Types, composition and methods of applying polyester paints. Polyester Epoxy Powder Coatings

As a raw material for the manufacture of products, our company uses steel with various types polymer coatings. Coatings are applied at factories - manufacturers of raw materials, on a complex technological equipment. The galvanized sheet is covered with a phosphate anti-corrosion layer, then a primer is applied to improve adhesion and coated with back side protective varnish, and with an outer polymer coating (polyester, matte polyester, plastisol, PVDF, pural, polyurethane) also having a certain color. It is also possible to manufacture products from a material having a double-sided polymer coating.

The appearance and durability of galvanized steel materials depend on a polymer coating that protects it from aggressive environmental influences. The coating is applied at the factory using special technologies.

The anti-corrosion properties of galvanized steel with a polymer coating depend on the thickness of the zinc layer. Pre-painted steel with a zinc layer weight of 275 g/sq. m will last until the first signs of corrosion of ferrous metal for 5-7 years longer than steel with a zinc layer mass of 180 g per sq. meter. The uncoated zinc layer is washed off the roof with normal rainwater over the years. Therefore, the steel sheet from which facade and roofing materials are made (metal tiles, corrugated board, metal siding, low tide, additional elements of the roof) are additionally covered with two protective layers of polymer on the front side and varnish on the back side. Materials with double-sided polymer coating are available.

Consider common coverage:

GALVANIZED STEEL

GALVANIZED STEEL - steel having protective covering from zinc. Special galvanized steel is used in the production of products. structural grades steel (S250GD, S280GD) of the world's leading plants with a zinc layer thickness of 18-20 microns on each side (275 g per m2). Thanks to this, the products are optimally suited for construction and have unsurpassed durability. Products for sale in Russia roofing made of steel coated with more thin layer zinc (140-200 g of zinc per sq. m). Profiled sheeting, ebbs and additional elements made of such steel are suitable in cases where the service life of the roof and elements is designed for 10-20 years.

Aluzinc®

Aluzinc ® is a steel with a protective metallic coating consisting of 55% aluminium, 43.4% zinc and 1.6% silicon. The thickness of the aluminium-zinc coating is 20 microns (150g/m2) Aluminum, due to the oxide film appearing on the coating, increases the corrosion resistance of the product material by an order of magnitude. In addition, products coated with Aluzinc® practically do not change their appearance during operation. It is thanks to the oxide film that Aluzinc ® has the highest corrosion resistance and appearance stability. Outdoor tests have shown that after 30 years of operation, subjected to various environmental conditions, no traces of rust appear on the material. High corrosion resistance allows the use of Aluzinc ® products on roofs with an inclination angle of less than 5 degrees.

• Aluzinc ® does not darken unlike galvanized steel.
• Aluzinc ® does not fade or scratch.
• Aluzinc ® With its 100% metallic finish, it has a highly sought-after natural silver sheen.

Aluzinc ® also contributes to building climate control with its excellent heat reflective property, which gives Aluzinc ® the characteristics of a heat shield. We recommend using Aluzinc ® profiles as cladding ( wall decking and siding). Aluzinc ® makes a building bright, attractive and durable. In terms of heat resistance, Aluzinc ® has the advantage among metal coatings, it does not emit toxic fumes, does not ignite or catch fire.

Polyester (PE)

POLYESTER (PE) - coating based on polyester. Products with this coating can withstand high air temperatures, and greater resistance to corrosion. The material is strong and durable enough: a roof made of steel sheets coated with polyester can properly last 20-30 years. Warranty period - 10 years. Polyester owes its popularity to high weather resistance, aesthetics, good color fastness, plasticity, durability, a huge selection color solutions and all this is quite reasonable prices. In Russia given material It is actively used for the manufacture of roofing and wall structures, both in private and in multi-storey and industrial construction. The wide scope of steel coated with polyester is primarily due to the fact that this coating is suitable for any climatic conditions. Polyester-coated galvanized steel products are a guarantee of durability and high corrosion resistance, a wide range of colors, a multi-purpose field of application, and an acceptable price.

coating color map

MATTE POLYESTER (PEMA)

MATTE POLYESTER (PEMA) is a polyester-based coating. This coating is chosen by people who do not like it when the roof is shiny. If you run your hand over matte polyester, it will seem velvety. The reason is that its surface is not smooth, like other coatings, but is dotted with microscopic irregularities. Sunlight, reflected from it, becomes scattered. Therefore, the finish is matte. Since it is impossible to determine exactly what the thickness of the coating is in this case, it is applied in a thick layer just in case, in reserve. Therefore, its service life is longer than that of the "polyester" coating, although chemical composition the same. Service life - 40 years. Warranty period - 15 years.
The material has high color fastness and mechanical resistance, retains its qualities in any climate. The original coating based on polyester, thanks to its velvety surface, imitates natural materials very accurately.
Matte polyester has an attractive texture. Due to the matte, rather than glossy surface, like traditional polyester, an imitation of natural materials is achieved. Improved chemical resistance and good mechanical characteristics matte polyester is achieved due to the thickness of the coating - 35 microns.

