The automobile engine is the device that provides power for the automobile. It is the heart of the automobile and determines the power, economy, stability and environmental protection of the automobile. According to different power sources, automobile engines can be divided into diesel engines, gasoline engines, electric vehicle motors and hybrids.     Common gasoline engines and diesel engines are reciprocating piston internal combustion engines, which convert the chemical energy of the fuel into the mechanical energy of piston movement and output power to the outside. The gasoline engine has high speed, low mass, low noise, easy starting, and low manufacturing cost; the diesel engine has a large compression ratio, high thermal efficiency, and better economic performance and emission performance than the gasoline engine. History development The engine is the power source of the car. Most automobile engines are thermal energy power devices, referred to as heat engines. Thermal engine converts the thermal energy generated by fuel combustion into mechanical energy by means of the state change of the working fluid. In 1876, the German Nicolaus A. Otto invented the reciprocating piston four-stroke gasoline engine based on the atmospheric pressure engine. Due to the use of four strokes of intake, compression, power and exhaust, the thermal efficiency of the engine is increased from 11% of the atmospheric pressure engine to 14%, while the mass of the engine is reduced by 70%. In 1892, German engineer Rudolf Diesel invented the compression-ignition engine (diesel engine), achieving the second major breakthrough in the history of internal combustion engines. Due to the high compression ratio and expansion ratio, the thermal efficiency was doubled compared to other engines at the time. In 1926, Swiss A. Buchi proposed the theory of exhaust gas turbocharging, which uses the energy of exhaust gas discharged from the engine to drive the compressor and supercharge the engine. After the 1950s, exhaust gas turbocharging technology began to be gradually applied to vehicle internal combustion engines, greatly improving engine performance and becoming the third major breakthrough in the history of internal combustion engine development. In 1956, the German Wankel invented the rotary engine, which greatly increased the engine speed. In 1964, the German NSU company installed a rotary engine on a car for the first time. In 1967, the German company Bosch introduced the electronic fuel injection system (Electronic Fuel Injection, EFI) controlled by an electronic computer for the first time, creating a history of the application of electronic control technology in automobile engines. After 30 years of development, the engine management system (Engine Management System, EMS) with electronic computers as the core has gradually become a standard configuration on automobiles (especially car engines). Due to the application of electronic control technology, the engine’s pollutant emissions, noise and fuel consumption have been greatly reduced, and its power performance has been improved. This has become the fourth major breakthrough in the history of internal combustion engine development. In 1967, the United States held a public demonstration of hydrogen car driving. The hydrogen car could run 121 kilometers in 10 minutes at a speed of 80 kilometers per hour. The car has 19 seats and is manufactured by the American Billings Company. In 1971, the first bus equipped with a Stirling engine started running. In 1972, Japan’s Honda Motor sold the Civic sedan equipped with a Compound Vertex Controlled Combustion (CVCC) engine on the market, marking the first launch of a lean gas combustion engine. In 1977, the first international electric vehicle conference was held in Chicago, USA. During the conference, more than 100 electric vehicles of various types were on display. In 1978, Japan successfully researched hybrid vehicles. In August 1979, Brazil produced an alcohol-fueled car. Brazil is the country with the largest number of alcohol-based cars in the world. In 1980, Japan successfully developed a liquid hydrogen vehicle. A special storage tank is installed at the rear to keep liquid hydrogen at a low temperature and at a certain pressure. The car used 85 liters of liquid hydrogen and traveled 400 kilometers at a speed of 135 kilometers per hour. In 1980, the United States successfully trial-produced a zinc-chlorine battery electric vehicle. In 1980, Spain successfully developed a solar car. In 1980, an engineer in Itzehoe, northwest of Hamburg, West Germany, invented a car powered by calcium carbide gas (acetylene gas). First turn calcium carbide into gas, and then use this gas to burn to propel a jet engine to drive a car. Its speed and safety are no less than that of a gasoline car. 20 kilograms of calcium carbide can enable the car to travel at least 300 kilometers. In 1980, John Cooper and Erwin Beren of the University of California began to study “burned aluminum” electric vehicles. In 1983, the world’s first car equipped with a diesel ceramic engine successfully ran tests. The engine