What is polycarbonate and where is it used? Polycarbonate - what is it? Production, dimensions, application Define what cellular polycarbonate is

Not so long ago, when during construction there was a need to install a roof with light-transmitting capabilities, alternatives ordinary glass there was almost none. But time passed, and developers discovered polycarbonate sheets, which blew up the market. Now it is popular and surrounds us everywhere.

What is polycarbonate

Polycarbonate is a material with high light penetration, which reaches 90%. The material is lightweight, it is several times stronger than glass, because it is not afraid of a hammer. Today it is preferred by summer residents for the construction of greenhouses. Such structures are not capable of being damaged by hurricanes and hail.

Polycarbonate consists of a viscous polymer, which makes it almost unbreakable. The cost of supporting structures is reduced due to the minimum specific weight and lightness of the material used. The panels can withstand strong winds and snow loads, which is important, for example, when constructing greenhouses.

The material has excellent heat resistance and is not affected by the environment. Electricity costs for heating greenhouses can be reduced due to the low thermal conductivity of polycarbonate. It also has soundproofing abilities.

Dimensions

Polycarbonate is a material that comes in two versions. Each variety has some differences. Sheets in monolithic format, depending on the predicted operating conditions and intended purpose, can have a thickness ranging from 2 to 12 mm. On sale you can find solid polycarbonate, which has anti-vandal functions.

The standard sheet dimensions are 2.05 x 3.05 m. Cellular, or, as it is also called, cellular polycarbonate, is not as strong as a monolithic sheet. It is used in other areas. Due to the cellular structure, the thickness of the sheet as a whole is greater. Standard thickness varies from 4 to 32 mm.

Cellular polycarbonate is a material that is sold in standard sizes: 2.1x6 or 2.1x12 m. If you need to purchase colored polycarbonate, you can buy it by telling the seller the footage. The length can be 9 m, while the minimum value is 1 m. The smallest width is 2.1 m. Sections longer than 9 m are not sold, in finished form You can only purchase 12th blanks.

Polycarbonate is a material that can be found on the market in another variety - profiled. It is not as popular as the two described above, but it also has its purpose, which determines the standard sizes. The sheet thickness is no more than 1.2 m, but the profiled structure also requires an indicator of the sheet height. It can reach 5 cm. The width according to the standard is equivalent to 1.26 m, while the length reaches 2.24 m.

Application area

The material described above combines several advantages, among which we should highlight:

accessible;
price;
aesthetic appearance;
ease of processing;
durability;
popularity in various fields of human activity.

Polycarbonate is widely used in construction, aircraft manufacturing and the military-industrial complex. It has found its distribution in the food industry, shipbuilding and advertising. You can meet polycarbonate in the field of medicine and computer technology, as well as architecture.

Polycarbonate, a photo of which you can see in the article, is used for glazing building facades for various purposes, they can be economic, residential and administrative. As for monolithic sheets, they are used for the manufacture of observation devices and lenses for sights. These canvases are also found in signal lamps, as well as aircraft windows. They found themselves in shipbuilding, where they form the basis of portholes that withstand waves of any force.

If polycarbonate, the dimensions of which were mentioned above, is produced by injection molding, it can form the basis kitchen utensils, she's not afraid high temperatures and does not break, and can also be exposed to detergents and various aggressive substances.

Monolithic canvases are also protective, so they act as barriers against vandals and the elements. In computer technology, cast polycarbonate is used for production of rigid disks for personal computers. The field of medicine also borrowed this material, which is used to make unbreakable, durable utensils. This material has also found its application in architecture, where it is used for the manufacture of canopies and canopies, bus stops and pavilions, bulletproof transparent partitions and fences.

Production

The USA and Germany were the first to produce polycarbonate. Today one of the German companies is the most famous in the production of polycarbonate products. 2000s became the time when this polymer plastic began to be manufactured in Russia. The first stamps were produced based on foreign-made technologies, but then the process changed a little and amendments were made to it. Additives and additional substances were added to the ingredients of the material. This was done to ensure that the final product would suit the Russian climate.

If you still don’t know which polycarbonate to choose, then perhaps you should pay attention to the one that is made in China. It has a low cost, but is ready to last no more than 6 years. If the structure is being built for a short time, then purchasing expensive canvases is unprofitable. But when the structure must last more than 20 years, it is better to purchase a more expensive analogue, then the money spent will be recouped by long years of service and preservation of the original properties.

The production technology is expressed in the production of aromatic compounds by the synthesis of bisphenol. It is obtained from phenol and acetone. In order to obtain monolithic polycarbonate, engineering amorphous plastic is used. The raw materials are polycarbonate granules, which undergo special processing. The manufacturing process is quite labor-intensive and complex; it requires special skills and knowledge, as well as equipment. At the first stage, the raw materials are prepared, the granules are melted, and then the webs are formed. The sheets are sent to cool, and then cut into separate sheets.

Making a greenhouse

You can make a greenhouse out of polycarbonate with your own hands. For it you can build a brick, stone, strip or wooden foundation. If you use timber for this, you should use a product whose cross-section is 50x50 mm. Supports are installed on a flat surface, and beams are attached to them.

Next, you can start installing the metal frame. For these purposes, a pipe is used whose dimensions are 20x40x2 mm. The distance between the elements of the sheathing should be minimal, but not more than 50 cm. When making a greenhouse from polycarbonate, at the next stage you can begin attaching the sheets to the profile using self-tapping screws. For a more attractive appearance and to eliminate micro-drafts, the sheets can be placed on thermal washers.

