Adhesive choices?

Discussion in 'Fiberglass and Composite Boat Building' started by leaky, Sep 28, 2020.

  1. sdowney717
    Joined: Nov 2010
    Posts: 1,175
    Likes: 85, Points: 58, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    I would avoid the Plexus stuff strongly! I have used multiple tubes of the Devcon (plexus), and at first seemed like a decent glue. Later on the stuff would separate itself from the surface, so fail. It has the strongest noxious solvent odor I ever smelled (likely deadly to whiff) . Then Devcon started having severe quality control issues, the stuff would never set up and stayed a gummy and stinky yellow goo. I called the company and complained and they admitted issues with it, they claimed production batches of it froze, it froze in delivery trucks shipping the stuff, and had mixing issues in their production runs when they made it. They finally got out of making this as they could not solve the chemistry problems and seems now this is marketed as Plexus. If you look at the Devcon plastic welder comments you will see all that negativity right there, so same experiences I had. It went from wonder glue to crap in a couple of years experience for me. I wont ever take a chance on it again and that price is astronomical.

    https://www.amazon.com/Devcon-22045...2TY2TM2FVW2&psc=1&refRID=VT2SFM3DA2TY2TM2FVW2


    https://www.amazon.com/Plexus-Purpose-Strength-Adhesive-cartridge/dp/B06ZY7KMWD
    • Replacement for discontinued Devcon Plastic Welder II (14340)
     
    leaky likes this.
  2. leaky
    Joined: Sep 2008
    Posts: 224
    Likes: 14, Points: 18, Legacy Rep: 14
    Location: nh

    leaky Senior Member

    I picked up some system III gelmagic and had some leftover system III SB epoxy, and performed a quick test.

    I will follow up with a better test. Based on past experiences I didn't think either epoxy would allow my other resins to cure, specifically system III advertises SB epoxy is good for this but my past experience is even under ideal conditions and prep it isn't better than anything else. My results were contrary to that past experience.

    I mixed up and layed down both some gelmagic and SB epoxy on this tin (BTW working time on both at 65 degrees F was easily 1.5 hours). 2 days later I did a half *** prep, quick sand, wipe with acetone. I know you want to ideally use soap & water but in my actual application where epoxy will be hiding in nooks and I can't be dosing the area with water, so I tested it how it needs to work.

    I applied both Mertons Hull & Deck putty as well as a Vipel VE to the 2 types of epoxy, as well as control patches to clean areas. It was applied at non ideal 55 degree temperatures, both mixed hot at around 3%.

    Today I found generally everything cured fine, no real problems would be encountered if I was tabbing over a bit of it how I intend to. When I destroyed the pieces though I found consistently the VE & PE products did not cure fully on the immediate area where they contacted the gelmagic epoxy, a sticky film was present but otherwise were cured. Over the SB epoxy though I am unable to remove the VE & PE products, ie it actually fully cured & bonded.

    Sooo it looks like my own Cabosil & SB epoxy glue will be the direction to head, even though either product would work OK. SB epoxy isn't quite the best epoxy for bonding on the planet but should hold parts together better than the VE bond to the core itself.

    20201003_120331.jpg

    20201003_121408.jpg
     
  3. ondarvr
    Joined: Dec 2005
    Posts: 2,929
    Likes: 573, Points: 113, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    2 days at 65F won't typically fully cure an epoxy, and it needs to be fully cured so the chemistry will be compatible.

    Time, sanding and water are the keys to a good bond.

    Don't catylize the VE at 3%, anything over about 1.75% can reduce the physical properties.
     
    leaky and fallguy like this.
  4. leaky
    Joined: Sep 2008
    Posts: 224
    Likes: 14, Points: 18, Legacy Rep: 14
    Location: nh

    leaky Senior Member

    Thanks, how long should I let it cure?

    Most of what I am worried about here is that I am able to conduct my tabbing w/ VE & some putty with some trace epoxy down in the crack between two panels. So in some sense I am testing to figure out what is most reliable and in a worst case scenario.

    The fact that I saw different behaviors with 2 epoxies steers me to the one that worked but I guess I should make sure that the epoxy gets its full cure time (did seem ok when I sanded it and used acetone though, epoxy hates both).

    The mix ratio was just a matter of it was a small batch so very hard to measure right and at those temperatures with it likely dipping to 45 F at night I wanted to witness a cure without running heat. Usually I do mix at 1.75% and when its warm I must cut that down otherwise this VE cures too quickly & with little warning. At < 50 though it may not cure at all.
     
  5. fallguy
    Joined: Dec 2016
    Posts: 7,598
    Likes: 1,674, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    You can warm the epoxy samples and post cure them. Typically 145F-165F for two hours will make them ready.

    For any ester questions Ondarvr is the expert.
     
    leaky likes this.
  6. leaky
    Joined: Sep 2008
    Posts: 224
    Likes: 14, Points: 18, Legacy Rep: 14
    Location: nh

    leaky Senior Member

    I didn't find a good slot for it today but next period of downtime am going to layout another test with both resins again, this time I will let them cure for longer, maybe even move them inside.

    At the same time, with the SB I got both PE and VE products to actually bond to it with minimal prep and a 2 day cure so that definitely gives me a comfort level. Should only work better in smaller doses of epoxy cured longer.
     

  7. leaky
    Joined: Sep 2008
    Posts: 224
    Likes: 14, Points: 18, Legacy Rep: 14
    Location: nh

    leaky Senior Member

    On aside, when I set the deck down due to working time and the nature of the way everything has to be, I need some adhesive like epoxy.

    I am starting to think though on the coosa spacers I can probably get results just as good if I use a thickened VE.

    Basically I have what I am showing below to shim up. It seems if I laminate the bottom side of coosa strips how I would normally with VE, then in close proximity I laminate the mating area of the top of my flange here, working with cured but green VE surfaces, I should get a perfectly sound bond by putting a thickened VE down and setting the shims on it - yes? Would seem if anything the bond there would be stronger than the secondary bond of the glass to the coosa?

    20201002_113453.jpg
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.