Adhesives and Adhesion

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Adhesives and Adhesion

Post by Ciaolo on Mon Mar 13, 2017 3:38 pm

Hi!

I was wondering how adhesive and adhesion work. I remember watching a short tv documentary about this topic many years ago, that essentially said that the strongest adhesives are based on water and that water is the main glue, with additives that try to isolate the mechanism so it doesn't brake.

So, I checked wikipedia just as a start. Found the Adhesive page and then the Adhesion one (here: https://en.wikipedia.org/wiki/Adhesion)

Well, I started reading and then I stopped at the first sentence:
Surface energy is conventionally defined as the work that is required to build an area of a particular surface.
Seriously? How am I supposed to think about this marvelous thing that is Adhesion (and apparently was discovered/invented in Italy 200,000 years ago) if you throw this nonsense as first sentence?

They started with that Surface Energy to dance on math principles and properties. As if we need that in this field...

Then they say
There is no single theory covering adhesion, and particular mechanisms are specific to particular material scenarios. Five mechanisms of adhesion have been proposed to explain why one material sticks to another
Intriguing, so this is actually a pioneering topic. What do the theoric physicists say about no more mysteries in the universe? They don't even know how glue works.

So, five mechanisms. The first, mechanical, is not adhesion, it is like clinging. The second one is 'chemical', described as sharing electrons, and the third is 'dispersive' which are the same. Since the official micro-physics is nonsense, they can't be officially grouped together. Too many unexplainable phenomena...

The remaining two are not adhesion phenomena. The 4th is electrostatic, and that is attraction, not adhesion. The last one is diffusive and it's just melting surfaces together with the use of heat and state changes.

What's your thoughts on the matter? I think that, like we can have all sort of shades between solids and liquids, we also can have a lot of different phenomena related to true adhesion. The first thing that comes to mind obviously is how often water (mainly droplets) attaches anywere

Ciaolo

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Re: Adhesives and Adhesion

Post by LongtimeAirman on Tue Mar 14, 2017 3:40 pm

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Hello Ciaolo, It seems to me that Adhesives and Adhesion is a very broad subject. You’ve pointed out that wiki describes several mechanisms: 1) Mechanical; 2) Chemical; 3) Dispersive; 4) Electrostatic; and 5) Diffusive.

I’ve been thinking about one of them, electrostatic, for some time now. I must correct your quote, “The 4th is electrostatic, and that is attraction, not adhesion”, please change “attraction” to “apparent attraction”. However that seems beside the point since you dismiss electrostatic as not adhesion. You've also dismissed: "Mechanical, is not adhesion, it is like clinging"; and diffusive too.

For discussion purposes, you’ve whittled wiki’s adhesion list down to "'chemical', described as sharing electrons, and 'dispersive' which are the same". Neither of these seem to me to match your primary interest from the short tv documentary you watched years ago – "the strongest adhesives are based on water and that water is the main glue, with additives that try to isolate the mechanism so it doesn't brake".

I guess adhesion involves separate objects, usually dissimilar materials, with adjacent faces or surfaces that share charge channels. Solids don’t normally fit together close enough, but if they do, their surfaces might begin to join on a molecular level. The presence of water can greatly impact the situation by filling in air gaps and enhancing charge flows far more than air alone can. Proper additives can no doubt provide significant additional characteristics to adhesion, such as strength or other effects.  

You asked for thoughts; sorry if I’ve missed your point. Perhaps you could be more specific?
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Re: Adhesives and Adhesion

Post by Ciaolo on Wed Mar 15, 2017 2:52 pm

About the electrostatic, obviously I meant apparent attraction.

I found your comment about water filling air gaps very interesting! Is there an example of chemical or dispersive adhesion between two solids?

And finally, you're right, I need to be more specific about adhesion: by that I mean the propension of a material to bond on contact with another material. It's different than [apparent] attraction because in adhesion the two materials are not interacting until they enter in contact.

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Re: Adhesives and Adhesion

Post by LongtimeAirman on Wed Mar 15, 2017 7:12 pm

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I suspect that Surface Energy, like so many details in current physics, was invented to fill a hole in the data. It is therefore likely better described as a physical attribute of matter better explained by the Charge Field. After thinking about it a bit, the entire subject of Adhesion may be relatively easy to translate into Charge Field terms.

I found a couple of interesting documents:

The first, a 1964 NASA Technical Note looks like it contains a lot of good discussion.

ADHESION BETWEEN ATOMICALLY CLEAN SURFACES
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19640004816.pdf
The purpose of the research on adhesion bonding between metallic solids under this program was to identify the underlying mechanisms and interaction processes involved when two atomically clean metallic surfaces are brought together and form a stable interface.

The next is a chapter from an engineering text, containing many formulas, but none seem too difficult – at least not when considered in light of the Charge Field.

Adhesion between Contacting Surfaces
http://www.ewp.rpi.edu/hartford/~ernesto/F2012/FWM/Notes/ch04.pdf
1 Introduction. As the free surfaces of two solid materials come in close proximity of each other, atoms in one material begin to experience the electronic environment of the other material. The result is often adhesive interaction. Adhesion is somewhat analogous to internal cohesion of atoms in the bulk, except that it is the result of interatomic interactions between atoms at or near the free surfaces of separate materials. Adhesion phenomena can result in the absence of intervening medium (e.g. solid surfaces in a vacuum environment) or through the agency of an intervening fluid phase (e.g. liquid mediated adhesion).

There are too many hits when you include water solutions.
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