installed was developed by Japan’s Kyoto Ceramics Company. Its main components are made of ceramics, eliminating the need for a cooling system. It is light in weight and has significant energy saving effects. It can travel 30% longer than a conventional engine under the same conditions. In 1984, the former Soviet Union developed a dual-fuel vehicle. When the car is started, it uses gasoline first and then natural gas. In 1984, Amocoby Chemical Company of Mobil Oil Company of the United States developed a synthetic material called Dulon plastic. The company used this plastic to successfully create the world’s first all-plastic automobile engine. The weight is only 84 kg. The American Lora T-616GT car uses this all-plastic engine. In 1984, Australian engineer Shalish successfully developed an OCP engine. In 1985, Australia’s Pilandin developed a steam engine car that was safe, reliable, flexible to start, high-speed and smoke-free. In 1986, Japan’s Sanyo Electric Company successfully developed the first solar cell car. In 1994, David Byrne of the United Kingdom invented another wind-powered car and has put it into mass production. Structure The engine is composed of two major mechanisms, the crank connecting rod mechanism and the valve mechanism, as well as five major systems including cooling, lubrication, ignition, fuel supply, and starting system. The main components include cylinder block, cylinder head, piston, piston pin, connecting rod, crankshaft, flywheel, etc. The working chamber of a reciprocating piston internal combustion engine is called a cylinder, and the inner surface of the cylinder is cylindrical. The piston that reciprocates in the cylinder is hinged to one end of the connecting rod through the piston pin, and the other end of the connecting rod is connected to the crankshaft. The crankshaft is supported by the bearing on the cylinder block and can rotate within the bearing to form a crank-connecting rod mechanism. When the piston reciprocates in the cylinder, the connecting rod drives the crankshaft to rotate. On the contrary, when the crankshaft rotates, the connecting rod journal makes a circular motion in the crankcase, and drives the piston up and down in the cylinder through the connecting rod. Every time the crankshaft rotates once, the piston moves up and down once, and the volume of the cylinder continuously changes from small to large, then from large to small, and the cycle continues. The top of the cylinder is closed with a cylinder head. The cylinder head is equipped with intake valves and exhaust valves. By opening and closing the intake and exhaust valves, the air is filled into the cylinder and the air is exhausted out of the cylinder. The opening and closing of the intake and exhaust valves are driven by the camshaft. The camshaft is driven by the crankshaft through a toothed belt or gear.

The preparation method of alkyd resin is to condense polyfunctional alcohols, polybasic acids and vegetable oils or vegetable oleic acids. Different types of vegetable oils or fatty acid molecules have different numbers of double bonds, which can be divided into drying, non-drying and Semi-dry alkyd resin. Dry alkyd resin can dry by itself in the air, and its drying is a process in which macromolecules are cross-linked and solidified by oxygen in the air. According to the content of vegetable oil or vegetable oleic acid used, there are short oil, medium oil, long oil, extra long oil and ultra short oil alkyd resin. The manufacturing methods of alkyd resin include melt method and solvent method. The melting method uses polyols, polybasic acids, vegetable oils or vegetable oleic acids to be heated under the protection of inert gas and lipidized at high temperature. When the acid value reaches the required level, solvent is added to dilute it. In the solvent method, the reaction raw materials are reacted in the solvent xylene. As a solvent, xylene can form an azeotrope with water to speed up the reaction. Compared with the melting method, the solvent method requires a lower reaction temperature, the reaction conditions are easy to control, and the synthesized alkyd resin is lighter in color. The performance of alkyd resin is related to the type of oil. The performance also varies with the molecular weight and structure. It is widely used in paints, coatings, ships, etc. Application areas    alkyd resins.glycerol-phthalic resin., oil-modified polyester resin formed by the condensation polymerization of polyol , phthalic anhydride and fatty acid or oil (glyceryl fatty acid ester) . According to the number and structure of double bonds in fatty acid (or oil) molecules, it can be divided into three categories : dry , semi-dry and non-dry. Drying alkyd resins can be cured in the air; non-drying alkyd resins must be mixed with amino resins and cured by heating. In addition, alkyd resins can also be divided into four oil degrees : short, medium, long and very long according to the content of fatty acids (or oils) or phthalic anhydride used . After the alkyd resin is cured into a film, it is shiny and tough, has strong adhesion, and has good wear resistance, weather resistance and insulation.    