To help you choose the right color - coating color map

PVDF

PVDF is a coating consisting of polyvinyl fluoride (80%) and acrylic (20%). The most resistant polymer coating of steel to any non-mechanical environmental influences. PVDF products are recommended for wall cladding, as it is in wall panels that PVDF coating will best show its characteristics and provide the longest service life. PVDF guarantees the longevity of roofing and wall cladding. PVDF is the most environmentally friendly coating, does not fade over time and provides increased resistance to the corrosive effects of water, snow, acids and alkalis. The maximum operating temperature is +120 degrees, the minimum is -50 0 C. The color of the cladding or roof of your house, if it is made of PVDF-coated steel, will not fade or fade in the sun over time.
If your premises are located in the industrial part of the city, near roads, near lakes or on the sea coast, if you are building or cladding a chemical production room, the walls of which will often be washed with water or disinfectants, then best material PVDF coated steel is also available for you.
Corus PVDF coated galvanized steel is available in standard colors, RAL catalog and colors imitating natural metals - aluminum, copper, gold.

PLASTISOL (PVC)

PLASTISOL (PVC) is a polymer consisting of polyvinyl chloride and plasticizers. Due to its large thickness (0.2 mm), this coating is the most resistant to mechanical damage, has high corrosion resistance, which provides additional protection in polluted environments or on the coast, but it has a relatively low temperature resistance and quickly fades in the sun. It is recommended to apply light colors plastisol, which fade less, heat up and better reflect light. The coating has a relief surface - embossing that imitates leather or a dashed notch, which does not give sun glare.

To help you choose the right color - coating color map

POLYURETHANE (PU)

POLYURETHANE (PU) - this coating is made from polyurethane modified with polyamide and acrylic. The polyamide gives it excellent UV resistance, while the acrylic provides high strength. Has a silky matte finish. The durability of the material consists of high corrosion resistance, resistance to the negative effects of ultraviolet radiation, and unsurpassed resistance to mechanical damage. Nominal coating thickness - 50 microns. In addition, polyurethane has a very high resistance to many acids, i.e. chemicals found in industrial environments. The results of the salt spray test confirm that the durability of polyurethane-coated materials is maintained even in maritime climates.
When processing and bending at low temperatures, the material does not form microcracks at the bends. This coating is more durable than polyester. Service life - 30-50 years. Warranty period - 15 years.
The polyurethane-based coating has become widespread in Russia due to its English counterpart. Colorcoat Prisma is produced in England by one of the world's largest metallurgical concerns Corus. Prisma coated steel has a Galvalloy 95% Zinc and 5% Aluminium, which provides unsurpassed corrosion protection for the material. Products made with Prisma coating have the highest resistance to ultraviolet radiation and mechanical stress.

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Polyester coatings reinforced with fiberglass require a dry, neutralized (for example, by fluation) concrete base. At 20 C, they show good chemical resistance in water, dilute and medium-concentrated solutions of inorganic and organic acids, solutions of salts having an acidic or alkaline reaction, benzoin and mineral oils. With an increase in the temperature of aggressive media, the chemical resistance of coatings decreases.
Polyester coatings differ from all others in their transparency, hardness, and mirror shine. Polyurethane coatings are close to them.
Glass fiber reinforced polyester coatings require a dry, neutralized (eg fluated) concrete base. At 20°C they exhibit good chemical resistance in water, dilute and moderately concentrated solutions of organic and organic acids, solutions of acidic or alkaline salts, gasoline and mineral oils. With an increase in the temperature of aggressive media, the chemical resistance of coatings decreases.
Polyester coatings have good adhesion to wood and paper; they differ in gloss and transparency, resistance to water, alcohol, fats and low temperatures.
Polyester coatings are characterized by high mechanical properties, which are maintained at elevated temperatures. Polyester film based on PE-943 lacquer provides good electrical properties. Thus, its specific volume resistance is 1 5 - 1015 - 5 3 - 1015 Ohm-cm and does not decrease after the action of water. The electrical strength in the initial state is 100 kV / mm and changes little at 200 C and after the action of water.
Polyester coatings are distinguished by good adhesion to wood, paper and some other materials, gloss and transparency, resistance to water, alcohol and gasoline; they can be easily dyed in all colors.
Polyester coatings are characterized by high mechanical strength, hardness, gloss and resistance to water, gasoline, oil and dilute acids.
Polyester coatings are characterized by high hardness, high gloss, satisfactory abrasion resistance. However, they do not resist well. impact loads and maloelastic; are used mainly for painting wooden (and concrete) surfaces, the adhesion of polyester varnishes to metals is low.
Kinetics of changes in internal stresses during the operation of PE-219 coatings on various substrates. 1 - birch. 2 - ash. 3 - mahogany. 4 - chipboard.| Kinetics of changes in internal stresses during the operation of PE-219 coatings on various substrates treated with a filler. For polyester coatings formed on ash, with an adhesive strength margin of more than 4, with a decrease in coating thickness from 1200 to 300 microns, the durability increases by more than 2 times. With a small initial value of internal stresses in the coatings and a small margin of adhesive strength, the durability of the coatings increases to a lesser extent with a decrease in the thickness of the coatings. In coatings with a thickness of 400–500 µm, formed on wood, a violation of the adhesive strength during operation in atmospheric conditions is observed at a value of critical internal stresses that are 5–10 times less than in the process of formation.
Polyester coatings formed on wood species, the most widely used in the industry, internal stresses measured across the fibers are always significantly greater than the stresses along the fibers.
Thanks to a single-layer polyester coating applied in a thickness of 1 25 - 1 5 mm on plumbing asbestos-cement pipes, their gas tightness is ensured at pressures up to 0 5 MPa, and with a two-layer coating - at pressures up to 0 7 - 1 MPa. It has high mechanical strength, abrasion resistance, resistance to aggressive environments, gasoline, natural and liquefied gases, but has insufficient resistance to prolonged exposure to low-mineralized water. Therefore, the composition of the coating is introduced special additives to increase its water resistance.
Epoxy or polyester coatings reinforced with fiberglass are obtained by applying several layers of epoxy or polyester mixtures to a concrete base, between which an inner layer is laid, which is a fiberglass mat or fabric. Such coatings are characterized by good adhesion to dry concrete surfaces, high mechanical strength, good abrasion resistance and no absorption of liquids even under high pressure.
Epoxy or polyester coatings reinforced with fiberglass are obtained by applying several layers of epoxy or polyester mixtures to a concrete base, between which an inner layer is laid, which is fiberglass mats or fabric. Such coatings are characterized by good adhesion to dry concrete surfaces, high mechanical strength, good abrasion resistance and no absorption of liquids even under high pressure.
When forming polyester coatings largest number functional groups are consumed at the first stage of polymerization for the formation of supramolecular structures, the nature of which depends on the nature of the substrate, the formation conditions, and the thickness of the coatings. At this stage of film formation, polymerization proceeds mainly within the supramolecular structures. This leads to the appearance of an induction period in the change of thermophysical parameters, internal stresses and other physical and mechanical properties of coatings.