Sheathing

The sheets should overlap within 8 cm. The seams should be sealed on top with self-adhesive aluminum tape or one made of galvanized steel. The internal part of the connections is covered with perforated tape, which will ensure condensation drainage and will prevent drafts and dust from appearing inside.

You can choose the dimensions of the polycarbonate greenhouse yourself. But if you have a sheet with dimensions of 2100x6000 mm, then it can be bent to form an arch. As a result, the arc will have a radius of 3800 mm. This size matches the height of the greenhouse industrial production. The resulting arcs will only need to be joined together. Typically, the length of a polycarbonate greenhouse is 6000 mm. These are three arcs. However, you can make a design of two arcs or, on the contrary, choose a project with more arcs. It all depends on personal wishes and the size of the plot.

How to avoid mistakes

Summer residents know that when it comes to constructing a greenhouse or greenhouse, the main enemy of plants is reflection. Curved surfaces create reflections of the sun. The reflected ray of light that did not pass through the surface of the covering material will be reflected from it. A curved surface transmits light rays worse, making efforts to reflect. For a greenhouse, this can be a real disaster.

Solution

Experts do not recommend using arched structures when it comes to early plant growing. The surface can be made straight, it will become the best option. In this case, you can make the walls facing the sun transparent. The rest should not transmit ultraviolet radiation, they should absorb it. As a result, it will be possible to create additional energy inside the greenhouse, which ensures normal plant growth. The north side of the greenhouse should be made of opaque material.

Conclusion

Cellular polycarbonate has become an excellent solution for completing construction tasks. It forms the basis of canopies and canopies, as well as roofs and greenhouses. In private construction it is also used quite often: for the construction of greenhouses and winter gardens.

Polycarbonate is the name given to a whole group of thermoplastics that have a general formula and a very wide range of uses. Due to the fact that polycarbonate has good impact strength and a high degree of strength, this material is used to create various designs in different industrial sectors. At the same time, in order to improve the mechanical properties of polycarbonate, compositions made from it are usually filled with glass fiber.

Polycarbonate is widely used in the manufacture of lenses, compact discs, and in construction. Canopies and awnings are made from this material, fences are built, gazebos are erected, roofs are made, etc.

Compared to glass, polycarbonate is like transparent material has a lot of advantages.

It is not entirely correct to compare polycarbonate and glass, but both materials are often used in architecture and construction precisely due to the presence of optical properties. Even if glass could be as strong as polycarbonate, it would still be inferior to this material, since it has much more weight. At the same time, polycarbonate is inferior to glass in hardness, transparency, resistance to aggressive influences, and durability. However, all shortcomings are more than compensated for by its strength, flexibility and low thermal conductivity.

Methods for producing polycarbonate and its composition

Currently, polycarbonates are produced in 3 ways:

By transesterification of diphenyl carbonate in a vacuum with the addition of complex bases (for example, sodium methoxide) with a stepwise increase in temperature. The process is carried out in the melt according to a periodic principle. The resulting viscous composition is removed from the reactor, cooled and granulated. The advantage of this method is the absence of a solvent during production, but the main disadvantage is that the resulting composition is of poor quality, since it contains catalyst residues. With this method it is impossible to obtain a composition that will have a molecular weight of more than 5000.
Phosgenation in a solution of A-bisphenol in the presence of pyridine at temperatures below 25 ° C. A composition containing anhydrous organochlorine compounds is used as a solvent, and a composition containing monohydric phenols is used as a molecular weight regulator. The advantage of this method is that all processes occur at low temperatures in a homogeneous liquid phase; the disadvantage of the method is the use of expensive pyridine.
Interfacial polycondensation of phosgene with A-bisphenol, which occurs in an environment of organic solvents and aqueous alkalis. The advantages of this method are the low temperature reaction, the use of only one organic solvent, and the ability to obtain high molecular weight polycarbonate. The disadvantages of the method are high water consumption when washing the polymer, and therefore large volumes Wastewater, polluting the environment.

The composition, which contains a UV absorber and polycarbonate, has become a real invention in the industry. This composition has been successfully used for the manufacture of glazing products, bus stops, billboards, car windows, ceilings, corrugated slabs, signs, protective screens, solid slabs, cellular slabs and cellular profiles.

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Types of polycarbonate and its properties

Polycarbonate is a complex linear polyester of phenols and carbonic acid, which belongs to the class of synthetic polymers. Manufacturers polycarbonate plates a material is obtained that has the form of inert and transparent granules. There are mainly 2 types of polycarbonate sheets on the market: cellular and monolithic sheets of various thicknesses. Cellular polycarbonate sheet is available in thicknesses of 4, 6, 8, 10 or 16 mm, width 2.1 m and length 6 or 12 m. Monolithic polycarbonate sheet has thickness 2, 3, 4, 5, 6, 8, 10, 12 mm , width 2.05 m and length 3.05 m.

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Monolithic polycarbonate

Monolithic polycarbonate appearance resembles acrylic glass. By mechanical properties this material has no analogues among the polymer materials used. It combines transparency, good impact resistance and high temperature resistance. Some experts call monolithic sheets of this material impact-resistant glass.

Due to its high strength combined with excellent optical properties, monolithic polycarbonate is used for protective glazing (in the manufacture of shields, fences and protective screens for law enforcement services, glazing of industrial and residential buildings, construction of hospitals, covered parking lots, shops, agricultural facilities, sports structures, etc.). This material is used to make helmets and safety glasses, and is used for glazing aircraft, buses, trains and boats.

