Plastic is a synthetic polymer material with a wide range of uses, and plastic products abound in our daily lives. From the toiletries we use when we get up, the tableware we use at breakfast, to the stationery we use when we work and study, the seat cushions and mattresses we use when we rest, as well as the shells of televisions, washing machines, computers, and the various shapes of lamps and lanterns that bring us light at night ......
Plastics have gradually replaced many Has been used for decades and centuries of materials and utensils, become an indispensable assistant in people's lives. Plastic set of metal hardness, lightweight wood, glass transparency, ceramic corrosion resistance, rubber elasticity and toughness in one, so in addition to daily necessities, plastic is more widely used in aerospace, medical equipment, petrochemicals, machinery manufacturing, national defense, construction and other industries.
One, the classification of plastics
There are many types of plastics, so far the world into the production of plastics about three hundred kinds. Plastic classification methods, commonly used in two ways:
1, according to the nature of the plastic heat is divided into thermoplastic and thermosetting plastics
Thermoplastic molecular structure is a linear structure, when heated, softening or melting, can be molded into a certain shape, and then harden after cooling. In the heat to a certain extent and re-soften, after cooling and harden, this process can be repeated many times. Such as polyvinyl chloride, polyethylene, polystyrene and so on. Thermoplastic molding process is relatively simple, can be continuous production, and has a fairly high mechanical strength, so the development is very fast.
Thermoset plastics molecular structure is the body structure, in the heat also occurs when the softening, can be molded into a certain shape, but heat to a certain extent or add a small amount of curing agent, on the hardening of the stereotypes, and then will not soften the heat and change the shape. Thermosetting plastics processed after molding, heat is no longer softened, and therefore can not be recycled, such as phenolic plastics, aminoplastics, epoxy resins, etc. belong to this type of plastic. Thermosetting plastic molding process is more complex, so continuous production has some difficulties, but its heat resistance is good, not easy to deformation, and the price is relatively inexpensive.
2, according to the different uses of plastics are divided into general-purpose plastics and engineering plastics
General-purpose plastics refers to the production of large, low-priced plastics with a wide range of applications, including polyolefins, polyvinyl chloride, polystyrene, phenolic plastics and aminated plastics five varieties. Many products used in people's daily life are made of these general-purpose plastics.
Engineering plastics are plastics that can be used as engineering structural materials and replace metal to make machine parts. For example, polyamide, polycarbonate, polyformaldehyde, ABS resin, PTFE, polyester, polysulfone, polyimide and so on. Engineering plastics with low density, high chemical stability, good mechanical properties, superior electrical insulation, easy processing and molding characteristics, widely used in automotive, electrical appliances, chemical, mechanical, instrumentation, instrumentation and other industries, but also in cosmic navigation, rockets, missiles and other aspects.
Second, the composition of plastic
We usually use plastic is not a pure substance, it is formulated by many materials. One of the polymer (or synthetic resin) is the main component of plastic, in addition, in order to improve the performance of plastic, but also in the polymer to add a variety of auxiliary materials, such as fillers, plasticizers, lubricants, stabilizers, coloring agents, etc., in order to become a good performance of plastic.
1, synthetic resins
Synthetic resins are the most important component of plastics, its content in plastics is generally 40% to 100%. Because of the large content, and the nature of the resin often determines the nature of the plastic, so people often see the resin as a synonym for plastic. For example, polyvinyl chloride resin and polyvinyl chloride plastics, phenolic resins and phenolic plastics mixed together. In fact, resin and plastic are two different concepts. Resin is a raw unprocessed polymer, it is not only used in the manufacture of plastics, but also coatings, adhesives and synthetic fibers raw materials. In addition to a very small number of plastics containing 100% resin, the vast majority of plastics, in addition to the main component of resin, but also need to add other substances.
2, filler
Filler, also known as filler, it can improve the strength and heat resistance of plastic, and reduce costs. For example, phenolic resin can greatly reduce the cost of adding wood flour, so that phenolic plastics become one of the cheapest plastics, but also significantly improve mechanical strength. Fillers can be divided into two categories of organic fillers and inorganic fillers, the former such as wood flour, rags, paper and a variety of fabric fibers, etc., the latter, such as glass fibers, diatomaceous earth, asbestos, carbon black, etc..