Finishing the surface of polyester coatings by grinding and polishing their surface is widely used to improve the decorative properties of coatings. These operations are included in the technological cycle for obtaining polyester coatings, which provides for the removal of floating paraffin additives, insufficiently cured layers and imparting surface gloss. The quality of this operation is usually assessed visually.
Shrinkage kinetics of polyester films at 80°C and subsequent cooling to 20°C, reinforced with various materials. When reinforcing polyester coatings with fibrous fillers - glass canvases, which are a mesh of short entangled fibers; shrinkage during polymerization is not manifested, and some increase in the size of the samples is observed. In the process of cooling reinforced films, shrinkage increases to a certain constant value.
Kinetics of growth of internal stresses during the formation of polyester coatings.| Dependence of internal stresses (/ and tensile strength (2) on the content of modified ODA (a and unmodified aerosil (b). When polyester coatings are filled with aerosil modified with octadecylamine, the formation rate practically does not change compared to unfilled coatings. This is due to the shielding of the aerosil surface groups of NH modifier.With an increase in the content of aerosil, internal stresses increase by more than 2 times, while the tensile strength of the films decreases accordingly, and the adhesion of coatings to glass increases.The effect of a sharp decrease in adhesion and internal stresses during the formation of polyester coatings is observed not only in the presence of a modifier on the surface of aerosil, but also during the direct formation of coatings on the surface of the substrate modified with octadecylamine. internal stresses. Attention is also drawn to the fact that the decrease in internal stresses in the direct deposition of coatings on a modified substrate is much greater than in the formation of coatings on an unmodified substrate in the presence of a modified aerosil.
During the formation of polyester coatings, the largest number of groups is consumed at the first stage for the formation of supramolecular structures, the nature of which depends on the nature of the substrate, the formation conditions, and the thickness of the coatings, and polymerization occurs mainly inside the supramolecular structures. This leads to the appearance of an induction period in the change in internal stresses and thermophysical parameters during the formation of coatings. At the second stage of formation, connections between these structures are established.
The structure of polyester blocks (a, d and coatings (b, c) formed at 80 C, revealed by the method of sections. c, d - with oxygen etching. The microstructure of polyester coatings obtained from 25% solutions of oligoethermaleinates in acetone was studied. -homeric systems, individual globular associates were revealed by fast freezing.When exposed to an electron beam for 5 min, the film practically does not reveal a structure.When exposed to an electron beam for 15 min, a fine globular structure is revealed, similar to the structure detected by the sectioning method (see Fig. 3.11) in cured coatings. Upon subsequent irradiation, aggregation of structural elements is observed with the formation of larger supramolecular structures. After 20 - 25 minutes of formation, along with globular structures, striped structures are detected. After 30 minutes of irradiation, cracking of the film is observed, with the displacement of one layer of the coating relative to another , which is due to different fine structure of the layers along the film thickness.
When removing a polyester coating, the best effect is achieved when using SM-2 and Autowash washes, when removing a polyurethane coating - using SM-2 and BEM-2 washes. After destruction, the coatings are removed with a spatula, and then the remains of the cellulose nitrate coating are removed with solvent 646, and the remains of polyester and polyurethane coatings are removed with white spirit. All these washes in terms of the efficiency of removing polyurethane coatings are significantly inferior to the above American composition [US Pat.
Polyester coatings are cured using various monomers (styrene, methyl methacrylate, chlorostyrene, etc.), which are copolymerized with polyesters, or reactive oligomers, for example, oligoether acrylates, used as polyester solvents.
For polishing nitro-lacquer, nitro-enamel, alkyd, polyester coatings, polishing pastes (G 2 wax, No. 290, 291, 300), wax polishing composition No. 3, etc. are used; shellac and other resin varnish coatings are polished with shellac polish.
Additives are used to improve the properties of polyester coatings for various purposes: to impart thixotropic properties - aerosil and cellulose ethers, to improve pouring - silicone liquids, for plasticization - resilient oligomers, etc. To increase storage stability, a polymerization inhibitor, hydroquinone, is also added to the semi-finished varnish. Semi-finished varnishes are supplied complete with an initiator solution, which is injected before use.
When studying the hardness of polyester coatings, it was found that their hardness reaches the limit value long before the end of the coating formation process due to more speed removal of the solvent and the occurrence of oxidative processes in surface layer. In contrast, when coatings are formed based on unsaturated oligoesters, the polymerization process of which is inhibited by atmospheric oxygen, a slower increase in the hardness of the surface layers is possible compared to the hardness of the coating as a whole. In addition, the hardness measurement method does not allow one to control initial stage process.
With an increase in the thickness of polyester coatings, a linear increase in internal stresses occurs both in the substrate at the border with the film and in coatings on wooden substrates.
Some specific requirements are also imposed on the operations of refining polyester coatings. The polyester coating, which is a three-dimensional polymer insoluble in organic solvents, cannot be leveled, so polyester coatings should only be sanded with thin sandpaper.