Polycarbonate is used in the construction of winter gardens and verandas, installation of skylights, in the manufacture of lighting equipment, in the construction of protective barriers against noise on highways, in the manufacture of signs and signboards.

Monolithic polycarbonate is considered ideal material to create elements with a curved shape, which can be obtained by thermoforming. Thanks to this material, it is possible to create various domes with a rectangular, square or round base, modular broaching light lanterns of various lengths, as well as individual sections of large domes, which reach 8-10 m in diameter. Many experts consider monolithic polycarbonate a unique material, but to create horizontal floors it is used very rarely. Most often this is due to its high cost, which greatly exceeds the cost of cellular polycarbonate, a more popular material in construction. In addition, the honeycomb material provides greater thermal insulation.

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Cellular polycarbonate

Polycarbonate honeycomb plastic refers to multilayer impact-resistant polycarbonate plates. Cellular polycarbonate, which is widely used in private construction, is a polymer profiled into panels that have several layers and internal longitudinal stiffeners. It is obtained by the extrusion method, in which the granules are melted, and then the resulting mass is extruded through a special device, the shape of which determines the design and structure of the sheet.

In recent years, cellular polycarbonate has gained great popularity. Initially, this material was developed to create roofing structures that are resistant to snow loads and hail - transparent, durable and at the same time lightweight. Today it is used not only for vertical and roof glazing of houses and buildings, but also to create greenhouses, greenhouses, winter gardens, shop windows, various decorative and protective, profile and flat partitions, as well as to create various elements with internal lighting. The correctly selected color of the material and the imagination of the designers will provide a variety of decorations for the created interiors.

According to the European classification, cellular polycarbonate is classified as class B1 - these are materials that are difficult to ignite. When using it in building structures, the same building regulations and standards that are observed when using materials of the above flammability level. Polycarbonate sheets are highly resistant to temperature changes from -40 to +120 ° C and to the negative effects of solar radiation.

Sometimes the material is coated with a special inseparable protective layer from ultraviolet radiation or a layer that prevents the formation of drops on the inner surface of the panel (in this case, moisture is distributed in a thin layer over the surface of the sheet, thereby not affecting the light transmittance of the material). The guaranteed service life of the material is 10-12 years.

In addition, experts especially highlight an important feature of polycarbonate sheets, thanks to which it has gained wide popularity - cost-effectiveness. The use of double-layer panels also provides significant energy savings - up to 30% (compared to single-layer glass).

Cellular polycarbonate is also called cellular, structural and channel. All these names indicate the hollowness of the material. It consists of 2 or more planes connected by transverse stiffeners separating cavities (honeycombs, channels, cells). The stiffening ribs additionally perform the function of blocking air, due to which the thermal conductivity of cellular polycarbonate is sharply reduced. A material 16 mm thick can completely replace a double-glazed window.

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Basic properties of polycarbonate

As mentioned above, one of the most important properties of the material is its very high impact strength. Polycarbonate, unlike silicate glass and other organic glasses, does not produce fragments. With a sufficiently powerful impact, the material can only crack. The viscosity of the material allows it to sharp blows deform. A crack can only appear under a load that exceeds its deformation threshold. Roofs made of cellular polycarbonate can withstand hail with a diameter of 20 mm. The material is so durable that it can withstand even a direct hit from a bullet. There are very few materials that can compare in physical properties to polycarbonate. It can be safely used to create a durable roof at home.
Polycarbonate is very light, with the same thickness, it is 16 times lighter than silicate glass and 6 times lighter than acrylic glass. Consequently, less powerful supporting structures are built for it. However, such lightness can also be a disadvantage: if the canopy is not installed correctly, it can fly away from a strong wind. In fact, a polycarbonate panel can withstand quite large snow and wind loads. The load-bearing capacity of a material is determined by its thickness.
Polycarbonate is a fireproof material. The critical temperatures at which it begins to lose its strength are outside the operating temperature limits. The material is characterized by a low flammability coefficient. It does not ignite in an open fire and does not contribute to the spread of flames. During a fire, it melts and flows down into fibrous threads. In this case, the combustion process is not supported, and no toxic substances are released during melting.
Polycarbonate has excellent optical properties. Its light transmittance reaches 93%, but the cellular structure can reduce optical properties by up to 85%. Light transmission is reduced due to the presence of transverse stiffeners in the structure. However, these same partitions, by reflecting light, compensate for part of the lost light transmission and provide a good degree of dispersion. This property makes polycarbonate a very suitable material for the construction of greenhouses and greenhouses. Thanks to it, softer sunlight enters the greenhouse, which has a very beneficial effect on the life of greenhouse plants.
Polycarbonate is a wear-resistant material. Its outer shell filters out the ultraviolet spectrum of the sun's rays, thereby extending the life of the material itself. It does not age and does not lose its original strength for 30 years.
Polycarbonate has a high noise absorption coefficient and does not conduct electricity. Structures with a cellular structure have excellent thermal insulation properties.

Polycarbonate

Structural formula of polycarbonate - bisphenol A ether

In the case of phosgenation under phase-transfer catalysis, polycondensation is carried out in two stages: first, by phosgenation of sodium bisphenolate A, a solution of a mixture of oligomers containing terminal chloroformate -OCOCl and hydroxyl -OH groups is obtained, after which the mixture of oligomers is polycondensed into a polymer.

Recycling

The synthesis process produces granular polycarbonate, which can be further processed by injection molding or extrusion. The extrusion process can produce cellular and monolithic polycarbonate.

