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Thread: NHMC and Duct Seal Heat-Resistance Trial - Experimental Design Help

  1. #11
    Founding Member IBcivic's Avatar
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    After 1 full hour at 200 deg. F.... the samples have softened up, but maintain their shape and position. No leaching of wax or oils is visible or detectable by touch. The odor inside the oven is of a faint hot rubber smell.
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  2. #12
    Founding Member TREETOP's Avatar
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    Quote Originally Posted by DS-21 View Post
    For what it's worth, this is the same stuff I used in my door panels. I had the truck in Florida in August of 2009 for over a week in 110 degree outside weather, parked on blacktop at Disneyworld, and had no problems with it releasing or oozing. The last couple months though it's been falling out on its own. It's been in there for well over a year but it's been starting to fail at least adhesion-wise. Maybe because of temperature changes causing it to expand/contract, or maybe vibration, or maybe it just releases its oil with age and loses its ability to hold on- I don't know. It still feels just as malleable as when it was new, and it sticks if I mash it around and push it back in place, but I think I'm going to use something different for mass loading next time around.

  3. #13
    Founding Member IBcivic's Avatar
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    For the 2nd part of the test, i raised the oven temp to 250F for an additional hour.
    The results were pretty much the same> Softening of the putty, no sagging or leaching.
    The surface of the putties have shown signs of very slight blistering, but after cooling down, both samples returned to their natural state and once rolled back into a ball, they both felt identical to virgin, unmolested product.

    EDIT> I did notice a faint odor of burning on the surface of both materials, that vanished ,when i rolled the putty back into a ball. My theory is that the outer layer that was exposed to the heat, reached the material's thermal limit and started to slowly decompose/ bake. this would probably explain the surface blisters that appeared on the exposed putty samples' surfaces. IMO a vehicle never reaches these types of temperatures, so for my purposes, this validates the Gardner Bender brand as a viable alternative to the pricier Thomas & Betts duct seal putty.
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    Last edited by IBcivic; 09-19-2010 at 09:16 PM.

  4. #14
    Founding Member capnxtreme's Avatar
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    Nice. Thanks guys.

    I never liked the idea of putting NHMC in my doors, but I don't see a good reason not to use duct seal. Is it just as dense as NHMC?

  5. #15
    Founding Member IBcivic's Avatar
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    I cannot confirm this since i have not fiddled with clay, because of it's tendencies to release it's oils with heat.

  6. #16
    Founding Member benny's Avatar
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    I've tried both. Nothing scientific, but IMO ductseal trumps modelling clay in every aspect.

  7. #17
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    Quote Originally Posted by amitaF View Post
    With my wife, out of town, I am using the oven ...
    Ah, memories. Before your wife returns, dump a cup or two of baking soda in a baking pan and bake it for an hour or so at 250. Should get rid of the odor that you can't smell but she will ;) Remember to take the pan out of the oven before she sees it. Experiments that involve kitchen appliances don't seem to make the same obvious sense to the women in our lives as they do to us.

  8. #18
    Founding Member IBcivic's Avatar
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    I see that you have had a taste of ''this is my kitchen'', you don't see me cooking in your workshop.....

    Thanx for the tip:thumbsup:

  9. #19
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    Quote Originally Posted by DS-21 View Post
    3) bake them at 250deg F for three hours
    The clay will be a puddle in 30 minutes or less. You can back the furnace temp down to 150-175. Even then you may still be a puddle after 30. certainly damn soft.

  10. #20
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    Quote Originally Posted by Rudeboy View Post
    I'd also want to put them on a vertical surface since that how they will be used. Put identical oven thermometers on either side of the experiment.
    .
    Also FYI, and your plastilina may come with directions, but you can affect adhesion with pretreatments, which if you are testing would also be valuable information.

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