For high-speed refining of nitrocellulose and polyester coatings, UralVNIIASH has developed and introduced into production an improved quality sanding paper on paper basis silicon carbide grain size 6 - 4 special granulometric composition; ligament - mezdrovy glue. The optimal granulometric composition of grinding powders narrowly classified by grain size, obtained as a result of additional vibration classification of the abrasive material, makes it possible to reduce specific consumption skins and improve performance.
Films applied to fiberglass, cotton, nylon, polyester or synthetic fiber nonwovens. Such structures carry either a dry or partially tacky binder. When in contact with the bonded material, part of the binder remains on it.
Hardness tests for polyester coatings are carried out indoors at an air temperature of 15 - 30 C, for nitrocellulose - 18 - 25 C.
Most effective method applying a polyester coating to the dry inner surface of pipes - centrifugal method, at which polymer composition, poured inside the pipe, is distributed in a uniform layer on the surface during the rotation of the pipe at a speed of 450 - 500 rpm for 1 - 2 minutes and is compacted at the same time. A factory installation for applying a polyester coating of pipes by this method has been created. Before coating, the pipes are cleaned with metal brushes and then blown with compressed air at a pressure of 0–6 MPa. The curing of the coating after application is carried out on racks at room temperature.
So, on the example of paraffin-containing polyester coatings cured by styrene, it was established [18, p.
Monolithic epoxy, polyurethane and polyester polyurethane and polyester floor coverings.
The dependence of the logarithm of the long-term adhesive strength of polyester coatings from PE-219 varnish on wood on the magnitude of internal stresses is linear. Coatings from this varnish, having a margin of adhesive strength (A: avn 2), do not peel off when tested in atmospheric conditions for 2 years or more. A similar effect of the nature of the substrate on the durability of the coatings is also found under other operating conditions. Thus, when testing by accelerated methods, it was found that the durability of coatings formed on mahogany and birch is an order of magnitude lower than the durability of coatings on ash and chipboard.
The process of forming polyester coatings on wood substrates has been studied due to the increasing use of polyester coatings in various industries for wood finishing and the lack of criteria to select and evaluate the optimal technological conditions for their production. It is shown that the process of forming coatings on wood has a number of specific features.
Significant impact on physical and mechanical properties Reinforced polyester coatings are rendered by the structure of the glass sheet, the nature of the weave and the thickness of the fibers, as well as the nature of their surface. For coatings reinforced with a stiffer paraffin emulsion-treated CLC web, the internal stresses are significantly lower compared to the internal stresses in unreinforced filled coatings. In table. 6.4 shows data on the effect of fillers on the mechanical properties of polyester coatings reinforced with explosive glass canvas.
Influence of fillers on the mechanical properties of polyesters. This is due to the fact that the adhesion of polyester coatings to cement and wood is much greater than to quartz sand. Consequently, internal stresses in filled coatings increase with increasing strength of the interaction between the binder and filler particles.
Influence of mineral fillers on mechanical and adhesive properties of polyester coatings reinforced with CLC glass canvas. Widely used to improve the performance properties of polyester coatings are canvases, which, unlike tapes and fabrics, are characterized by a random arrangement of fibers.
Flange connections of suction air ducts of polyester coating grinding areas should be equipped with special conductive jumpers that provide reliable electrical contact. In the premises of painting shops, it is necessary to provide for the installation of automatic gas analyzers that warn of the occurrence of explosive concentrations of solvents in the air.
The kinetics of the increase in shear strength 0T (1, internal stresses Rvn (2), tensile strength cgr (3 and modulus of elasticity E (4) during the formation of coatings from oligoethermaleinates at 20 (a and 80 C (b.
The stresses that occur during the curing of polyester coatings are small. A sharp increase in internal stresses is observed during cooling of thermally cured coatings.
Dependence of the durability of PE-220 coatings on the nature of the substrate | Dependence of durability of PE-220 coatings on internal The time dependence of the adhesion strength of polyester coatings based on unsaturated polyesters cured with styrene and triethylene glycol diester of methacrylic acid and formed on various substrates was studied, as well as alkyd coatings. The time dependence of the adhesive strength of coatings from oligoethermaleate on the value of internal stresses was obtained when coatings were formed at 18 C. The value of limiting critical stresses that cause spontaneous peeling of coatings was determined by heating the samples for 10 h at 80 C at various time intervals.
Flow-mechanized and automatic lines for refining paintwork polyester coatings (the most modern) have pass-through machines for grinding edges, one or two pass-through machines for grinding the face with mutually intersecting sanding belts, multi-drum (six or eight) polishing machines connected to each other vehicles. Line productivity is determined by feed speed and is usually in the range of 3 - 12 m/min.
Scheme of a thermoradiation drying chamber with heating sources of infrared rays with hot gases.| Schemes of chambers for photochemical curing of coatings by sources of low (a and high (b) pressure. The advantages of this method are that polyester coatings first polymerize slowly, paraffin floats to the surface. The SFKh-2M photochemical drying chamber, which consists of a metal frame, works according to this principle. , apron conveyor and fixtures.
The kinetics of growth and relaxation of internal stresses during the formation of coatings on the surface of glass modified with various compounds at 80 C substituent in the series (C2H5) 2N, H, CH3O and an increase in the distance between active centers, internal stresses decrease more than adhesion.To elucidate the reason for this phenomenon, the surface structure of the substrate and coatings in the boundary layer was studied.
Effect of surfactants on the physical and mechanical properties of unsaturated polyesters.| The structure of coatings from the original polyester (a and polyester modified with 4% ODA (b). This is evidenced by the data on the occurrence of an absorption band in the region of 3500 cm 1, characteristic of hydrogen bonds, for polyester coatings modified with surfactants, which is characteristic of hydrogen bonds. During curing, the intensity of this band increases The decrease in intermolecular interaction and the ordering of the structure of unsaturated polyester molecules at the optimal content of surfactants leads to a change in the morphology of the supramolecular structures that appear during polymerization.Figure 3.8 shows replicas from the surface of polyester coatings, unmodified and modified with surfactants, taken with an electron microscope. oxygen etching.As can be seen from the figure, in coatings of unmodified resin, a network of supramolecular structures of the globular type arises.At the introduction of 1% ODA, a structure in the form of globuled packs with microporosity in the center is observed.With increasing concentration ODA up to 2%, incomplete unfolding of globules is detected, and at a concentration of 3–4%, the coatings are characterized by a striped structure. A subsequent increase in surfactant to 6% leads to the formation of large structures of the striped type.
In this case, the thermophysical properties with a change in the thickness of polyester coatings change antibatically to internal stresses (Fig. 2–2), while the thermophysical properties of free films do not depend on their thickness.
A photochemical method for curing polyester coatings has been developed in the Soviet Union. However, its disadvantage lies in the fact that it is necessary to additionally introduce photosensitizers into the cured systems, the curing time of the coatings is relatively long - up to 5 minutes; the method is unacceptable for pigmented systems.
With the introduction of unmodified aerosil, internal stresses in polyester coatings increase by more than 2 times, while the tensile strength of the films decreases accordingly, and the adhesion strength to glass increases. With incomplete modification of the Aerosil surface with octadecylamine, a sharp decrease in internal stresses and adhesive strength is observed only at a high degree of filling, while when the Aerosil surface is completely filled with a modifier, these same parameters decrease by 3–4 times.
The type of wood has a significant influence on the magnitude of internal stresses in polyester coatings. Data were obtained on the dependence of internal stresses on the thickness of polyester coatings formed on the surface of samples veneered with wood of various species.
Kinetic data on the change in internal stresses in polyester coatings on substrates made of wood of various species during aging in atmospheric conditions show that this dependence is nonmonotonic. The greatest relaxation of internal stresses is observed in the wettest months of coating operation and is probably associated with the plasticizing effect of moisture. During the subsequent operation of coatings, internal stresses increase, not reaching their initial value. A pronounced irreversible change in internal stresses during operation was noted for coatings formed on mahogany and is due to their local flaking in places where internal stresses are concentrated.

