Polyester resin application. Features of the technology of production of polyester resins. Fields of application of polyester resins.
There are hardly any industries National economy wherever polyester resins are used. At the same time, industries are singled out in which the volume of their consumption is especially large. These include: shipbuilding, automotive and transport engineering, construction, chemical industry, electrical industry, furniture industry, consumer goods. In this case, as a rule, polyester resins are used in combination with glass fabrics that enhance their mechanical properties. Such materials are called - polyester fiberglass. Below is a detailed description of the application of polyester resins in these areas.
The positive shape is shown in the following figure for a vacuum formed body. The hot plastic is placed on the positive mold. The difference between positive and negative shapes may not seem significant, since the shapes of the parts are almost identical, as shown in the diagrams. However, if the part is embedded in a negative shape, then outer surface will have an exact contour of the mold cavity. The inner surface will have an approximation of the contour and finish corresponding to the surface of the sheet or the original sheet.
Construction
Polyester resins are widely used in construction. The domestic industry produces sheets of polyester fiberglass based on PN-1 resin reinforced with fiberglass. Such plastics have high mechanical properties, low weight, transparency and high aesthetic qualities and are used in the manufacture of street lamps, roofs of public and industrial buildings, pavilions, sheds, wall panels and partitions, incl. decorative, used for interior decoration. Also, polyester fiberglass is used for the manufacture of window sills, canopies, cornices, stair railings, gutters, monolithic bathrooms, showers, ventilation ducts.
On the contrary, if the sheet covers the positive form, then the inner surface will be identical inner surface convex shape, and the outer surface will follow it approximately. Depending on the requirements of the product, this distinction can be important. Another difference is the thinning of the plastic sheet, which is a thermoforming problem that must be taken into account. If the shape outline is shallow, there will be significant differences if the sheet is stretched to form within the shape outline.
Positive and negative forms produce different thinnings in the same part. For example, consider a bath. In the positive form, by placing the sheet on the convex form, the part in contact with the upper surface hardens quickly and hardly stretches. This results in a thick base but significant thinning on the tub walls. In contrast, a negative shape will give a more even distribution of stretch and thinning of the sheet before it comes into contact with the cold surface of the mold.
Sheet decorative polyester plastics are easily painted in any color.
Shipbuilding
Shipbuilding and shipyards are the largest consumers of polyester resins. The hulls of various ships: motor ships, yachts, boats, boats, catamarans, as well as their other elements: portholes, propellers, ship furniture are made on the basis of polyester resins and fiberglass. Polyester resin coatings are also often used to protect the skins of wooden boats, making them resistant to rot and woodworms. Often polyester resins are also used for decorative finishes courts.
One way to improve the dilution distribution in the positive form is to pre-stretch the sheet to cover the convex form. As shown in the picture below, hot plastic sheet evenly stretched under vacuum to a spherical shape before being placed on the mold.
The step described in the first frame of the next can be used as a method for making balloon-shaped parts such as transparent domes or skylights. At the same time, tightly controlled air pressure is used to purge the soft sheet. The pressure is maintained until the blow mold hardens.
In shipbuilding, resins PN-1, PN-609-21M, NPS-9119 and imported brands are most widely used.
Automotive and car building
Polyester resins are now increasingly used in the automotive industry for the manufacture of bodies, bumpers, fenders, sills, tuning elements, fairings, doors, interior decoration salon. There are automotive polyester enamels, fillers and sealants.
It is similar to direct vacuum forming, except once the plastic is placed in the structure and heated, it is mechanically stretched onto the male mold. A vacuum is then applied which presses the hot plastic onto all parts of the mold. Male objects with a depth to diameter ratio of up to 4 can be formed: male forms can be easily obtained and generally cost less than female forms, although they are also more prone to deterioration.
Supplied grades of polyester resins
In this method, a heated sheet is fixed and formed between two dies. The material of the stamps can be wood, gypsum, epoxy resin and other materials. Precise parts can be quickly produced to close tolerances in expensive water-cooled moulds.
Polyester resins are used to make walls, floors, doors, roofs, bus and rail car seats, and even entire passenger and freight cars.
Aviation
Light aircraft and gliders can be made entirely of polyester fiberglass. Thanks to their use, a reduction in the weight of aircraft is achieved, which makes it possible to increase the payload and flight range.
For bending, drawing or clamping a hot plate, only mechanical force. Plain wood chip insoles can be used to achieve the desired shape using ovens, band heaters and heat guns as heat sources. You can mechanically form pipes, rods and other profiles.
In thermoforming, the deformation of a flat sheet to a bubble requires the application of work on a softened, but not molten material; Therefore, the thermoforming of amorphous materials is always much easier, since they have a much longer reservoir elastomeric than crystalline ones. Even in these cases, it is advisable to use high molecular weight grades that maintain a certain stiffness and tensile strength above the crystalline melting point; This is called melt strength.
