Glue, an indispensable small object in daily life, brings convenience to our lives with its magical adhesive ability.
But have you ever wondered why glue doesn't stick to the container in which it is kept? What kind of development process has glue undergone? How do we untie our hands if we get stuck with the commonly used 502 glue?
The development of glue
Glue, as a medium that binds different substances together, has a long history. As early as ancient times, humans have begun to take advantage of the bonding properties of natural substances. Archaeological evidence suggests that about 5,300 years ago, people were able to mix soil and clay to glue the stones together.
In China, about 4,000 years ago, people used natural lacquer as a binder to make various utensils. By the Zhou Dynasty, 3,000 years ago, animal glue was used to glue ships. The cornerstone of the Great Wall, as we know it, was bonded by a glutinous rice flour and lime mixed with a binder during the Qin Dynasty.
In ancient Egypt, people had mastered the technique of extracting natural binders from plants and animals, such as gum arabic from acacia trees, rosin from pine trees, and bone glue from bird eggs and animal bones.
With the development of science and technology, synthetic glue came into being, opening a new chapter in adhesives. In 1909, Baekeland invented phenolic resins, which marked the birth of synthetic resin glues. By the 50s of the 20th century, the invention of epoxy resin glue, with its diversity, high strength and wide adaptability, quickly became one of the widely used adhesives.
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How glue works
Synthetic glues are known for their superior adhesion and durability. So, how exactly do they work?
The bonding process between objects is actually achieved through the chemical composition of the glue. In the glue, there are spherical polymer particles, usually with a radius between 0.5 and 5 nanometers, that form the bonding core of the glue. If these polymer adhesives are present alone, they will be difficult to apply effectively and conveniently. For ease of use, water is often used as a solvent to dissolve these polymer binders in water.
When glue is applied to the surface of an object, these polymer adhesives penetrate into the tiny pores of the surface with the moisture. As the solvent-water evaporates, the polymer particles connect to each other and form a strong pulling force, which is the key to their ability to bond the two objects firmly. In some industrial applications, the solvent of the glue may not be water, but a more volatile organic solvent may be used instead of the traditional water-based solvent.
In the process of using 502 glue, we will find that most of the other ordinary liquid glue leaves a lot of room for regret, but only 502 glue always sticks things firmly in an instant, why is this?
In fact, this is because it has a completely different bonding principle from other glues. 502 glue does not rely on solvent evaporation, but rather relies on a very fast chemical reaction to achieve bonding. The core ingredient of 502 glue is cyanoacrylate, which exists as a monomer in a sealed state. Once exposed to air, when it comes into contact with moisture, it quickly initiates a polymerization reaction to form a strong polymer that holds the object firmly together.
502 Chemistry of Super Glue
Very little water is required for this polymerization reaction, and even trace amounts of moisture on the surface of the skin or water vapor in the air are enough to start the process. Cyanoacrylates polymerize much faster than solvents dry, which leads to the possibility that 502 glue can accidentally stick together objects that shouldn't be glued together, such as the user's fingers.
This bonding mechanism also explains why 502 glue dries out easily once opened. After opening, it is difficult to return to the original sealed state even if the cap is tightened. When the glue comes into contact with moisture in the air, it will begin to polymerize spontaneously inside the bottle, eventually forming a solid state that can no longer be squeezed out.
Why glue doesn't
Sticking to the container where it was held?
The glue does not stick to the container in which it is placed, first of all, it depends on the material of the container. Containers for glue are usually made of materials that do not react easily with glue, such as plastic (polyethylene, polypropylene) or glass. These materials have a low surface energy and are not easily able to form effective adhesion to glue molecules.
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Secondly, when designing the glue, the manufacturer will deliberately adjust its viscosity and fluidity to keep it liquid at room temperature and pressure. This design ensures that the glue does not cure until it is used. For example, 502 glue only polymerizes when it comes into contact with water and air, sticking to other objects. And when it is packed in a closed bottle, there are no conditions for the polymerization reaction to occur, and naturally it will not stick in the bottle.
How do you remove 502 glue?
502 glue is often used for emergency repairs and small crafts due to its fast curing and strong adhesion. However, sometimes the 502 glue is accidentally stuck to the skin or other undesirable areas, and how to remove it becomes a tricky problem.
The process of removing 502 glue with nail polish remover containing acetone
Acetone is one of the most commonly used solvents and can effectively dissolve 502 glue. Therefore, a small amount of acetone can be applied to the area being glued and gently rubbed until the glue dissolves. This ingredient is found in many nail polish removers, and there are also specialized acetone detanglers for sale. However, it should be noted that acetone has an irritating effect on the skin and certain materials, and prolonged contact should be avoided as much as possible.
bibliography
[1]https://mp.weixin.qq.com/s/KizGuCZxbUGnY9XQ4CmFbQ
[2]https://mp.weixin.qq.com/s/KuqdZeE53SnrGLGg-_1OvA
[3]https://mp.weixin.qq.com/s/C98DSr98CDTUj61PXKiOVw
[4]https://mp.weixin.qq.com/s/1Rw8lZKushQbRmSlBDXesw
Planning and production
Source: Popular Science of Mechanics