Kinetic data on the change in internal stresses in polyester coatings made of PE-219 lacquer on wood substrates treated with KF-1 filler during aging in atmospheric conditions showed that the irreversible decrease in internal stresses in this case is 75–85% and is probably due to , local destruction of adhesive bonds. The effect on internal stresses and adhesive properties of polyester coatings of various compositions modifying the wood surface was also studied.

Powder coating materials began to be used in the early 50s in the United States, and since then the need for these materials has been constantly increasing. In 2000, the world production of powder paints in the world was estimated at 720 thousand tons, in 2003 it amounted to 875 thousand tons. According to forecasts by Western experts, by 2008 it will amount to 1,220,000 tons. At the same time, the share of powder paints will reach 18% of the total volume of produced coatings.

For 40 years, powder paints (PC) have been widely introduced into all spheres of our life. They paint refrigerators, dishes, garden and surgical instrument, fittings, furniture (garden, office, medical, kitchen), vacuum cleaners, washing machines, microwave ovens, scientific instruments, electrical and metalwork tools, machine tools, computers, semiconductors, air conditioners, bicycles, motorcycles, cars, kiosks, shop windows and museums, agricultural machinery, aircraft and sea vessels, drilling tools and pipes (water, gas, oil diameter from 10 mm to 2 m), pumps for all types of liquids, including highly aggressive, elements of architecture and roofs, electrical, radio and Appliances, toys, microelectric motors and space stations and much more.

