What is PVC? This material is polyvinyl chloride. It belongs to the group of thermoplastics - plastics that, after the product is molded, remain recyclable. Pure PVC material consists of 43 percent ethylene. The remaining 57 percent is combined chlorine.
PVC material comes in powder form and is used in many industries. The most famous product in the production of which this material is used is metal-plastic windows. To produce window profiles, special pigments, stabilizers, modifiers and many other auxiliary additives are added to powdered polyvinyl chloride. Thanks to them, the product becomes virtually invulnerable to direct sunlight, temperature changes and other environmental factors.
What is PVC? Physical Features
The main feature of PVC material is its strength. Due to its properties, polyvinyl chloride is practically not subject to deformation and other mechanical stress. The very degree of strength of this material depends on the structure of macromolecules, as well as on the structure of the polymer.
PVC material - what is it? Characteristic
This substance is characterized as a non-flammable thermoplastic material that can be easily machined on conventional machines and is easily welded with hot air at a temperature of 200-300 degrees Celsius. In addition, it can stick to various types of glue (often these are based on perchlorovinyl resin). Moreover, this material can be glued to wood, concrete and metal products. PVC is not afraid of the effects of many types of acids, as well as aliphatic, chlorinated and The strength of adhesive and welded joints is about 85-90 percent of the strength of the material itself.
Due to its high elastic and bending strength, polyvinyl chloride is widely in demand among fishermen who make the upper parts of spinning rods in a handicraft way, and also, as practice shows, such products do not lose their properties even at a temperature of minus 45 degrees Celsius.
Dielectric properties
When listing the properties of PVC, it is also necessary to note the fact that polyvinyl chloride is a good dielectric (does not conduct electric current through itself). However, when heated to a temperature of 85 degrees Celsius or more, this material quickly loses these properties. As for weight, PVC is heavier in density than polyethylene, but lighter than fluoroplastic and phenol-formaldehyde plastic.
The high fire resistance of PVC is achieved through the use of a component such as chlorine in its production. It is this that reduces the risk of flammability of rigid polyvinyl chloride.
Chemical properties
As we noted earlier, PVC is practically invulnerable to certain types of acids. This is true - polyvinyl chloride does not change its properties when exposed to alkalis, gasoline, kerosene, salt solutions and metals.
Also, up to 60, this material is resistant to hydrochloric and formic acid. PVC is resistant to oxidation and the effects of glycerol, fats and glycols. As for alcohols, polyvinyl chloride does not dissolve in ethyl and methyl alcohols, higher alcohols, as well as lubricating and vegetable oils. It is not vulnerable to the effects of acidic wastewater.
Where is it used?
We have already found out what PVC is, now let’s talk about in which industries this material is used. Polyvinyl chloride is widely used in the production of flexible plastic sheets (for wall finishing and flooring), films, protective gloves and many other materials and products. Rigid, unplasticized polyvinyl chloride is used to produce pipes that are invulnerable to corrosion, as well as some parts of doors and windows. In the field of electrical engineering, this material is used to insulate wires. They also make toys, stationery and sporting goods from it. Polyvinyl chloride fibers are used for the manufacture of fishing nets, medical linen, knitwear and various technical filter fabrics. As you can see, PVC is used in almost all industries and households.
Characteristics of PVC products
On the Russian market you can most often find the following products made of polyvinyl chloride:
- Floor covering (in other words - linoleum).
- Film.
- PVC panels.
Below we will briefly look at each of these above types of products.
What is PVC coating? This is a surface in which special PVC tiles were used, intended for laying the floor. They can have either a simple square or a complex shape design.
PVC film - what is it? According to its properties, it is a highly transparent, flexible and slightly stretchy material. Like all other products, it is resistant to alcohols and acids, but has a unique ability to transmit oxygen. That is why containers packed in this film do not lose their presentation for a long time.
What are PVC panels? This is a material that is used for finishing ceilings and walls in various rooms. Often used for wall cladding in the kitchen and bathroom.
How does polyvinyl chloride affect the human body?