3, plasticizers
Plasticizers can increase the plasticity and flexibility of plastics, reduce the brittleness of plastics easy to process molding. Plasticizers are generally miscible with the resin, non-toxic, odorless, light, heat-stable high-boiling organic compounds, the most commonly used is phthalate esters. For example, the production of polyvinyl chloride plastic, if you add more plasticizers can be obtained soft polyvinyl chloride plastic, if you do not add or add less plasticizers (dosage < 10%), the hard polyvinyl chloride plastic.
4, stabilizers
In order to prevent synthetic resins in the processing and use of the process of light and heat decomposition and destruction, to extend the service life, to add stabilizers in plastic. Commonly used are stearate, epoxy resin and so on.
5, colorants
Colorants can make plastics have a variety of bright, beautiful colors. Commonly used organic dyes and inorganic pigments as colorants.
6, lubricants
The role of the lubricant is to prevent the plastic in the molding does not stick to the metal mold, at the same time can make the surface of the plastic smooth and beautiful. Commonly used lubricants are stearic acid and its calcium and magnesium salts.
In addition to the above additives, plastics can also be added to the flame retardant, foaming agent, antistatic agent, etc., to meet the different requirements of use.
Three, the characteristics of plastic
1, plastic has plasticity
As the name suggests, plastic is a material that can be molded. The so-called plasticity of plastic is a solid plastic can be softened by heating methods, and then the softened plastic in the mold, so that it is cooled and re-solidified into a certain shape of the solid. This property of plastic also has certain defects, that is, easy to soften and deform when exposed to heat, and some plastics will be deformed even with higher temperature water, so plastic products should not be in contact with boiling water in general.
2, plastic with elasticity
Some plastics are also like synthetic fibers, with a certain degree of elasticity. When it is stretched by external forces, the curled molecules are straightened by the flexibility, but once the tension is canceled, it will return to the original curled state, which makes the plastic with elasticity, such as polyethylene and polyvinyl chloride film products. But some plastics are not elastic.
3, plastic has high strength
Plastic is not as hard as metal, but compared with glass, ceramics, wood, etc., or has a relatively high strength and wear resistance. Plastic can be made into strong gears and bearings on the machine.
4, plastic has corrosion resistance
Plastic is not like metal in the moist air will rust, not like wood in the wet environment will rot or be microbial erosion, in addition to plastic corrosion resistant to acids and alkalis. Therefore, plastics are often used as water and liquid pipelines in chemical plants, doors and windows in buildings, and so on.
5, plastic has insulating
Plastic molecular chain is atoms to *** valence bonding combined, the molecules can not be ionized, but also in the structure of the transfer of electrons, so the plastic has insulating properties. Plastics can be used to make wrappings for electrical wires, electrical sockets, and housings for electrical appliances.
Attachment: Commonly used types of plastics are:
①Polyvinyl Chloride (PVC)
It is one of the most used plastics in construction. Rigid polyvinyl chloride density of 1.38 ~ 1.43g/cm3, high mechanical strength, good chemical stability, the use of temperature range is generally between -15 ~ +55 ℃, suitable for the manufacture of plastic windows and doors, downpipes, trunking and so on.
② polyethylene (PE)
Polyethylene plastic in the building is mainly used for water supply and drainage pipes, sanitary ware.
③ Polypropylene (PP)
Polypropylene density in all plastics is the smallest, about 0.90 or so. Polypropylene is commonly used to produce pipes, sanitary ware and other building products.
④Polystyrene (PS)
Polystyrene is a colorless and transparent glass-like plastic. Polystyrene is mainly used in construction to produce foam insulation materials, translucent materials and other products.
5 ABS plastic
ABS plastic is a modified polystyrene plastic, acrylic eye (A), butadiene (B) and styrene (S) as the basis of the three-component composition. ABS plastic can be used to make plastic decorative panels embossed with patterns, etc.
Plastic
ABS plastic is a colorless, transparent glass-like plastic.