Classification   1. According to the types of vegetable oils or fatty acids, alkyd resins can be divided into three types: dry, non-drying and semi-drying. Alkyd resin synthesized from unsaturated fatty acids or oils is a dry oil alkyd resin, which can be dried by itself or at low temperature. No. 200 solvent oil is used as its solvent. Through the method of oxidative cross-linking, dry alkyd resin can self-dry in the air. In a certain principle, dry alkyd resin is a modified product of dry oil. The drying principle of this kind of paint film is that alkyd resin molecules cross-link into macromolecules through a series of reactions. The molecular weight of drying oil is low, and the formation of macromolecules requires multi-step cross-linking, so it takes a longer time for the paint film to dry. After the alkyd resin is synthesized from the dry oil, it is equivalent to increasing the molecular weight of the dry oil. It only requires fewer cross-linking points to solidify into a film. At the same time, the paint film performance of the alkyd resin is significantly better than that of the dry paint film. . Non-drying oil alkyd resin, which cannot dry by itself in the air, is often used as a plasticizer and multi-warp-based polymer. Non-drying oil alkyd resin contains warp groups, so amino resin can be combined with it to make paint. If a two-component self-drying paint is prepared, it can be formulated with polyisocyanate. The paint film properties of semi-drying alkyd resins are between those of drying and non-drying alkyd resins.   2. Classified according to the content of fatty acids or oils in alkyd resins. Alkyd resin can be divided into long oil, medium oil and short oil alkyd resin according to the content of fatty acids in the resin. Oiliness refers to the amount of oil or fatty acids in the alkyd resin. The oil or fatty acid content of long oil alkyd resin is 60%~70%, the oil or fatty acid content of medium oil alkyd resin is 40%~60%, and the oil or fatty acid content of short oil alkyd resin is 30%~40%. In addition, there are ultra-long oil (greater than 70%) and ultra-short oil (less than 30%). The comprehensive performance of alkyd resin is closely related to the type and oiliness of the oil or fatty acid used.   Dry short oil alkyd resin   The oil or fatty acid content of dry short-oil alkyd resin is 30% to 40%. It is mainly made from linseed oil, some tung oil, soybean oil, castor oil, catalpa oil and other dry oils and their fatty acids. Alkyd resin has high viscosity and requires aromatic hydrocarbon solvents to dissolve it. The alkyd resin paint is sprayed or dipped, preferably without brushing. It can oxidize and dry automatically at room temperature. It has good self-drying performance, average softness, good gloss, gloss and color retention, weather resistance, and fast drying speed. Short-oil alkyd resin has high hardness, good gloss and wear resistance, and is suitable for metal products such as automobiles and machine parts. It can be used as topcoat and primer. Short-oil alkyd resin can be used alone as drying paint, or mixed with urea-based resin, urea-formaldehyde resin, etc.   Dry medium oil alkyd resin   Medium-oil alkyd resin contains 40% to 60% oil or fatty acid. It is the most commonly used among alkyd resins. The paint made from it can be sprayed, brushed, and edited. The paint film dries quickly and has good gloss and weather resistance. , can be dried by itself or mixed with oxygen-based resin for drying. The drying time is shorter than oil-based alkyd resin paints, and the gloss and color retention is slightly worse. Dry medium oil alkyd resin is used as self-drying varnish, primer, etc. It can also be used as decorative paint, construction paint, furniture paint, metal primer, etc. It can be applied to metal, wood and other materials.   Non-drying oil alkyd resin   Vegetable oils for non-drying oil alkyd resins can be coconut oil, sesame oil, etc., and can also be made from lauric acid and some saturated fatty acids and medium-low carbon synthetic fatty acids. Short-oil alkyd resin has an oil content of 30% to 40%. It is made from the above-mentioned oils or fatty acids, and uses aromatic solvents as solvents. Non-drying medium-oil alkyd resin is mainly synthesized from castor oil, which is highly polar and uses aromatic hydrocarbons as solvents. Non-drying oil alkyd resin is often used in nitrocellulose paint, amino resin paint, etc.   Long oil alkyd resin   The oil or fatty acid content of long-oil alkyd resin is 60% to 70%. Dry long-oil alkyd resin has good drying performance, good paint film elasticity, good gloss and color retention and weather resistance, but the paint film hardness and wear resistance are worse than medium-oil alkyd resin. Long-oil alkyd resin is soluble in aliphatic hydrocarbon solvents, has low viscosity, is easy to apply and has good leveling performance. It can be used for indoor and outdoor architectural coatings and ship coatings. It is compatible with oil-based resin paints and can be used to enhance Oil-based resin paint and latex paint.