Vinyl chloride itself is characterized as a very strong poison, releasing toxic substances when burned. In humans, this substance has terato-, carcinogenic and mutagenic effects. As a result of numerous studies, scientists have proven that exposure to PVC in humans causes cancer in various organs and tissues (including the brain, lungs and liver), and also disrupts the lymphatic and hematopoietic systems. With constant exposure to high concentrations, vinyl chloride can even cause paralysis of the nervous system, including complete cessation of breathing. However, modern manufacturers have taken all these properties into account and therefore produce PVC using a special technology. Modern products made of polyvinyl chloride (if they are of high quality) do not have such a terrible effect on humans. Therefore, in order not to risk your health, when purchasing PVC products you should trust only well-known global manufacturers.
So, we found out what PVC is and what effect it has on the human body.
PVC is an artificial fabric of mixed composition. The abbreviation stands for polyvinyl chloride. Other names of the material: awning, banner fabric, film. There is a foreign language version - PVC.
Polyvinyl chloride fabric is called according to its top layer. It has become widespread in various industries: from consumer goods to mechanical engineering.
Polyvinyl chloride was first produced from vinyl chloride in 1835 by Henri Victor Regnault in France. This happened during random experiments. The scientist’s notes have been preserved, in which he was unable to characterize and name the resulting substance.
The next wave of research into the polyvinyl chloride compound dates back to 1878. But even then there was no use for it and the experiments were suspended.
In 1913, in Germany, chemist Fritz Klatte, having studied the properties of the substance, patented the production of PVC. The outbreak of the First World War prevented the implementation of his ideas.
Almost in parallel with Klatte in Germany, polyvinyl chloride was studied by Waldo Silon in America. In 1926, he patented the idea of creating bathroom curtains from the new fiber.
Industrial production of objects from the new material began in 1931.
In less than 15 years, polyvinyl chloride fabric has become firmly established in many industries. They also began to make dishes, household items, automobile parts, etc. from it.
Features of production and composition
The fabric is based on a network of polymers. Their threads (polyester, nylon, or lavsan) are tightly woven together. This network is covered with a layer of PVC.
The interweaving of threads can have different ratios. The most common options:
- 12x12.
To give the product certain properties, it is coated with varnish and all kinds of chemical additives. For example, polyurethane ensures the elasticity of the item and indelibility.
Main characteristics of PVC
There are a number of parameters by which the quality of a material is determined. Among them:
- Density. Measured in grams per square meter. Varies widely. Popular high rates: 550-800 g/sq.m.
- Strength, stretchability. It must comply with the following standards: ISO - international, DIN - German, EN - European.
- Thread thickness. Measured in tex. The most popular fabrics have a strength of 110 tex.
- Fire resistance.
- Oil resistance.
- Flammability.
- Temperature conditions for use. Can reach +70 degrees.
For specialized industries, the qualitative and quantitative indicators are different.
Pros of PVC
Polymer coating provides products with a number of general advantages. Among them:
- Elasticity.
- Density and strength.
- Water resistance. The material does not allow moisture to pass through.
- Air tightness. Being a minus in light industry, this quality becomes a plus when used in the right field.
- Heat resistance. The fabric is not afraid of extremely low and high temperatures.
- Sun resistance. Quality items made to high standards will not fade in direct sunlight.
- Non-oxidizability.
- Budgeting. Polyvinyl chloride fabrics have an affordable price.
- Relatively long service life. Ranges from 5 to 15 years, depending on the specific characteristics and type of product.
Cons of PVC
Products made from polyvinyl chloride are considered non-ecological.
The material is “famous” for the following disadvantages:
- Does not completely decompose.
- Its breakdown products are toxic.
- You cannot burn the canvas: the hydrogen chloride released from this is dangerous.
- The production process itself is accompanied by emissions harmful to the environment.
Types of fabric
It is difficult to classify according to composition and individual parameters, since there are many options in this regard.
Based on the coating, the material is distinguished:
- unilateral;
- bilateral.
According to what product the canvas is intended to create, it is divided into:
- boat;
- tent;
- banners, etc.
For construction purposes and for the production of boats, two types of polyvinyl chloride are used:
- reinforced (safer, equipped with additional “retaining” elements);
- unreinforced (simple film, suitable for creating children's swimming circles, etc.).
Depending on the number of added layers, PVC is divided into:
- multilayer;
- single layer.
