Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 26-09-2021, 18:55   #1
Registered User

Join Date: Jul 2014
Location: Southeast US
Posts: 215
Why does some epoxy yellow more than others?

I've noticed that some brands of epoxy turn more yellow than others and in a shorter period of time. Some epoxy I've used become noticeably yellow after one day, but other brands might take a week or two. I understand that all epoxy will yellow because of exposure to UV light and would like to know if the degree of yellowing and how quickly it turns yellow is any indication of the quality of the epoxy.

Thanks y'all.
scherzoja is offline   Reply With Quote
Old 26-09-2021, 19:11   #2
Deep Water Deliveries
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 27,596
Images: 2
pirate Re: Why does some epoxy yellow more than others?

Epoxy should not yellow that quickly..
Are you talking about on wood or some other material.
__________________


Born to be Wild.
boatman61 is online now   Reply With Quote
Old 26-09-2021, 19:17   #3
Registered User

Join Date: Jul 2014
Location: Southeast US
Posts: 215
Re: Why does some epoxy yellow more than others?

I'm using epoxy to patch polyester deck of a 30 yo production boat. I had to switch suppliers (progressive epoxy). The one I usually used was out because of production issues from last winter storms and COVID. The only temporary alternative (Raka Epoxy) I could find is the one that yellows really quickly. I also have US Composites epoxy, but have not tested that out in the sunlight.
scherzoja is offline   Reply With Quote
Old 26-09-2021, 19:22   #4
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Port Credit, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 5,063
Re: Why does some epoxy yellow more than others?

Some epoxies produce an amine blush in the curing process, these yellow a little slower than amine free epoxies as the amine slows the UV effect.
__________________
it's not that I'm set in my ways but it's taken me 69 years to get it right and I ain't changin' now !
boatpoker is offline   Reply With Quote
Old 26-09-2021, 19:26   #5
Deep Water Deliveries
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 27,596
Images: 2
pirate Re: Why does some epoxy yellow more than others?

Ahh okay... I'll butt back out now..
__________________


Born to be Wild.
boatman61 is online now   Reply With Quote
Old 26-09-2021, 19:27   #6
Registered User

Join Date: Jul 2014
Location: Southeast US
Posts: 215
Re: Why does some epoxy yellow more than others?

Boatpoker,

That's interesting because the Progressive Epoxy is advertised as "no blush" and I 'm using the 'no blush' hardener with the Raka Epoxy. I wish I knew more chemistry then I might be able to not rely on vendors' statements. Alas, I can't know everything.
scherzoja is offline   Reply With Quote
Old 26-09-2021, 19:37   #7
Registered User

Join Date: Jan 2018
Boat: 50ft Custom Fast Catamaran
Posts: 5,380
Re: Why does some epoxy yellow more than others?

Raka is actually a great epoxy for general purpose projects like yours. Although I’ve never seen it yellow, I wouldn’t be at all concerned with it being more yellow that what you are used to.

Your project isn’t one that pushes epoxy anywhere near its limits. As long as you UV protect it, it’ll be stronger than the rest of the deck.
__________________
Epoxy can kill me like a kid smelling peanuts across the lunch room. Even the freshly machined dust from cured epoxy. Please donít suggest using it.
Chotu is online now   Reply With Quote
Old 27-09-2021, 03:14   #8
Marine Service Provider

Join Date: Dec 2010
Location: Little Compton, RI
Boat: Cape George 31
Posts: 1,983
Re: Why does some epoxy yellow more than others?

My epoxy expert told me that hardener tends to turn yellow on the shelf--his theory was that it was picking up oxidation from the inside of the can. I use a fair bit of West System, and can confirm that the older the hardener, the yellower it is.
__________________
Ben
zartmancruising.com
Benz is online now   Reply With Quote
Old 27-09-2021, 04:10   #9
Registered User

Join Date: Jan 2018
Boat: 50ft Custom Fast Catamaran
Posts: 5,380
Re: Why does some epoxy yellow more than others?

Ok, one area of concern. It’s not this yellow is it??

You didn’t get the UV hardener by mistake, right?

