Production, properties and procedure for working with polyester resins. Unsaturated polyester resins in shipbuilding

The differences of which we will consider in this article belong to the class of thermosetting. This means that after the solidification process, they can no longer be returned to the liquid state. Both compositions 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.

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 proper use, you need to know the pros and cons of epoxy. Resin of this type is valued for its strength characteristics. 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 temperature range, but the recommended range in everyday life is from +18 to +25 degrees. The hot hardening method is used in the production of high-strength products that can withstand extreme loads.

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 different resins and hardeners, completely different epoxy mixtures can be obtained.

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. An effective way to speed up the process is to increase the temperature of the mixture. Increasing the 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 are reduced. 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 special purpose alcohols. 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 increasing protection against water and ultraviolet radiation. The 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 by a 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 process 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 part of the 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 a higher cost, but it is more durable. Possessing excellent adhesive properties, it firmly connects surfaces of various structures. Epoxy resin differs from the polyester product in low shrinkage, better mechanical characteristics, and 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 a resin is accompanied by increased safety measures: when working with a liquid material, gloves are required, and 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 cured under conditions 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 a material for decorative products, it is not suitable, as it has low mechanical properties. When mixing the composition of polyester, a small amount of catalyst is used. 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. The top layer is removed from the surface of the material using sandpaper or a special tool. 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. Failure to follow simple rules can result in skin damage, burns or lung problems when working with 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 of finished products is carried out in a respirator and special glasses.
• If the 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.

Polyester resins have found wide application in absolutely all areas of production, both serial and industrial, as well as single, handicraft. Private craftsmen use this polymeric material in their exclusive products; in factory production, such high-quality quick-drying compositions are also indispensable. Unsaturated varieties of polyesters have special properties.

Benefits of using

Unsaturated resins offer several important benefits:

• high reaction rate;
• ease of operation;
• safety for those who work with them.

Hardening does not require additional conditions. Even room temperature is enough. At the same time, the material does not emit any substances into the air and is environmentally friendly. The finished product is more durable, it is not afraid of direct sunlight. Working with this type of resin is not at all difficult, it is plastic and hardens quite quickly, so it becomes possible to work with small elements and large products with complex shapes. You can buy high-quality material of this type, for example, on the page http://www.polypark.ru/catalog/polyester-resins.

Scope of application

The use of unsaturated polyesters is virtually unlimited. Initially, they were used in reinforcement for shipbuilding, but then they became a favorite material for manufacturers of various electronics, and gradually penetrated into the sports environment, into decorating art.

Unsaturated resin can be an excellent base for artificial stone surfaces and products. After mixing with a filler of natural origin, it is poured into a special mold, where it solidifies, turning into a monolith. Having passed the grinding stage, such a workpiece turns into a perfectly smooth and incredibly beautiful countertop, sink, tile, and so on. Unlike other compounds, unsaturated resin gives the product maximum strength, durability and value for money. Polymer concrete has similar properties. Thanks to the combination of two structures, it receives unique characteristics of thermal conductivity, waterproofing. If ordinary concrete blocks quickly absorb moisture and because of this collapse when freezing, then the addition of an unsaturated type of resin solves this problem completely.

Resins of this type are also resistant to most negative external influences. That is why they are actively used in the creation of sports and tourist equipment, in the production of modern plumbing. Unsaturated polyesters do not deteriorate under the influence of chemical compounds, they do not burn out, are not afraid of extreme overheating, do not crack during sudden cooling, and do not deform even after prolonged use in adverse conditions. That is why the best surfboards and skiing boards contain resins, as well as elite bathtubs, high-quality shower trays, original and durable sinks.

Unsaturated polyester resins used in reinforced plastics are products of the interaction of reactive polymers and monomers. This combination was proposed by C. Ellis in the 1930s, who discovered that unsaturated polyester resins obtained by reacting glycols with maleic anhydride cured into an insoluble solid material when a peroxide initiator was added. Ellis patented this discovery in 1936.