Scope of application
Polyvinyl chloride is actively used for the manufacture of:
- small and large sports equipment (trampolines, gymnastic mats, wrestling flooring and various equipment for athletes);
- special professional footwear, boots;
- camping clothes (capes, raincoats);
- fishing equipment;
- mattresses for swimming pools;
- inflatable boats, kayaks;
- tourist and trade awnings, tents and similar frame structures;
- advertising banners and banners;
- suspended ceilings;
- curtains, etc.
Features of operation
- The main requirement for using items and clothing made from this fabric is compliance with the care conditions. Be sure to carefully study the instructions for the product after purchasing it.
- Curtains, mattresses, and raincoats made of PVC cannot be machine washed.
- It should be remembered that burning PVC things is dangerous.
Reviews
Opinions about polyvinyl chloride are mixed.
On the one hand, it is valued for its practicality and high performance characteristics.
On the other hand, the non-ecological nature of the material is considered a big disadvantage.
Photo gallery
Polyvinyl chloride (PVC) [-CH 2 -CHCl-] n- this is a high-molecular chlorine-containing chlorine, the elementary units in the macromolecule of which are mainly connected in a “head to tail” manner.
Polyvinyl chloride is glass transition temperature 70-80 °C and viscous flow temperature 150-200 °C depending on . PVC polymerization degree industrial brands range from 400 to 1500 .
The properties and purpose of polyvinyl chloride are largely determined by the method of its preparation. The properties of PVC can also be changed through chemical modification. The availability of raw materials (), relatively simple production methods, and valuable technical properties have led to the rapid growth and large scale of its production.
Plastics based on polyvinyl chloride are widely used in the electrical and chemical industries, in construction, as well as in other areas of technology and everyday life.
Brief historical sketch
In 1835, Regnault discovered the ability of gaseous vinyl chloride to turn into powder under the influence of light. In 1872, the polymerization of vinyl chloride was investigated by Bauman. And 40 years later, Ostromyslensky and Klatte proposed using photopolymerization as an industrial method for producing polyvinyl chloride. Later, methods were developed for the polymerization of vinyl chloride under the influence of initiators that decompose into free radicals when heated. The industrial synthesis of polyvinyl chloride in an aqueous emulsion was first carried out in 1930. The next important step was the development and industrial implementation of suspension polymerization of vinyl chloride. Relatively recently, the industrial method of bulk polymerization of vinyl chloride was developed.
Polymerization of vinyl chloride
Polyvinyl chloride (PVC) obtained by radical polymerization of vinyl chloride:
- in solution.
Most widely used in industry suspension method. The process is initiated by free radicals formed during the homolytic decomposition of peroxides or azo compounds. The primary radical attaches mainly to the methylene group of vinyl chloride:
Due to the tendency of polyvinyl chloride to dehydrochlorinate at temperatures above 75 °C it is possible to transfer the chain to the polymer due to the abstraction of the allylic chlorine from the carbon atom, which is located next to the double bond formed due to partial polymer dehydrochlorination:
As a result of this reaction, low-active allylic radicals appear, causing a slowdown in polymerization. To prevent dehydrochlorination and obtain PVC with a theoretical chlorine content, it is advisable to carry out the polymerization process at temperatures no higher 70-75 °C.
Due to their high activity, vinyl chloride radicals easily interact with various impurities contained even in small quantities.
Some of the impurities, e.g. acetylene, react as chain transfer agents and can cause the formation of low-active radicals, slowing down polymerization. In the presence of other impurities, chain termination occurs.
Chain transfer reactions are often used to control the molecular weight of a polymer. In this case, substances capable of participating in chain transfer are introduced into the polymerization medium - regulators. The regulators are chosen so that the radicals formed as a result of chain transfer are sufficiently active, otherwise the regulators used slow down or even inhibit polymerization.
In all cases of producing polyvinyl chloride, oxygen has a negative effect on the course of polymerization and the properties of the polymer. The presence of oxygen in the system determines the induction period of the polymerization process, a decrease in the polymerization rate, and a decrease in the average molecular weight PVC, appearance of branching, decrease in thermal stability PVC, deterioration of its compatibility with plasticizers.
Therefore the oxygen content is higher 0,0005-0,001% (in relation to vinyl chloride) is undesirable.
When vinyl chloride polymerizes, a large amount of heat is released 1466 kJ/kg, which significantly affects the polymer production technology.