__________________
Epoxy can kill me like a kid smelling peanuts across the lunch room. Even the freshly machined dust from cured epoxy. Please donít suggest using it.
Chotu is online now   Reply With Quote
Old 27-09-2021, 04:53   #10
Registered User

Join Date: Jul 2014
Location: Southeast US
Posts: 215
Re: Why does some epoxy yellow more than others?

It's not the UV hardener because I've used it down below and it cures in the shade, but does not yellow down below: no direct UV down there. The resin and hardener in the bottles are mostly clear, with the hardener having a bit of a slight amber-ish hue.

I've got a partial bottle of slow-cure hardener that is pushing 4years old and it is a much darker orange than it was when new because of the oxidation, but I used new hardener with new resin (well, I bought them at the same time in July, not sure how 'new' they are). Either way, the hardener and resin are almost the same color in the bottles, Raka just yellows must faster and with a darker hue.

The color by itself it not a big deal because non-skid paint is going over the top. I just don't know if the degree of yellowing with one brand over another is indicative of any kind of post-cure structural inferiority or superiority.
scherzoja is offline   Reply With Quote
Old 27-09-2021, 05:15   #11
Registered User

Join Date: Jan 2018
Boat: 50ft Custom Fast Catamaran
Posts: 5,380
Re: Why does some epoxy yellow more than others?

Ok. I’ve used around 50+ gallons of Raka on various parts after the hulls were joined and bulkheads put in and stuff on my boat. I opted for Mas infusion epoxy for fabricating the hulls and bulkheads and beams.

I used raka for fairing, making rudder cassette boxes, holding rudder bushings in place, building steps outside on deck... and I left some in the Florida sun for a year. Part of the steps weren’t painted. It turned yellow but I can’t break it in any way.

Get the paint on soon to protect it (or at least get a tarp or sheet of plywood or something over it), but I’m going to mention again that your application is in no way stressing the epoxy anywhere near its limits. Even Slightly yellowed, the surrounding polyester would mostly likely fail before your repair work if stressed to the breaking point through destructive testing.
__________________
Epoxy can kill me like a kid smelling peanuts across the lunch room. Even the freshly machined dust from cured epoxy. Please donít suggest using it.
Chotu is online now   Reply With Quote
Old 27-09-2021, 13:06   #12
Registered User

Join Date: Jul 2014
Location: Southeast US
Posts: 215
Re: Why does some epoxy yellow more than others?

Thank you for the insight. I'll continue on with the hardware removal and patching with Raka and go worry about something else.

Thanks again.
scherzoja is offline   Reply With Quote
Old 27-09-2021, 15:43   #13
Registered User

Join Date: Feb 2010
Location: US
Boat: Sunward 48
Posts: 193
Re: Why does some epoxy yellow more than others?

Typically the more "aromatic" "double-bond" epoxies exhibit more yellowing since they absorb UV light closer to the visible range. Bisphenol-A epoxies are very aromatic and lead to yellowing. But in my experience even "hydrogenated" double-bond-removed epoxies eventually turn yellow or brown.

The formulator can add stabilizers that slow or reduce the yellowing. It is not always clear that yellowing affects properties. The yellowing actually increases UV absorption, so once the yellowing starts, the UV is predominately absorbed at the surface and penetrates into the lower regions is exponentially reduced. One could add carbon black, copier toner, or titanium dioxide to reduce the UV penetration. Or just paint the surface.
Locquatious is offline   Reply With Quote
Reply

Tags
epoxy

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is "marine epoxy" any different than regular epoxy? SKMT Construction, Maintenance & Refit 29 21-07-2021 00:34
Which countries are better/cheaper for some things than others AndrewA2 Construction, Maintenance & Refit 22 27-04-2020 16:47
Are some damper plates more reliable than others? Rowglide Engines and Propulsion Systems 23 24-08-2017 06:19
Some yachts are plain ugly and some beautiful, why and does it matter? brightontrader General Sailing Forum 160 10-06-2015 00:54

Advertise Here


All times are GMT -7. The time now is 03:04.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.