Chemical industry
Polyester resins are widely used in the chemical industry due to their high resistance to aggressive media. In the shops of chemical industries, they are used for the manufacture of floors. Polyesters are used to manufacture pipes for pumping oil and gas, various liquid chemical products, chemical instruments and apparatus, vessels, containers, bunkers and tanks for storing acids, alkalis, salts, oxidizing agents, organic substances, tanning solutions, pickling and galvanic baths. In addition to the use of polyester resins in pure form often other polyester-based coated materials are used for this purpose. On the basis of resins PN-1, PN-609-21M, oxidizer-resistant and acid-resistant putties are made. Floors in chemical plants are often made from polyester resins.
During the expansion of the bubble, the orientation of the growing macromolecules and crystalline ones occurs, which gives the stretched materials better mechanical characteristics. When the original sheet maintains a certain orientation because it is made in a unidirectional pattern, it must be heated to a sufficient high temperature to lose the anisotropy of its mechanical properties.
Greater thickness uniformity is obtained by rapidly expanding a sheet of preheated material to a suitable temperature before the bubble hits the mold walls, whether male or female. For this reason, the purge and alternatively the vacuum application must be carried out with a strong air flow which justifies the need for high-capacity tanks.
Electrical industry
Compounds, varnishes and topcoats based on unsaturated polyester resins are widely used as electrical insulation for transformers, choke coils, motor windings, generators, cables, electronic boards, start-regulating devices, elements of power lines. On the basis of polyester resins, support insulators for pantographs of electric locomotives, brackets and fingers for brush holders of traction motors, seals for stator windings of large turbogenerators are also produced.
However, rapid expansion followed by too rapid cooling causes residual stresses due to material memory. Again, these stresses produce anomalous deformations when the material is heated. The macromolecules of the amorphous matrix were expanded and tended to elastically recover their equilibrium state in the form of a ball. These residual stresses show up in the polystyrene cups of coffee machines that withstand hot liquids, but if they are used to boil water, they shrink, especially in the region of the cup edges where the residual stresses are higher.
Polyester adhesive varnishes are used for the manufacture of electrical insulating materials based on mica.
mechanical engineering
Polyester fiberglass is used for the manufacture of bodies of various machines, casings, protective fences, ventilation pipes, containers, tanks, pipelines, fans, pumps, molds. Putties based on PN-1 resin are used to eliminate defects in steel castings. Polyester compositions based on PN-1 resin are used for bonding various designs from materials such as aluminum, steel, glass, porcelain, plastic, and are also used as fluxes for soldering.
In crystalline materials, cooling must be slow enough to reach an equilibrium degree of crystallinity and avoid compression problems caused by post-crystallization phenomena, which are more pronounced the higher the operating temperature. Thus, the molds must be stored in a hardened state at a well controlled temperature.
Where can polyester resins be used?
Briefly, the two main operating variables are sheet temperature and mold temperature. The higher the first, the more uniform the thickness will be and the smaller the elastic contractions; But there is a danger that the material will be stripped due to lack of fluid resistance and that it will be thermally degraded. The following table lists the materials that are processed by this technology with their melt characteristics, stability and the most suitable sheet temperature range.
Furniture manufacture
Unsaturated polyester resins are widely used as varnishes for furniture finishing. Such varnishes are distinguished by a high content of film-forming substances, as a result of which they can be applied in one or two layers. In addition to furniture varnishes, enamels are also produced, as well as putties to make surfaces smooth. particle boards and plywood. Polyester coatings have a strong adhesion to the surface with wood, have gloss and transparency, water resistance, resistance to alcohols, fats, oils and low temperatures. Recently, the volume of consumption of polyester fiberglass in the production of plastic furniture has been growing. They are made from them country chairs, chairs, tables, benches, etc.
The higher the temperature of the mold, the less shrinkage will be caused by the post-crystallization effect and aging of the amorphous matrix, but the typical performance of the machine will decrease. An Introduction to the Science and Modernity of Materials, Volume Plastic Industry: Industrial Plastics. Shaping processes for plastics. . polyester resin most commonly used for fiber.
Usually the resin is already activated with cobalt, so the only thing we have to purchase next to the resin will be a catalyst or a dryer. The catalyst will be the one that performs the chemical reaction to start setting up and drying the resin. The amount of catalyst will depend on the work that the person who applies it has to do, since each of them uses it in accordance with the way we work. The average measure says it should be between 2 ml and 5 ml per kilogram of resin, although in some cases we can use up to 10 ml per kilogram of resin or more.
Household goods and sporting goods.
