Polycarbonate (PC for short) is a polymer containing carbonate ester group in the molecular chain. According to the structure of the ester group, it can be divided into aliphatic, aromatic, aliphatic - aromatic and other types. Due to the low mechanical properties of aliphatic and aliphatic aromatic polycarbonates, their application in engineering plastics is limited. At present, only aromatic polycarbonate has been industrially produced. Due to the structural particularity of polycarbonate, it has become the fastest growing general engineering plastic among the five engineering plastics.

Synthesis of polycarbonate

Polycarbonate is a strong thermoplastic resin that gets its name from the -CO3 group inside it. It can be synthesized from bisphenol A and oxychlorinated carbon (COCl2). The most commonly used method is melt transesterification, that is, bisphenol A and diphenyl carbonate are synthesized by transesterification and polycondensation.

Reaction principle of bisphenol A and diphenyl carbonate

Properties of polycarbonate

Chemical property

Polycarbonate (PC) is a polyester class of carbonic acid, carbonic acid itself is not stable, but its derivatives (such as phosgene, urea, carbonate, carbonate) have a certain stability.

Polycarbonates can be divided into aliphatic and aromatic groups according to the different structure of alcohols.

Aliphatic polycarbonate. Such as polyethylene carbonate, polytrimethylene carbonate and their copolymers, low melting point and glass transition temperature, poor strength, can not be used as structural materials; However, with its biocompatibility and biodegradable properties, it can be applied in drug slow release carrier, surgical sutures, bone support materials and so on.

Polycarbonate is resistant to weak acid, weak alkali and neutral oil. Polycarbonate is not resistant to ultraviolet light, not resistant to strong alkali.

PC is a linear carbonate polyester, in which the carbonate groups in the molecule are alternately arranged with some other groups, which can be aromatic, aliphatic, or both. Bisphenol A PC is the most important industrial product.

PC is an almost colorless glassy amorphous polymer with excellent optical properties. PC high molecular weight resin has high toughness, the impact strength of the cantilever beam notch is 600~900J/m, the thermal deformation temperature of the unfilled grade is about 130°C, and the glass fiber reinforcement can increase this value by 10°C. The bending modulus of PC can reach more than 2400MPa, and the resin can be processed into large rigid products. Below 100°C, the creep rate under load is very low. PC has poor hydrolysis resistance and cannot be used for products repeatedly subjected to high pressure steam.

The main performance defects of PC are not high enough hydrolysis stability, sensitive to notch, organic chemical resistance, poor scratch resistance, long-term exposure to ultraviolet light will turn yellow. Like other resins, PC is susceptible to attack by certain organic solvents.

PC material is flame retardant. Resistance to oxidation.

Physical property

Density: 1.18-1.22 g/cm^3

Linear expansion rate: 3.8×10^-5 cm/°C

Thermal deformation temperature: 135°C Low temperature -45°C

Polycarbonate is colorless and transparent, heat resistant, impact resistant, flame retardant BI class, and has good mechanical properties in ordinary use temperatures. Compared with similar properties of polymethyl methacrylate, polycarbonate has good impact resistance, high refractive index, good processing performance, and has UL94 V-2 flame retardant performance without additives. However, the price of polymethyl methacrylate is lower than that of polycarbonate, and large-scale devices can be produced by bulk polymerization.

The wear resistance of the material is relative, and the ABS material is compared with the PC material, that is, the wear resistance of the PC material is better. However, compared with most plastic materials, the wear resistance of polycarbonate is relatively poor, and it is in the middle and lower level, so some polycarbonate devices for easy wear use need special surface treatment.

Classification of polycarbonate

Anti-static PC, conductive PC, fibre-added fireproof PC, UV resistant PC, food grade PC, chemical resistant PC.

The application of polycarbonate

The three major application areas of PC engineering plastics are the glass assembly industry, the automotive industry and the electronics and electrical appliances industry, followed by industrial machinery parts, optical discs, packaging, computers and other office equipment, medical and health care, film, leisure and protective equipment. PC can be used as Windows and doors glass, PC laminate is widely used in banks, embassies, detention centers and public places of protective Windows, for aircraft cabin covers, lighting equipment, industrial security plates and bulletproof glass.

PC board can do a variety of signs, such as gasoline pump dial, car dashboard, warehouse and outdoor commercial signs, point sliding indicators, PC resin for automotive lighting system, instrument panel system and interior decoration system, used as a front lampshade, with reinforced car front and rear baffle plate, reflective mirror frame, Door frame sleeves, operating rod sleeves, choke plates, PCS are used as junction boxes, receptacles, plugs and bushings, gaskets, television conversion devices, connectors for communication cables under telephone line supports, electrical gate boxes, telephone switchboards, switchboard components, relay housings. PC can be used as low-load parts for household appliance motors, vacuum cleaners, hair shampooers, coffee makers, toasters, power tool handles, all kinds of gears, worm wheels, shaft sleeves, guide gauges, refrigerator shelves. PC is the ideal material for optical disk storage media.

