and getting that nice all white color. I think since the spackle is really just a hard arcylic sealer/primer the bond is stronger, which would reinforce the fact it has better peel strength. The foam I was refering to is made of both EPE and EPP bead, both bond together by a certain elsatic adhesives that only attaches the beads at the contacts points. This allows the foam to be porous. Water can go straight through without ill effect. the foam is more elastic plus it has rebound properties. Would be intersting to see how it reacts to pressure dings, dents, as well as hard landings from air drops and big airs…
like Bert said the EPS sealing is mostly cosmetic and to help reduce weight and is not needed.
Greg, uses light weight water based spakle that has been watered down a lot to make it quite runny. He then aplies it very thin and most of it gets sanded back off. It is mainly just there to fill the voids.
Greg also stated that the epoxy will still soak through the thin sealer and still acquire a bond with the foam. The sealer will just reduce how much gets into the foam.