Re: How much can a glue endure?

The following answer has been compiled from the following references:
1. Encyclopedia of Polymer Science and Technology, Vol.1 3rd Edition.
2. Adhesive Materials, I. Katz, 1964.
3. Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 1.

Since so many types of adhesives (also referred to as cements, pastes or glues) exist and are commonly used, it is difficult to give a general answer to the endurance of glues or adhesives. These are also questions that, I believe, require detailed answers as this is a very large and important field. It is also interesting to note that as polymers began to play a significant role in the world, adhesives became a significant item of commerce in manufacture and construction. I will try to keep the answer general for the most part and get specific when I think it is necessary. I will assume that some basic knowledge of polymers is known as they play a very important role in synthetic adhesives, if not plenty of sites on the web are available (e.g., http://www.psrc.usm.edu/macrog/index.htm).

I have included a table giving the tensile strength (strength to pull apart) of some adhesives (in italics) and some common materials.

This should give a rough idea of how strong some adhesives are. Since so many adhesives are used and an adhesive is defined by its usage, I have included a list of adhesives and some common uses for those adhesives. The answers to the others question posed are also answered among this list as they can be applied specifically to certain types of adhesives.

First, let's look at the physical nature of adhesives (i.e. how used and/or activated). These include the following. (You may need to look up some of the structures of the materials in a chemistry or polymer chemistry textbook.)

Adhesives may be activated by the drying of a solution, heat or catalyst (or both) among others. The adhesive can be crosslinked (molecules tied together through chemical bonds becoming insoluble and more permanent) or remain soluble. So depending on the adhesive and its ingredients, an adhesive can be either permanent or removed. The adhesive can be chemical (that is a reaction takes place as the adhesive is made) or mechanical (the adhesive uses its strength to hold parts together). The type of adhesive used is determined by the conditions to which the adhered parts will be exposed. One thing that I will also point out is that many ingredients go into adhesives and depending on what is present, the use and usage of a glue can be dramatically changed. These formulations are for the most part proprietary. Also, almost any polymer can be used as an ingredient in an adhesive. The following list explains the chemical types of adhesives (though by no means is this list complete). Once again, a chemistry book may be necessary to see what these look like. Some common uses are listed in parentheses.

In summary, we can see that adhesives can endure quite a bit if the proper "glue" is chosen for an application. If the adhesive is formed by a chemical reaction (crosslinking, ring-opening etc.), heating the adhesive may result in more of the reaction occurring. This may result in brittleness if too much crosslinking occurs. It may also melt the material weakening the adhesion. Also, the formulation of the glue is very important. Silicone glues become thermally resistant by just changing how the polymer is synthesized (i.e. adding a different repeat unit). This is not to say that silicones are the most thermally resistant glues as the above lists names other adhesives which although not as common have higher thermal stability. I hope this answers your questions, I would suggest looking at the web page I referred to earlier or getting some polymer chemistry textbooks to further understand the science behind adhesives.