PC bottle (container) transparent, light weight, good impact resistance, resistant to a certain high temperature and corrosion solution washing, as a recyclable bottle (container). PC and PC alloy can be used as computer frame, shell and auxiliary machine, printer parts. Modified PC is resistant to high energy radiation sterilization, cooking and baking disinfection, can be used for blood sample apparatus, blood oxygenator, surgical instruments, kidney dialyzer, etc. PC can be used as helmets and helmets, protective masks, sunglasses and sports eye masks. PC film is widely used in printing charts, pharmaceutical packaging, film commutator.

The application and development of polycarbonate is to develop in the direction of high composite, high function, specialization and serialization, and has launched a variety of special grades for optical discs, automobiles, office equipment, boxes, packaging, medicine, lighting, film and other products.

Building materials industry

Polycarbonate sheet has good light transmission, impact resistance, resistance to ultraviolet radiation and the dimensional stability of its products and good molding processing performance, so that it has obvious technical performance advantages over inorganic glass traditionally used in the construction industry. China has built more than 20 production lines of polycarbonate building materials hollow board, with an annual demand of about 70,000 tons of polycarbonate, which will reach 140,000 tons by 2005.

Automobile manufacturing industry

Polycarbonate has good impact resistance, thermal distortion resistance, good weather resistance and high hardness, so it is suitable for the production of various parts of cars and light trucks, mainly concentrated in the lighting system, instrument panel, heating plate, defroster and polycarbonate alloy bumper.

According to the developed data, polycarbonate in the electrical and electronic, automotive manufacturing industry use ratio of 40% to 50%, China in the field of use ratio of only about 10%, electrical and electronic and automotive manufacturing industry is China's rapid development of pillar industries, the future demand for polycarbonate in these areas will be huge. China has a large number of cars and a large demand, so the application of polycarbonate in this field is very potential for expansion.

Medical device

Because polycarbonate products can withstand steam, cleaning agents, heating and high doses of radiation disinfection without yellow and degradation of physical properties, they are widely used in artificial kidney hemodialysis equipment and other medical equipment that needs to be operated under transparent, intuitive conditions and require repeated disinfection. Such as the production of high pressure syringes, surgical masks, disposable dental appliances, blood separators and so on.

aerospace

With the rapid development of aviation and aerospace technology, the requirements for various components in flight 9 aircraft and spacecraft continue to improve, making the application of PC in this field is also increasing. According to statistics, there are 2,500 polycarbonate parts used in only one Boeing aircraft, and the single machine consumes about 2 tons of polycarbonate. On the spacecraft, hundreds of different configurations and fiberglass reinforced polycarbonate components are used, as well as astronaut protective equipment.

Packaging field

A new growth point in the packaging field is the various models of water bottles that can be re-sterilized and used. Because polycarbonate products have the advantages of light weight, impact resistance and good transparency, no deformation and transparency when washed with hot water and corrosive solutions, PC bottles have completely replaced glass bottles in some areas. It is predicted that with the continuous improvement of people's attention to the quality of drinking water, the growth rate of polycarbonate consumption in this area will remain above 10%, and it is expected to reach 60,000 tons by 2005.

Electronics industry

Because polycarbonate has good and constant electrical insulation over a wide range of temperature and humidity, it is an excellent insulating material. At the same time, its good flame resistance and dimensional stability, so that it has formed a broad field of application in the electronic and electrical industry.

Polycarbonate resin is mainly used in the production of various food processing machinery, power tool shell, body, bracket, refrigerator freezer drawer and vacuum cleaner parts. And for the important parts of computers, video recorders and color TV sets with high accuracy requirements, polycarbonate materials have also shown high value.

Optical lens

Polycarbonate occupies a very important position in this field because of its unique characteristics of high transmittance, high refractive index, high impact resistance, dimensional stability and easy machining. The optical lens made of optically grade polycarbonate can not only be used for cameras, microscopes, telescopes and optical testing instruments, but also for movie projector lenses, photocopier lenses, infrared autofocus projector lenses, laser beam printer lenses, as well as various prisms, multi-sided mirrors and many other office equipment and home appliances, and its application market is very broad.

Another important application area of polycarbonate in optical lenses is as a lens material for children's glasses, sunglasses and safety goggles and adult glasses. The average annual growth rate of polycarbonate consumption in the world glasses industry has been maintained at more than 20%, showing great market vitality.

Optical disc manufacturing industry

With the rise of information industry, optical polycarbonate made of optical disc as a new generation of audio and video information storage media, is developing rapidly. Polycarbonate has become the main raw material of the world optical disc manufacturing industry because of its excellent performance characteristics. The amount of polycarbonate consumed by the world's optical disc manufacturing industry has exceeded 20% of the overall consumption of polycarbonate, and its annual growth rate exceeds 10%. China's disc production is growing rapidly, according to the figures released by the General Administration of Press and Publication, in 2002, the country had a total of 748 disc production lines, the annual consumption of optical grade polycarbonate about 80,000 tons, and all imports. Therefore, the application prospect of polycarbonate in the field of optical disc manufacturing is very broad.