Ellis later discovered that more valuable products could be obtained by reacting an unsaturated polyester alkyd resin with monomers such as vinyl acetate or styrene. The introduction of monomers significantly reduces the viscosity of the resin, which makes it easier to add initiator to the system and allows the curing process to be more vigorous and complete. In this case, the polymerization of the mixture is faster than each component separately. The right to this process was claimed in 1937; it was patented in 1941. The new materials met certain industrial needs. Now, more than 40 years later, the annual unsaturated polyester resin in the US has reached ~0.5 Mt.

Unsaturated polyester resins have a variety of properties. At room temperature, liquid resins are stable for many months and even years, but with the addition of a peroxide initiator, they solidify in a few minutes. Curing occurs as a result of an addition reaction and the transformation of double bonds into simple ones; it does not form any by-products. Styrene is most commonly used as the addition monomer. It interacts with the reactive double bonds of polymer chains, crosslinking them into a strong three-dimensional structure. The curing reaction takes place with the release of heat, which in turn contributes to a more complete process. It has been found that usually about 90% of the double bonds present in the polymer enter into the reaction during the curing of the resin. 28

Polyester resins are used in a wide range of products including boats, building panels, automotive and aircraft parts, fishing rods and golf clubs. Approximately 80% of the polyester resins produced in the USA are used with reinforcing fillers, mainly fiberglass. Non-reinforced polyester resins are used in the production of buttons, furniture, artificial marble and body putty.

Unlike most other plastics, which are made from a single ingredient, the polyester resins used in AP; contain several components (resin, initiator, filler and activator). Both the chemical nature and the ratio of these components can vary, which makes it possible to obtain a large number of different types of polyester resins. When creating any polyester resin, they try to give it the properties necessary for a particular application.

Maleic anhydride is used as a source of reactive double bonds for a large number of unsaturated polyester resins. When it interacts with glycols (usually propylene glycol is used), linear polyester chains with a molecular weight of -1000 ... 3000 are formed. Despite the lower cost of ethylene glycol compared to the cost of propylene glycol, the former is used only to obtain several special resins. This is due to the poor compatibility of ethylene glycol-based polyesters with styrene. In the process of esterification, the cis-configuration of maleic anhydride passes into the fumaric transstructure. This is useful due to the greater reactivity of the double bonds of the fumaric fragment in the reaction with styrene. Thus, a high degree of trans isomerization is an important factor in the production of reactive polyester resins. Despite the high degree of maleic anhydride isomerization, which reaches more than 90%, more expensive fumaric acid is used to obtain polyester resins with increased reactivity.

Other diaxial acids or anhydrides, such as adipic and isophthalic acids or phthalic anhydride, are often added to the base reagent to measure the final properties of the resin and control the number of double bonds. A typical polyester resin structure is shown below (where ^ is the alkyl or aryl group of the modifying dibasic acid or anhydride):

O O CH3 O O CH3 I

H [O-C-R-C-O-CH-CH2-O-C-CH=CH-C-O-CH-CH2 Jn he.

Due to the variety of properties and low cost, polyester resins are widely used for various products. However, processors lack knowledge of polyester resin chemistry and require ongoing technical assistance. Resin suppliers provide consumers with complete information on resin types, manufacturing techniques, prices and properties. Initiator suppliers also provide advice on the use of their products in combination with various activators and inhibitors.

The rapid development of research and application of wound materials has led to the creation of a large number of specifications and standards for their testing methods. The following ASTM standards are of interest: ASTM D2290-76. Determining the limit...

A number of tests should be carried out at elevated temperatures. It depends on the type of composite material and its area of ​​application. Conventional composites should not lose strength and modulus after half an hour exposure at a temperature of ...

Index Initial values ​​After holding at a depth of 1737 m for 1045 days Index Initial values ​​After holding at a depth of 1737 m for 1045 days А0Ж(MPa £ssh, GPa …

In recent years, polyester resins have gained great popularity. First of all, they are in demand as leading components during the production of fiberglass, strong and lightweight.