During bulk polymerization of vinyl chloride, the polymer precipitates as a solid phase due to the insolubility of PVC in the monomer. In this case, the reaction rate first increases from the beginning of the process to high degrees of monomer conversion, and then it slowly decreases.
The increase in the polymerization rate is due to the formation of the solid phase. As a result of the transfer of the chain to the polymer, active centers are formed on the macromolecules that have precipitated from the liquid phase and are capable of continuing polymerization. Due to the low mobility of growing chains attached to the polymer surface, the rate of chain termination decreases, while the growth rate remains high due to the high mobility of monomer molecules. Therefore, with the appearance of the solid phase, the rate of polymerization increases.
The increase in the rate of polymerization of vinyl chloride is also affected by the ability of the polymer to swell in the monomer. Polymerization occurs in swollen polymer particles, in which the rate of movement of macroradicals and the probability of their collision and bimolecular chain termination are low. The mobility of monomer molecules in swollen particles and the growth rate of polymer chains remain high.
The above-described phenomenon of autocatalysis during the polymerization of vinyl chloride under heterogeneous conditions is often called the gel effect. However, this phenomenon during the polymerization of vinyl chloride is not analogous to the typical gel effect observed in cases where the resulting polymer is soluble in its own monomer.
Properties of polyvinyl chloride
Polyvinyl chloride is a white powder with a density 1350-1460 kg/m 3. Molecular weight of industrial grade product 30000-150000
. The degree of crystallinity reaches 10%.
Polyvinyl chloride is characterized by significant polydispersity, increasing with increasing degree of conversion.
Number average molecular weight ‾ M n(close in value to the mass average ¯ M w) can be calculated from the value intrinsic viscosity [η]:
In practice, the molecular weight of polyvinyl chloride is characterized by Fikentscher constant (Kf): K f =1000k
Coefficient k determined by the equation: 
Where η rel- relative viscosity of a solution of polyvinyl chloride in cyclohexanone (usually 0.5 or 1 g of polymer per 100 cm 3 of solvent).
Below is Fikentscher constant K f, characterizing the average molecular weight of polyvinyl chloride obtained by various methods:
Reduced viscosity ( η pr), Fikentscher constant ( K f) and number average molecular weight ( ¯М n) polyvinyl chloride bonded as follows:
| η pr | 1,80 | 1,98 | 2,20 | 2,44 | 2,70 |
| K f | 55 | 60 | 65 | 70 | 75 |
| M n | 50 000 | 65 000 | 80 000 | 90000 | 100 000 |
Due to its high chlorine content (about 56%), polyvinyl chloride is practically non-flammable. At 130-150 °C starts slowly, and when 170 °C faster decomposition of polyvinyl chloride, accompanied by the release of hydrogen chloride.
Polyvinyl chloride is insoluble in the monomer (vinyl chloride), in water, alcohol, gasoline and many other solvents. When heated, it dissolves in tetrahydrofuran, chlorinated hydrocarbons, acetone etc.
Polyvinyl chloride has good electrical and thermal insulation properties, as well as high resistance to strong and weak acids and alkalis, lubricating oils, etc.
Under the influence of energetic and mechanical influences, reactions of dehydrochlorination, oxidation, destruction, structuring, aromatization and graphitization occur in polyvinyl chloride. The main reaction responsible for the loss of polymer performance properties is the release HCl.
To prevent decomposition, stabilizers are added to polyvinyl chloride. Phenol derivatives and urea derivatives are used as antioxidants.
When thermally plasticized at 160 °C, polyvinyl chloride turns into a hardened block, hard and durable at room temperature.
Polyvinyl chloride combines well with plasticizers.
Polyvinyl chloride is widely used in technology as an anti-corrosion material. Due to its good electrical insulating properties, it is used for cable insulation and other purposes.
Polyvinyl chloride (PVC) is a universal thermoplastic polymer obtained by polymerization of vinyl chloride. The raw materials for the production of vinyl chloride are table salt and petroleum products.
PVC is a product of large-scale chemical production. World consumption of PVC is about 25 million tons per year. PVC has a very wide range of uses - sidings, roofing elements, plastic window profiles, water pipes, gramophone records, cable products, decorative and technical films and plastics, mechanical engineering and electrical parts, textile and technical fibers, floor coverings, sports and leisure products, toys, medical products, packaging and much more.