Epoxy resin is a high molecular polymer with the molecular formula (C 11 H 12 O 3 ) n . It refers to a class of polymers containing more than two epoxy groups in the molecule. It is the condensation product of epichlorohydrin and bisphenol A or polyol . Due to the chemical activity of the epoxy group , a variety of compounds containing active hydrogen can be used to open the ring and solidify and cross-link to form a network structure , so it is a thermosetting resin . Bisphenol A-type epoxy resin not only has the largest output and the most complete varieties, but also new modified varieties are still increasing, and the quality is constantly improving.   Physical and chemical properties   material properties   Epoxy resin has secondary hydroxyl groups and epoxy groups , and the secondary hydroxyl groups can react with isocyanates . Epoxy resin is directly added as a polyol to the hydroxyl-containing component of the polyurethane adhesive . Using this method, only the hydroxyl group participates in the reaction, and the epoxy group fails to react.   Use the carboxyl group of the acidic resin to open the epoxy ring, and then react with the isocyanate in the polyurethane adhesive . Epoxy resin can also be dissolved in ethyl acetate , phosphoric acid is added for heating reaction, and its adduct is added to the polyurethane adhesive, which can improve the initial tack, heat resistance , and hydrolysis stability of the adhesive. Alcoholamines or amines can also be used to react to generate polyols. The presence of tertiary nitrogen atoms in the adduct can accelerate the NCO reaction.   Using epoxy resin as the polyhydroxy component combines the advantages of polyurethane and epoxy resin, and has better bonding strength and chemical resistance. Epoxy resins used in manufacturing polyurethane adhesives generally use EP-12 and EP-13. , EP-16 and EP-20 and other varieties.   Modification method   1. Choose a hardener ; 2. Add reactive diluent ; 3. Add fillers ; 4. Add specialty thermosetting or thermoplastic resins ; 5. Modify the epoxy resin itself.   Application areas   Introduction to the preface   Epoxy resin’s excellent physical, mechanical and electrical insulation properties , bonding properties with various materials, and flexibility in its use process are not available in other thermosetting plastics . Therefore, it can be made into coatings, composite materials, casting materials , adhesives, molding materials and injection molding materials, and is widely used in various fields of the national economy .   Coating use   Epoxy resin accounts for a large proportion of applications in coatings, and it can be made into varieties with different characteristics and uses. Their common features: 1. Excellent chemical resistance , especially alkali resistance. 2. The paint film has strong adhesion , especially to metal. 3. Has good heat resistance and electrical insulation. 4. The paint film has good color retention . However, bisphenol A-type epoxy resin coatings have poor weather resistance . The paint film is easily powdered and loses its luster and lacks fullness when outdoors. It is not suitable for outdoor coatings and highly decorative coatings. Therefore, epoxy resin coatings are mainly used as anti-corrosion paint, metal primer , and insulating paint , but coatings made of heterocyclic and alicyclic epoxy resins can be used outdoors.   Adhesive use   In addition to poor adhesion to non-polar plastics such as polyolefins , epoxy resin also has good adhesion to various metal materials such as aluminum, iron, and copper; non-metallic materials such as glass, wood, concrete, etc.; and thermosetting plastics such as phenolics and amino acids. , unsaturated polyester, etc. all have excellent bonding properties, so they are called universal glue . Epoxy adhesives are an important variety of structural adhesives .   Basic classification   Classification criteria   The classification of epoxy resin has not yet been unified. It is generally classified according to strength, heat resistance level and characteristics. There are 16 main varieties of epoxy resin, including general glue, structural glue , high temperature resistant glue , low temperature resistant glue , and water and wet surface use. 16 types of adhesives , conductive adhesives , optical adhesives , spot welding adhesives, epoxy resin films, foam adhesives , strain adhesives, soft material adhesives, sealants , special adhesives , latent curing adhesives, and civil construction adhesives.   several classifications   There are several ways to classify epoxy resin adhesives in the industry: 1. According to its main components, it is divided into pure epoxy resin adhesive and modified epoxy resin adhesive; 2. According to their professional uses, they are divided into mechanical epoxy resin adhesives, construction epoxy resin adhesives, electronic epoxy resin adhesives, repair epoxy resin adhesives, traffic glues, and shipbuilding glues. wait; 3. According to its construction conditions, it is divided into normal temperature curing glue, low temperature curing glue and other curing glue; 4. According to its packaging form, it can be divided into single-component glue, two-component glue and multi-component glue; There are other classification methods, such as solvent-free glue, solvent-based glue and water-based glue. However, component classification is widely used.

