The secretions of some trees often form resins, but amber is a fossil of resin. Although shellac is also regarded as a resin, it is a deposit of lac insects secreted on trees. The shellac paint made of shellac was originally used as a preservative for wood, but it was the earliest used varnish with the invention of the motor. However, after entering the 20th century, natural products have been unable to meet the needs of electrification, prompting people to find new cheap substitutes.
As early as 1872, the German chemist A. Bayer first discovered that phenol and formaldehyde could quickly form reddish brown lumps or viscous when heated under acidic conditions, but they could not be stopped by classical methods. After the 20th century, phenol has been widely available from coal tar, and formaldehyde is also produced as a preservative. Therefore, the reaction products of the two are more attractive, and it is hoped that useful products will be developed, although many people have spent a lot of work on it. , but did not achieve the expected results.
In 1904, Baekeland and his assistants also carried out this research. The original purpose was only to make an insulating varnish instead of natural resin. After three years of hard work, in the summer of 1907, not only the insulating varnish was produced. It also produces a true synthetic plastic material, Bakelite, which is known as "bakewood" or "bakelite" or phenolic resin.
As soon as Bakelite came out, it was discovered by the manufacturers that it could not only manufacture a variety of electrical insulation products, but also make daily necessities. T. Edison used to make records, and soon announced in advertisements that it had made thousands of Bakelite. A variety of products, so at the same time, Beckland's invention was hailed as the "alchemy" of the 20th century.
Phenolic resin with coal tar as raw material has been the first in various synthetic resin productions before 1940, reaching more than 200,000 tons per year. However, with the development of petrochemical industry, polymerized synthetic resins such as polyethylene and The production of polystyrene is also expanding. With the establishment of many large-scale plants with an annual output of more than 100,000 tons of these products, they have become the four types of synthetic resins with the most production. Synthetic resin plus additives, through various molding methods to obtain plastic products, today there are dozens of plastic varieties, the world annual output is about 120 million tons, China is also more than 5 million tons, they have become production, life And the basic materials for national defense construction.
Synthetic resin is the most important component of plastics, and its content in plastics is generally 40% to 100%. Because of the high content and the nature of the resin often determines the nature of the plastic, the resin is often considered synonymous with plastic. For example, a mixture of polyvinyl chloride resin and polyvinyl chloride plastic, phenolic resin and phenolic plastic. In fact, resin and plastic are two different concepts. Resin is a raw, unprocessed polymer that is used not only in the manufacture of plastics, but also as a raw material for coatings, adhesives, and synthetic fibers. In addition to a small part of plastic containing 100% resin, most plastics, in addition to the main component resin, need to add other substances.