What is a molecular eraser?

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What is the principle of eraser?

Prince Yuan Shao

2022-03- 14 06:20:26

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Eraser is a learning tool for erasing pencil words. Pencil lead is made of graphite and clay. The hardness of pencil lead can be changed by adjusting the proportion of graphite and clay.

When writing on paper with a pencil, pencil lead rubs against the paper, and pencil lead will be ground into fine powder. Some of these powders enter the invisible gaps between the fibers of the paper, and some are adsorbed on the paper surface due to the intermolecular force between the paper and the refill powder.

The pencil words on the paper can be erased with an eraser. In one case, the intermolecular force of the eraser on the refill powder is greater than that between the paper and the refill powder, so it will be absorbed by the eraser. You can try. Press the pencil words on the paper hard with the eraser, and the pencil words will stick to the eraser, as shown below.

However, part of the refill powder enters the paper deeply, so it is difficult to adsorb the refill powder only by the intermolecular force between the eraser and the refill powder. Therefore, it is necessary to rub the handwriting with an eraser and use the friction force to overcome the intermolecular force to make the refill powder fall off. Of course, the surface of the paper also falls off a little, and the eraser also falls off. Three kinds of powder are rolled with an eraser and stuck together, which is a linear thing.

A small eraser can erase the pencil marks. We have known this function since childhood, so what is its principle?

Let's see why pencils can write on paper. The main components of pencil lead are graphite and clay. These two kinds of raw materials are mixed in different proportions, mixed, mechanically pressed, baked at high temperature, and finally soaked in oil. The different proportions of graphite and clay determine the hardness of pencils. The higher the clay content, the greater the hardness. For example, 6h is harder than 3h. In addition, B in the pencil label stands for blackness, representing the content of graphite, and 6b is the deepest color, while hb pencil commonly used in painting indicates that the content of graphite and clay is equivalent, giving consideration to both texture and blackness.

Because the graphite in pencil lead is soft and the internal molecules are layered, the layers are easy to peel off. There are many tiny folds and fiber gaps on the surface of paper. When writing hard, the friction between the pen core and the paper will make the graphite of the pen tip form powder, which will attach to the paper surface or the gap on the fiber surface, forming pencil marks.

Let's look at the eraser again. The main component of rubber is rubber, in addition, sulfur, vegetable oil and tiny sand grains are added. In the process of rubbing characters on the rubber, the temperature of the contact surface between the rubber and the paper increases due to friction, which has a strong adsorption force on graphite and clay molecules attached to the paper surface, so it "sticks" to the rubber surface, and the pencil characters fade from the paper until they disappear. At the same time, due to the existence of sulfur and fine sand particles in rubber, it is easy to lose chips when rubbing, so the absorbed pencil foam, rubber residue and paper fiber will be kneaded into long strips, similar to the putty that rubs off the skin when taking a bath.

As for why it is difficult for an eraser to erase the words written by pens and ballpoint pens, it is mainly because the words written by them are formed after ink and ink are dried. Ink and ink molecules are not attached to the paper surface, but have penetrated into the paper fibers. Unless these impregnated paper fibers are wiped off with great force, they will not be wiped off at all.

To understand the principle of eraser, let's first understand the paper and pencil we use to write.

Although the paper feels clean and smooth, in fact, these papers are made of wood pulp fibers, so if you enlarge the surface of the paper dozens of times, you can see that the surface of the paper is actually uneven, with some bumps and gullies left by wood pulp fibers, but it is precisely because of this structure of the paper surface that the pencil can write traces on the paper.

Secondly, let's see why pencils can write on paper. The black pencil lead in the pencil is actually made of graphite and sticky soil, stirred with water and qualitatively fired. This specially treated graphite refill has good flexibility and adsorption, and because it is made of graphite, its color is black. Because of the strong adhesion of this black pencil lead, the surface of the writing paper is uneven. When you are writing, the graphite powder on the pencil lead will be rubbed off when it comes into contact with the paper, and then it will be adsorbed on the paper, so what you see is the pencil words with distinct colors.

After understanding the principle of pen and paper, the working principle of eraser can be solved easily.