Resin making: the first stage

Where does the production of polyester resins begin? This process begins with the distillation of oil - during this, various substances are released: benzene, ethylene and propylene. They are necessary for the production of antihydrides, polybasic acids, glycols. After cooking together, all these components create the so-called base resin, which at a certain stage must be diluted with styrene. The last substance, for example, can be 50% of the finished product. As part of this stage, the sale of ready-made resin is also allowed, but the production stage is not yet completed: one should not forget about saturation with various additives. It is thanks to these components that the finished resin acquires its unique properties.

The composition of the mixture can be changed by the manufacturer - a lot depends on where exactly the polyester resin will be used. Specialists select the most optimal combinations, the result of such work will be substances with completely different properties.

Resin production: second stage

It is important that the finished mixture is solid - they usually wait until the polymerization process reaches the end. If it is interrupted, and the material is on sale, it is only partially polymerized. If nothing is done with it, the polymerization will continue, the substance will definitely harden. For these reasons, the shelf life of the resin is very limited: the older the material, the worse its final properties. Polymerization can also be slowed down - refrigerators are used for this, hardening does not occur there.

In order for the production stage to be completed and obtained, two important substances must also be added to the resin: a catalyst and an activator. Each of them performs its own function: heat generation begins in the mixture, which contributes to the polymerization process. That is, a heat source from the outside is not required - everything happens without it.

The course of the polymerization process is regulated - the proportions of the components are controlled. Since contact between the catalyst and the activator can result in an explosive mixture, the latter is usually added to the resin exclusively as part of the production, the catalyst is added before use, it is usually supplied separately. Only when the polymerization process is completely completed, the substance hardens, it can be concluded that the production of polyester resins is completed.

Initial resins

What is this material in its original state? It is a honey-like, viscous liquid that can range in color from dark brown to light yellow. When a certain amount of hardeners is introduced, the polyester resin first thickens slightly, then acquires a gelatinous state. A little later, the consistency resembles rubber, then the substance hardens (becomes infusible, insoluble).

This process is called curing, since it takes several hours at ordinary temperature. When the resin is in its solid state, it resembles a hard, durable material that can be easily dyed in a wide variety of colors. As a rule, it is used in combination with glass fabrics (polyester fiberglass), it acts as a structural element for the manufacture of various products - such is polyester resin. Instructions when working with such mixtures are very important. It is necessary to comply with each of its points.

Main advantages

Polyester resins in the cured state are excellent structural materials. They are characterized by hardness, high strength, excellent dielectric properties, wear resistance, and chemical resistance. Do not forget that in the process of operation products made of polyester resin are safe from an environmental point of view. Certain mechanical qualities of mixtures that are used in conjunction with glass fabrics resemble parameters in their performance (in some cases they even exceed them). The manufacturing technology is cheap, simple, safe, since the substance cures at ordinary room temperature, even the application of pressure is not required. There is no emission of volatile or other by-products, only slight shrinkage is observed. Thus, in order to manufacture a product, expensive bulky installations are not needed, and there is no need for thermal energy, thanks to which enterprises quickly master both large-capacity and small-capacity production. Do not forget about the low cost of polyester resins - this figure is two times lower than that of epoxy counterparts.

Production growth

It is impossible to ignore the fact that at the moment the production of unsaturated polyester resin is gaining momentum every year - this applies not only to our country, but also to general foreign trends. If you believe the opinion of experts, this situation will certainly continue in the foreseeable future.

Disadvantages of resins

Of course, polyester resins also have some disadvantages, like any other materials. For example, styrene is used as a solvent during production. It is flammable and highly toxic. At the moment, such brands have already been created that do not have styrene in their composition. Another obvious drawback: flammability. Unmodified, unsaturated polyester resins burn just like hardwoods. This problem is solved: powder fillers are introduced into the composition of the substance (low molecular weight organic compounds containing fluorine and chlorine, antimony trioxide), sometimes chemical modification is used - tetrachlorophthalic acid, chlorendic acid, some multimers are introduced: vinyl chloroacetate, chlorostyrene, other compounds that contain chlorine.

