In the past 100 years, the Nobel Prize in Chemistry has been awarded to 10 scientists who have made outstanding contributions to the development of polymer science directly or indirectly. This shows the importance of polymer materials.
Polymer materials are materials based on polymer compounds, which are composed of compounds with relatively high molecular weight. According to the source, it can be divided into natural, semi-synthetic (modified natural polymer materials) and synthetic polymer materials. Natural polymers are the basis of the origin and evolution of life. Many natural materials we come into contact with are usually made of polymer materials, such as natural rubber, cotton, human organs and so on. Since the beginning of human society, natural polymer materials have been used as living and production materials, and their processing technology has been mastered. For example, silk, cotton and wool are used to make fabrics, and wood, cotton and hemp are used to make paper. At the end of 1930s, 19 entered the stage of chemical modification of natural polymers, and semi-synthetic polymer materials appeared. The appearance of 1907 synthetic polymer phenolic resin marks the beginning of the application of synthetic polymer materials. In modern times, polymer materials, like metal materials and inorganic nonmetal materials, have become important materials in science and technology and economic construction. Polymer materials are divided into ordinary polymer materials and functional polymer materials according to their uses. Functional polymer materials not only have the general mechanical properties, insulating properties and thermal properties of polymers, but also have special functions such as conversion, transmission and storage of matter, energy and information. Polymer information conversion materials, polymer transparent materials, polymer mimetic enzymes, biodegradable polymer materials, polymer shape memory materials and medical and medical polymer materials have been applied. The above two classifications are only explained systematically here. This paper focuses on the classification of polymer materials to illustrate their uses.
General polymer materials are divided into five categories according to their characteristics, namely rubber, fiber, plastic, adhesive and coating.
Rubber is a linear flexible polymer. There are two kinds of natural rubber and synthetic rubber: low valence between molecular chains, good flexibility of molecular chains, large deformation under the action of external force, and quick recovery after removing external force. The main component of natural rubber is polyisoprene; The main varieties of synthetic rubber are butyl rubber, cis-butadiene rubber, chloroprene rubber, EPDM rubber, acrylate rubber, polyurethane rubber, silicone rubber and fluororubber. Natural rubber is widely used in industry, agriculture, national defense, transportation, machinery manufacturing, medical and health care and daily life, such as various tires used in transportation, because of its strong elasticity, good insulation, strong plasticity, water and gas insulation, high tensile strength and wear resistance. Industrial conveyor belts, transmission belts and various sealing rings; Medical gloves and blood transfusion containers; Rubber overshoes, raincoats and warm water bags used in daily life are all made of rubber as the main raw material. Planes, cannons, tanks for national defense, and even rockets, satellites, spaceships and space shuttles in cutting-edge technology need a lot of rubber parts. At present, there are more than 70,000 kinds of articles made of natural rubber partially or completely in the world, of which the amount of tires accounts for more than half of the amount of natural rubber. Compared with natural rubber, there are many kinds of synthetic rubber with similar properties, and most of them are different from natural rubber, but both of them are high elastic polymer materials, which generally need vulcanization before they are practical and useful. Synthetic rubber began to be produced in the early 20th century, and has developed rapidly since the 1940s. Synthetic rubber is generally not as comprehensive as natural rubber in performance, but it has high elasticity, insulation, air tightness, oil resistance, high temperature resistance or low temperature resistance, so it is widely used in industry and agriculture, national defense, transportation and daily life. For example, butyl rubber is used to manufacture the inner tube of various tires, the inner liner of tubeless tires and various sealing gaskets. Used as lining, pipeline and conveyor belt for containers containing corrosive liquids in chemical industry, and used as waterproof material in agriculture. Another example is silicone rubber, the faucet of synthetic rubber. It has good electrical insulation, anti-oxidation and anti-aging, light and mildew resistance, chemical stability, tasteless and non-toxic, and is not afraid of high temperature and cold. Therefore, it has played an important role in modern medicine, such as silicone rubber anti-noise earplugs, silicone rubber fetal head aspirators, silicone rubber artificial blood vessels, silicone rubber tympanic membrane patches, silicone rubber artificial trachea, artificial lungs, artificial bones and so on.