Polymer compounds, referred to as macromolecules, also known as high molecular polymers, generally refer to compounds with a relative molecular mass of several thousand to millions. The vast majority of polymer compounds are mixtures of many homologues with different relative molecular masses , so they are highly The relative molecular mass of a molecular compound is the average relative molecular weight. Polymer compounds are composed of thousands of atoms connected to each other by covalent bonds . Although their relative molecular masses are large, they are all connected in a simple structural unit and in a repetitive manner.   Introduction   The molecules of high molecular compounds are much larger than the molecules of low molecular organic compounds. Generally, the relative molecular mass of organic compounds does not exceed 1000, while the relative molecular mass of polymer compounds can be as high as 10 4 to 10 6 . Due to the large relative molecular mass of polymer compounds, their physical, chemical and mechanical properties are very different from those of low molecular compounds .   Although the relative molecular mass of polymer compounds is large, their composition is not complicated. Their molecules are often composed of specific structural units connected repeatedly through covalent bonds.   The molecular chains of the same polymer compound contain different numbers of links, so polymer compounds are essentially mixtures composed of many compounds with the same link structure but different degrees of polymerization. Their relative molecular mass and degree of polymerization are both different. is the average.   Polymer compounds are almost non-volatile and often exist in solid or liquid state at room temperature. Solid polymers can be divided into crystalline and amorphous states according to their structural forms . The molecules of the former are arranged in an orderly manner; while the molecules of the latter are arranged irregularly. The same polymer compound can have both crystalline and amorphous structures. Most synthetic resins have an amorphous structure.   The atoms that make up a polymer chain are combined by covalent bonds. Polymer chains generally have two different shapes: chain type and body shape.   A large number of polymer compounds used as materials in the world today are made from low-molecular organic compounds using coal, petroleum, natural gas, etc. as starting materials, and then through polymerization reactions. These low molecular compounds are called “monomers”, and the high molecular compounds generated by their polymerization reactions are also called polymers . Polymerization reactions are usually divided into two categories: addition polymerization and condensation polymerization , referred to as addition polymerization and condensation polymerization. Classification   Sort by source   According to the source, polymers can be divided into two categories : natural polymers and synthetic polymers .   Classified by performance   Polymers can be divided into three major categories : plastics , rubber and fibers .   Plastics can be divided into two categories according to their hot melt properties: thermoplastic plastics (such as polyethylene , polyvinyl chloride, etc.) and thermosetting plastics (such as phenolic resin , epoxy resin , unsaturated polyester resin, etc.). The former is a polymer with a linear structure that can soften and flow when heated, and can be plasticized and molded repeatedly. Defective and waste products can be recycled and reprocessed into products. The latter is a polymer with a body structure that solidifies once it is formed. It cannot be heated and softened, and cannot be processed and formed repeatedly. Therefore, defective products and waste products have no recycling value. The common feature of plastics is that they have good mechanical strength (especially polymers with body-shaped structures) and are used as structural materials .   Fibers can be divided into natural fibers and chemical fibers . The latter can be divided into man-made fibers (such as viscose fiber , acetate fiber, etc.) and synthetic fibers (such as nylon , polyester, etc.). Man-made fibers are made of natural polymers (such as short cotton linters, bamboo, wood, hair, etc.) that are chemically processed and spun. Synthetic fibers are synthesized from low molecular raw materials. The characteristic of the fiber is that it can be spun into shapes, has good strength and flexibility, and is used as textile materials .   