Legal basis: Article 44 of the Education Law of the People's Republic of China. The educated shall perform the following obligations:
(1) Abide by laws and regulations;
(2) Abide by students' code of conduct, respect teachers, and develop good ideological and moral character and behavior habits;
(three) study hard and complete the prescribed learning tasks;
(4) Abide by the management system of schools or other educational institutions.
Perm is a kind of hairdressing method, which can be divided into physical perm and chemical perm, of which chemical perm is the most commonly used one. Perm can make hair richer (with curling effect); Change the shape and direction of hair (curling is not very effective).
The basic process of perm is divided into two steps. The first step is to break the sulfur bond and hydrogen bond in hair through chemical reaction. Step 2, arrange the stable hair core structure.
In daily life, hair is regarded as an ornament. Throughout history, people have been looking for ways to curl their hair. Perm is closely related to the development of perm tools, which can be said to be the promotion of perm tools.
In 1990s, North Korea invented ceramic ironing, and then it spread to Japan, Taiwan Province Province from Japan, and finally to Chinese mainland. This is a long process, and ceramic ironing has been popular until the beginning of the 20th century.
Hair is mostly composed of insoluble keratin, accounting for more than 85%. Keratin is formed by amino acids shrinking synthetic peptide chains and then cross-linking polypeptide chains through disulfide bonds (-S-S-), which makes hair have a firm structure. In about 1930, Rockefeller Institute researchers found that in weakly alkaline solutions, these thio groups can be interrupted by sulfides or molecules containing sulfhydryl groups (-SH). This discovery provides a method for the popular "cold perm" (also known as "chemical perm").
During cold perm, the hair is soaked in a solution containing mercaptoacetate ion (HSCH2COO-). Because of its reducibility, disulfide groups in hair can be decomposed into two sulfhydryl groups:
2 hsch2coo-(AQ)+-s-s- (hair) →(SCH2COO-)2 (water) +2HS- (hair)
Hair that loses cross-linking will become very soft. Curling the hair with a curling tool, and the induced polypeptide chain is transferred from polypeptide chain to polypeptide chain under the action of mechanical external force. At this time, a "fixing agent" is added to fix the bent hair. The so-called "stationary liquid" is actually an oxidizing solution, such as the solution of hydrogen peroxide, potassium bromate and potassium persulfate. Its function is to make hair form new disulfide bonds:
2HS- (hair) +H2O2 (AQ) →-s-s- (hair) +2H2O (length)
Because many disulfide-based crosslinks are re-formed between hair polypeptide chains, the original rigidity and toughness are restored, and a lasting curly hairstyle is formed. Generally speaking, about 20% of disulfide bonds in human hair are broken, and about 90% of the broken disulfide bonds are re-formed during the styling process.