The molding of plastics is the process by which a polymer made by a synthetic resin manufacturer is made into a final plastic product. Processing methods (often referred to as primary processing of plastics) include compression molding (molding), extrusion molding (extrusion molding), injection molding (injection molding), blow molding (blow molding), calendering, and so on.
Compression molding
Compression molding, also known as molding or compression molding, compression molding is mainly used for phenolic resins, urea-formaldehyde resins, unsaturated polyester resins and other thermosetting plastics molding.
Extrusion
Extrusion, also known as extrusion molding, is the use of extrusion machine (extruder) will be heated resin continuously through the mold, extrusion of the desired shape of the product method. Extrusion is sometimes used for thermosetting plastics and can be used for foam molding. The advantage of extrusion is that various shapes of products can be extruded, high production efficiency, automation, continuous production; disadvantage is that thermosetting plastics can not be widely used in this method of processing, the product size is prone to deviation.
Injection molding
Injection molding is also known as injection molding. Injection molding is the use of injection molding machine (or injection machine) will be thermoplastic melt under high pressure into the mold by cooling, curing to obtain the product method. Injection molding can also be used for thermosetting plastics and foam molding. The advantages of injection molding are fast production speed, high efficiency, operation can be automated, can mold complex shaped parts, especially suitable for mass production. Disadvantages are high cost of equipment and molds, injection molding machine cleaning is more difficult.
Blow molding
Blow molding is also known as hollow blow molding or hollow molding. Blow molding is the pressure of compressed air to make the closed in the mold of the hot resin billet blowing for a hollow product method, blow molding, including blow molding film and blow molding hollow products two methods. Blow molding method can produce film products, a variety of bottles, barrels, pots and containers and children's toys.
Calendering
Calendering is the resin and a variety of additives by the expected treatment (kneading, filtration, etc.) through the calender of two or more calendering rollers turning the opposite direction of the gap processed into a film or sheet, and then peeled off from the calender rollers, and then cooled by a molding method. Calendering is a molding method mainly used for polyvinyl chloride resins, which can produce films, sheets, plates, artificial leather, floor tiles and other products.
Engineering plastics engineering plastics English name: engineering-plastics, engineering plastics refers to be used as industrial parts or shell materials of industrial plastics, is the strength, impact resistance, heat resistance, hardness and aging resistance are excellent plastic. The Japanese industry defines it as "a high-performance plastic that can be used for construction and mechanical parts, with a heat resistance of more than 100 ℃, mainly used in industry", and its properties include:
1. Thermal properties: glass transfer temperature (Tg) and melting point (Tm); high heat distortion temperature (HDT); long-term operating temperature (UL-746B), high (UL-756B), and high (UL-776B). High (UL-746B); large operating temperature range; small coefficient of thermal expansion.
2. Mechanical properties: high strength, high mechanical modulus, low latent change, strong wear and fatigue resistance.
3. Others: chemical resistance, electrical resistance, flame resistance, weather resistance, good dimensional stability.
As a general engineering plastics, including polycarbonate (PC), polyamide (nylon), polyacetal (POM), modified polyphenylene ether (modified PPE), polyester (PETP, PBTP), polyphenylene sulfide (PPS), polyarylate, thermosetting plastics, unsaturated polyester, phenolic plastics, epoxy plastics and so on. Their basic characteristics are tensile strength of more than 50Mpa, tensile strength of 500kg/cm, impact resistance of more than 50J/m, bending elasticity of 24000kg/cm, load bending temperature of more than 100 ℃, hardness, aging excellent. Polypropylene can also be included in the scope of engineering plastics if its hardness and cold resistance are improved. In addition, it also includes fluorine plastics with weak strength and excellent heat and chemical resistance of the more specialized ones, silicone fusion compounds with excellent heat resistance, and polyamideimide, polyimide, Polybismaleimide, Polysufone (PSF), PES, acrylic plastics, denatured honey amine plastics, BTResin, PEEK, PEI, liquid crystal plastics, and so on.