Monolithic polycarbonate is a very resistant material, it can be used for the manufacture bulletproof glass. The properties of monolithic polycarbonate are quite similar to those of polymethyl methacrylate (also known as acrylic), but monolithic polycarbonate is stronger and more expensive. This most often transparent polymer has best characteristics light transmittance than traditional glass.

Properties and applications of polycarbonate

Polycarbonate (PC, PC) has a set of valuable properties: transparency, high mechanical strength, increased resistance to impact loads, low water absorption, high electrical resistance and electrical strength, low dielectric losses in a wide frequency range, high heat resistance, products made from it retain stable properties and sizes in a wide temperature range (from -100 to +135°C).

Polycarbonate is processed using all methods known for thermoplastics. The quality of products made from it depends on the presence of moisture in the processed material, processing conditions and product design.

The properties of polycarbonate listed above have led to its widespread use in many industries instead of non-ferrous metals, alloys and silicate glass. Due to its high mechanical strength, combined with low water absorption, as well as the ability of products made from it to maintain stable dimensions over a wide range of operating temperatures, polycarbonate is successfully used for the manufacture of precision parts, tools, electrical insulation and structural elements devices, electronic and household appliances etc.

High impact strength combined with heat resistance allows the use of polycarbonate for the manufacture of electrical installation and structural elements of automobiles operating under severe conditions of dynamic, mechanical and thermal loads.

Good optical properties (light transmittance up to 89%) led to the use of polycarbonate for the manufacture of lighting technical parts of filters, and high chemical resistance and resistance to atmospheric phenomena - for light diffusers of lamps for various purposes, incl. used on the street, and car headlights. Also, polycarbonate is widely used in construction in the form of cellular and monolithic panels (cellular polycarbonate and monolithic polycarbonate).

The biological inertness of polycarbonate and the ability to sterilize products made from it have made this material indispensable for the food industry. It is used to make food utensils, bottles for various purposes, machine parts, processing food products(for example, chocolate molds), etc.

In general, the properties of polycarbonate correspond to the following values:

Density - 1.20 g/cm 3
Water absorption – 0.2%
Shrinkage – 0.5÷0.7%
Notched Izod impact strength – 84÷90 kJ/m2
Impact strength according to Charpy with a notch – 40÷60 kJ/m 2
Application temperature - from −100°C to +125°C
Melting point about 250°C
Ignition temperature approx. 610°C
The refractive index is 1.585 ± 0.001
Light transmittance - about 90% ± 1%

Due to the high impact resistance of polycarbonate, laboratory methods do not allow the determination of Charpy impact strength without a notch, so test results usually indicate “no rupture” or “no fracture.” However, a comparative analysis of impact strength obtained using other measurement methods and indicators for other plastics allows us to estimate this value at the level of ~ 1 MJ/m2 (1000 kJ/m2)

Russian nomenclature of polycarbonate grades

The designation of polycarbonates of various brands is as follows:

PC-[processing method][modifiers included]-[PTR],

wherein:

PC - polycarbonate
Recommended processing method:
- L – injection molding processing
- E – processing by extrusion
Modifiers included in the composition:
- T – thermal stabilizer
- C – light stabilizer
- O – dye
MFR - maximum melt flow rate: 7 or 12 or 18 or 22

In the Soviet Union, until the early 90s of the last century, polycarbonate "Diflon" was produced, brands:

PK-1 - high-viscosity grade, PTR=1÷3.5, later replaced by PK-LET-7, at present. vr. high-viscosity brands of imported materials are used;

PK-2 - medium-viscosity grade, MTR=3.5÷7, later replaced by PK-LT-10, at present. vr. medium-viscosity grades of imported materials are used;

PK-3 - low-viscosity grade, PTR=7÷12, later replaced by PK-LT-12, at present. vr. low-viscosity brands of imported materials are used;

PK-4 - black heat-stabilized, present. vr. PK-LT-18OM black;

PC-5 - for medical purposes, currently vr. medical grade brands of imported materials are used;

PK-6 - for lighting purposes, at present. vr. Almost any brand of imported materials is suitable for light transmission;

PK-NKS - glass-filled, later replaced by PK-LSV-30;

PK-M-1 - increased anti-friction properties, at present. vr. special brands of imported materials are used;

PK-M-2 - increased resistance to cracking and self-extinguishing;

PK-M-3 - can be operated at extremely low temperatures, at present. vr. special brands of imported materials are used;

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Synonyms: Author Chemical encyclopedia b.b. I.L. Knunyants

POLYCARBONATES, polyesters of carbonic acid and dihydroxy compounds of the general formula [-ORO-C(O)-] n, where R-aromatic or aliphatic. remainder Maximum prom. Aromatic POLYCARBONATES (Macrolon, Lexan, Jupi-lon, Penlight, Synvet, polycarbonate) are important: homopolymer of formula I based on 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) and mixed POLYCARBONATES based on bisphenol A and its substituted-3,3",5,5"-tetrabromo- or 3,3",5,5",-tetramethylbisphenols A (formula II; R = Br or CH 3, respectively).

Properties. POLYCARBONATES based on bisphenol A (homopolycarbonate) - amorphous, colorless. polymer; molecular weight (20-120) 10 3 ; has good optical properties. The light transmission of 3 mm thick plates is 88%. The temperature of the onset of destruction is 310-320 0 C. soluble in methylene chloride, 1,1,2,2-tetrachloroethane, chloroform, 1,1,2-trichloroethane, pyridine, DMF, cyclohexanone, insoluble in aliphatic. and cycloaliphatic. hydrocarbons, alcohols, acetone, ethers.