The widespread use of powder paints is primarily due to the fact that they do not contain solvents and are 100% composed of substances that, when cured, turn into a thin layer, practically impervious to moisture, oxygen, acids, salts and other chemicals, a high-strength and hard abrasive-resistant coating with a service life, sometimes exceeding the service life of the painted product.

Powder paints have the following advantages over traditional solvent-based paints:

Ready to use

Powder paints are always supplied as a ready-to-use mixture and do not need to be diluted or otherwise prepared.

No solvent

Powder paint does not contain solvent or volatile substances, which greatly reduces the risk of fire, eliminates the problem of solvent disposal, and minimizes the harmful effects on maintenance personnel.

Low waste

The completeness of use of powder paint during application reaches 98%. Paint that does not get on the product can be returned and reused when painting. Using liquid paints up to 60% of it is lost during application due to evaporation of the solvent.

Cost reduction

Powder coating technology saves materials (PC usage by 93-97%), energy (air volume used is renewed twice per hour instead of 15 times/hour with traditional painting methods), production space (30% reduction) and labor costs ( by 40-50%).

Manufacturability

Powder paint is easier to apply and there is no need to attract highly qualified personnel. The dyeing technology allows obtaining the required film thickness from 35 to 250 microns when applied in one layer.

Improved Properties

Powder paints make it possible to obtain coatings with high physical-mechanical, protective and decorative properties in the presence of a wide range of colors and effects ("metallic" and top varnishes different colors, structured surfaces(small and large structure, “leather effect”, “antique”, “moiré”), coatings varying degrees gloss (glossy, semi-gloss, semi-matte, matte).

Due to these advantages, the unit cost of painting a unit surface area of ​​a product with powder paint is lower than when using conventional paints, despite their higher cost. At the same time, the resulting coating has an increased complex of protective and decorative properties.

What are powder paints?

Powder paints are solid dispersed compositions, which include film-forming agents (resins), hardeners, fillers, pigments and targeted additives. Regardless of the composition, the finished powder composition is a free-flowing dispersed powder, which must have uniformity, physical and chemical stability and composition invariance during storage and use.

The quality of preparation of the composition largely determines the appearance and properties of coatings. PC manufacturing technology consists of several stages:

1) Dry mixing of components in a mixer. AT
the result is the so-called premix,
which is then sent to the extruder.

2) Extruding: mixing components into
melt. The output is a homogeneous material.
in the form of a tape, which is further crushed to obtain
so-called "chips" 0.5-1 cm in size.

3) "Chips" are loaded into the mill, where they are crushed
up to particle size, typically from 10 to 100 microns. At
the maximum share is the fraction with
particle size 40-50 microns.

The finished PC is applied to products made of steel, aluminum, non-ferrous metals, glass, ceramics, wood, plastics and silicate materials in an electrostatic field (electrostatics, tribostatics, in "fluidized bed" baths).

The greatest application was found by PC-based
thermoset film formers.

Initially, these were epoxy, polyester and acrylic PCs. Later, epoxy-polyester (or hybrid), as well as polyurethane and polyester, cured by triglycidyl isocyanurate (TGIC) were developed. Currently, the most common polyester, epoxy-polyester and epoxy powder materials.

The choice of one or another type of powder paint should be determined primarily by what properties the coating should have, its purpose and the conditions for its operation.

Epoxy powder paints

The main advantage of epoxy powder paints is the optimal combination of good physical, mechanical and electrical insulating properties. Coatings based on them are characterized by exceptionally high adhesion, mechanical strength and chemical resistance. They can be used when painting products from different metals without pre-priming the surface. In turn, they can be applied as a primer under liquid and powder paints and varnishes. If increased corrosion resistance is required when using epoxy powder coating, it is recommended to phosphate ferrous metals and galvanized steel, and chromate aluminum and its alloys.

Good resistance to alkalis and acids, aliphatic and aromatic hydrocarbons, oils, fuels, water allow the use of epoxy PC for outdoor and internal protection main pipelines. Using epoxies it is possible to obtain coatings up to 500 µm thick with equally good hardness, elasticity and impact resistance.

Traditional consumers of epoxy powders are electrical and radio engineering, where these coatings replace many types of complex electrical insulation. A significant disadvantage of epoxy coatings is their limited weather resistance (chalking in outdoor use) and the tendency to yellow due to overheating in the curing oven, especially if it is gas heated.

Epoxy polyester powder paints

If the powder coating does not have increased anti-corrosion requirements and / or does not require solvent resistance, epoxy powders are replaced by epoxy-polyester (a combination of epoxy and polyester resins is used), which are called hybrid powders.

When hybrid powders appeared, consumers were more attracted to low price, but subsequently the expansion of their marketing was due to technological advantages (for example, their coatings are resistant to overheating during curing), increased mechanical properties, chemical resistance, and reduced sensitivity to ultraviolet radiation (for compositions with a low content of epoxy components). The use of epoxy polyesters with different ratios of epoxy and polyester resins allows them to be widely used for finishing household items, metal, garden, office, medical and school furniture, sports equipment, commercial, lighting and electrical equipment, etc. Epoxy polyesters are in great demand due to the high decorative qualities of coatings based on them. Modern technology obtaining powder paints allowed not only to expand color scheme coatings, but also to achieve different coating textures. These are coatings such as “moiré”, “leather” coating, coatings with a fine and large structure, a series of “antiques”, metallics of various colors. A special position is occupied by the so-called top coats used to protect non-ferrous metals (bronze, copper, brass) and a thin layer of metal. vacuum deposition from oxidation, allowing to advantageously shade the surface, as well as varnish and filled compositions for glass (bottles for perfumes and cosmetics, etc.).