The chemical structure of each engineering plastic is different, so their drug resistance, friction characteristics, motor characteristics, etc. differ. Due to the different molding properties of each engineering plastic, some are suitable for any molding method, and some can only be processed in a certain molding method, which results in limitations in application. Thermosetting engineering plastics have poor impact resistance, so most of them have glass fibers added. Engineering plastics in addition to polycarbonate and other impact resistance, usually with hard, brittle, small elongation properties, but if you add 20-30% of the glass fiber, it will improve the impact resistance.
Engineering plastics refers to a class of high-performance polymer materials that can be used as structural materials to withstand mechanical stress in a wide range of temperatures and in more demanding chemical and physical environments. : - Generally refers to the ability to withstand a certain degree of external force, and have good mechanical properties and dimensional stability, in high and low temperatures can still maintain its excellent performance, can be used as engineering structural parts of the plastic. Such as ABS, nylon, polyalum and so on.
Can be used as construction and mechanical parts with high-performance plastics, heat resistance in more than 100 ℃, mainly used in industry
Its properties include:
1. Thermal properties: glass transfer temperature (Tg) and melting point (Tm) is high, the heat distortion temperature (HDT) is high, the long term use of the temperature is high (UL-746B), the use of a wide range of temperatures, the coefficient of thermal expansion is small. coefficient of thermal expansion is small.
2. Mechanical properties: high strength, high mechanical modulus, low latent change, wear resistance, fatigue resistance.
3. Others: chemical resistance, excellent electrical resistance, flame resistance, weather resistance, good dimensional stability.
The general-purpose plastics include Polycarbonate (PC), Polyamide (PA), Polyacetal (POM), Poly Phenylene Oxide (PPE), Polyester (PET), and Polyethylene Oxide (PPE). Polyacetal, Polyoxy Methylene, POM, Poly Phenylene Oxide (PPE), Poly Phenylene Oxide (PETP, PBTP), Polyphenylene Sulfide (PPS), Polyarylate, and thermosetting plastics are unsaturated polyester, phenolic, epoxy, etc. The tensile strength is more than 50MPa, and the tensile strength is more than 50MPa. Tensile strength are more than 50MPa, tensile strength of more than 500kg/cm2, impact resistance of more than 50J/m, bending elasticity rate of 24000kg/cm2, the load deflection temperature of more than 100 ℃, its hardness, aging excellent. Polypropylene if you improve the hardness and cold resistance, can also be included in the scope of engineering plastics. In addition, the more special for the strength of the weak, heat-resistant, drug-resistant fluorine plastic, heat-resistant silicone fusion compounds, polyamide imide, polyamide imide, Polybismaleimide, Polysufone (PSF), PES, acrylic plastics, denatured nylon plastics, BT Resin, PEEK, PEI, liquid crystal plastics and so on. Because of the different chemical structures, there are some differences in chemical resistance, friction characteristics, and motor characteristics. And because of the difference in molding, there are those who are suitable for any molding method, and there are those who can only be processed by a certain molding method, resulting in application limitations. Thermosetting engineering plastics, its impact resistance is poor, so most of the glass fiber added. Engineering plastics in addition to polycarbonate and other large impact resistance, usually with a small elongation, hard, brittle nature, but if you add 20 ~ 30% of the glass fiber, it can be improved.
Abrasion-modified engineering plastics
Abrasion-modified engineering plastics can provide a lower coefficient of friction to reduce wear rates. For example, the lid of a glucometer can be made to last longer with the use of abrasion-resistant materials to increase its lifespan as it opens and closes. Abrasion-modified engineering plastics are also used in color-matched products, even between different materials. Single-use products, such as needles and blades, also benefit from the lubricating effect of the material. In addition, other applications for wear-resistant materials include catheters, cannulas, actuators and vacuum tubes. Other effects include reduced noise due to the movement of smooth parts, improved plastics processing and extrusion molding efficiency.