The physical and mechanical properties of POLYCARBONATES depend on the molecular weight. POLYCARBONATES, the molecular weight of which is less than 20 thousand, are brittle polymers with low strength properties, POLYCARBONATES, the molecular weight of which is 25 thousand, have high mechanical strength and elasticity. POLYCARBONATES are characterized by high breaking stress in bending and strength under impact loads (POLYCARBONATE samples do not break without a cut), and high dimensional stability. Under the action of a tensile stress of 220 kg/cm 2, no plasticity was detected during the year. deformation of samples POLYCARBONATES Based on their dielectric properties, POLYCARBONATES are classified as mid-frequency dielectrics; dielectric constant is practically independent of current frequency. Below are some properties of bisphenol A based POLYCARBONATES:


	Density (at 25 0 C), g/cm 3

	T. glass, 0 C
	T. softening, 0 C


	Charpy impact strength (notched), kJ/m 2
	KJ/(kg K)
	Thermal conductivity, W/ (m K)
	Coef. thermal linear expansion, 0 C -1	(5-6) 10 -5
	Heat resistance according to Vicat, 0 C
	e (at 10-10 8 Hz)
	Electric strength (sample 1-2 mm thick) kV/m

	at 1 MHz
	at 50 ha	0,0007-0,0009
	Equilibrium moisture content (20 0 C, 50% relative air humidity), % by mass
	Max. water absorption at 25 0 C,% by weight

POLYCARBONATES are characterized by low flammability. The oxygen index of homopolycarbonate is 24-26%. The polymer is biologically inert. Products made from it can be used in the temperature range from - 100 to 135 0 C.

To reduce flammability and obtain a material with an oxygen index of 36-38%, mixed POLYCARBONATES (copolymers) are synthesized based on a mixture of bisphenol A and 3,3",5,5"-tetrabromobisphenol A; when the latter content in macromolecules is up to 15% by weight, the strength and optical properties of the homopolymer do not change. Less flammable copolymers, which also have lower smoke emission during combustion than homopolycarbonate, are obtained from a mixture of bisphenol A and 2,2-bis-(4-hydroxyphenyl)-1.1-dichloroethylene.

Optically transparent POLYCARBONATES with low flammability, obtained by introducing into homopolycarbonate (less than 1%) alkaline or alkaline-earth salts. aromatic or aliphatic metals. sulfonic acids For example, when the homopolycarbonate contains 0.1-0.25% by weight of the dipotassium salt of diphenylsulfone-3,3"-disulfonic acid, the oxygen index increases to 38-40%.

The glass transition temperature, resistance to hydrolysis and weather resistance of POLYCARBONATES based on bisphenol A are increased by introducing ether fragments into its macromolecules; the latter are formed by the interaction of bisphenol A with dicarboxylic acids, for example iso- or terephthalic, with their mixtures, at the stage of polymer synthesis. The polyester carbonates thus obtained are glass-like. up to 182 0 C and equally high

optical properties and mechanical strength similar to homopolycarbonate. Hydrolysis-resistant POLYCARBONATES are produced on the basis of bisphenol A and 3,3",5,5"-tetramethylbisphenol A.

The strength properties of homopolycarbonate increase when filled with glass fiber (30% by weight): 100 MPa, 160 MPa, tensile modulus of elasticity 8000 MPa.

Receipt. In industry, POLYCARBONATES are produced by three methods. 1) Transesterification of diphenyl carbonate with bisphenol A in vacuum in the presence of bases (for example, Na methylate) with a stepwise increase in temperature from 150 to 300 0 C and constant removal of the released phenol from the reaction zone:

The process is carried out in a melt (see Polycondensation in a melt) according to a periodic scheme. The resulting viscous melt is removed from the reactor, cooled and granulated.

The advantage of the method is the absence of a solvent; The main disadvantages are the low quality of polycarbonates due to the presence of catalyst residues and bisphenol A degradation products, as well as the impossibility of obtaining polycarbonates with a molecular weight of more than 50,000.

2) F osgenation of bisphenol A in solution in the presence of pyridine at a temperature of 25 0 C (see Polycondensation in solution). Pyridine, which serves both as a catalyst and an acceptor for the HCl released in the reaction, is taken in large excess (at least 2 moles per 1 mole of phosgene). Solvents are anhydrous organochlorine compounds (usually methylene chloride), and molecular weight regulators are monohydric phenols.

Pyridine hydrochloride is removed from the resulting reaction solution, the remaining viscous solution of POLYCARBONATES is washed from pyridine residues with hydrochloric acid. POLYCARBONATES are isolated from solution using a precipitant (for example, acetone) in the form of a fine white precipitate, which is filtered and then dried, extruded and granulated. The advantage of the method is low temperature process occurring in homogeneity. liquid phase; The disadvantages are the use of expensive pyridine and the inability to remove bisphenol A impurities from polycarbonates.

