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Topic: Relationship between adhesion failure modes and the thickness?  (Read 1254 times)

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Offline craken66

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Relationship between adhesion failure modes and the thickness?
« on: October 08, 2023, 08:48:31 PM »
Dear everyone,

Now I'm studying the ahesive.
There are two kinds of failure mode when the adhesvie is detached ;
Adhesive failure and cohesive failure.
The first is detaching without any parts of the adhesive from the adherend.
The second is vice-versa of the first.
Here I have a question.
How could the thickness be affected to such the failures?
The thinner it is the closer to cohesvie failure it is, right?
I think when the adheive would be thinner, intermolecular interaction would be smaller, so it would be to make the cohesive failure.
Please leave your comment freely.
Thank you.
« Last Edit: October 08, 2023, 08:59:13 PM by craken66 »

Offline marquis

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Re: Relationship between adhesion failure modes and the thickness?
« Reply #1 on: October 11, 2023, 08:57:28 AM »
Yeah, point of contention.  Most of the work done in the polymer field would have been considered cohesive.  But...  Many times the cohesive( which was usually labelled an adhesive, by the way) would have to be applied in a thin layer, bonded, and heated for best function.  To a polymer person, this sounds a lot like crosslinking.  Then take a look at the bonds.  Usually, the testing is done on an instron.  A small piece of sample is out between the two fingers.  The  sample is then pulled until it breaks apart.  The force is then measured.  We usually examined the sample under a microscope to find the failure mode.Usually, the some of the polymer was attached to both sides of the adhesive.  Since the Polymer was attached to both sides, you would probably call this a cohesive failure.  Polymer people tend to call this crosslinking and go from there.

Offline marquis

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Re: Relationship between adhesion failure modes and the thickness?
« Reply #2 on: October 11, 2023, 09:16:38 AM »
Let me describe the joint a little better.  You would have the elastomer on one side, then the adhesive, then attached to it were small pieces of the elastomer it was bound to that had been ripped off in the one from test. If you had a failure in the dealing compound ( which did happen from time to time), you would have elastomer on both sides. The only difference was They were coated light white.  When you went to the Instron from data, the force required to separate the two pieces was also much lower. 

Offline marquis

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Re: Relationship between adhesion failure modes and the thickness?
« Reply #3 on: October 12, 2023, 09:44:36 AM »
A little more explanation is in order.  Physical properties of plastics, latex, and elastomer are always a customer's interest.  So they will frequently request tests like tensil, elongation, and modulus.  These tests are done on a variety of instruments, but one of the most common is called an Instron.  The Instron is pretty flexible,and other tests, such the ones describrd above, are also often done on it. 

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