Conductive Modified Engineering Plastics
When a thermoplastic material has a conductive component, it has permanent electrostatic dissipative (ESD) and protection against static buildup. Conductive thermoplastic materials allow for continuous discharge of static electricity rather than rapid buildup and discharge. Static electricity can damage sensitive electronic components and can cause explosions in flammable environments. Static buildup can clog the material's transmission and interrupt the transmission of machinery. Conductive thermoplastics can be used in a wide range of color-matched products, and some conductive materials are transparent. Applications include ECG sensors, suction tubes, electrical protection devices, and new medical delivery devices such as inhalation products, including PMDI spacers.
Radiation Resistant Modified Engineering Plastics
Specific additives can increase the density of thermoplastics. These higher density thermoplastics have the texture of metal but maintain the processing characteristics of plastic. The medical products industry is looking for such alternatives to lead for environmental reasons. These high specific gravity additives are also radiation resistant. Injection molded parts, catheters or sheets made of radiation-resistant compounds attract X-rays without being passed through them. Soft, fabric-like sheets used in radiation therapy or surgery can help protect machines and people from scattered and direct X-rays. Catheters containing barium sulfate can be tracked by fluoroscopy or X-ray imaging after they are implanted in the body.Instruments used by Baxter Healthcare in performing heart valve repair procedures (reusable handles and disposable snap closures) are constructed of polycarbonate specialty-modified engineering plastics.X-ray-visible (i.e., radiation-protected) stoppers are molded using an embedded injection process on a The plugs that are X-ray visible (i.e., have radiation protection) are molded into the template using an embedded injection molding process, while the plugs that are resistant to steam treatment are made of polyethersulfone, which ensures that the entire device can withstand high temperature steam sterilization treatment.
Pre-Colored Modified Engineering Plastics
Plastic color matching technology has evolved rapidly in recent years. In medical applications, designers can choose from FDA-compliant and non-migrating pigments. Unique color effects can contribute to a product's unique selling point and provide benefits to medical device designers. As medical products move from the hospital to the home consumer market, lovely colors and fluorescent effects can add value to the product. In addition, the use of elastomers can add value by providing a soft touch. Medical devices with pleasant colors can also make patients more willing to cooperate with treatment while reducing their pain.
[Edit] Development status of China's engineering plastics industry
China's engineering plastics industry after 10 years of development, fruitful, has gradually formed a complete industrial chain with resin synthesis, plastic modification and alloying, processing and application of the relevant supporting capacity. This is the China Engineering Plastics Industry Association Chairman Yang Weicai said on May 27 in Beijing, China Engineering Plastics Industry Association Summit.
10 years ago, China's engineering plastics industry just started, production capacity and demand compared to the serious lag, more than 85% of the raw material resin rely on imports, more than half of the modified resin materials using foreign products. And today, China's engineering plastics resin can be produced at home, polymerization capacity has reached about 600,000 tons per year, the annual output of modified resin materials have more than 2 million tons, even in the past, foreign embargoes on China's special engineering plastics resins, are now almost all domestic production and a small number of exports.
China Engineering Plastics Industry Association data show that in the past 10 years, China's engineering plastics output value of an average annual growth rate of more than 20%, the scale of enterprises continue to grow and develop, and increasingly improve the level of science and technology. At present, in the synthesis of engineering plastics has been in the blue group, yuntianhua group, shenma group, yizheng chemical fiber, deyang science and technology and other large-scale enterprises. As engineering plastics have particularly excellent performance, its level of technological development by the government level of attention, has been included in the national medium- and long-term scientific and technological development program of high-tech key options. In this year's Ministry of Science and Technology Industrial Support Program, there are non-photogas method of polycarbonate and other 7 engineering plastics projects are included. In addition, after a long period of technical research, China's engineering plastics technology level is developing faster, in the modified materials and resin alloys, some product technology, quality indicators have been close to foreign advanced level. Some special engineering plastics product technology has entered the international advanced ranks.
Although China's engineering plastics in the synthesis and processing has made great progress, but overall there still seems to be an excessive concentration of production capacity in a number of relatively low technical content of the shortcomings of the product. Zheng Kai said that enterprises should look long term, grasp the current such as large aircraft and a number of national key project construction opportunities, enhance the level of science and technology, accelerate the upgrade of product structure, and promote China's engineering plastics industry faster and healthier development.