3) Interfacial polycondensation of bisphenol A with phosgene in aqueous alkali and an organic solvent, for example methylene chloride or a mixture of chlorine-containing solvents (see Interfacial polycondensation):

Conventionally, the process can be divided into two stages, the first is phosgenation of the disodium salt of bisphenol A with the formation of oligomers containing reactive chloroformate and hydroxyl end groups, the second is the polycondensation of oligomers (triethylamine catalyst or quaternary ammonium bases) with the formation of a polymer. An aqueous solution of a mixture of disodium salt of bisphenol A and phenol, methylene chloride and an aqueous solution of NaOH are loaded into a reactor equipped with a mixing device; with continuous stirring and cooling (optimum temperature 20-25 0 C), phosgene gas is introduced. After complete conversion of bisphenol A is achieved with the formation of an oligocarbonate, in which the molar ratio of the end groups COCl and OH must be greater than 1 (otherwise polycondensation will not proceed), the supply of phosgene is stopped. Triethylamine and an aqueous solution of NaOH are added to the reactor and, with stirring, polycondensation of the oligocarbonate is carried out until the chloroformate groups disappear. The resulting reaction mass is divided into two phases: an aqueous solution of salts sent for disposal, and a solution of POLYCARBONATES in methylene chloride. The latter is washed from organic and inorganic impurities (sequentially with a 1-2% aqueous solution of NaOH, a 1-2% aqueous solution of H 3 PO 4 and water), concentrated, removing methylene chloride, and POLYCARBONATES are isolated by precipitation or by transferring from solution to melt using a high boiling solvent such as chlorobenzene.

The advantages of the method are low reaction temperature, the use of one organic solvent, the possibility of obtaining polycarbonates of high molecular weight; disadvantages - high water consumption for washing the polymer and, consequently, a large volume of waste water, the use of complex mixers.

The interfacial polycondensation method is most widely used in industry.

Processing and application. P. is processed by all methods known for thermoplastics, however Ch. arr. - extrusion and injection molding (see Polymer materials processing) at 230-310 0 C. The choice of processing temperature is determined by the viscosity of the material, the design of the product and the selected casting cycle. The pressure during casting is 100-140 MPa, the injection mold is heated to 90-120 0 C. To prevent destruction at processing temperatures, POLYCARBONATES are pre-dried in vacuum at 115 5 0 C to a moisture content of no more than 0.02%.

POLYCARBONATES are widely used as structures. materials in the automotive industry, electronic and electrical engineering. industry, household and medical. technology, instrumentation and aircraft manufacturing, industrial and civil construction. Precision parts (gears, bushings, etc.) are made from POLYCARBONATES. fittings, car headlights, safety glasses, optical lenses, protective helmets and helmets, kitchen utensils, etc. In medical. technology from POLYCARBONATES forms Petri dishes, blood filters, various surgical. instruments, eye lenses. POLYCARBONATE sheets are used for glazing of buildings and sports facilities, greenhouses, and for the production of high-strength laminated glass - triplex.

World production of POLYCARBONATES in 1980 amounted to 300 thousand tons/year, production in the USSR - 3.5 thousand tons/year (1986).

Literature: Schnell G., Chemistry and physics of polycarbonates, trans. from English, M., 1967; Smirnova O.V., Erofeeva S.B., Polycarbonates, M., 1975; Sharma C. P. [a. o.], "Polymer Plastics", 1984, v. 23, no. 2, p. 119 23; Factor A., Or Undo Ch. M., "J. Polymer Sci., Polymer Chem. Ed.", 1980, v. 18, no. 2, p. 579-92; Rathmann D., "Kunststoffe", 1987, Bd 77, No. 10, S. 1027 31. V.V. Amerik.

Chemical encyclopedia. Volume 3 >>

2017-03-17T10:20:31+03:00

Today we will look at the properties of polycarbonate. This is a very important and useful topic, especially for those who have just begun to study and get acquainted with wonderful material called polycarbonate.

Polycarbonate, at first glance, may seem quite simple and does not require special attention material. But this is far from true.

Any polycarbonate, be it cellular or monolithic, is a rather complex polymer, both physically and chemically, and ignorance of the basic properties of polycarbonate can play a role cruel joke with those who engage in it and neglect knowledge in this area. A lot of mistakes when using and installing this material are made only because all its properties were not properly studied, and in most cases it turned out that after a short period of time they became unusable. That is why many “unfortunate craftsmen” claim that polycarbonate is a bad and not durable material.

Properties of polycarbonate

Study this material carefully and many of the mistakes that are made when choosing, installing and caring for polycarbonate will be of no use to you.

And so let's get started...

physical characteristics

As you know, physical parameters include all external indicators of materials: width, length, height, thickness, etc. All these parameters are summarized for convenience in the tables presented below.

Table 1: Cellular polycarbonate (main characteristics)

Table 2: Monolithic polycarbonate (main characteristics)

Light transmitting and translucent properties

Of course, glass is the world leader in light transmission and transparency. Its degree of light transmittance tends to 100%. What about polycarbonate? Not everything is clear here, since there are also its representatives.

Regarding monolithic polymer, when compared with glass, their transparency parameters are practically the same. The difference is only 5%, that is, molded transparent (industrial) polycarbonate has a transparency of 95%. In modern laboratories, they have learned to purify polycarbonate from impurities almost 100%, which has made it possible to make glasses, laboratory lenses, headlight optics, and even windshields for airplanes from it. That is, monolithic polycarbonate in this area is practically a direct competitor to glass.

As for cellular polycarbonate, its light transmission properties are significantly lower than glass and can reach 86% in transparent sheets. Its colored representatives can drop to a light transmittance of 25%, which is very good for shading the space directly under the polycarbonate. There is no need to talk about the translucency of this material, since cellular polycarbonate perfectly scatters and refracts the rays falling on its surface. Thus, this material seems to blur the objects behind it. This property makes it possible to use cellular polycarbonate not only in structures covering the space, but also in partitions, piers and other enclosing products.

