QUESTION: How does glue stick?

ANSWER: Glue can be prepared from plant-, animal- or oil-based substances. It is thought that the first glues were produced by using liquid from trees and, later, by boiling animal cartilage, rubber or milk.

We can prepare some simple glue at home by using wheat flour, boiled rice or other kitchen ingredients.

Glue is prepared by a simple mixing process known as emulsification. This process is used to mix the collagen or polymers into a solvent, such as water. The emulsification process can differ based on whether a high-shear or a low-shear mixer is used. Low-shear mixing utilizes a low-speed propeller to slowly fold the polymer into a solvent. High-shear mixing utilizes a high-shear blade to thoroughly break apart polymer particles and mix it with the solvent. Glue for industrial applications are produced by high-speed processes using equipment like high-pressure homogenizers or colloid mills. 

When we apply glue to two things we want to stick together, the solvent used to prepare the glue, i.e. water, evaporates because it is exposed to the air. The time taken for the solvent to evaporate depends on various factors, like the quality of the glue, or environmental factors like the temperature and air conditions. When the glue dries and hardens, the only things left are the sticky polymers holding the two objects together. So, the final thing lefts are the two objects held together by dry polymers.

These days, we have various advanced glues that use additional substances to accelerate the process of glue hardening and glue strength. LORD Adhesives, for example, is producing some of the most advanced structural glues, aiming to replace traditional fastening methods such as rivets, welds and tapes. These advanced glues are being used to bond various materials like metals, composites and thermoplastics.

Glue are used in various applications such as furniture, plumbing, shoes, books, buildings and automobiles. A rough estimate says that 40 pounds of glue are used per year for every person in America!

School: Johnson City Intermediate School, Johnson City Central School District.

Title: Graduate student, Department of Mechanical Engineering, Binghamton University.

Research area: Composites, 3-D printing, finite element method, design and optimization, Mars mission, entrepreneurships.

Interests/hobbies: Running, martial arts, cooking, networking.

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