Polyester Powder Coatings

Polyester coatings are distinguished primarily by weather resistance, mechanical strength and increased abrasion resistance. In terms of weather resistance of coatings, polyester paints are superior to any other powder materials. Dielectric properties are close to those of epoxy coatings. They have high gloss and good adhesion to metals, including light alloys. However, the alkali resistance of polyester coatings is low.

Polyester PCs are divided into two types:

1) cured by triglycidyl isocyanurate (TGIC);

2) cured with a hydroxyl curing agent
PRIMID type.

Coatings based on TGIC are the most resistant to weathering and are used in architecture. However, there is rather conflicting information on toxicity. this component, which entails the use of an alternative based on PRIMID in cases where there is no need for particularly high weather resistance.

Purpose of polyester coatings: aluminum shaped profiles, architectural and building structures, wheel disks and machine parts, agricultural equipment, garden tools, etc. Polyester topcoats for coatings with high weather resistance and high gloss are used in multilayer technology(for example, when painting wheel rims) for the final finishing of the product.

Polyester PCs also include the so-called "polyurethanes", which are cured by blocked isocyanate and differ in a number of features. Polyurethane coatings are characterized by stable gloss, water and weather resistance, resistance to liquid fuel, mineral oils, solvents. They are used to protect products subjected to friction, abrasive wear, some types of chemical equipment and containers for storing liquid and gaseous chemicals. However, in Western Europe and Russia, such materials are not widely used.

Technological process of product painting powder material consists of the following stages:

Surface preparation: degreasing, removal of contaminants and oxides, if necessary and possible - transformation (conversion) of the surface to increase adhesion and protection against corrosion (phosphating, chromating); applying a layer of powder paint to the surface to be painted;

Coating film formation: reflow,
curing, cooling.

Polyester varnishes and primers unusual materials for painting. Materials with excellent consumer characteristics, but a short life time, requiring efficiency from the painter. Of course, about the application in living conditions there is no question, you will understand this from the description. The article will be useful for those who are a fan of the painting business.

Polyester paints, varnishes, primers usually consist of three components: base, catalyst and accelerator. When the components are combined as a result of a complex chemical reaction, a stable paint film is obtained.

Polyester paints, varnishes, primers have an originality that determines many of them performance characteristics, so it makes sense to briefly familiarize yourself with it.

Polyester paints, varnishes, primers are usually supplied as a solution of resins in a monomer (styrene), which does not evaporate during drying, but takes part in the copolymerization reaction. From here follow two technological features of PE (polyester) materials: high dry residue, reaching up to 96% and a limited shelf life - one year.

Features of the use of polyester paints and varnishes

Before use, a small amount (2%) of a catalyst is introduced into the working mixture - a substance that initiates the reaction, and an accelerator that activates the catalyst. As a result of the copolymerization of the polyester with the monomer, a branched spatial polymer is formed.

It is good to know that the addition of one accelerator (usually blue) does little to change the pot life of the mixture (i.e. it can be kept for many days). The addition of one catalyst to the material reduces the viability to ten hours.

A working mixture containing a "fast" catalyst and accelerator has a pot life of only 10-40 minutes, a "slow" catalyst and accelerator give a pot life of several hours.

An original feature of some PE materials (paraffin-containing) is also the fact that they contain a small amount (0.1-0.3%) of paraffins in their composition.

The fact is that in the presence of oxygen, free radicals, into which the initiator decomposes, react mainly with it, without causing a copolymerization reaction. The paraffins introduced into the composition float up, form a film on the surface that prevents the access of oxygen, and then only the polymerization of the paintwork material occurs.

The paraffin layer on the surface is then removed by grinding or polishing, which are mandatory components of the technology for imputing paraffin-containing PE materials.

Thinning polyester paints

Polyester paints, varnishes, primers are diluted with very fast thinners based on acetone, most of it evaporates during application, so that the applied layer is quite viscous and does not smudge. The rest of the acetone evaporates in 10-15 minutes. After sanding after a few hours, the shrinkage is very small.

Technological features of PE materials, resulting from the fact that the main thinner should not evaporate, are a large recommended amount of the applied layer - 200-250 g/m2. and a weak dependence of the drying time on the thickness of the wet layer.

Large thickness wet film and high dry residue allow you to get a very thick paint film in one application. These features, along with good physical and chemical resistance, determine the advantages of working with polyester coatings, especially in the case of glossy finishes.

Drying polyester primers before sanding

Drying of polyester primers for high gloss finishes usually takes much longer than the minimum drying time before sanding.

In order for the glossy finish not to deteriorate over time with “pockmarks” of subsidence, the applied primer must be kept for 1-2 days before grinding, and for a reference mirror gloss - a week.

Thick, rigid, perfectly even and smooth bases for mirror-gloss finishes are exactly what PE materials can best provide.

Preparation of a working mixture of polyester paints and varnishes

When preparing a working PE mixture, care must be taken. It is impossible to mix the catalyst and the accelerator in the same container, as they enter into a violent reaction with the release of heat, which is dangerous for personnel and premises.