Rubber includes natural rubber and synthetic rubber . Rubber is characterized by its good high elasticity and is used as an elastic material.   Classified by use   It can be divided into general polymers, engineering material polymers, functional polymers, biomimetic polymers, medical polymers , polymer drugs , polymer reagents , polymer catalysts and biopolymers. The “tetraenes” in plastics ( polyethylene , polypropylene , polyvinyl chloride and polystyrene ), the “four fibers” in fibers ( nylon , polyester , acrylic and vinylon ), the “four rubbers” in rubber ( styrene-butadiene ) Rubber , butadiene rubber , isoprene rubber and ethylene-propylene rubber ) are all polymer materials with a wide range of uses and are general-purpose polymers.   Engineering plastics refer to polymer materials with special properties (such as high temperature resistance, radiation resistance, etc.). For example, polyformaldehyde , polycarbonate , polysulfone , polyimide , polyarylene ether, polyaramid, fluorine-containing polymers , boron- containing polymers, etc. are relatively mature varieties and have been widely used as engineering materials.   Ion exchange resins , photosensitive polymers , polymer reagents and polymer catalysts are all functional polymers.   Medical polymers and pharmaceutical polymers have special requirements in medicine and physiological hygiene, and can also be regarded as functional polymers.   Classified by main chain structure   It can be divided into four categories: carbon chain polymers , heterochain polymers , elemental organic polymers and inorganic polymers .   The main chain of carbon chain polymers is composed of carbon atoms linked together.   In addition to carbon atoms, the main chain of heterochain polymers also contains oxygen, nitrogen, sulfur and other elements, such as polyester , polyamide , cellulose, etc. Easy to hydrolyze. The main chain of elemental organic polymers is composed of atoms of carbon and other elements other than oxygen , nitrogen , sulfur , etc., such as silicon , aluminum , titanium , boron and other elements, but the side groups are organic groups, such as polysiloxane .   Inorganic polymers are composed of main chain and side chain groups composed of inorganic elements or groups. Natural inorganic polymers such as mica, crystal, etc., and synthetic inorganic polymers such as glass.   The systematic naming of polymer compounds is relatively complex and is rarely used in practice. It is customary to use common names for natural polymers. Synthetic polymers are usually named according to the preparation method and the name of the raw materials. For example, polymers prepared by addition polymerization are often named with the word “poly” in front of the name of the raw materials. For example, the polymer of vinyl chloride is called polyvinyl chloride , the polymer of styrene is called polystyrene , etc. For example, polymers produced by polycondensation reaction are mostly named by adding the word “resin” after the simplified raw material name. For example, phenolic resin , epoxy resin, etc. Addition polymers are often called “resins” before they are made into products. For example, polyvinyl chloride resin , polyethylene resin , etc. In addition, polymer substances are often given trade names in business. For example, polycaprolactam fiber is called nylon-6, polyethylene terephthalate fiber is called polyester, polyacrylonitrile fiber is called acrylic, etc.   Features   Compared with low molecules, polymers have the following characteristics: 1. From the perspective of relative molecular mass and composition, the relative molecular mass of polymers is very large and has “polydispersity”. Most polymers are polymerized from one or several monomers. 2. From the perspective of molecular structure, there are basically only two types of molecular structures of polymers, one is linear structure and the other is body structure. The characteristic of the linear structure is that the atoms in the molecule are connected to each other by covalent bonds to form a long, curled “chain” (called a molecular chain). The characteristic of the body structure is that there are many covalent bonds cross-linking the molecular chains to form a three-dimensional network structure. These two different structures have great differences in performance. 3. From the perspective of performance, polymers are usually in a solid or gel state due to their large relative molecular mass and have good mechanical strength; and because their molecules are combined by covalent bonds, they have relatively high mechanical strength. Good insulation and corrosion resistance; because its molecular chain is very long and the ratio of the length to diameter of the molecule is greater than one thousand, it has good plasticity and high elasticity. High elasticity is a unique property of polymers. In addition, the solubility, meltability, solution behavior and crystallinity are also very different from low molecules.   