Chemical formula of polyvinyl chloride: (-CH 2 -CHCl-) n. The spatial structure of the PVC molecule is shown in the diagram.
International abbreviations:
- RPVC, PVC-R, PVC-U, uPVC - unplasticized, i.e. rigid PVC used for structural purposes,
- FPVC, PVC-F, PVC-P - plasticized, for example, with phthalates, used in the cable industry, in the manufacture of hoses, linoleum, toys, etc. and having more or less elasticity. Plasticized forms of PVC are easier to cast and extrude.
PVC is sold on the market under a large number of brand names.
The approximate properties of PVC are given in the table.
| Names of indicators | Indicator values |
|---|---|
| Bulk density of suspension | 0.450 -700 kg/cu.m. m |
| Density at 20°C | 1.35 - 1.43 g/cm3 |
| Pour point | 180 - 220° and above |
| Glass transition temperature | 78 - 105 °C |
| Thermal conductivity | 0.15 - 0.175 W/(mhK) |
| Specific heat | 1- 2.14 kJ/(kgxK) |
| Temperature coefficient of linear expansion | 6x10-7 - 8x10-7 °С-1 |
| Temperature coefficient of volumetric expansion (25 - 50°C) | 3x10-8 - 4x10-8 |
| Heat resistance according to Martens | 50 - 80 °C |
| Water absorption: | in 24 hours - 0.4-0.6% (g/m2) in 1000 hours - 4 g/m2 |
| Strength: tensile | 40-60 Mn/m2 |
| when compressed | 78-160 Mn/m2 |
| when bending | 80-120 Mn/m2 |
| Modulus of elasticity | 3-4 Gn/m2 |
| Impact strength according to Izod | 2-10 kJ/m2 |
| Brinell hardness | 130-160 Mn/m2 |
| Yield strength | 10-30 Mn/m2 |
| Elongation | 5-100% |
| Source http://www.big-av.ru | |
The operating temperature range of PVC products is from - 50 to + 80 °C. PVC products resist external influences well. Like wood, polyvinyl chloride is hydrophilic, so it combines well with wood filler and pigments.
The nature of the bonds between the elementary links allows for several options for constructing a molecular chain, which in practice, during the industrial production of polyvinyl chloride, leads to low regularity (syndiotacticity) of its macromolecules: in one macromolecule several options for the bonds of elementary links are realized at once, regular sequences of elementary links are not created and industrial the samples have a low degree of crystallinity.
Polyvinyl chloride is characterized by a very wide molecular weight distribution (polydispersity). The degree of polymerization for different fractions of the same brand of polymer can vary several tens of times (from 100 to 2500).
Polyvinyl chloride is resistant to moisture, acids, alkalis, salt solutions, industrial gases (for example, NO2, Cl2), gasoline, kerosene, fats, and alcohols. Insoluble in its own monomer. Limited soluble in benzene and acetone. Soluble in dichloroethane, cyclohexanone, chlorine and nitrobenzene. Physiologically harmless.
Pure polyvinyl chloride is a horn-like material that is difficult to recycle. Therefore, it is usually mixed with plasticizers. The properties of the final product range from rigid to very flexible plastic depending on the percentage of plasticizer added, which can be up to 30% by weight.
The properties of PVC can be modified by mixing it with other polymers or copolymers. Thus, impact strength increases when PVC is mixed with chlorinated polyethylene, chlorinated or sulfochlorinated butyl rubber, methylvinylpyridine or butadiene-nitrile rubber, as well as with copolymers (styrene-acrylonitrile or butadiene-styrene-acrylonitrile).
Depending on the method of polymerization, PVC is available in three different forms:
- blocky,
- in the form of a suspension,
- in the form of an emulsion.
Based on polyvinyl chloride, the following is obtained:
- rigid forms - vinyl plastics,
- soft forms - plastic compounds,
- plastisols (pastes),
- polyvinyl chloride fiber.
Vinyl plastic is used as a rigid structural material used in construction in the form of moldings, profiles, and pipes. The plastic compound is used for the manufacture of films, hoses, oilcloth, and linoleum.
