Obviously brought gloves, why do you eat crayfish or one hand?

Ask who is the big star on the summer dining table, it is the crayfish!

Picture source: sohu.com

Peel the smooth and full shrimp out one by one, and then let the aroma and taste bloom between the lips and teeth ...

Stop, wipe your mouth!

But the disadvantage is that eating shrimp for a while and two hands. I heard it, but also with the taste of crayfish. Obviously we have been with gloves to peel shrimp, why are you still getting oil?

Picture source: sohu.com

Is the glove been broken by the shell of the crayfish? But don't you be broken every time? Is there any other reason for gloves? Let's study it together.

Why does gloves leak oil?

Most of the merchants provided to our shrimp gloves are made by polyethylene (PE). Polyethylene, as its name implies, is a polymer material formed by a lot of ethylene molecules through a polymerization reaction.

Just as the little partners were holding hands, these small ethylene molecules were connected in order through carbon-carbon single keys. This long team continued, and eventually formed a polyethylene long chain. Countless polyethylene long chains are entangled and accumulated, and the polyethylene material is formed.

Many ethylene molecules "handle hands" form a long chain of polyethylene (PE)

Picture source: omnexus

There are many types of polyethylene materials. The polyethylene of shrimp gloves is mainly low -density polyethylene (LDPE) and linear low -density polyethylene (LLDPE). They have a characteristic that there are many chains on the long chain of polyethylene. For example, there are many small splits like a branch.

Compared to low -density polyethylene, the branches of linear low -density polyethylene are shorter and the length is more uniform. The presence of these branches makes the polyethylene material softer and easy to extend, so it is suitable for the production of gloves.

Low -density polyethylene (LDPE) and linear low -density polyethylene (LLDPE), they have many chains on the long chain

Picture source: Reference materials [1]

At the same time, these branches also provide the opportunity to penetrate the oily. Due to the existence of the branch chain, the accumulation of polyethylene long chains will not be too close, and a large gap is left between the chain and the chain. Of course, the bigger here is aimed at the size of the oil molecules. Oil molecules passed through one by one in the gaps larger than themselves, and slowly broke through the obstruction of the gloves.

There is a large gap between the polyethylene long chain, and the oil molecules can slowly penetrate it

Photo source: author painting

Why does it leak oil and do not leak?

Then at this time, someone must ask: The water molecules are much smaller than that of the oil molecules. Since the oil molecules can cross the gap between the polyethylene long chain, should the molecule be okay? But life experience seems to be a glove to prevent waterproof? What's going on?

This is to mention the principle of "similarly dissolved". In terms of chemistry, according to the distribution of the internal charge of the molecule, the molecules can be divided into two types: polar molecules and non -polar molecules. For example, water molecules are typical polar molecules, while edible oil molecules and polyethylene molecules are mostly non -polar molecules.

The principle of "similarly dissolved" is that the solubility composed of polar molecules is easily soluble in solvents composed of polar molecules, and solvents composed of non -polar molecules; The solvent composed of molecules is difficult to dissolve in a solvent composed of polar molecules.

Popularly, it is not a family. If you do not enter a family, the attributes can come together

Photo source: author painting

Is it a little dizzy by this password? In fact, this is similar to "not a family, not entering a family". If the attributes of the solvents and solvents are the same, they can get along well and dissolve. If the attributes of solvents and solvents are different, they do not deal with each other, and it is difficult to dissolve.

Although water molecules are smaller than oil molecules, it is a polar molecule, so it is difficult to walk too close with non -polar polyethylene molecules and it is difficult to wear gloves. On the contrary, the oil molecules belong to non -polar molecules are "interested" with polyethylene molecules, so they can easily pass through the gap between polyethylene molecules. Therefore, in addition to the size of the molecule, the type of molecular attributes also determines whether it can break through the protection of gloves.

How can I enjoy crayfish "elegantly"?

The penetration of oil requires a certain time, so it is effective to change gloves or bring a few more layers of gloves. Of course, if you can find him/her who is willing to peel you crayfish, then you don't have to worry about this problem again!

You can also write it to everyone if you have any oil -proof tricks.

references

[1] Hackl, R., & Perret, S. (2009). Power production with Organic Rankine Cycle technology utilizing waste heat from a cracker and three polyethylene units. Chalmers University of Technology.

Author: Dangerous, Ph.D. in Engineering Mechanics, Shanghai Jiaotong University

Edit: Little Dingdang

Xie Xie: Cai Li, an associate researcher at the School of Environmental Science and Engineering of Donghua University, provides scientific guidance for this article.

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Reprinted content only represents the author's point of view does not represent the Institute of Physics of the Chinese Academy of Sciences

If you need to reprint, please contact the original public account

Source: Shanghai Science and Technology Museum

Edit: Just_iu

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