Polyester / Vinylester / Epoxy - which resin to use

[Randy V]

Hi Guys,

I've got a LOT of Fiberglass work to do on my car and would like opinions on which resins would be the best to use and why.

I've got a bunch of Polyester Resin and some old hardener - I don't know if this stuff has a shelf life or not. It's never been frozen (which I know screws up some paints)..

Some of the work is repair, some is construction, some is strengthening existing work.

Thanks for your help..

 

Randy, Mix up a batch and see if it cures. The problem I see most often, is people do not use enough hardener. Temp. has a big effect on how fast it will cure. 77F is ideal! Epoxy resin doesn't work with chopped strand fiberglass mat, but works well with cloth.10 once cloth works best with four layers. One layer of 10 oz. cloth isn't enough. Polyester and chopped strand mat; three layers works well. Be sure to rough up the surface that you are bonding to.

 

[Peter Delaney]

Randy, I would be inclined to go with nice fresh vinylester resin.

I have learned from bitter experience that all resins/hardeners have a shelf life, & that you are usually lucky if it hasn't already run out by the time you buy it !!

Scott, a mate of mine (who is doing all the hard work on restoring the body of my '71 Vette) is an expert - he has worked on Vettes for over 20 years. He now uses vinylester resin for everything - its a bit more expensive than polyester, but its worth it. The polyester is ok for full new panels, but occasionally has a problem bonding to older polyester surfaces & tends to take a long time to finally settle. Once Scott changed to vinylester, he has not had a single problem.

I have had a similar experience with the GT40 - all my initial mods were done with polyester, & whilst I had no adhesion problems, I have had some "print-throughs" as the new stuff aged : (little "lines" around the door handle inserts & across the joints under the rear glass). However, I used vinylester when doing all the more recent repairs / strengthening on the front clip after my "disaster" (run-in with the corner of a brick wall) & have found that it seems to be way more stable over time than the polyester.

As FRPGUY says, make sure you prep the old surface really well - Dremel / die-grind it, work it with 36 grit sandpaper, & wash it off with lots of acetone.

I hope this helps a bit.

Kind Regards,

Peter D.

 

Randy, I'll second all of what Peter D says ! When find a supplier of vinylester resin, make sure it "promoted "( has all the correct chemicals in it so when you add the hardener, it's going to cure). I've been using vinylester for a long time. It really needs to be heated to reach full cure. Do what FFR recommends by leaving out in the sun. It makes a good fiberglass body for cars in hot climates. I've found it's a little bit more fire resistant than polyester! Good stuff!!

 

[EGLITOM]

Randy

As always there is an easy answer and more complex one

PE resin is not equal to PE resin
VE resin is not equal to VE resin
EP resin is not equal to EP resin

FRPguy is correct vinylester need to be tempered( by the way the whole car is in vinylester and is not tempered, so thats the reason why i will put mine ihn the oven before doing any cutting and filing on the body), but it also has a higher adhesive power than PE.

As with a lot of other chemicals there are a lot of different specs out there. These are related to the strengts, curing times ,curing curves , lamination processes (handlaid, prepreg, vacuum injection, and so on ).
Also the fiberglassmaterial is much differrent. Woven material can be purchased in a lot of different wove technologies, depending on your use.
If you want to build lightweight structural parts, the best is to go with woven material. laid up in the correct direction it makes the part much stronger by beeing light at the same time. Check also the different weights of the fiberglass ( usually speced in the weight of resin it takes per surface for the ideal resin to fiber ratio).
check this link
Sicomin - Composites, résines epoxy, fibre de verre, carbone, kevlar, peintures, gelcoat
a lot to read about different specs and materials.
THere are alos good books out there. Take your time to learn the theory.
You are a very good craftsmann, the practical doing shouldn´t be an issue, but learn as much as you can upfront. It will pay out later.
And throw away the old shit.

TOM

 

[Jac Mac]

Randy

As always there is an easy answer and more complex one

PE resin is not equal to PE resin
VE resin is not equal to VE resin
EP resin is not equal to EP resin


And throw away the old shit.

TOM

Tom, thats a bit confusing, I think what your stateing is dont mix brand Y with brand X in any of the three popular systems.

Agree with your last comment- only thing its good for is making small patterns etc, where it wont be a part in any way of the finished product.

 

[Randy V]

Thank you very much Gents!

I will definitely take all your recommendations in my work... I've done a fair amount of fiberglass / carbon fiber repair work and some mold making on racecars - generally the stuff you would call 20/20 work (20 feet or 20 miles per hour)..
I've got to sharpen my skills some for this. I'll post updates on the work on my web site...

What say you all on Fiberglass laden fillers known to many as Kitty or Tiger-Hair ?
I have some areas that I need to build up and would rather not do it all in matt and resin.

I would take it that Featherfill G2 Polyester Primer should work well on that work that I do to help seal the work and eliminate print-through.. Actually I was planning on doing the entire car in Featherfill.. Thoughts?

Any and all recommendations are appreciated immensely..

Thank you...

 

[Brian]

For surface imperfections I am using Fibreglass Evercoat Glass-Lite, in the gallon size it is number # 639. The guys up here use it on Vetts and they like it.

Before we get to far though, I went to my paint guy and we selected the full range of products that I'll be using from soup to nuts, then verified my paint codes to ensure everything was compatible and available. My notes are in the garage, but I'll be using a spray filler which is likely similar to Featherfill.


Mark Worthington arranged a painting class for several of us at PPG, he posted his class notes a while back which I am sure you can find with a search. I agree with Mark in that the class was likely the best money I have spent on the GT to date.

Brian

 

[Peter Delaney]

Randy, please don't be tempted by that Kitty / Tiger Hair stuff - it is mostly made from the cheapest polyester resin & you can bet it won't be too compatible with your substrate.