structure   The molecular structure of polymers can be divided into two basic types: the first is a linear structure, and polymer compounds with this structure are called linear polymer compounds . The second type is body structure . Polymer compounds with this structure are called body type polymer compounds . In addition, some polymers have branched chains , called branched polymers, which also fall into the category of linear structures. Although some polymers have cross-links between molecular chains, there are fewer cross-links. This structure is called a network structure and belongs to the category of body structure.   There are independent macromolecules in polymer materials with linear structures (including those with branched chains). The macromolecules can be separated from each other in the solvent of such polymers or in the heated and molten state . In polymer materials with a body structure (a large number of cross-links between molecular chains), there are no independent macromolecules, so there is no meaning of relative molecular mass, only the degree of cross-linking . Network-structured polymer materials with few cross-links may also exist as separated macromolecules.   Two different structures showing opposite properties. Polymers with linear structures (including branched structures) have the characteristics of elasticity and plasticity due to the existence of independent molecules, can be dissolved in solvents, can be melted when heated, and have low hardness and brittleness. Because there are no independent macromolecules in the body structure polymer, it has no elasticity and plasticity, cannot dissolve and melt, can only swell, and is relatively hard and brittle. Therefore, from a structural point of view, rubber can only be polymers with a linear structure or a network structure with little cross-linking, and fibers can only be linear polymers, while plastics can have polymers with both structures.   Synthesis of polymers   There are two basic types of reactions for synthesizing polymer compounds: one is called condensation polymerization (referred to as condensation polymerization ), and the other is called addition polymerization (referred to as addition polymerization ). The monomer structures, polymerization mechanisms and specific implementation methods of these two types of synthetic reactions are different.   polycondensation reaction   Condensation polymerization refers to a polymerization reaction in which monomers with two or more functional groups condense with each other and produce small molecule by-products (water, alcohol, ammonia, hydrogen halide, etc.) to form polymer compounds. like:   In the monomer , terephthalic acid and ethylene glycol each have two functional groups. When forming macromolecules, they extend in two directions, resulting in linear polymers .   Although phenol and formaldehyde are monofunctional compounds, the initial products of their reaction are multifunctional. These multifunctional molecules are condensed into linear or three-dimensional polymers, namely phenolic resins.   addition polymerization reaction   Addition polymerization refers to a reaction in which one or more monomers are synthesized into a polymer. During the reaction, no low molecular substances are generated. The generated polymer has the same chemical composition as the raw material, and its relative molecular mass It is an integer multiple of the relative molecular weight of the raw material, and the addition polymerization reaction that occurs only from one monomer is called a homopolymerization reaction. For example, polyvinyl chloride is synthesized from vinyl chloride: The polymerization of two or more monomers is called copolymerization. For example, styrene is copolymerized with methyl methacrylate. Copolymer products are called copolymers, and their properties are often better than homopolymers. Therefore, product properties can be improved through copolymerization methods.The addition polymerization reaction has the following two characteristics: (1) The monomer used in the addition polymerization reaction is a compound with an unsaturated bond of double or triple bonds. For example, ethylene , propylene , vinyl chloride , styrene , acrylonitrile , methyl methacrylate , etc. are commonly used important monomers, and the addition polymerization reaction occurs on unsaturated bonds. (2) The addition polymerization reaction is completed through a series of mutual addition reactions between monomer molecules: And once the reaction occurs, it will proceed quickly in the form of a chain reaction to obtain a polymer compound (often called an addition polymer). The relative molecular mass growth is almost independent of time, but the monomer conversion rate increases with time.   