The symbol of domestic emulsion polyvinyl chloride, produced in accordance with GOST 14039-78 and representing a product of emulsion polymerization of vinyl chloride, consists of the name of the product - PVC and the following designations:
- polymerization method - E (emulsion);
- processing method through pastes (for paste-forming brands) - P;
- the lower limit of the range of the Fikentscher constant K, which characterizes its molecular weight - the first two digits;
- bulk density indicator - third digit: 0 - not standardized, 5 - from 0.45 to 0.60 g/cm3;
- indicator of residue on a sieve with mesh No. 0063 - fourth digit: 0 - not standardized; 2 - up to 10%;
- applicability of emulsion polyvinyl chloride: M – for processing into plasticized products; F – for processing into rigid products; C – for processing through medium-viscosity pastes.
After designating the brand of emulsion polyvinyl chloride, indicate the grade and GOST.
An example of a symbol for emulsion polyvinyl chloride, manufactured using the emulsion polymerization method, with a K value from 70 to 73, with a bulk density from 0.45 to 0.60 g/cm3, with non-standardized residue on a sieve with mesh No. 0063, for processing into plasticized products , premium:
PVC-E-7050-M, highest grade GOST 14039-78.
An example of a symbol for emulsion polyvinyl chloride, manufactured using the emulsion polymerization method, for processing through pastes, with a K value from 66 to 69, with non-standardized bulk density, with a residue on a sieve with mesh No. 0063 - 5%, for processing through medium-viscosity pastes, first grade :
PVC-EP-6602-S, grade 1 GOST 14039-78.
The symbol of domestic suspension polyvinyl chloride, produced in accordance with GOST 14332-78 and representing a product of suspension polymerization of vinyl chloride, consists of the name of the product - PVC and the following designations:
- polymerization method – C (suspension);
- the lower limit of the range of the Fikentscher constant K, which characterizes its molecular weight K - the first two digits;
- bulk density indicator in g/cm3 – third digit: 0 – no data; 1 – (0.30-0.40); 2 – (0.35-0.45); 3 – (0.40-0.50); 4 – (0.40-0.65); 5 – (0.45-0.55); 6 – (0.50-0.60); 7 – (0.55-0.65); 8 – (0.60-0.70); 9 – more than 0.65;
- indicator of the residue after sifting on a sieve with mesh No. 0063 in% – fourth digit: 0 – no data; 1 – less than or equal to 1; 2 – (1-10); 3 – (5-20); 4 – (10-50); 5 – (30-70); 6 – (50-90); 7 – (70-100); 8 – (80-100); 9 – (90-100);
- applicability of suspension polyvinyl chloride: F – processing without plasticizers for (rigid products); M – processing with plasticizers (for plasticized products); Y – processing with or without plasticizers (for rigid, semi-rigid or plasticized products).
After designating the brand of suspension polyvinyl chloride, indicate the GOST grade.
An example of a symbol for suspension polyvinyl chloride, produced by suspension polymerization, with a K value from 70 to 73, with a bulk density from 0.45 to 0.55 g/cm3, with a residue after sifting on a sieve with mesh No. 0063 - 90%, for the production of plasticized products:
PVC-S-7059-M GOST 14332-78.
Symbol of domestic polyvinyl chloride plastic compound obtained by processing a polyvinyl chloride composition in accordance with GOST 5960-72, intended for insulation and protective sheathing of wires and cables, operating depending on the grade of plastic compound and the design of the wire and cable in the temperature range from minus 60 to plus 70 ° C , and for IT-105 plastic compound – up to plus 105 °C, has the following form.
- The first two letters in the symbol of polyvinyl chloride plastic compound of types I and IO indicate the type of plastic compound: I - insulating, IO - insulating and for shells.
- The first two numbers indicate the frost resistance of the plastic compound.
- The next two digits indicate the order of magnitude of the specific volumetric electrical resistance at 20°C.
- For plastic compound type O (for shells) - the first letter indicates the type of plastic compound, the next two numbers indicate the frost resistance of the plastic compound.
- The designation of plastic compound brand IT-105 (insulating heat-resistant) consists of letters indicating the type of plastic compound and subsequent numbers indicating the upper limit of the operating temperatures of the plastic compound.
- The symbol of the plastic compound intended for oil and petrol resistant casings is OMB-60.
