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Bonding UHMW

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  • ckelloug
    replied
    Here is garland Manufacturing's page on how to glue UHMW. They actually manufacture it and they give specific glue recommendations. None of the lap joint strengths are all that high but they might suffice.

    http://www.garlandmfg.com/plastics/bonding.html

    I've had problems with UHMW warping when heated as it seemed to allow internal stresses to have their way with the material.

    Regards,

    Cameron

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  • Harvey Melvin Richards
    replied
    Originally posted by PTSideshow
    thistothat.com

    another site for info on adhesives
    The multi-grip is great stuff works on a large assortment of materials. Nothing more than a satisfied user
    I looked at the this to that site, and it's marginal at best. Your choice for plastic is Plastic. Teflon behaves much different than ABS or PVC or any of the hundreds of other choices. It's a home hobbiest site at best, certainly nothing I would recommend for serious applications.

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  • darryl
    replied
    I'm curious as to the application. Also, I'm questioning the use of the 4x8 sheet- is that the size of the final part or is that the parent material from which many parts are cut?

    In the past I've made mold parts from mdf which were destined to go in the oven with a piece of plexiglass on it, or abs or pvc sheet. While I got the results I wanted, the mdf outgassed at heat (under 300F) and that's something you really don't want going up your nostrils. It's pungent, noxious, and a considerable irritant. Who knows- if I was to spawn a child- well who knows if it would be a child or a - thing. That stuff can not be good for you.

    Here's an idea though- if the uhmw can work by being attached to the mdf in many small pieces, you can just use small screws. Countersink the heads and drill pilot holes. Use a method like they do for setting tiles- you can buy bags of those little plastic spacers for cheap. Use them to set the grid pattern and screw away. Were it me doing it just as I've described, I'd make a jig to make easy work of cutting the sheet of uh into equal size and shaped pieces, then I'd make a hole drilling pattern and spot drill all the pieces, then I'd set up one cordless drill with a combination countersink/pilot hole/depth stop and a second cordless with a driver for the screws. I'd be making good use of the torque limiter on the drill as well.

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  • Evan
    replied
    Pretty risky with only .125" material.

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  • Grind Hard
    replied
    Evan speaks of corona treatment.

    You can achieve the same effect by kissing the surface of the sheet with the VERY EDGE of a gas flame. Move the torch VERY quickly or you will end up with a melted puddle of very hot plastic.

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  • jgedde
    replied
    I've heard of guys making skid plates for ATVs and welding it with a plastic welder setup. Seemed like it worked well.

    John

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  • Evan
    replied
    Assuming the UHMW was absolutely bonded to the MDF it is my understanding that the expansion will happen resulting in something bad happening.
    Sure. Thermal expansion is a powerful force, greater than the yield strength of the material. Just like freezing water can break rocks thermal expansion can deform materials. In the case of two flat parts with different rates bonded together the laminate will bend/warp in one direction and the other when the temperature changes. The amount of force can be enough to permanently deform the materials.

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  • PTSideshow
    replied
    thistothat.com

    another site for info on adhesives
    The multi-grip is great stuff works on a large assortment of materials. Nothing more than a satisfied user

    Leave a comment:


  • Horst
    replied
    Thermal expansion is the new issue. Assuming the UHMW was absolutely bonded to the MDF it is my understanding that the expansion will happen resulting in something bad happening. I am now looking at mechanical fastening that will allow for expansion.

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  • Evan
    replied
    It will glue ok with several types of glue if the surface if roughed up and especially if the substrate is non porous. The problem is when there are major temperature changes.

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  • JMS6449
    replied
    Made in feed and outfeed tables for a table saw. They were 30" x 120" and used contact adhesive. Still together, after 10 years in a solid surface fabrication shop.

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  • Evan
    replied
    I get the same and I checked 3 different places and all gave the same CLE for UHMW.

    However, there is a gotcha. Once past the 116F deflection temp for UHMW the expansion is no longer linear as the material softens.

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  • Horst
    replied
    If my math is right a 48" sheet would expand 1.96" with a 200* rise. Doesn't sound right.

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  • Evan
    replied
    For UHMW natural I find 2x10^-4

    http://www.sdplastics.com/uhmwphys.html

    Don't know about the Tivar. You may want to check the deflection temp if it will be subject to heavy weights while hot.

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  • Horst
    replied
    Tivar H.O.T. (High Temp UHMW) - McMaster-Carr - +275 degrees

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