Resin composition

If we consider the composition of unsaturated polyester resins, here we can note a multicomponent mixture of chemical elements of different nature - each of them performs certain tasks. The main components are polyester resins, they perform different functions. For example, polyester is the main component. It is the product of a polycondensation reaction that reacts with anhydrides or polybasic acids.

If we talk about polyhydric alcohols, then diethylene glycol, ethylene glycol, glycerin, propylene glycol, dipropylene glycol are in demand here. As anhydrides, adipic, phthalic and maleic anhydrides are used. The casting of polyester resin would hardly be possible if the polyester had a low molecular weight (about 2000) when ready for processing. In the process of molding products, it turns into a polymer with a three-dimensional network structure, mass (after curing initiators are introduced). It is this structure that provides chemical resistance, high strength of the material.

Solvent-monomer

Another essential component is the solvent monomer. In this case, the solvent performs a dual function. In the first case, it is required in order to reduce the viscosity of the resin to the level required for processing (because the polyester itself is too thick).

On the other hand, the monomer takes an active part in the process of copolymerization with polyester, due to which the optimal polymerization rate and a high depth of material cure are ensured (if we consider polyesters separately, their curing is rather slow). Hydroperoxide is the very component that is required to convert to a solid state from a liquid - this is the only way polyester resin acquires all its qualities. The use of a catalyst is also mandatory when working with unsaturated polyester resins.

Accelerator

This ingredient can be introduced into the composition of polyesters both during manufacture and when processing takes place (before the addition of the initiator). Cobalt salts (cobalt octoate, naphthenate) can be called the most optimal accelerators for polymer curing. Polymerization must not only be accelerated, but also activated, although in some cases it is slowed down. The secret is that if you do not use accelerators and initiators, they will form independently in the finished substance, due to which polymerization will occur prematurely - right during storage. To prevent such a phenomenon, one cannot do without a curing retarder (inhibitor).

The principle of the inhibitor

The mechanism of action of this component is as follows: it interacts with free radicals that periodically arise, resulting in the formation of low-active radicals or compounds that do not have a radical nature at all. The function of inhibitors is usually performed by such substances: quinones, tricresol, phenone, some of the organic acids. Inhibitors are introduced into the composition of polyesters in small quantities during manufacture.

Other additives

The components described above are the main ones, it is thanks to them that it is possible to work with polyester resin as a binder. However, as practice shows, in the process of forming products, a fairly large number of additives are introduced into polyesters, which, in turn, have a variety of functions and modify the properties of the original substance. Among these components, powder fillers can be noted - they are introduced specifically to reduce shrinkage, reduce the cost of the material, and increase fire resistance. It should also be noted glass fabrics (reinforcing fillers), the use of which is due to an increase in mechanical properties. There are other additives: stabilizers, plasticizers, dyes, etc.

Glass mats

Both in thickness and in structure, fiberglass can be different. Glass mats are fiberglass that are chopped into small pieces, their length varies between 12-50 mm. The elements are glued together using another temporary binder, which is usually a powder or emulsion. Epoxy polyester resin is used for the manufacture of glass mats, which consist of fibers arranged randomly, while fiberglass in its appearance resembles an ordinary fabric. To achieve the maximum possible strengthening, different grades of fiberglass should be used.

In general, glass mats have less strength, but they are much easier to process. When compared with fiberglass, this material better repeats the shape of the matrix. Since the fibers are quite short, have a chaotic orientation, the mat can hardly boast of great strength. However, it can be very easily impregnated with resin, since it is soft, while being loose and thick, somewhat reminiscent of a sponge. The material is really soft and moldable. Laminate, for example, which is made from such mats, has excellent mechanical properties, has a high resistance to atmospheric conditions (even within a long period).

Where are glass mats used?

