Phenolic resin is also called phenolic molding compound.
It is a colorless or yellowish-brown transparent substance, and it is often colored in red, yellow, black, green, brown, blue, granular and powdery when sold in the market. Resistant to weak acid and alkali, decomposed in strong acid and corroded in strong alkali.
insoluble in water, soluble in organic solvents such as acetone and alcohol. Phenolic resin is a general term for resinous substances obtained by polycondensation of phenol and its homologues or substituted phenols with aldehydes.
Among them, phenolic resin obtained by polycondensation of phenol and formaldehyde is the most important. It includes linear phenolic resin, thermosetting phenolic resin and oil-soluble phenolic resin.
It is mainly used to produce compression molding powder and laminated plastics; Manufacturing varnish or insulating and corrosion-resistant coating; Making daily necessities and decorations; Manufacturing sound insulation and heat insulation materials.
Second, the historical development of synthetic resin
The secretions of some trees often form resin, but amber is a fossil of resin. Although shellac is also regarded as resin, it is a deposit secreted by lac insects on trees.
shellac paint made of shellac was originally used only as a preservative for wood, but it became the earliest insulating paint with the invention of the motor. However, since the 2th century, natural products have been unable to meet the needs of electrification, prompting people to find new cheap substitutes.
As early as 1872, German chemist A.Bayer first discovered that phenol and formaldehyde can quickly form reddish-brown lumps or sticky substances when heated under acidic conditions, but the experiment was stopped because they could not be purified by classical methods. Since the 2th century, phenol has been obtained in large quantities from coal tar, and formaldehyde is also produced in large quantities as a preservative. Therefore, the reaction products of the two have attracted more attention. I hope to develop useful products. Although many people have spent a lot of labor on it, they have not achieved the expected results.
In 194, Baekeland and his assistant also carried out this research. At first, they only hoped to make insulating paint instead of natural resin. After three years of hard work, in the summer of 197, they finally made not only insulating paint, but also a real synthetic plastic material-Bakelite, which is known as bakelite or phenolic resin. As soon as Bakelite came out, manufacturers soon found that it could not only make a variety of electrical insulation products, but also make daily necessities. T.Edison used it to make records, and soon announced in an advertisement that thousands of products had been made with Bakelite, so he praised Baekeland's invention as "alchemy" in the 2th century.
Before 194, the phenolic resin with coal tar as the original particle always ranked first in the output of various synthetic resins, reaching more than 2, tons per year. However, with the development of petrochemical industry, the output of polymeric synthetic resins such as polyethylene, polypropylene, polyvinyl chloride and polystyrene also expanded continuously. With the establishment of many large-scale factories with an annual output of more than 1, tons, they have become the four types of synthetic resins with the largest output today. Up to now, synthetic resin and additives can be used to obtain plastic products through various molding methods. There are dozens of kinds of plastics, with an annual output of about 12 million tons in the world and more than 5 million tons in China. They have become the basic materials for production, life and national defense construction.
。 Third, what is the discovery history of vanadium
Vanadium has been discovered twice.
It was first discovered in 181 by Gerhard Riva, a professor of mineralogy in Mexico City. He found that it was in the vanadate sample, and the vanadium ore sample was Pb5(VO4)3Cl. Because the salt solution of this new element showed bright red when heated, it was named "Ellie Troni", which means "red", and he sent it to Paris.
However, French chemists concluded that it was a kind of polluted chromium ore, so it was not recognized by people. The second discovery was made in 183 by Swedish chemist Safstrom (1787-1845). )
When studying the iron ore in Smaran mining area, iron was dissolved with acid, and vanadium was found in the residue. Because the compounds of Vanadium are colorful and beautiful, we named this new element "Vanadium" after a beautiful goddess named Vanadis in ancient Greek mythology.
Chinese is named vanadium according to its transliteration. Safstrom, Willer, Bezerius and others have all studied vanadium and confirmed its existence, but they have never separated vanadium.
Later, in 183, he wrote that Fo Si Te Le Mu found it in the iron extracted from Swedish iron ore, and affirmed that it was a new element called vanadium. He was able to prove that it was a new element, and therefore he defeated a rival chemist, FriedrichW? Hler, he is also studying another kind of vanadium ore. More than 3 years after the discovery of vanadium in Safstrom, in 1869, the British chemist Roscoe He (1833-1915) reduced vanadium dioxide with hydrogen, and made pure metal vanadium for the first time, and he proved that the previous metal sample was actually vanadium nitride (VN).