Why can an eraser erase words? Why can I easily wipe off graphite powder with strong adhesion? Rubber is made of rubber. Unlike the smooth surface of paper, most erasers have obvious concave and convex surfaces. Therefore, if you rub against each other, the friction of the rubber is greater. Therefore, compared with paper, the eraser will thin the paper by virtue of its stronger friction, peel off the graphite powder from the surface of the paper, let the graphite powder adsorb on the eraser, and then form a lot of rubber ash, and the paper will become clean.

But if it is a water-based pen or pen, the eraser can't be erased, because this type of pen will penetrate the ink into the fibers of the paper, and the eraser can't be erased.

Tell the story of pencils and erasers. Most people think that pencils are made of lead, but it turns out that this is wrong. Although we call it a pencil, pencil lead is actually graphite, which is made of carbon. When you write with a pencil, the graphite particles in the central cylinder will rub and stick to the paper being written. Without interference, these graphite particles will stay on the paper for a long time (about ten years).

With an ordinary pencil, you can draw a line about 56 kilometers long. You can also write * * * with a pencil, but you are likely to make many mistakes in the process. It is human nature to make mistakes, so if you have an eraser, you can correct them.

The function of eraser is based on the principle in our daily life: friction. Only because of friction can we walk on the ground. So your hands get hot when you rub them. Eraser is the result of friction between eraser and paper. When the eraser rubs on paper, the generated friction will generate heat, which will help the eraser to become sticky enough to "absorb" graphite particles. Usually, erasers are made of synthetic rubber, but more expensive erasers use vinyl and plastic. These materials are used because they are more sticky than paper fibers, so it is easier to stick graphite particles to them. In essence, anything more sticky than paper fiber can be used as an eraser, as simple as that!

The earliest rubber used by humans was wet crust. The first piece of rubber was invented by English engineer Edward Nain in 1770. It is said that the invention of the eraser was actually an accident. Nain picked up the eraser while trying to pick up the crust. Then, when he erased the pencil marks with an eraser, he realized the erasing characteristics of the eraser.

Erasers are called erasers because they are made of rubber, and because the erasing process involves "erasing" pencil marks from paper-so they are rubber. Friends, this is a story about pencils and erasers. It tells us that we should not be afraid of making mistakes, but should learn how to correct them.

difficulty

The principle is simple, one is friction and the other is adsorption.

Before the invention of rubber, people used bread to wipe pencils. 1770, British scientist Priest discovered for the first time that rubber can erase pencil handwriting, which brought great convenience to people. It can also be seen that rubber first uses the viscosity and adsorption of rubber to erase pencil handwriting (mixed powder of clay and graphite) through friction and adsorption.

The earliest eraser was made of natural rubber. When you erase the words, there is no crumb. Just stick the pencil tip on the eraser, and the more you rub it, the dirtier it gets. Later, when people made rubber, sulfur, oil and other substances were added, which made rubber fragile and easy to fall off. Erased pencil powder leaves crumbs on the eraser, so that the eraser can always be clean and the paper will not be stained.

With the development of products, the classification of rubber is getting finer and finer. Some are dedicated to erasing pencil handwriting, and later some can erase pen handwriting. By adjusting the proportion of rubber in rubber and changing the hardness, the pen mark can be erased. People also added different directional components to the plasticine species, which made the rubber have different fragrance.

In the field of painting, the classification of rubber is more detailed. According to the hardness of drawing pencils, the higher the numbers of 6H, 5H, 4H, 3H, 2H, h, HB, 1B, 2B, 3B, 4B, 5B, 6B, 7B, 8B and h, the harder the pencil, the higher the number of b, the softer the pencil and the higher the graphite content, and the easier it is to erase the handwriting. And there are corresponding special erasers for different pencils.

In addition to pencils, there are also painting tools such as carbon rods and carbon crystal rods in the field of painting. In order to cope with this opponent, softer "plasticine" products have appeared in the rubber field. (This kind of plasticine is not a plastic plasticine for children's toys, but a special plasticine for art.) And plasticine mainly relies on viscosity and adsorption ability to wipe away the traces of painting.

Friction principle

High resistance

Consume the body and take away the dirt.

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