Table 3: Light transmittance of cellular polycarbonate, %

Thermal insulation properties

Any polycarbonate, be it monolithic or cellular, transmits heat much worse than glass or plexiglass, and, accordingly, is able to retain heat indoors longer. Of course, for monolithic polycarbonate this figure is not much higher, only 15-20% compared to glass, but for cellular polycarbonate this figure is noticeably higher. Thus, 4 mm cellular polycarbonate is equal in all respects to conventional glazing, and 6-8 mm polycarbonate is comparable to double-glazed windows. This effect is achieved due to the presence of air in the honeycombs, and as you know, isolated air is an excellent heat insulator. What can we say about the thermal conductivity of cellular polycarbonates above 10 mm or with a reinforced structure that divides the honeycomb into several parts. Yes, they are just off the charts. But be that as it may, you need to know that this effect is achieved when the honeycombs are sealed with end tapes and put on them.

Table 4: Thermal conductivity coefficients for glass and polycarbonate

Low specific gravity

Regular cast polycarbonate weighs half as much as glass and is almost the same as plexiglass. But this is molded polycarbonate. What about cell phones?

But cellular polycarbonate weighs almost 10 (ten) times less than glass and 5 times less than plexiglass of the same thickness. This property of polycarbonate, of course, provides its advantages. Thus, frames or bases for cellular polycarbonate can be made in a lightweight version, and accordingly, the cost of materials will be lower. To this we can also add that the low weight of cellular polycarbonate sheets allows for free installation without additional lifting mechanisms, with a minimum amount work force. In turn, this gives additional opportunity designers can create fancy and intricate designs, and installers can easily assemble them.

Table 5: Comparison specific gravity(kg/m2) polycarbonate

UV protection

Polycarbonate, like any other polymer, is not resistant to direct sunlight, in particular ultraviolet radiation, and can quickly degrade. Yes, this is the nature of all plastics.

But don't be upset about this. This problem was solved a long time ago, back in the 70s of the last century. Scientists have been conducting various experiments for a long time to increase the resistance of polycarbonate to sunlight. One of the correct and inexpensive solutions was to apply it using a co-extrusion method (implantation of particles) on the front surface of polycarbonate. Subsequently, the front surface is set towards the sun. This layer does not transmit ultraviolet rays and thereby protects polycarbonate from harmful radiation. Now polycarbonate has one more property - ultraviolet protection.

It is worth paying attention to the fact that some manufacturers, mainly from the cheap segment of goods, do not co-excise the UV layer, but spray it. This is not good, since this layer, during operation, is abraded by particles of sand and dust in the air. This process accelerates in windy weather. Naturally, such polycarbonate does not last long and becomes unusable within 2-3 years.

In recent years, during its production, it has become possible to add various additives with stabilizers against UV radiation to polycarbonate. But due to the high cost of such additives, polycarbonate turns out to be quite expensive. Therefore, such polycarbonate is mainly used in aircraft and automobile construction.

Impact strength

It's unlikely you'll find a transparent one construction material stronger than polycarbonate. Although polycarbonate is lighter than glass, it is more than 200 times stronger than glass. Of course, one could call plexiglass or acrylic a competitor to polycarbonate in this regard, but they are also inferior to it, since they are 10 times weaker than it.

Polycarbonate has this property due to its viscosity. Tests were carried out between monolithic polycarbonate and 8 mm thick acrylic. Plates measuring 50x50 cm were taken. The following participants took part in the test: a standard construction hammer, a bat, a powerful air gun 5.5mm and 16mm shotgun. All items were used at a distance not exceeding 3 m. As a result, not a single acrylic plate passed the test, while the polycarbonate plate remained intact, albeit with minor damage.

Another important and useful fact is that when destroyed, although this happens rarely, polycarbonate does not leave dangerous cutting fragments that are formed when glass or acrylic breaks.

And remember, high-quality polycarbonate is not destroyed by hail. Yes, after a serious hailstorm, for example with egg, there may be minor dents and scratches, but not through holes. Holes appear on low-quality polycarbonate or on polycarbonate that has served for 15-20 years and during its service the upper UV layer simply became unusable, which led to the loss of the original properties of the polycarbonate.

Fire safety

Such a characteristic as fire resistance is almost the most important thing when commissioning any construction project, and the higher the fire resistance of a material, the correspondingly higher its safety.

So, polycarbonate is one of the safest plastics in terms of fire safety. In an open fire it burns very weakly, one might even say it doesn’t burn, but melts. When melted, a specific web-like mass is formed, which does not flow down, like many plastics. Without a source of ignition, polycarbonate goes out almost immediately. We can say about polycarbonate that it is a self-extinguishing material. When burning and melting, it does not emit caustic or toxic substances.

On many sites, as an example of the fire resistance properties of polycarbonate, you can see a video of acrylic and polycarbonate burning. Perhaps this is to some extent obvious. But you yourself can experiment and once again be convinced of the correctness of what is written above if you carry out some actions. Surely, any company that sells or installs polycarbonate has unnecessary waste, ask them for a piece of high-quality, branded polycarbonate and try to set it on fire with matches or a lighter. As long as you hold the polycarbonate over the flame, it will burn, but as soon as you remove the flame from a piece of polycarbonate, it will immediately go out. This will be evidence of the fire safety of polycarbonate.

By the way, according to European standards and classifications, fire safety polycarbonate belongs to category B1 - difficult to ignite materials.