Polyester resins are widely used for the manufacture of jewelry and haberdashery, incl. buttons (colorless, transparent and mother-of-pearl), trays, lampshades, household items, children's toys, as well as a variety of sports equipment and inventory: racing cars, sports boats, motorcycles and scooters, swimming pools, boards sports grounds, rollers, modern plastic skis, skateboards, bows, fishing rods, safety helmets, etc.
The greater the amount of catalyst, the stronger will be chemical reaction, so that the temperature of the resin increases even to the level until it catches fire, so we must work with great care. It is also necessary to comment that large quantity the resin will be stronger than the reaction, so the piece will dry faster, but will have less elasticity and may crack more easily. Less quantity: dry more slowly, but the piece will be stronger. The shaking mixture must also be taken into account, it should be a flat and clean stick and never a round one, because when using a small amount of catalyst, the round stick moves the catalyst around the edges and the mixture will not be complete.
Art
Due to their high decorative qualities, polyester resins are widely used in various types of art: painting, architecture, sculpture, interior decoration in the manufacture of panels, bas-reliefs, decorative tiles etc. Polyester resins in the manufacture of products are often successfully used to imitate various materials: natural stone, metals (bronze, etc.), gypsum.
Obtaining poor drying or drying in detail. Be very careful with the catalyst as it can cause skin burns. such as irritation of the nostrils or eyes. Now we will talk about fibers or fabrics. Suppose it is a polyester resin, but the white finish, like the resin catalyst and air-dried, can be used to work in the construction of parts, but due to its cost, it is only used as a finishing paint.
Polyester and fiber putties: 2-component putties that we will use to fill and coat small flaws, which we will have when working with fiber. Styrene is the main resin thinner, although the thinner is not recommended to omit the resin, if it is not used to give a primer, it will lose most their properties.
The differences of which we will consider in this article belong to the class of thermosetting. This means that after the curing process, they can no longer be returned to liquid state. Both compounds have different characteristics, which determines the scope of their application. To understand the purpose of these materials, it is useful to read the overview of polyester and epoxy resins.
Acetone: This is the ideal cleaning solvent. metal hands and utensils, brushes and brushes that are not recommended to be cleaned as we will spend more in acetone than a new brush costs. Liquid Paraffin: This product is mixed in small proportions with resin, we will get resin when sanding is not so difficult and stick to the sandpaper.
Damping wax: This is a wax for shaping fiber pieces, it is recommended to ensure that it is properly shaped so that there are no problems when gluing. Alcohol release: Like wax, we will use it as a press release, being liquid, we can access more complex sites, the most a big problem is that you need to give multiple layers to get good result.
Epoxy resin
Epoxy refers to materials of synthetic origin. In its pure form, it is unsuitable for use, since it is not able to go into a solid state on its own. For curing, a special hardener is added to the epoxy resin in the right proportion.
For correct use need to know the pros and cons of epoxy resin. Resin of this type valued for its durability. It is resistant to aggressive chemicals such as acids and alkalis. The advantages of epoxy include: moderate shrinkage, high wear resistance, and excellent strength. The solidification process occurs over a wide range of temperatures, but the recommended range in everyday life is from +18 to +25 degrees. hot method hardening is used in the production of high-strength products that can withstand extreme loads.
Titanium Dioxide: Titanium dioxide will serve to bleach the resin and obtain best result, while it can serve as a base for resin coloring. With universal dyes. Polyurethane Saddle: Polyurethane silicas are ideal for sticking pieces together in their intended places as well as filling their joints.
Before using resins and fibers, it must be taken into account that we will be using very toxic materials, so we must work in well-ventilated areas protected by masks, especially when sanding and gloves. One of the first things to keep in mind is that all the materials we are going to use are clean and do not have any residue of any product, especially water or moisture. Brushes must be new best use, always have all the material at hand and very well identified so as not to make a mistake, when preparing the resin, always prepare the material that we are going to spend or something and never exceed, since we will have about thirty minutes to work comfortably and then we have to quit.
This type of resin is used both in industry and at home. The scope of their use is becoming wider due to the creation of new compositions with optimized properties. Through mixing different types epoxy resins and hardeners, you can get a final product with completely different characteristics.
Epoxy Resin Application
Epoxy type resin is primarily used as a material for bonding surfaces: wood, leather, metal and other non-porous. Such a composition is in demand in electronics, mechanical engineering and aviation. Fiberglass, which is actively used in construction, is also made from epoxy. The resin is used for waterproofing floors and walls, including external ones. Finished products made of fiberglass after grinding and additional processing are popular in decorating interiors.
Epoxy hardener
Epoxy material consists of two components, after mixing of which the polymerization process begins. The component that causes the epoxy to cure is called the hardener. Depending on the use of various resins and hardeners, completely different results can be obtained. epoxy mixtures.
