How does glue work? How does it bond two things?

Glue is an essential part of anyone’s stationery supply. It is one of the very commonly used products amongst artists, students, teachers – in short, everyone. There are different variations of this particular product. It is produced in several forms, from sticks to runny liquids. But, all of them serve the same purpose of sticking two or more materials together. But the question here is, how does it work? Let’s debunk the mystery behind the magic of this wonderful product!

As stated above, glue is an adhesive substance that is used to stick or paste two or more objects together. Glue has several forms like cement, mucilage, or paste. It is a nonmetallic substance applied to one or more surfaces of two separate items to bind them together and resist their separation.

Glue is generally applied in liquid form and dries hard to hold objects and materials together. Technically, true glues are made of organic compounds like animal collagen. However, many products marketed as glue are synthetic adhesives made with polyvinyl acetate (PVA) emulsions.

One might guess that the glue we use to mend a broken teacup works by chemical bonding or mechanical interlocking. Its molecules stick to the surface by spreading like millions of microscopic magnets.

In some cases, adhesives can make much stronger chemical bonds with the materials they touch. The effects do play a part, but the essential reason adhesives work is this: If two materials are close enough together, they will adhere. This adhesion is due to the universal attraction between molecules in very close proximity.

Glues can also form physical (mechanical) bonds with the surface they’re sticking to. When you put some glue on a piece of paper, the solvent (water) is exposed to air. The water ultimately evaporates (changes from liquid to gas). As it evaporates, the glue dries and becomes hard. All that’s left behind are the sticky polymers that hold things together.

This phenomenon of attraction or the forces of this attraction is called Van der Waals forces. It was named after the Dutch physicist who postulated them, stem from the arrangement of electrons around an atom’s nucleus. Although electrons’ orbit is symmetrical paths, at any given instance their electrical charges are not evenly balanced. An atom has a positive and negative electrical pole.

Van der Waals forces are the weak forces that contribute to intermolecular bonding between molecules. These are weak, short-range electrostatic attractive forces between uncharged molecules, arising from the interaction of permanent or transient electric dipole moments. In molecular physics, the Van der Waals force is a distance-dependent interaction between atoms or molecules.

How are Van der Waals forces formed? These are weak intermolecular forces caused by attractions between tiny dipoles in molecules. With the increase in the number of electrons, the size of the oscillating and induced dipoles also increases along with the size of the attractive forces between the molecules as well as the size of the van der Waals forces.

Why are Van Der Waals forces important? This force quickly vanishes at longer distances between interacting molecules. It plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics.

Van der Waals forces are produced as a result of the attraction between opposite poles on different atoms. Individually, they are fairly weak, but when combined, they form a strong bonding strength when acting among countless atoms. Why then do we need adhesives at all? If we press two solid objects together closely enough, won’t Van der Waals forces hold the objects together?

No. They generally won’t. The reason is that the molecules of the two objects’ surfaces must be within a few angstroms of each other – and an angstrom is only ten-billionth of a meter. A polished material, for example, has greater angstroms. This makes the actual area of molecule contact minimal, even if the surfaces are similar. An adhesive makes contact with molecules of both surfaces and holds them together. For the most intimate and extensive contact, the ideal adhesive is a liquid. It should also solidify into a strong material that won’t shear off easily.

Just like that, with simple molecular chemistry, we can use glue to bond two things together efficiently.