Plastruct Plastic Weld

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  • Monahan Steam Models
    Captain
    • Apr 2020
    • 755

    Plastruct Plastic Weld

    Anyone know if Plastruct Plastic Weld (orange label) goes bad overtime when stored after it has been opened?

    I’ve been using this stuff to bond strips of styrene to what I believe is a ABS hull(Arkmodel type VII) but the bond between the these parts has been failing fairly easily. Both parts are given a coat and held together in place while curing.

    I’ve never had this problem in the past, so I’m curious if it is possible the Methyl Ethyl Ketone has lost some of its effectiveness? The bottle I have is probably 6 years old but has always been quickly resealed after each use.

  • He Who Shall Not Be Named
    Moderator
    • Aug 2008
    • 12255

    #2
    That cohesive of yours (it welds, does not 'stick') is volatile, but chemically stable. Ain't the cements fault.

    Did you scrub the hull and polystyrene strips with automotive primer-paint prep., like Dio-Sol (you'll find that stuff at your local automotive refinishing supply house)? Or, at least scrubbed all the parts with a slurry of water and gritty scouring cleanser followed by a thorough rinsing and drying?

    Over time the surfaces of things sitting in the shop get a coating of dirt and oil. Not to mention that periodically during creation of the kit parts the tools used to injection form your kit parts get a blast of an oil-like substance to insure a non-stick situation during a fast production run. Look on that likely cause of no-stick problems as a form of roulette: if you get a kit whose tool was blasted before the high pressure molten polystyrene/ABS is injected to form the parts, those parts and trees will retain some of that oil and remain as the trees are bagged and stuffed into pretty boxes. If you got an early number in the cycle, you're ****ed unless you take the above measures to de-grease the parts. (Or, you can luck out and get the kit that was number nine in a ten unit spray cycle).

    You want a clean surface with microscopic scratching (tooth) to increase the surface area of the parts being fused (welded) together.

    Cohesive (solvent) cements weld two or more parts together. And that's the type of goo you're using. And, like many forms of welding to insure a complete fusion at the edges you should bevel those edges and introduce a filler rod as you lay on the solvent cement; that filler rod melting along with the edge of the parts and becomes part of the fused whole. Very strong.

    Use the same tree that your injection formed kit provided as stock for heat stretching as you make up your filler rod.

    Adhesives stick by introducing an adjoining material that so thoroughly wets the surface of the parts being bonded so that the atoms of the adhesive and part(s) being bonded are so close that atomic forces pull things together. Solder and brazing are adhesives. They don't fuse, they bond.











    Last edited by He Who Shall Not Be Named; 11-29-2021, 02:14 PM.
    Who is John Galt?

    Comment

    • KumaDog
      Lieutenant, Junior Grade
      • Sep 2021
      • 36

      #3
      David,
      Sometimes you scare me. Is there a way to download your brain, before it crashes? I have a 32MB memory card, is there someplace to plug it in?

      Comment

      • Monahan Steam Models
        Captain
        • Apr 2020
        • 755

        #4
        David,

        Thank you for your very helpful reply. It sounds like the cohesive is chemically stable so that rules that out. More likely it is a contaminant issue as you point out. Admittedly I did not clean the parts first. I had lightly sanded the areas first thinking that would be good enough. Will do the walk of shame down to my shop and see if I still have any prep-sol on hand. Need to take a trip down to the automotive paint supply store today to pick up a tube of Nitro-Stan so I can pick up more prep-sol then if I’m all out.

        Thank you,

        Nick

        Comment

        • He Who Shall Not Be Named
          Moderator
          • Aug 2008
          • 12255

          #5
          Originally posted by KumaDog
          David,
          Sometimes you scare me. Is there a way to download your brain, before it crashes? I have a 32MB memory card, is there someplace to plug it in?
          Don't get your hopes up, pal. Everything I say is made up on the spot; total bull-****; fantasy-land!

          Download my walnut to a 32MB card and you'll still have room for the Vatican archives, the Encyclopedia Britannica, and the entire content of Porn-Hub.

          Sorry.


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          David
          Last edited by He Who Shall Not Be Named; 11-29-2021, 04:48 PM.
          Who is John Galt?

          Comment

          • He Who Shall Not Be Named
            Moderator
            • Aug 2008
            • 12255

            #6
            Originally posted by Monahan Steam Models
            David,

            Thank you for your very helpful reply. It sounds like the cohesive is chemically stable so that rules that out. More likely it is a contaminant issue as you point out. Admittedly I did not clean the parts first. I had lightly sanded the areas first thinking that would be good enough. Will do the walk of shame down to my shop and see if I still have any prep-sol on hand. Need to take a trip down to the automotive paint supply store today to pick up a tube of Nitro-Stan so I can pick up more prep-sol then if I’m all out.

            Thank you,

            Nick
            This early in your assembly we've identified the likely cause of your joining problem. Now that you're going to scrub EVERTHING with Prep-Sol you won't suffer any adhesion problems between the model parts and fillers, putties, primer, and paint. Imagine your joy after masking and painting your model to find that everthing under the tape is liftedd off the model when removing the masking! Won't happen now, Nick. Continue with confidence with this WIP.

            David
            Who is John Galt?

            Comment

            • trout
              Admiral
              • Jul 2011
              • 3545

              #7
              I asked this question on another forum because another person was sharing issues with gluing the Arkmodel. It is interesting that your Plastruct Plastic Weld does not work, but Bondene does. I have always preferred the Plastruct Plastic Weld over the white bottle of Bondene. I wonder if dipping the brush brings material back into the bottle contaminating it?
              If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

              Comment

              • Monahan Steam Models
                Captain
                • Apr 2020
                • 755

                #8
                I usually clean and scrub all the surfaces before paint and filler work. Makes sense now to do this step before assembly too! New lesson learned as I face palm myself for being a dumb***!

                Tom,

                I read somewhere the same thing somewhere that other folks were having issues bonding the model together and or bonding styrene to it but not having issues bonding abs sheet to it. Go figure?

                I like the Plastruct Plastic weld better than the Bondene as well. I tried the Bondene with the styrene to abs hull and the results were worse than the Plastruct plastic weld. Somewhat not surprising as the Bondene is advertised for bonding similar materials together where as the plastic weld is for bonding dissimilar materials together. The formulas are different between the two. Maybe the Bondene is less susceptible to contamination?

                Comment

                • redboat219
                  Admiral
                  • Dec 2008
                  • 2735

                  #9
                  Originally posted by KumaDog
                  David,
                  Sometimes you scare me. Is there a way to download your brain, before it crashes? I have a 32MB memory card, is there someplace to plug it in?
                  Just stick his head in a pickle jar.
                  Click image for larger version

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                  Make it simple, make strong, make it work!

                  Comment

                  • redboat219
                    Admiral
                    • Dec 2008
                    • 2735

                    #10
                     
                    Make it simple, make strong, make it work!

                    Comment

                    • Monahan Steam Models
                      Captain
                      • Apr 2020
                      • 755

                      #11
                      LOL! Good one

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