Epoxy resin question

[Buttanic]

I keep seeing that regular glass mat should not be used with epoxy resin. I am doing some non structural repairs to a console and engine box and would like to use epoxy resin. Would this be OK.

 

[Boomyal]

Re: Epoxy resin question

I don't know where you heard that epoxy should not be used with glass mat. That's a new one on me. Just bought a bunch of it, along with the epoxy from US Composites. You'd a thunk they would have mentioned it if it were the case. I'm currently using it in my floor reconstruction and other than my post RE bubbles, it works just fine. It may not be the right form of glass in certain structural situations but that would hold true for polyester as well.

 

[Rudderman]

Re: Epoxy resin question

I have the Glen-l book "how to fibreglass boats" and it says that the binders used to hold together the mat are very compatible with polyester resins. <br />It also says that the binder may create a problem if other resins are used, especially epoxy resins which may not be compatible with the mat binders.<br /><br />It says that in general, epoxy & mat combinations should be avoided unless you are sure that your particular brand of mat is compatible with epoxies.<br />You'll also use up more resin by using mat rather than cloth.

 

[Boomyal]

Re: Epoxy resin question

...apologies, Rudderman and Butanic, I did not distinquish between 'mat' and 'cloth'. I am using 'cloth'. I did use some biaxial that had mat on the back side.

 

[Buttanic]

Re: Epoxy resin question

If it is not compatible what will happen. US Composites does have an epoxy compatible mat.

 

[petrolhead]

Re: Epoxy resin question

Advice from my local GRP supplier is that there is no compatibility problem, unless you are looking for a clear finish.<br />Apparently the binders may not dissolve completely in epoxy resin and a cloudy finish results, but I can't imagine you'd be using mat if you wanted a clear finish anyway. If I wanted a clear finish, over natural wood for example, I'd be using a woven cloth which has no binders. <br />The supplier tells me there should be no strength issue, just cosmetic.

 

[BillP]

Re: Epoxy resin question

Wait a minute Petrohead, I think your GRP expert's advice doesn't apply to us in the USA. It is difficult to near impossible to saturate mat NOT specifically made for epoxy. Like already and accurately posted, the binders in polyester mat do NOT dissolve with epoxy...which means the fibers don't let epoxy into them. Some resin gets in but the majority of the fibers remain unsaturated. This results in a dry, weak laminate. It doesn't saturate...no if ands or buts. It is a disaster to use poly mat with epoxy.

 

[thehermit]

Re: Epoxy resin question

Gang,<br />Check the West System Site for an article they published on using chopped strand mat with epoxy. They say "yes" it can be done and is OK. There is some discussion on the binder that like BillP says does not sturate (rather is suspended). The stiched mat at us composites (no binder) avoids all this. The west system article does test the product strenth. The non saturated binder (like BillP says) causes it to be a bit weaker....give it a read. I have used the two succesfully (for non structural work) but will recomend you make your own call here.

 

[petrolhead]

Re: Epoxy resin question

I read the WEST article some time ago, and it does seem to confirm what my supplier (a WEST stockist) told me.<br />As I said this is just the advice I was given, I don't use chopped strand mat with epoxy because I've never needed to, I only use woven cloth so I have no direct experience to report.<br />As for differences between fibres available in the UK/Europe and the US, again this is something I have no direct experience of as I don't import my materials from the US.

 

[BillP]

Re: Epoxy resin question

Don't screw up your boat project. Do a test sample on your material first. I experimented with straight "poly" mats from two different mfgs and they didn't saturate. Working the resin fully into the mat was difficult, like oil on water. Strength was compromised more than a little. My opinion is you should try it on a sample before believing anything posted anywhere. The majority of FRP mfgs here in the USA are going to tell you NOT to use regular mat with epoxy. <br /><br />I would want to know all the data on WEST's testing mat with epoxy before commiting to use. There is something wrong with that advice. Not to discredit WEST but they also say not to use pressure treated wood...that info is bogus and outdated by 15+yrs in the industry when CCA processes started. It's well proven to work by the boating industry. Check how many boats have used Greenwood XL without problems.

 

[thehermit]

Re: Epoxy resin question

Buttanic.....can you just use roven woving and aviod all the unknowns?<br />BillP-I am going to duck out of this thread but have used the mat with epoxy. In all cases it was for non-structural work and has held up fine over the years (5 now). It does take a LOT of resin to saturate the stuff and given the cost of epoxy it hurts your wallet to use the stuff. But nothing bends aournd wierd shapes like a bunch of mat. <br />hermit<br />PS: whats great about the post here or anywhere is you get "e"pinons...all of 'em great! Cheers

 

[Rudderman]

Re: Epoxy resin question

Why not use a couple or more layers of glass cloth and avoid the potential problem?

 

[Buttanic]

Re: Epoxy resin question

Thanks for all the info guys.

 

[BillP]

Re: Epoxy resin question

Originally posted by thehermit:<br /> Buttanic.....can you just use roven woving and aviod all the unknowns?<br />BillP-I am going to duck out of this thread but have used the mat with epoxy. In all cases it was for non-structural work and has held up fine over the years (5 now). It does take a LOT of resin to saturate the stuff and given the cost of epoxy it hurts your wallet to use the stuff. But nothing bends aournd wierd shapes like a bunch of mat. <br />hermit<br />PS: whats great about the post here or anywhere is you get "e"pinons...all of 'em great! Cheers

I'm going to duck out too...but why not just use the mat that is made for epoxy? That's what I do. It's a lot easier to use the right material.

 

[Buttanic]

Re: Epoxy resin question

After searching the West System web site I found that they don't see any major problems with using regular mat with their epoxy resin.

 

[ThomWV]

Re: Epoxy resin question

Folks, this really isn't a problem, just make sure you buy compatable matt. Its been in the product description of every bit of matt and cloth I've bought in the last 10 years, and I always look before I buy. Now if you've just got some old matt laying around, well, I'd buy some new stuff, but any dealer will tell you if its compatable or not. They don't want to sell you the wrong stuff and if they don't sell you the one you were asking about they will have another one to sell you, so they make the sale either way.