Why do adhesives prefer polymers?

The scientific name of glue in chemistry is adhesive (binder), which is a sticky substance that connects two separated materials together

In the general direction, the adhesive is divided into two kinds, one is to be cured, the other does not need to be cured, that is, the so-called sticker, pressure sensitive adhesive coating online coatingol.

So, how does the adhesive bond the object to the object?

1, the first need to smooth the surface, very long ago someone found that the smooth surface of the two objects will have adhesion phenomenon, such as two ultra-flat glass plates, this is the intermolecular force in action, smooth surface can make the contact area of the two objects increase

2, water as a binder is obviously not hot enough, the direct problem is that the water will volatilize, after drying, it will be gone, and the force within the water molecules is too weak, it is easy to tear, so if the water is frozen into ice, it will be better? Yes, after freezing the water between the two objects into ice, people found that the two objects could be firmly glued together, such as the scene that often appeared in the refrigerator freezer room at home, and when people used their tongues to lick the iron pipe at minus thirty degrees, the saliva on the tongue instantly solidified, and the tongue stuck to the

3, the intermolecular force of water is not in place, although the hydrogen bond is still relatively strong, but the molecular force is after all positively correlated with the molecular weight, so if the polymer is used as a binder is obviously more appropriate, and it is best to have a polymer with intermolecular hydrogen bond to strengthen the force

4, then the problem to be said is how to solidify

a) The way of freezing water into ice mentioned above, such a curing method is the principle of hot melt adhesive, but there are not many types of hot melt adhesives, because there are very few polymer materials that can present fluidity at not too high temperatures, mainly SBS, SIS, SEBS, these block polymers

b) So a variety of curing methods appeared, the most is the solvent method, the glue with the solvent to give liquid (in fact, accurately said to have the fluidity), this way is very common, such as batter and cement is done with water, the water is dry, the glue is cured, of course, the batter and cement at this time is only partially dissolved in the water, similar to the emulsion state, more or with toluene, cyclohexane and the like, yes, many furniture, clothing are used in the kind

c) This method was soon found not very good, because the dissolved concentration is generally less than 20%, a large amount of solvent is needed, waste of resources to pollute the environment, not to mention, the curing process is very slow, energy consumption is also more, so it is necessary to find ways to improve the solid content, so the emulsion type glue began to flourish, the water in the emulsion is not a solvent but a dispersant, but many people can not distinguish the emulsion and solution, here is not much to say the principle, in short, this glue curing will be much faster, the current mass production of active ingredients can be up to 60%, EVA milk, Many of the natural rubber are cured in this way
.

d) Can't you use solvents or dispersants? Of course, the problem is to solve the problem of how to cure the pure glue, one way is to choose a glue with creep properties such as tianjiao, yes, pure tianjiao can be used as a binder, it is solid, but it has creep (can be understood as the fluidity of solid), this kind of glue that does not need to be cured is often used for pressure-sensitive adhesive, and later; More glue is the way of reinforcing agent, that is, it is liquid, adding some reactive substances, this curing method is often called vulcanization, many two-component glue are this principle, a small number of one-component glue is also this principle, most of the use is to react
with water or carbon dioxide.

e) The more alternative 502 appears here, its curing method is polymerization, when extruded it is a monomer, but it can quickly polymerize when it encounters air.

f) The more fashionable curing method is UV light curing and particle curing, that is, using electromagnetic waves or particles to promote their reaction
.
In short, there are many ways to cure, and there may be more
in the future.

5.
Is it true that all glues are intermolecular forces that are used? At present, it is not all, one scheme is to customize the locking mode, the molecular chain grown on the two surfaces of the bond is buckled up like a chain, which is the physical role of the use, but the pulling off needs to destroy the chemical bond, and its strength is an order of magnitude stronger than the general glue; There is also a way that the two surfaces undergo a chemical reaction to form a chemical bond, and the chemical bond needs to be destroyed when it is destroyed, so if you want to be strong, you have to rely on stronger chemical bonds
.

6, the last is to say that the pressure sensitive glue, in the past was called self-adhesive
.
Pressure sensitive adhesive is a very common glue in daily life, tape, stickers, and generally the kind of adhesive that needs to be uncovered on occasions that need to be used pressure sensitive adhesive
.
The important principle of pressure-sensitive adhesive is that it does not need to be cured, and the important apparent phenomenon is that it is easy to stick, and it takes a little effort to uncover it, what does it mean, that is, when it is glued, it may only need to apply 1 cow force, and it may take 10 niu when it is uncovered, and it is best to destroy the force between the rubber layers to reach 20 niu, otherwise the glue flow is everywhere when it is uncovered (many inferior tapes are like this), and the force that destroys the object may require 100 niu, which has the exact term in chemistry, and there is not much to say
here.