The functioning of the glues is based on the evaporation of the water that they carry in their composition. When turning to steam, the liquid that was aqueous ends up forming a solid adhesive layer. “Liquid school glue, for example, is formed by combining water with polyvinyl acetate (PVA), a synthetic polymer and an excellent adhesive for paper and wood,” says Vladimir Barroso, research and development manager at Faber Castell. Glue stick works in a similar way, but with another polymer, polyvinylpyrrolidone (PVP). The different glues are silicone, which has polyurethane as an adherent, and superglues, such as Super Bonder. It is composed of ethyl cyanoacrylate, which needs moisture in the air to become tacky. That’s why he doesn’t stick to the cap: in the package, he’s vacuum closed and without any moisture.
United of glue
Glue loses moisture and forms a layer that keeps surfaces sticky
1. While your school glue is in its packaging, it remains mixed with the formula water. The presence of water molecules works as a solvent that prevents the polyvinyl acetate from starting work prematurely, sticking everything together. As long as there is no contact with the outside, there is no evaporation – it is as if the glue is “hibernating”
2. To roll the glue, two conditions are necessary: the surface must be clean (ie, without grease or dust, for example) and the local temperature must be above 5 ºC. Once this is done, the glue leaves the bottle and the water evaporates and the formation of a polymeric film begins, which will be responsible for the adhesive layer that holds the two surfaces together.
3. The more porous the surface of the objects to be glued, the better the adhesion between them, facilitating the penetration of the sticky liquid in these crevices. Wood and paper are perfect materials, as they are full of holes, while glass and plastic surfaces, very smooth materials, do not stick easily.
4. Getting into the pores of objects, the glue sticks and, after drying, does not come off. The problem is that sometimes the surfaces can come unstuck. This happens because of the degradation of the polymer, which can be caused by the passage of time itself, by changes in temperature or by the action of humidity, which softens the adhesive substance.
Make your own glue!
Homemade recipe uses water and flour
Homemade glue can be made by anyone: just mix a cup and a half of water, a spoon and two tablespoons of flour, rich in starch – a natural polymer. To make it work, boil the water, mix the flour and stir for 10 minutes. After turning off the fire, pour in a spoonful of vinegar. This glue breaks a branch and sticks papers straight