。 Is the first artificial polymer in human history phenolic resin
It seems not
In April 1997, Dr. Frank Baker, an emergency medicine expert from Chicago, took part in a clinical trial to test the shape of artificial skin suitable for insulin-dependent diabetic patients, whose tissues deteriorated due to the side effects of chronic hyperglycemia. Baker himself has been suffering from diabetes for 4 years, and he himself is in danger of losing a foot due to incurable skin ulcers. For him, the result of this experiment is simply a miracle: the skin cultured in the laboratory not only covers and protects his wound, but also releases a chemical, which makes his own tissue begin to recover at a much faster speed. In Dr. Baker's own words, artificial skin saved my foot.
The substance that makes this medical miracle work is synthesized from polymers, which are actually long molecular chains formed by combining many different small molecules in a chemical way.
The first artificial skin was invented by Baker and Janas. Baker is the head of trauma department of Massachusetts General Hospital, and Janas is a chemistry professor at MIT. V. What are the types of phenolic resin < P > A kind of paint made of phenolic resin or modified phenolic resin as the main film-forming substance is called phenolic aldehyde paint.
Phenolic resin is one of the earliest developed synthetic resins, and it has been used to make coatings for nearly 7 years. Although the synthetic resin is quite developed at present, it still occupies a large proportion in the coating industry because of its low cost and endowing coatings with certain properties such as hardness, luster, quickness, water resistance, acid and alkali resistance and insulation, and is widely used in wood, architecture, ships, machinery, electrical and chemical corrosion-resistant coatings.
Phenol-formaldehyde resin is a kind of resin prepared by condensation polymerization of phenol and aldehyde. The main raw materials are phenol and formaldehyde. In addition, other phenols, such as cresol, xylenol, hydroquinone and other aldehydes, such as furfural, can also be used for polycondensation, and sometimes aniline, phenol and formaldehyde can also be used. The common reaction of forming phenolic condensate is that formaldehyde and phenol form hydroxymethylphenol, and then further condensation, removing water, resulting in condensate and forming methylene bridge. The reaction formula is as follows:
According to the chemical structure of raw materials used, the molar ratio of phenol to aldehyde and the nature of catalyst, the phenolic resin prepared has different properties. The types of phenolic resin for coatings, phenolic resin coatings and their applications are discussed below.
1. Types of phenolic resins for coatings
There are three types of phenolic resins for coatings: alcohol-soluble phenolic resins, modified phenolic resins and oil-soluble phenolic resins.
among these three resins, the paint made of 1% oil-soluble pure phenolic resin and tung oil has the best performance, but the resin source is scarce and the cost is high, so it is not widely used. Rosin modified phenolic resin has wide sources, low cost and easy operation in refining. The paint refined with tung oil still partially retains the chemical resistance, weather resistance, water resistance and insulation of phenolic resin, and the paint film is bright and hard, which can be dried or dried in white, accounting for a large proportion in phenolic resin paint. Alcohol-soluble phenolic aldehyde is not widely used.
2. phenolic resin paint uses
1) Alcohol-soluble phenolic resin paint
These paints are made by dissolving alcohol-soluble phenolic resin in alcohol solvents, and generally belong to thermosetting novolaks. They are a kind of paints without grease. After baking and drying, the paint film is tough, with good adhesion, oil resistance, water resistance, heat resistance, acid and alkali resistance and solvent resistance, and also has good insulation and certain bonding strength. For example, F1 6 phenolic resole has good moisture resistance and insulation, and is used for adhesive layer products and insulating parts.
2) Modified phenolic resin
Unmodified phenolic resin is immiscible with oil and other resins. If paint is made separately, the paint film is brittle, so it is rarely used. In phenolic paints, most of the phenolic resins used are modified phenolic resins. After modification, the oil solubility and miscibility of other resins are improved, and they have been widely used in phenolic paints and other paints. The modification of phenolic resin generally includes rosin modification and butanol modification.
① phenolic resin paint modified by rosin: This kind of paint is made of rosin modified phenolic resin and drying oil, etc., which are all kinds of oil paints, then added with drier, solvent and pigment, and ground and prepared. The products include various varnishes, enamels, primers and putty.
The paint film of phenolic resin paint modified by rosin is hard, durable, dry, water-resistant, acid-base-resistant and insulating, and has low price and many varieties, which plays an important role in phenolic aldehyde paints. The disadvantage is that the paint film is easy to yellow. This kind of paint is widely used in wood furniture, buildings, general mechanical products, ships, insulating paints and so on.