Another widely used polymer material is fiber. Fibers are divided into natural fibers and chemical fibers. The former refers to silk, cotton, hemp, wool and so on. The latter is made of natural polymer or synthetic polymer through spinning and post-treatment. Fiber has high valence, low deformability and high modulus, and is generally a crystalline polymer. Fiber can be regarded as a "hot figure" in all walks of life. It was first used in the textile industry. Most clothing items in daily life are made of fibers, which not only makes them comfortable to wear, but also protects them from cold and sunshine. Nowadays, the greater role of fiber has not only stayed in daily wear, but also played a decisive role in military, medical and environmental protection fields. For example, carbon nanotubes can be used as electromagnetic wave absorbing materials to make invisible materials, electromagnetic shielding materials, electromagnetic radiation pollution protection materials, wave absorbing materials and so on. Because of its biodegradability, the surgical suture made of polylactic acid or chitosan fiber will automatically degrade and absorb after wound healing, which directly avoids suture removal after operation. In environmental protection, PLA, as a completely biodegradable plastic, has attracted more and more attention. In the field of architecture, anti-seepage and anti-crack fibers can enhance the strength and anti-seepage performance of concrete. Combining fiber technology with concrete technology, steel fiber and synthetic fiber can be developed to improve the performance of concrete and the quality of civil engineering. The former can play a role in cracking resistance, impermeability, impact resistance and bending resistance for dams, airports, highways and other projects, while the latter can prevent early cracking of concrete and play a role in surface protection at the initial stage of concrete material manufacturing. In addition, with the development of biotechnology, the characteristics of some fibers can come in handy. For example, muscle-like fibers can be made into "artificial muscles" and "human organs", which is a good substitute for human tissues.
In contemporary life, there is a kind of polymer material that accounts for half of the materials, and that is plastic. Plastic is made of synthetic resin or chemically modified natural polymer as the main component, and then additives such as fillers and plasticizers are added. Its intermolecular valence, modulus and deformation are between rubber and fiber. According to the characteristics of synthetic resins, they are usually divided into thermosetting plastics and thermoplastic plastics; According to the purpose, it is divided into general plastics and engineering plastics. The application of plastics can be seen everywhere in life, from plastic bags and various mechanical appliances to engineering and aviation. It is no exaggeration to say that plastics have become a part of the world. In addition to other uses, this paper also introduces its latest application: transparent plastic integral sheet roof. The new concept of sheet roof is based on transparent and flexible polycarbonate or silicone material, which can be permanently molded into a single polycarbonate sheet and can also be used as a foldable hinge and seal. The prototype developed by Bayer Material Science and Technology is equipped with four flexible sheet parts, forming four "top windows", each of which can be opened and closed independently. The guide rail is used to connect thin plate parts to form a solid and transparent polycarbonate roof shell. An equally transparent tube is placed longitudinally along the center of the roof structure to adjust the folding plate after the "top window" is opened. This can form a three-dimensional structure, which is stronger than a flat sheet. At the same time, the number of individual components is greatly reduced. The roof made of plastic provides designers with more design space. They can create three-dimensional geometric shapes and push molten glass compounds to the highest limit.
Adhesive is a kind of adhesive material mainly made of synthetic natural polymer compounds. There are two kinds of natural and synthetic adhesives. Synthetic adhesives are widely used. The production of adhesive has solved the bonding problems between polymer and nonmetal or metal, metal and metal, and metal and nonmetal, and made great contributions to industry and engineering. As small as household three-second adhesive, corrugated cardboard, paper bags, labels, tapes and stamps, as large as building adhesive and industrial adhesive, there is no shortage of adhesive even for the bonding of aircraft wings or tails to the fuselage. Compared with the traditional knitting method, metal welding method and mechanical connection methods such as riveting, bolting or nailing, the bonding method is faster and more economical, and different materials can be combined together. Moreover, when bonding two metals, the adhesive can separate them, prevent corrosion, and reduce the fatigue damage of components, which is lighter and stronger than mechanical connection. Therefore, the application of adhesives in life has gradually replaced the traditional trend of France and Germany.
Since there has been civilization, there has been decoration, and decoration is bound to be inseparable from paint. The coating is made of polymer as the main film-forming substance, and solvent and various additives are added. According to the different film-forming substances, it can be divided into grease coatings, natural resin coatings and synthetic resin coatings. Traditionally, we also call these paints paints, which are an indispensable dish in decoration. Whether it is high-grade decoration or ordinary decoration, it will be more or less related to paint, so it is also closely related to our lives. For coated objects, the first purpose of coating is to protect the surface, and the second purpose is to modify the surface. As far as wood products are concerned, because the surface of wood products is porous, they are not resistant to dirt. At the same time, the surface of wood products is not beautiful enough, and coatings can solve this problem at the same time. Nowadays, the application of coatings has already broken through the tradition and extended to a wider field such as aerospace and military. For example, coatings used in military equipment play an important role in protecting or covering users.
To sum up, polymer materials have been closely related to our lives. From the appearance of semi-synthetic polymer materials in the chemical modification stage of natural polymers to the appearance of synthetic polymer phenolic resin in 1907, it indicates that human beings began to apply synthetic polymer materials, and then became important materials in science and technology and economic construction together with metal materials and inorganic non-metallic materials in modern times. Polymer materials will shine brilliantly in various fields and play an increasingly important role.