In addition, the working mixture usually has a short pot life (10-40 minutes), and the shelf life of the materials themselves is also limited. Despite the low evaporation of thinners, some PE materials have sharper and bad smell than PU materials.

To improve the manufacturability of PE materials, "slow" catalysts and accelerators have been developed that increase the pot life up to several hours, however, the drying time of the material with such additives also increases.

In order to get around the difficulties associated with a short lifetime, sometimes special two-component pumps are used that mix the materials immediately before application, or spray guns with mixing the components in the torch.

Consumer properties of polyester paints and varnishes

Films of PE materials withstand temperature fluctuations from -40°C to 60°C, but have low weather resistance. PE materials do not cure well on resinous softwood, rosewood and some other oily woods.

The large thickness of PE primers results in a tendency to separate from the base under loads, which is especially unpleasant with a transparent finish. However, a finish containing a PE primer and a PU finish appears to be quite impact resistant. Additives have been developed that increase the elasticity of PE coatings.

PE materials are mainly used as primers (clear and white) for high gloss finishes. Sometimes glossy PE topcoats are also used to obtain a thick, high-gloss (“piano”) finish.

Tab. 3.

These results prove that hydrophobic fumed silica performs better than hydrophilic fumed silica or precipitated silica. The use of precipitated silica has had mixed results, but it can be said that it is not a panacea that fixes the problem.

Hydrophilic fumed silica is the most commonly used thixotrope with polyester resins and has also been shown to give mixed results. Hydrophobic fumed silica, which in this case is characterized by a special treatment of silicon, has consistently shown good results, regardless of the combination of fillers or pigments used.

Table 4 presents the results of changing the rheology of the jelly-like coating by simply diluting it with a solvent. The results obtained are clearly disappointing. For example, if you need to change the rheology to make the coating easier to spray, you cannot simply dilute it with a solvent, otherwise the risk of cracking the resin layer increases.

Effect of Thinner Addition on Resin Cracking Rate

Tab. 4.

The study identified the following additional points of interest: (1) the use of talc and silica consistently proved to be more effective in controlling flaking than the use of alumina; (2) the type of resin used for the jelly coating is important because the use of NPG ortho-resins in the coating formulation has consistently improved coating performance compared to coatings made using standard NPG isomeric resins; (3) Proper application of air-release agents and humectants is likely to have a positive effect on anti-peel resistance in all jelly coating formulations tested.

findings

Cracking is a mechanical phenomenon, so in order to solve the problem, it is necessary, first of all, to maximize the parameters of the coating technology and coating equipment used by the manufacturer. Fluid pressure or air pressure when spraying should be at a minimum level that allows the coating to be applied at a rate sufficient to meet the production plan. Nozzle selection can be helpful in lowering application pressure while maintaining the quality of the sprayed coating. The operator spraying the coating should use a fan-shaped spray pattern that provides a distance from the nozzle to the surface of the mold within 18-36 inches with a material thickness of 18 ± 2 roils applied. The material is applied in 2-3 passes with an interval between passes of the order of several seconds. Low temperature operation should be avoided and the coating formulation should not be diluted. The level of catalytication should correspond to the recommended one.

These measures minimize the three types of shear stresses mentioned in the previous section. Attentive attitude to the level of catalyzation, operating temperature and eliminating the use of thinners improves the rheology of the applied coating, providing easy spraying and gel time needed to reduce the likelihood of cracking. The coating solution should be thoroughly mixed before spraying to obtain an appropriate suspension of particles of the solid components of the solution and reduce the likelihood of cracking.

The jelly coater can assist the coater by supplying a coating solution with viscosity and thixotropy to allow spraying at reduced pressures without the addition of diluents and maintaining gel time with the desired level of catalysis. The coating manufacturer must also consider a coating formulation that provides the best combination pigments, fillers, resins and additives. It is proposed to use talc and silicon oxide as fillers in amounts that improve fluidity and ensure the removal of air bubbles from the jelly-like coating. Pigments should be triturated in a single binder solution that is compatible with the particular type of resin being used. When rubbed, the pigment particles must be completely wetted. The more homogeneous the mixture of pigments and resins, the less chance of flaking. Correct Application hydrophobic humidifiers and air release agents can greatly improve the balance between various components coatings and especially improve the wettability of pigments and fillers with resins. The greater the relationship between the main components, the less the likelihood of cracking.

A final consideration is the use of thixotropic agents, such as low molecular weight glycols, which, in combination with silica, provide sag resistance. To select a reagent that is less polar and provides a more stable system using resins, pigments and fillers, it may be necessary to conduct tests. The use of more polar reagents may, in some cases, worsen delamination.

A more careful approach to formulation of coatings and collaboration with coating users to improve application techniques will greatly help coating manufacturers to minimize and possibly eliminate the problem of cracking in the jelly coatings of their polyester resins.

The current situation and forecast of the development of the Russian market of polyester resins can be found in the report of the Academy of Industrial Market Studies

Literature

1. Stahlke, N.P., and Lester, M., Modern Plastics, Oktober 1979
2. Polyester Application Manual, Cook Paint and Varnish Company, 5th Edition, p.29, 1981
3. Gel-Kote Application Manual, Glidden Coatings and Resins Division of SCM Corp., p.31
4. Additives For Plastics, Byk-Mallinckrodt Air Release Agents In Polyester Composites, Technical Bulletin 401, p.5. 1980.