The proportion of the hardener in the composition may be different and depends mainly on the brand of resin. The polymerization reaction of epoxy resin is irreversible, that is, it is not possible to melt an already solidified material.
It is a mistake to believe that by overestimating the amount of hardener, hardening will be faster. Effective way acceleration of the process - an increase in the temperature of the mixture. Raise operating temperature by 10 degrees allows you to speed up the process by 3 times. For these purposes, special components are commercially available. There are also epoxy mixtures that harden at low temperatures.
Incorrect selection of the amount of hardener adversely affects the quality of the finished product. First of all, its strength and resistance to chemicals. With a small amount of hardener, the consistency of the part becomes sticky, with an excess, the polymer is released on the surface of the material. The most common resin/hardener ratios are 1/2 or 1/1. Before mixing, it is recommended to read the instructions for the correct ratio of components.
polyester resin
Such a resin is formed during the processing of alcohols special purpose. The basis of the material is polyester. To speed up the hardening process, specialized solvents and inhibitors are used. Depending on the scope of the material, it may have a different structure and properties. The resulting product needs additional processing aimed at improving protection against water and ultraviolet radiation. An additional coating also enhances the strength characteristics of the product. Polyester resin, unlike epoxy, is characterized by low mechanical properties. But at the same time, polyester is distinguished low price, due to which the material is more popular.
Such resins are actively used in the construction of buildings, in the automotive industry, shipbuilding and the production of containers for chemical compositions. Polyester components, when mixed with glass, form high-strength compounds. Thanks to this, the resulting material is used in the manufacture of canopies, roofs for buildings and lighting fixtures.
Polyester resin is also included artificial stone. The plastic produced using this component is used in the production of window sills, shower cabins, partitions and decorative elements. Polyester resins, unlike epoxy resins, are easy to color.
The main advantages of polyester resin
Polyester resin, unlike epoxy, is more practical. After mixing with glass, the composition acquires strength characteristics that exceed those of steel. Polyester hardening does not require special conditions and temperatures. Work with it is considered less laborious, and the material itself is cheaper.
What is the difference?
When asking the question: "Which is better, polyester or epoxy?", you need to understand why and where the resin is needed. Both materials have their pros and cons, and the final choice depends on the conditions of use, as well as the type of surface to which the resin will be applied.
Epoxy has more high cost, but at the same time it is more durable. Possessing excellent adhesive properties, it firmly connects surfaces of various structures. Epoxy resin differs from the polyester product in slight shrinkage, better mechanical characteristics as well as wear resistance.
At the same time, unlike polyester, epoxy needs more time to harden, which slows down the process of manufacturing parts from this material. Working with such resin is accompanied by increased safety measures: when working with liquid material gloves are required, a respirator is needed to process a solid product. The danger is not so much the resin itself, but the components used to give it a solid state. When hardening at high temperature, there is a chance to lose the viscosity of the material, which creates additional difficulties in work.
Which resin is better, epoxy or polyester? Reviews indicate that in most cases the first is used in the form of glue, since its properties are much higher than those of a polyester-based material. In other situations, it seems more rational to use polyester resin, which, firstly, will save money, and secondly, will simplify the work.
Benefits of using polyester
Polyester does not emit toxic elements, is easy to use, and special knowledge is not required to work with it. The composition is used to cover various surfaces followed by treatment with a strength-enhancing agent. In terms of adhesive properties, polyester is significantly inferior to epoxy, and it is irrational to use it for gluing surfaces. as material for decorative items not suitable, as it has low mechanical performance. When mixing the polyester composition, it is used a small amount of catalyst. The material hardens quickly, within 2-3 hours.
The finished part has elasticity and resistance to bending. The downside of polyester resin products is flammability. Do not apply polyester resin to an item made from epoxy. To repair an epoxy product, it is better to use it.
How to properly prepare the surface
Resin should only be applied to previously prepared surfaces. The first step is degreasing with a solvent. After removing dirt and traces of fat, the grinding process is carried out. From the surface of the material with sandpaper or a special tool is removed upper layer. Then the dust removal process is carried out. After that, you can start applying the working component.
Safety
In order not to cause harm to health when working with resins and hardeners, it is necessary to take all precautions to the maximum. non-compliance simple rules may cause skin injury, burns or lung damage when handling epoxy or polyester resins. Safety features when working with chemicals:
- Do not use containers intended for cooking.
- All manipulations must be carried out in special clothing and gloves. Before carrying out work on the hands should be applied with a protective cream. grinding finished products carried out in a respirator and special glasses.
- If resin comes into contact with the skin, it must be washed immediately with soap or alcohol.
Epoxy components should be handled in a well ventilated area.