I used a bit early on, but noticed that it soon sank back after sanding - so I ground it out & re-did the area with real mat & resin - much better.

A couple of extra hours building up with mat & PVE resin is way better than a full strip-back & respray later on !! (Don't forget to fully consolidate the layers with a grooved roller).

Brian is on the money with his advice - select a total paint system from one manufacturer, & make sure you lay on a LOT of spray filler before you go for the primer coat. The spray filler stabilises the substrates & is easy to block back (if you sand thru it, put some more on, then block back again - when you have an unbroken coat of the filler, block back to about 400 grit, you are good to go with the primer.

The prep for painting will seem a major PITA for a while, but it will be the best investment you'll make !

Kind Regards,

Peter D.

 

[EGLITOM]

JAC mAC:
What i meant is, that there so many different resins available that even in the same category ( for example PE resins) there are so many different specs available and one should choose very carefully the spec which fits best to his purpose.

Randy
I totally agree to Peter regarding the PE stuff, but on the website i send you they also have epoxy based fillers, which you can mix by yourself with different materials ( glass bubbled, cotton strands and so on). This stuff is used on multi million dollar yachts. Our experience is very good. doesn´t set, a little heavier to sand.
They also have sprayable epoxy filler and combined epoxy filler/primers.

I would avoid any PE based materials (bondo, filler, primer) on the final car (they are ok for mockups like my flares, but thats about it) and just use EP based stuff.= Much higher quality

TOM

 

[keohep]

Just to add to this thread

If your using Vynlester just be carful if your doing a fairly high build up of layers ,eg csm cormat then final csm or woven glass, the thing is make sure you use the same mekp quantity as in all your mixes.

If you add lower level of mekp in your first batch and is slower to gel than your last mix then your in real trouble.the first vlayer wont cure as Vylnle needs air to cure.

In my experience with Vynlester you need to have great experience in the use of vynle as it can be very un predictable esp with changes of climat etc age of resin and how its promoted when puchased. Plus it stinks...

If you want quallity use epoxy its down side is probebly trying to get other resins to stick and that can include paint.

If you want total strenght and your useing carbon or kevlar esp theres no comparison nothing comes close to epoxy but remember you need high quallity scales .Mixing needs to be with in 3% accurate. If not stick with polester or try surfboard resin.

Has anyone tried to use gelcoat for the final colour and as the filler coat .The colours available these day is realy good and the more i think about it it makes more sence.
Gel coat is far more stronger then Paint even 2 Pac. Its much more scratch resistant much easyer to repair.

And by the way... Cheaper!!! And you dont need to be a Spray painter nor need a thousand dollar spray Gun and $10k spray booth. just loads of elbow grease.

 

[keohep]

pardon my spelling it was late !!!

 

[Jim Rosenthal]

From my experience with boats and boat repair, which now spans a few decades:

Polyester is fine for layup and laminating to make parts. However it is not a good adhesive and bonds poorly to cured laminates. If you need to bond something to polyester or to repair a panel or part made with polyester, use either vinylester resin or epoxy. Repairs should not be made with polyester resin.

I have used the West System brand of epoxy resin for decades. It is not the only one out there, but it is the most reliable and their company has published quite a lot of good literature on how to build and repair things with epoxy. (www.gougeonbrothers.com, I think). For vinylester, I would use 3M- these are also marine repair products that the local boatbuilders swear by. Again, not the cheapest but very reliable.

As far as I know, polyester can be used as the layup or laminating resin with any fiber substrate (S-glass, E-glass, Kevlar, carbon, Dynel). However, since polyester is not a strong as the other resins and it is heavier, if you were investing a lot of funds in expensive fabrics for the construction, it would make logical sense to use a stronger and lighter resin such as VE or Epoxy.

I know of no GT40 body structure that is being built using what I would call advanced fiberglass layup technology (doesn't mean no one is doing it, just that I haven't heard about it). Advanced construction would be the use of vacuum bagging, pre-impregnated fabrics, postcuring, etc. It is possible to make FRP structures that are very strong and very light, but the technology cost is formidable. A GT40 nose section made with carbon fiber in a lightweight laminate schedule is half the weight of the nose of my car, which was done with polyester resin, E-glass cloth, and an extra inner layer to reduce cracking.

 

[Jack]

Jimbo,
I wholeheartedly agree with your comments. The only question is one of expense.
All additions/modifications/repairs on a polyester based body should be done with minimum VE or epoxy (preferred). I too have used the "West System" products from Gougeon Brothers with great success. Plexus makes some fantastic adhesives as well for bonding things together.

 

[Cliff Beer]

If you're looking to not add a whole bunch of weight but you have some serious shaping to do then take a look at some of the marine filler products using "microballons" These are lighter weight fillers with good workability and good durability.

Incidentally, I've used kevlar instead of fiberglass and had very good results - the layup can be about 15% less than fiberglass but achieve the same strength IMHO.

 

[keohep]

You can not use vynlester and epoxy in the same sentence vynlester in only marginally better the poyester less than 3% even in bonding quallity.

If you vacuum bag then your trying to eliminate weight ie resin and hopefully get a percentage 60/40 ,the weight is in the resin the very thing that holds it all together.

To this end epoxy is the only resin to use. If you look at the matix of the resin youll see epoxy has spikes or finger type things that actually bond to the surface of which the repair is,Vynle is not much better than Poly

Just make somthing then sand it on all three types youll see the difference .One thing in the favour of vynle is its barcol strenght as is harder than Epoxy and more ridgid.

Lastly vynle and poly struggles to bond to Kevlar epoxy is the go.And epoxy does not have fillers like that of Poly and Vynle thus weekens the resin again how ever you can guy poly an vynle with out the fillers if you ask for it.