The function of glue is to firmly combine two identical or different solids by the action of another substance. It is mainly made of synthetic molecules or natural proteins and carbohydrates, mostly in liquid form, and belongs to the chemical industry.
The viscosity of glue is measured with a Brinell viscometer, and the unit is "cps" (centipoise · s). Generally, temperature will affect the viscosity of glue. The lower the temperature is, the higher the viscosity is. The higher the temperature is, the lower the viscosity is.
Historical development of glue
People have used adhesives for thousands of years. When talking about the ancient adhesives, we would first think of the paste used to paste Spring Festival couplets when we were young. The paste was boiled with starch and water to change the molecules in the starch, which turned into a transparent paste. In the age when there was no chemical glue, making simple paste was the most widely used glue,During the construction of the Great Wall, glutinous rice was used as a binder, which remained solid after thousands of years and became a symbol of the ancient civilization of the Chinese nation.
The viscosity of the paste is limited. It can only stick some simple paper. There are still many things to be bonded in life. People began to make adhesives from the fur and viscera of plants or animals. There are historical records in our country long ago that fish bladders were used to make adhesives, and the fish bladders can be steamed and crushed to stick things. This material is called fish glue, which is used to bond furniture or seal joints.
Later, due to the emergence of polymer materials, synthetic glue was developed. This glue has higher strength, longer durability and wider application range. Glue has also become an indispensable product in production.
Working principle of glue
The bonding between objects is achieved by the chemical composition in the glue. In the water-based environment, the polymer of glue is round particles. Generally, the radius of particles is between 0.5 and 5 um. Water is the carrier of the polymer. The glue is coated on the surface of the object. The water in the glue carries the high molecular weight and slowly immerses into the tissue of the object. When the water disappears,The polymer tightly combines the two objects by pulling force between them.
****
The principle of AB glue is that A is glue and B is curing agent. This glue cannot dry itself, or it dries very slowly. It can only work if curing agent is added. The role of B is to accelerate the rapid evaporation of water in A, and the principle of sticking to objects is the same as other glues.
Why can glue stick firmly
In order to make the glue stick firmly, not only must the polymer have a good contact with the object, but also must smoothly complete the curing, so that the glue can form a solid with high strength.
In the use of glue, too much glue will make the water between the polymers not easy to volatilize, and also make the polymers crowded together, which can not form the strongest tension. Too much glue can only play the role of filling, and the bonding effect will be much smaller.
Why doesn't glue stick to the bottle
****
As mentioned above, glue is composed of adhesive and water, which is also called volatilizer. To take an inappropriate analogy, adhesive is equivalent to bear child, and water is adults. When adults are around, bear children are honest. Once adults leave, bear children start to struggle, which means that as long as volatilizer is around, the adhesive will not work,Once the poured water runs away, the glue starts to play its role. The glue will dry after being kept for a long time, which means that the water will evaporate completely. Of course, the bottle materials are specially selected according to the activity of the glue. They are basically inert materials, which also have some functions.
We will find that the adhesive strength between different objects is different. When the glue is still in the bottle, they attract each other through the force between molecules. When the glue is applied to the object, the molecules on the surface of the object attract each other with the molecules in the glue, and the glue will enter the object due to the attraction and stick together,If the molecules in the glue and the molecules in the object cannot attract each other, the molecules in the glue will remain the same, will not enter the solid, and will not stick firmly or fall off under the action of gravity.
The stickiness of glue is the only standard to measure good or bad. If the stickiness of glue is not enough, it can only be said that this is a failed product. However, there is also a saying that "I am made of natural materials and will be useful". This kind of glue has contributed to the birth of new office supplies.
Researchers are developing a kind of strong glue. This ideal glue should not only be tightly combined with the object, but also not leave traces on the surface. This requires adding more chemical reactants in the formula, which results in the polymerization of polymers, greatly reducing the viscosity. Researchers think this glue is useless, and later used it to stick some paper strips,Unexpectedly, the effect is very good. The stickiness can neither tear off the paper on the lower layer nor leave glue. It can also be stuck anywhere again. A new product, "Post it Notes", was born.