The mat finds its application in the field of contact molding, in order to be able to produce goods with complex shapes. Products made from this material are used in a variety of areas:

• in the field of the shipbuilding industry (construction of canoes, boats, yachts, fish cutters, various internal structures, etc.);
• glass mat and polyester resin are used in the automotive industry (various machine parts, cylinders, vans, diffusers, tanks, information panels, housings, etc.);
• in the construction industry (certain elements of wooden products, the construction of bus stops, dividing walls, etc.).

Glass mats have different density, as well as thickness. The material is divided by the weight of one square meter, which is measured in grams. There is a fairly thin material, almost airy (glass veil), there is also a thick one, almost like a blanket (they are used in order for the product to acquire the desired thickness, to obtain the required strength).

Epichlorohydrin is filled into a stainless steel reactor using twisted steam and a stirrer and heated to 40-50°C.

Which is better to use polyester resin or epoxy resin

The mixing procedure with diferylolpropane is gradually introduced. After dissipation of diphenylolpropane and a homogeneous solution in a thin stream from the added solution of the measuring vessel with sodium hydroxide and at 60-70 ° C, a condensation process is carried out for 1.5-2 hours.

All this time she has to mix things up. After that, the heating of the device is turned off, water is filled during mixing.

After stopping stirring, the resulting resin can be leveled.

Layer separation is faster at 40-50°C. The cured aqueous layer (top) is separated and the remaining resin is washed with warm water at 40-50°C. The amount of water is determined by volume (usually two, three times).

Washing (mixing, leveling, separation of the aqueous layer) continues until the complete removal of the salt removed from the reaction.

Washing is controlled by decomposition (washing water) for the presence of chlorine and alkali.

Dry the resin in one device. To do this, the resin is heated to 40-50 ° C, the refrigerator is directly connected (with vacuum) and dried until the condensation of water in the refrigerator stops and the resin foams.

The resin is dried without vacuum at atmospheric pressure and at a temperature of about 120 °C.

The resin is dried to a clear resin sample at 20-25°C. The final resin is discharged into aluminum containers.

Depending on the molar ratio of the initial components, the final products can be liquid, viscous and solid.

Due to the fact that the washing liquid (low molecular weight) resin is much easier to produce than the viscosity (high molecular weight) is first obtained with a weight of low molecular weight resin, which is then poured with the required amount calculated by propane difenilol, and thus obtains the required high molecular weight resins.

Characteristics of epoxy resins

Epoxy resins are liquid, viscous or solid transparent thermoplastic products from light to dark brown.

They easily dissolve in aromatic solvents, ethers, acetone, but do not form a film, because they are not cured in a thin layer (the film remains thermoplastic).

Epoxy resins are in the structure of polyethers having epoxy groups at the ends that are highly reactive (Fig.

When compounds containing a mobile hydrogen atom act on epoxy resins, they are able to dry to form three-dimensional insoluble and insoluble products with high physical and technical properties.

Thus, thermosetting is not only epoxy resin, but its mixtures with hardeners and catalysts.

Since epoxy resins claimed various substances: diamines (hexamethylenediamine, metaphenylenediamine, polyethylenepolyamine), carboxylic acids or their anhydrides (maleic, phthalic).

The composition of epoxy resins

Epoxy resins mixed with cured hardeners form thermoset compositions having valuable properties:

• high adhesion to the surface of the material on which it hardens;
• high dielectric properties;
• high mechanical strength;
• good chemical resistance and water resistance;
• during healing, do not emit volatile products and are characterized by a low contraction (2-2.5%).

Properties of epoxy resins

The high physical and technical properties of epoxy resins, which separate them from many other resins, determine the structure of their molecules and, in particular, the presence of an epoxy group.

1. The number of epoxy groups in mass percent.

   The epoxy group suggests an equivalent total weight of 43.

2. Epoxy number, equal to the number of gram equivalents of epoxy groups per 100 g of resin.
3. Epoxy equivalent by weight chewing gum, in grams, containing 1 g of epoxy equivalents.

The method for determining epoxy groups is based on the interaction of epoxy groups with hydrochloric acid and the formation of chlorohydrin.