- The symbol for plastic compound intended for shells with low migration of plasticizer into polyethylene is ONM-50.
- The symbol for plastic compound intended for casings with low odor is ONZ-40.
- In addition, the symbol of the plastic compound indicates its color, formulation and grade.
An example of a symbol for a plastic compound for black oil- and petrol-resistant casings, formulation M 317:
plastic compound OMB-60, black, formulation M 317 GOST 5960-72;
An example of a symbol for heat-resistant insulating plastic compound IT-105 with an upper operating temperature limit of 105 °C, unpainted, T-50 formulation, premium grade:
IT-105 plastic compound, unpainted, T-50 formulation, premium grade GOST 5960-72.
Ready-made PVC compounds for various applications are supplied in granular form.
In the production of WPC, rigid, unplasticized forms of PVC are usually used.
Abroad, there are many critics of polyvinyl chlorides for reasons related to ecology and safety (the use of chlorine in production, the possibility of chlorine release during processing, operation and disposal).
Add. literature: Polyvinyl chloride, Ulyanov V.M. et al., ed. Chemistry, 1992,
PVC is produced by block (PVC-M), suspension (PVC-S) and emulsion (PVC-E) polymerization. Its chemical formula:
[-CH 2 -CHN1-] n.
This is an amorphous thermoplastic with MW = 40-150 thousand. PVC is highly polydisperse. The melting point of PVC is 165-170 °C, however, when heated above 135 °C, destruction processes begin in it, accompanied by the elimination of atomic chlorine with the subsequent formation of hydrogen chloride, causing intense destruction of macrochains.
The decomposition of the polymer is accompanied by a change in its color from ivory to cherry brown. To prevent this phenomenon, a complex of stabilizers is introduced into PVC, of which the best known are lead compounds (oxides, phosphides, carbonates), salts of fatty acids, melamine, and urea derivatives.
At the same time, the high chlorine content makes PVC self-extinguishing.
PVC is available in the form of powders, granules and plastisols.
Depending on the degree of plasticization, PVC is produced in the form of vinyl plastic and plastic compound.
Viniplast- rigid, practically non-plasticized PVC, containing stabilizers and lubricating additives. With the correct selection of stabilizer complexes, the destruction temperature rises to 180-220 ° C, which allows its processing from the melt. Viniplast has high physical properties (Table 7), which makes it a structural material widely used in mechanical engineering and construction (pipes, moldings, fittings, double-glazed windows, etc.).
Table 7
Physical properties vinyl plastic and plastic compound
|
Properties |
Viniplast |
Plastic compound |
|
Density, kg/m:! |
1380-1400 |
1100-1300 |
|
Breaking stress. MPa. when: stretching bending |
35-65 100-120 |
10-13 |
|
Elongation at break, % |
10-50 |
100-250 |
|
Impact strength, kJ/m 2 |
10-50 |
|
|
Brinell hardness, MPa |
130-160 |
|
|
Heat resistance according to Martens. °C |
65-70 |
|
|
Frost resistance, °C |
Up to -10 |
Up to -50 |
|
Dielectric constant at 10 6 Hz |
3,1-3,4 |
|
|
Dielectric loss tangent at 10 6 Hz |
0.015-0.020 |
0,05-0,10 |
|
Specific volumetric electrical resistance, Ohm M |
1014-1015 |
1010-1013 |
Viniplast has good light resistance, is welded and glued. The non-toxicity of PVC up to 80 °C allows its use in the food industry and medicine.
The plastic compound is PVC containing up to 50% plasticizer (phthalates, sebacates, tricresyl phosphate and others), which greatly facilitates its processing into products and expands the range of practical use (films, hoses, artificial leather, linoleum, oilcloths, etc.). Plastics are frost-resistant (Table 7).
In the PVC brand, numbers indicate the value of the Fikentscher constant, which characterizes its MM, bulk density group and, if necessary, the residue on sieve No. 0063. The letters after the number indicate the recommended area of application (M - for soft products, F - for hard ones, C - medium-viscosity pastes). For example, PVC-6358 Zh means: C - suspension, the value of the Fikentscher constant is 3, bulk density group 5, that is0.45-0.60 g/cm3, sieve residue 8%, recommended for the production of rigid products.