② Butanol-modified phenolic resin paint: This kind of paint is made of butanol-modified phenolic resin dissolved in benzene solvent as the main film-forming substance. Its paint film has good water and acid resistance, but it is brittle and needs to be baked and dried at high temperature. Therefore, it is generally used in combination with oil or other resins. The paint film prepared by this method has good corrosion resistance and flexibility, such as F23-2 phenolic canned paint and F52 1 phenolic anticorrosive baking paint.
3) Oil-soluble pure phenolic resin paint
This kind of paint is made of oil-soluble phenolic resin and hot-rolled products from drying oil.
according to the ratio of pure phenolic resin to oil, it can also be divided into three types of paints with short, medium and long oil content, which can be made into primer, enamel and varnish.
Pure phenolic resin has good water resistance, acid resistance, solvent resistance and electrical insulation performance. The paint film made by hot smelting with drying oil, especially with tung oil, is hard and tough, quick to dry, good in adhesion and slightly inferior to alkyd paint in weather resistance, but better in water resistance and chemical corrosion resistance than alkyd paint. Therefore, pure phenolic resin paint is suitable for underwater and outdoor anti-corrosion coating. It is used in ships, chemical equipment and electrical insulation. Like epoxy primer, it is an important variety of metal primer and has been widely used.
However, all kinds of phenolic paints have different degrees of yellowing, so there is generally no white enamel in phenolic paints.
3. Key points of phenolic resin paint construction
The following points should be paid attention to in phenolic resin paint construction:
① Alcohol-soluble phenolic resin paint uses ethanol as diluent. Modified phenolic resin paint uses 2OO solvent gasoline or turpentine as diluent, oil-soluble pure phenolic short-oil paint uses xylene as diluent, medium-oil paint uses 5% mixture of xylene and 2∞ solvent gasoline < P > as diluent, and long-oil paint uses 2 solvent gasoline or turpentine as diluent.
② this kind of paint can be brushed or sprayed. Working viscosity: 2s~3s for spraying and 7s~11s for brushing.
③ drying conditions: it takes 18h to dry at room temperature.
④ The drying paint must be baked according to the technical requirements. Who can talk about the history of plastics
1. The history of plastics
The use of natural resins can be traced back to ancient times, but the modern plastics industry was formed in 193 and has achieved rapid development in the past 4 years.
The name resin is derived from the lipid secreted by trees. The earliest natural resins used by human beings are rosin, shellac and so on. The production of natural resin is limited by the region, but the output is not large, the quality is not high, and the use is limited. In order to find a substitute for natural resin, people made nitrocellulose from cellulose (cotton) and nitric acid in 1846, and mixed wet nitrocellulose with camphor to make a substitute for shellac, which was built in 1872. Although it has been more than 1 years since its discovery, it is still widely used, and its common name is celluloid, such as table tennis, toys, combs and buttons. With the growth of human demand for plastic materials and the improvement of scientific and technological level, people have developed synthetic resins which are much more widely used than natural resins. Synthetic resin is a high molecular weight resinous substance made by chemical reaction of low molecular weight compounds, which is generally solid at normal temperature and pressure, and some are viscous liquids. The first synthetic resin is thermosetting phenolic resin (bakelite), which is made of phenol and formaldehyde under the action of catalyst. Since the establishment of the first phenolic resin factory in 197, it began to enter the period of synthetic polymers. In 1931, the industrial production of the first thermoplastic resin, polyvinyl chloride resin, began. Since then, the synthetic polymer industry has developed rapidly, and polystyrene, polyvinyl acetate and polymethylmethacrylate have been industrialized one after another. At present, there are about 3 kinds of resins produced in industry. Among the three synthetic materials (synthetic resin and plastic, synthetic rubber and synthetic fiber), synthetic resin is the earliest, the largest in output and the most widely used. According to statistics, in 1995, the output of synthetic resin in the world was about 12 million tons, and that in mainland China was about 4.4 million tons. VII. Discovery History of Molecules
history of plastics industry Since the birth of the first plastic product celluloid, the plastics industry has a history of 12 years.
its development history can be divided into three stages. The processing stage of natural polymers is characterized by the modification and processing of natural polymers, mainly cellulose.
in 1869, American J. W。
Hai Ete found that adding camphor and a small amount of alcohol to nitrocellulose can make a plastic substance, which can be molded into plastic products under hot pressing, named celluloid. In 1872, it built a factory in Newark, USA.
At that time, it was not only used as a substitute for ivory, but also processed into windshields and movie films for carriages and cars, which started the plastic industry and developed accordingly.