The above two characteristics are the most basic differences between addition polymerization and condensation polymerization. The addition polymerization reaction can be divided into two categories: free radical addition polymerization reaction and ionic addition polymerization reaction according to the different reaction active centers.   application   Polymers are widely used in people’s clothing, food, housing, transportation, various sectors of the national economy and cutting-edge technology. The advent of functional polymers has developed the application of synthetic polymers to a more refined and advanced level. It not only plays an important role in promoting industrial and agricultural production and cutting-edge technology, but also plays an important role in exploring the mysteries of life, conquering cancer and treating genetic diseases. Promoting effect. It is estimated that the population on earth will exceed 10 billion in the 21st century. By then, food, energy, environment, resources, etc. will become more troubling issues for human society. In this regard, polymer science will play an important role. For example, polymers can be used to adjust the evaporation and loss of water to improve soil, green deserts, expand cultivated land, control ecological systems, and promote food production; produce high-conversion photovoltaic cells to split water to produce hydrogen and oxygen, which can be used as fuel cells and Chemical raw materials; develop new polymer catalysts to use nitrogen in the air to synthesize ammonia at normal temperature and pressure, etc. Controlling environmental pollution in modern society is also inseparable from the application of polymers.   However, polymers are flammable, easy to age, cannot be degraded, are not corroded by bacteria, and are not absorbed by the soil. Discarding after extensive use has caused serious public harm. There is an urgent need to develop new polymers that can degrade and decompose in the natural environment without causing pollution. This is one of the important new topics and new directions for the future development of polymer science.

Titanium ore refers to minerals containing a large amount of titanium ore. The main ones utilized in China are ilmenite , rutile and titanium magnetite .   Raw material characteristics   Titanium is a typical lithophile element and often appears as an oxide mineral. There are more than 80 kinds of minerals containing more than 1% TiO2 in the earth’s crust, and 15 kinds have industrial value. The main ones used in China are ilmenite , rutile and titanium magnetite (Table 3.5.1). They are both primary (rock minerals) and secondary (weathered residual slope accumulation and sedimentary sand minerals ).   Properties of titanium   Because titanium metal is silvery white, it has a high melting point (1727°C), light specific gravity (4.5), high mechanical strength (5), low temperature resistance (resistivity is almost 0 at ultra-low temperatures), abrasion resistance, and good plasticity of titanium wire (can Thin-walled use), not easily oxidized, and highly reducible; the oxide of titanium, titanium dioxide (titanium dioxide), is non-toxic and has good physical and chemical stability (it does not melt in any acid and alkali after calcining at 1000°C) , high refractive index (2.55~2.70), as well as strong whiteness, tinting power (1150~1650), hiding power (40~50g/m2), temperature resistance, anti-powdering and other characteristics, it is called “pigment” King of”. Therefore, titanium and its oxides and alloy products are important coatings, new structural materials, and anti-corrosion materials . They are known as “the third metal in development after iron and aluminum” and “strategic metals”, and are also “promising” Metal materials” are widely used in aviation, aerospace, ships, military industry, metallurgy, chemical industry, machinery, electricity, desalination, transportation, light industry, environmental protection, medical equipment and other fields, and have created a huge economy Benefits and social benefits play an important role in the development of the national economy.   A brief history of mining   In 1789, the British amateur mineralogist Father William Gregor discovered a new element (titanium) in the black magnetic sandstone ( ilmenite ) in the Manakin Valley in his parish, Gonaval State. It was named “Menaccanite” at the time.   In 1795, the German chemist MHKlaproth discovered a new metal oxide , which is now rutile (TiO2), while conducting systematic analysis and examination of rock minerals. He named this new element as In Greek mythology, the Titans, the sons of heaven and earth, were named Titanium. “Titanium” is what Gregor calls “Mernaginite”.

China’s white talc resources are mainly produced in Liaoning, Shandong, Guangxi and other provinces and regions. The current production has reached its limit, and further expansion of production is un

China’s white talc resources are mainly produced in Liaoning, Shandong, Guangxi and other provinces and regions. The current production has reached its limit, and further expansion of production is un