uv rays and epoxy after additaves/ high density

[bigbad4cyl]

i used epoxy mixed with high density filler on the boat gouges, after i ground them out .......they are on the bottom of the boat that is on a trailer . they recive moderate light .... do i need to paint them with somthing while they cure for weeks or are they ok with the filler added.

 

[crab bait]

Re: uv rays and epoxy after additaves/ high density

good question.. <br /><br />uv does hurt epoxy in a major way.. <br /><br />i'd sand litely.. wash with 50/50 ammonia an water an paint.. no primer required..

 

[BillP]

Re: uv rays and epoxy after additaves/ high density

Here in Florida it takes direct UV years and years to do damage on most unprotected resins. A few weeks or months hurts nothing. Most resins have UV inhibitor in them anyway. Also, you are in SF...way low on the intensity scale.

 

[fishingdan]

Re: uv rays and epoxy after additaves/ high density

I disagree BillP. Epoxy resins do not have any UV inhibitor in them. Check out any major brand epoxy website. <br /><br />I have found that discoloration starts within about 10 days. The discoloration may not indicate that anything is breaking down yet, but certainly changes are starting to happen. I live in New England which I would think would be similar to SF in sun exposure.

 

[jim dozier]

Re: uv rays and epoxy after additaves/ high density

Although I have no experience with which to back it up everything I have ever read says epoxy resins are susceptible to UV degradation and should be painted with a UV filter coating. Polyester resins are less suceptible to UV and that is why you see boats made out of unpainted gelcoat. But we all see what eventually happens to gelcoat. <br /><br />If you are just repairing a small non-structural gouge with Marine-Tex or similar it probably doesn't make any difference but it you are laminating a structural area with epoxy resin that is exposed to the outside (not the bilge) I vote for painting it.

 

[18rabbit]

Re: uv rays and epoxy after additaves/ high density

Originally posted by fishingdan:<br /> I disagree BillP. Epoxy resins do not have any UV inhibitor in them. Check out any major brand epoxy website. <br /><br />I have found that discoloration starts within about 10 days. The discoloration may not indicate that anything is breaking down yet, but certainly changes are starting to happen. I live in New England which I would think would be similar to SF in sun exposure.

That’s about right. After a week or so in the sun unprotected epoxy will start to yellow in the SF bay area. None of the epoxy I use (West and US Composite) has UV inhibitors, but I believe it is available as an additive. Isn’t polyester resin more UV resistive? Perhaps that’s what BillP is thinking...’cause unlike me, BillP knows what he’s talking about when he posts.<br />

 

[BillP]

Re: uv rays and epoxy after additaves/ high density

Some uv treated resins yellow in the sunlight and many totally "uv destroyed" fiberglass boat parts still show "non yellow" resin. So I personally don't know if yellow is the way to tell for sure if the resin is going bad from uv or not. <br /><br />It's been a long time since I dealt with uv inhibitors and checked with vendors. In the 1950/60s none of them had uv inhibitors. You bought (it was pennys to treat a gal when bulk resin was $5 a gal) inhibitor and mixed it in if you wanted uv protection. Later on most resin mfgs mixing for boats, surfboards, etc included the inhibitor. It became industry standard and nobody advertised having it anymore but it was in the resin. Epoxy was similar. It's always best to paint or gel coat over raw resin and mfgs will always tell you to cover it. Regardless, IMHO, worrying about a few weeks in direct tropical sunlight is bordering on paranoia. The process takes years and years, not weeks.

 

[ondarvr]

Re: uv rays and epoxy after additaves/ high density

BillP has it right.<br /><br />Now few resins have UV inhibitors ($$), they rely on the gel coat for protection, most gel coats don't have them either though. They rely on the pigments and fillers to protect them from UV. Most UV inhibitors are yellow in color and tend to tint the resin or gel coat when added, so it can create problems in color matching. Base resins for gel coat are formulated to not yellow or break down in direct sun light, over time they will though. Normally for unprotected surfaces short term exposure is no problem, it's long term exposure that is a concern.

 

[bigbad4cyl]

Re: uv rays and epoxy after additaves/ high density

i actualy used west system 207 special coating , it says it had uv inhibitors added , but i baught it at the west marine bargan store... it had already turned yellowish orange so i got a big discount.....any way thnks for the replys ill try and be safe and get it leveled and put some paint on it .

 

[jim dozier]

Re: uv rays and epoxy after additaves/ high density

One point that keeps getting glossed over here or misinterpreted is that virtually all of the boat hulls and surfboards etc referenced here are made of polyester or vinylester resins which are inherently more resistant to UV. Epoxy repairs whether on existing polyester or epoxy substrates are epoxy not polyester and are different. I only know what I have read I haven't tested the stuff but the books say epoxy is sensitive to UV not polyester. <br /><br />This post is about sensitivity of epoxy, don't use polyester products as an example of the need or lack of need for UV protection, different animal.<br /><br />I'll repeat my earlier assessment, if the repairs are small cosmetic gouges using epoxy it probably doesn't matter, particularly because the filler on the outside will block the UV on the inside and the repair is non structural. That is a different situation from a structural repair using clear resin in a UV exposed area.

 

[ondarvr]

Re: uv rays and epoxy after additaves/ high density

The topic did kind of shift to polyester. Long term use, cover the epoxy, short term, or on the hull, not a big deal.

 

[BillP]

Re: uv rays and epoxy after additaves/ high density

For what it's worth...WEST web site says the UV inhibitor gives a yellow tint to their resin.