Childhood mystery: Why can't the beautiful fragrant rubber always wipe clean?

A while ago, I saw such a stalk picture "If you feel useless, think about these guys" - "

I have to say that this picture is really full of childhood memories!

While the memories are aroused, we have to ask: Why are these beautiful fragrant rubber in childhood memories that are often not easy to use, and those rubber that is very clean is often ugly and ugly?

In fact, this problem has emerged since the birth of rubber.

Rubber: rubber erasers

When it comes to rubber, you must first talk about a pencil.

Previously, the wooden pen poles were wrapped in the real "lead". By the 16th century, the lead in the pencil was replaced by graphite, and the handwriting became obvious and easy to erase, and it was naturally widely used. For engineers who need to draw drawings, it is simply a technological revolution.

But the problem followed.

Initially, people generally used bread to remove pencil marks. The principle behind it is not complicated: graphite adsorbing on the surface of the paper forms a handwriting. Just find something stronger than the paper, you can erase it. Although scribbled, it was dealt with.

This eradication method ushered in a turnaround in the 18th century. At that time, in Europe, there was an exotic product from the American continent that caused many people's interest, that is: natural rubber.

In 1770, British chemist Pribli (also one of the earliest founders of oxygen) noticed that this substance seemed to be used to erase the handwriting of pencils. This is mainly because natural rubber has good elasticity, and it can better fit with rough paper surface, and the eradication effect is naturally improved.

Therefore, according to this feature, Priestell named the rubber "Rubber", which is literally the "eraser". So far, "Rubber" also has the meaning of "rubber" and "rubber rubbing". However, in daily life, it will also refer to "rubber condoms". A cold knowledge here: The English textbook of the Middle School published by our country in 1993 is the version of the famous "Li Lei and Han Meimei". The English English in the textbook is "Eraser". It's "Rubber".

However, this "rubber erasers" have a disadvantage that the natural rubber is too soft and the experience is not good enough.

In 1839, the transfer came again. An American named Charles Goodyear developed a rubber treatment process. He mixed sulfur and natural rubber to heat up to make the earliest sulfide rubber. The so -called vulcanization is that the molecules of rubber are connected by sulfur atoms, and sulfur plays a fixed position in it. In this way, rubber molecules can no longer move at will, and the shape of the finished product is determined.

In this way, modern rubber was born.

Astronomical paradox: easy to use or not smelling,

It's not easy to smell well, it's not easy to use

However, the new problem also followed. The advantage of the rubber rubbing made of natural rubber is fixed in shape, more durable, and the eradication effect is really good, but the taste is really bad. This is not surprising. The earliest raw material used by vulcanization technology is sulfur, a chemical element known as "hell element", and the smell is a bit pungent. Even with modern sulfur, many of them still contain sulfur, which will inevitably have an unpleasant taste.

The rubber rubbing made of natural rubber, the color of the goose is yellow to brown yellow 丨 putitalPaper.bigcartel.com

By the 20th century, artificial synthesis polymers became the development trend of new materials. Among them, a polymer called polyvinyl chloride, due to the advantages of low cost, quickly ranked among the most common and most dosage artificial synthetic materials.

Polyethylene (PVC) is generally regarded as plastic. Sometimes, you will see the triangle logo on the packaging of some plastic products. If the number in the logo is "3", it means that it is polyvinyl chloride, and sometimes people also use the "ethylene group" for short.

Figure@图 小 图/Zhihu

However, this kind of plastic is very special. It is relatively crispy and not easy to set, so it is necessary to add plasticizers (also known as plasticizers), and then mixed heating to shape.

The proportion of plasticizers in PVC can have a lot of room for adjustment. If the amount of addition is about 10%, then the final finished product is only able to set it, and it is still crispy, usually used to make a water pipe; There are also elasticity, just like rubber. Therefore, PVC in this state is often called plastic, and it can also erase the handwriting like natural rubber.

There are some advantages in PVC rubber rubbing. For example, when the amount of plasticizer is added, it becomes a translucent state. At this time, if some pigments are added, it can be made into various interesting shapes, such as fruits or various animals. On the other hand, a large amount of plasticizer is equivalent to solvents, and rubber can dissolve some flavors, which becomes fragrant rubber rubbing. Good -looking, a bit fragrant, who does such an eraser doesn't like it?

Who doesn't like such a rubber?丨 SKSIDDHARTThan / Wikimedia Commons

For manufacturers, the production of PVC rubber is very tested. Once the condition is not ideal, it is easy to cause the quality of rubber to be unstable.

Such as the hardness of rubber. If the content of plasticizers is not controlled, the rubber may be too hard or too soft, not very practical, because the friction of hard rubber is too small, the eradication effect is relatively weak, and the soft rubber wear resistance has poor abrasion resistance. There are a lot of rubber dandruff as soon as it wipes. Moreover, after long -term use or heating, the plasticizer will still be separated. In this way, the material of the rubber rubbing will become harder until the ability of the eradication; on the other hand The plastic ruler is put together, and the oozed plasticizer will also dissolve the plastic material of the ruler, and then stick together. This is probably a nightmare for many people's childhood.

Figure@图 乎/Zhihu

The rubber head at the top of the pencil,

Originally for emergency

There is also a special form of existence on childhood rubber: the kind of rubber head installed on the top of the pencil.

Time to return to 1858, an American painter named Hyman L. Lipman suddenly wondered, combining pencils and rubber, and applied for a patent for this. This "Eraser Pencil" was welcomed by consumers. As a result, the poor Lipman made a lot of money and transferred the patent to the manufacturer at a high price of $ 100,000 after 14 years.

There is also an episode here: because there are other people in the market, this two -in -one tools provoked a patent war. Li Pan's patent did not receive the support of the court, and the judge believed that this invention was not innovative. Nevertheless, this patent war has become a classic case in the field of intellectual property rights.

Unfortunately, although this classic design has been reserved so far, from a practical perspective, the rubber on this pencil is slightly chicken, and it is also a bad part of many people's childhood memories. However, I do n’t know if anyone noticed that although this rubber scratching pencil handwriting is not effective, it can wipe off the pen.

This is because the design of the two -in -one pencil rubber is for emergency, and the manufacturer is not very attentive. Often, the cheapest "office rubber" will be installed. This rubber contains some "light stones" minerals, which has a low production cost, but it can scrape off the surface of the paper to erase the strokes that penetrate in the paper fiber Pencil handwriting.

Rubber on the pencil 丨 UNSPLASH

Today, although the scenarios of application are getting less and less, as consumers have higher requirements for it, rubber has also improved a lot.

For example, the most common PVC rubber, where plasticizers often use phthalate, and may have precocious impacts such as early maturity after intake. As a result, PVC rubber began to transform and use more environmentally friendly and safe plasticizers. At the same time, the natural rubber rubber that was left out of the country was reopening again because of the low face value. Of course, this was also related to the smell of sulfur's sulfur.

In addition, the kind of pencil craft with rubber has also made great progress. Some producers have combined the rubber and pencils that are more suitable for wipe off the handwriting. It is convenient to use and the rubber is not easy to lose. The eradication effect has also improved.

Perhaps when the current children grow up, the childhood memory of rubber will be better.

references

[1] Historial Note. Mrs Bulletin 19, 69 (1994) .https://doi.org/10.1557/s0883769400036824

[2] Grady, M. F., Alexander, J. I. (1992). Patent Law and Rent DISSIPATION. VA. L. Rev., 78, 305-350. Https://doi.org/10.230733310

Author: Sun Yafei

Edit: malt Yang

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