Weather resistance

As mentioned above, polycarbonate perfectly resists hail and is able to withstand the sun's rays with the help of UV protection. In addition, products made from this polymer are able to withstand temperature changes from -40°C to +120°C without visible deformation, at least that’s what polycarbonate manufacturers say, and what’s most interesting is that all the properties of polycarbonate will work in this range. From practice, we can say for sure that this material can withstand temperatures of -35°C in winter and up to +65°C in summer, it just doesn’t happen above the temperature in summer. withstands boiling water treatment in industrial plants (dairies, breweries, wineries, bottling plants mineral waters), and this is a temperature of about +100°C, although for a short time. That is, the parameters declared by the manufacturers can, in principle, be considered valid.

It is worth adding that recently, in the production of polycarbonate, many companies have begun to treat sheets on the inner surface with a “no drop” coating, due to which, when air condenses, large drops do not form on the polycarbonate for a long time. This property is good because polycarbonate remains equally transparent in any weather.

Acoustic properties

Polycarbonate is a good noise absorber. Some of its panels are capable of absorbing noise of more than 45 dB (decibels). It is a generally accepted fact that a person calmly perceives noise up to 60 dB, and is able to tolerate noise from 60 dB to 90 dB, but noise above 90 dB can become destructive for the human ear. Therefore, a noise reduction of 45 dB using polycarbonate is quite noticeable. If you live in a big city, you've probably noticed the tall noise barriers along highways; they are usually made of polycarbonate. If possible, stop somewhere near the edge of such a screen and go behind it, you will immediately feel a significant reduction in noise coming from the roadway.

Table 6:

Chemical resistance

Polycarbonate is resistant to most chemical substances, which makes it possible to use many detergents when caring for it. Such substances include solutions of salts, saturated carbohydrates, mineral acids (very saturated ones at that) and almost the entire spectrum of alcohols.

Yes, one of the properties of polycarbonate is its chemical resistance to many chemicals, but you also need to know that there are a number of chemicals that have a destructive effect on polycarbonate. These substances include: ketones, aldehydes, alkalis, chlorinated hydrocarbons, aggressive acids. Polycarbonate can also be affected esters and aromatic hydrocarbons. This information will be especially useful when selecting cleaning agents for removing paints, varnishes and sealants from the surface of polycarbonate.

Well, try to avoid using chemicals. The simplest, most proven and reliable detergent for polycarbonate it is dissolved in water laundry soap. When washing, use a soft cloth, and if you are unable to immediately wash something with this solution, then pour this solution onto the contaminated area for 5-10 minutes, and it will definitely wash off.

High load-bearing capacity

One of the properties of polycarbonate is its high load-bearing capacity. This is largely due to its durability. As is known, for the installation of any construction plastic panels proper lathing is required in order to evenly distribute the weight of the load over the entire structure. Polycarbonate sheets are no exception in this case. In order not to describe the lathing parameters for each thickness of cellular and monolithic polycarbonate, all data for convenience was summarized in tables.

Table 7: Lathing for cellular polycarbonate at various loads

The table below shows examples of sheathing for monolithic polycarbonate in various snow regions. You can freely find snow load parameters by region on the Internet. There is no point in simply posting a map in this article. All table parameters are given based on standard sizes sheets 3.05x2.05 and for convenience divided into equal 2 (two) or 3 (three) parts along the width of the sheet, that is, 1.02 and 0.7, respectively.

Table 8: Lathing for monolithic polycarbonate at various loads

Panel flexibility

Another amazing property of polycarbonate is its ability to bend when cold, that is, without heating. Thanks to this property, modern designers give transparent structures all kinds of architectural forms. In this regard, polycarbonate, of course, has no competitors, and if you wanted a transparent structure of a complex geometric shape, then polycarbonate will be the only solution to your problem.

But still, polycarbonate is not a rubber substance, and naturally has its own permissible bending radii. They should not be neglected, since bending the polycarbonate beyond the prescribed parameters can destroy the protective UV layer and the internal structure of the polycarbonate, which will ultimately reduce the service life of the polymer.

Table 9: Bend radius of various polycarbonate panels

Easy to prepare, assemble and install

If you do not go into the details of the installation itself, then we can say with confidence that polycarbonate can be easily installed by a team of 2-3 people. In this case you will need minimum set tools: a screwdriver, a drill, a small grinder, a utility knife and a screwdriver, a typical set of any builder. Such a team can easily handle even the longest 12-meter polycarbonate sheets.

Of course, all this is very simple in theory. In practice, such a team will definitely need to study all the properties of polycarbonate and its basic rules. In principle, there is nothing complicated in the installation itself; the only question is the clear and consistent execution of all instructions. At the same time, you must remember one most important rule: measure a hundred times, cut once.

Lifetime

If, after purchase, the polycarbonate was correctly transported, stored, and then installed correctly, then its minimum service life will correspond to the manufacturer’s declared period.

Typically, manufacturers provide a 10-year warranty on polycarbonate, and some even 15 years. And these statements are actually true. But there is one BUT. Polycarbonate also requires proper care. It needs to be washed periodically, at least 2 times per season (spring and autumn) and a technical inspection must be carried out regularly (once every 1-2 years) to ensure the integrity of all components used during installation. If necessary, repair or replace failed elements. In practice, there are cases where, with proper care and timely maintenance, polycarbonate products have served for more than 20 years.

Well, that's all for today. We have looked at the basic properties of polycarbonate. We learned some of the subtleties of choosing, installing and caring for it. We hope that this information was timely and useful for you.

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