In addition to the content of epoxy groups in the final resins, determine:

1. volatile content at 110°C;
2. chlorine content;
3. softening or lowering the temperature (for solid ED resins);
4. viscosity (for liquid resins such as ED-5 and ED-6);
5. solubility in acetone.

Table 1.

Some properties of epoxy resins based on diphenylolpropane.

polyester resins. General information.

Appearance
The original polyester resins are viscous honey-like liquids from light yellow to dark brown. With the introduction of a small amount of hardeners, polyester resins first thicken gradually turning into a gelatinous state, after which they become rubbery and finally hard, soluble and infusible.

This process, called curing, takes place at normal temperature for several hours. In the solid state, polyester resins are strong, rigid materials that can be easily dyed in any color and are most often used in combination with glass fabrics (such materials are called polyester fiberglass) as structural materials for the production of a wide variety of products.

Main advantages
Cured polyester resins are excellent structural materials with high strength, hardness, wear resistance, excellent dielectric properties, high chemical resistance, and environmental safety during operation.

Some of the mechanical properties of polyester resins used in combination with glass fabrics approach or even exceed those of structural steels.
The technology for manufacturing products from polyester resins is simple, safe and cheap, because polyester resins are cured at room temperature without applying pressure, without emitting volatile and other by-products with little shrinkage. Therefore, for the manufacture of products, neither complex bulky expensive equipment, nor thermal energy is required, which makes it possible to quickly master both small-tonnage and large-tonnage production of products.

To the above advantages of polyester resins, it is necessary to add their low cost, which is two times lower than the cost of epoxy resins.
It should be noted that at present the production of unsaturated polyester resins both in our country and abroad continues to increase and this trend will continue in the future.

Flaws
Of course, polyester resins have their drawbacks. Thus, styrene, often used as a solvent, is toxic and flammable.

Styrene-free grades have now been developed.
Another disadvantage is flammability. Unmodified, unsaturated polyester resins burn like hardwood. This problem is solved by introducing into their composition powder fillers (antimony trioxide, chlorine- and phosphorus-containing low-molecular organic compounds, etc.) or chemical modification by introducing chlorendic, tetrachlorophthalic acids, as well as monomers: chlorostyrene, vinyl chloroacetate and other chlorine-containing compounds.

Compound
The composition of unsaturated polyester resins is a multi-component mixture chemical substances different nature, performing certain functions.

The main components of which polyester resins are composed and the functions they perform are described in the table:

Polyester, which is the main component, is a product of the polycondensation reaction of polyhydric alcohols with polybasic acids or anhydrides containing ester groups in the main chain -CO-C.

The most commonly used polyhydric alcohols are ethylene glycol, diethylene glycol, propylene glycol, glycerin and dipropylene glycol. Fumaric acid, adipic acid, maleic anhydride and phthalic anhydride are used as acids and anhydrides. In the state of readiness for processing, polyester has a low molecular weight (about 2000), and in the process of molding products after the introduction of curing initiators, it turns into a polymer with a high molecular weight and a three-dimensional network structure, which causes high strength and chemical resistance of the material.

The second necessary component is a monomer - a solvent. Moreover, the solvent plays a dual role. On the one hand, it reduces the viscosity of the resin to the level required for processing, because.

the polyester itself is too thick. On the other hand, the monomer-solvent is actively involved in copolymerization with polyester, providing an acceptable polymerization rate and a high depth of material cure (polyesters themselves cure very slowly).

Most often, styrene is used for this purpose, which is highly soluble, very effective and cheap, but has the disadvantage of toxicity and flammability.
The component necessary for the transfer of polyester resins from a liquid to a solid state is the curing initiator - peroxide or hydroperoxide.

When interacting with another necessary component - the accelerator, the initiator decomposes into free radicals, which excite the chain polymerization process, turning polyester molecules into free radicals as well. The chain reaction proceeds at high speed and with the release of a large amount of heat.

The initiator is added to the resin just before molding. After the introduction of the initiator, the form must be completed within 12-24 hours, because after this time, the resin will turn into a gelatinous state.
The fourth component of unsaturated polyester resins is the curing accelerator (catalyst), which, as mentioned above, is needed for the reaction with the initiator, as a result of which free radicals are formed that initiate the polymerization process.

The accelerator can be introduced into the composition of polyesters both at the stage of manufacture and directly during processing before the introduction of the initiator. The most effective accelerators for curing polyesters at room temperature are cobalt salts, in particular cobalt naphthenate and cobalt octoate, sold under the trademarks NK and OK, respectively.
The polymerization of polyester resins must not only be activated and accelerated, but sometimes also slowed down.

The fact is that polyester resins, even without initiators and accelerators, can themselves form free radicals and polymerize prematurely during storage. To prevent premature polymerization, a curing inhibitor (retarder) is needed. The mechanism of its action consists in interaction with periodically occurring free radicals with the formation of inactive radicals or compounds of non-radical nature.

Phenol, tricresol, quinones and some organic acids are used as inhibitors. Inhibitors are introduced into the composition of polyesters in a very small amount (of the order of 0.02-0.05%) at the manufacturing stage.
The components described above are the main ones of which polyester resins are actually composed as binders.

However, in practice, when molding products into polyesters, a huge amount of additives is introduced that carry a wide variety of functions and modify the properties of the original resins.

These components include powder fillers introduced to reduce the cost, reduce shrinkage, increase fire resistance; reinforcing fillers (fiberglass) used to improve mechanical properties, dyes, plasticizers, stabilizers and others.

polyester resin

polyester resins, Unsaturated oligomers (oligos), such as polymaleins and oligoester acrylates. Mixtures of these solutions and their oligoesters copolymerizing monomers (styrene, methyl methacrylate, diyl phthalate, etc.) are also commonly referred to as polyester resins.

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Composite group of companies is the official distributor of the company Ashland on the territory of Russia and Belarus.

Ashland is a world leader in polyester resins and gelcoats.

Production, properties and procedures for processing polyester resins

Our product range includes a wide range of polyester resins for various purposes. See the relevant sections for more information.

Resin types by application

1. Resins for general use
2. Low Styrene Resins
3. Resins based on DCPD
4. PET resins
5. Chemically resistant polyester resins based on isophthalic acid
6. Fire retardant resins
7. Resin for polymer concrete, artificial stone, hard surface
8. Special resins
9. Resins for the manufacture of matrices and accessories

Ashland polyester resin labeling

In order to better meet the different needs of customers, polyester resins come in a number of different modifications.

A number of polyester resins are pre-accelerated with the addition of thixotropic additives.

The following information will help you understand the labeling of polyester resins.

Marking example: M 105 TB- polyphosphate resin based on orthophthalic acid with low styrene emissions, thixotropic and pre-accelerated.

The first letter indicates the group of polyester resins

Pre-accelerated polyester resin (benzene peroxide curing)
F= Flame retardant polyester resin
G= polyester resin for general use
TO= chemical resistant polyester resin
M= low styrene polyester resin (LSE)
= polyester resin with special properties
Q= light thixotropic polyester resin

The numbers indicate the type of polyester in the polyester resin

100-299 = orthophalic-based polyester resins with a heat distortion temperature below 80 °C
300-399 = orthophalic-based polyester resins with a heat distortion temperature above 80 °C
500-599 = polyester resins on isophthalic and terephthalic substrates
700-899 = polyester resin based on special raw materials
900-999 = Developed grades of polyester resins

The last letter indicates the properties of the polyester resin

A, B, C, D= pre-accelerated polyester resin, modified gel time
E= pre-accelerated polyester resin
F= polyester resin filled and/or colored
H= high viscosity polyester resin
L= stabilized polyester resin
P= polyester resin with reduced styrene content
R= moderately strong polyester resin
= low viscosity polyester resin
T= thixotropic polyester resin
U= polyester resin for warm climates
= slightly modified polyester resin
W= white polyester resin
X= increase predefined properties
Y= fast curing resin
With= polyester resin with LP added

Using this information, you can evaluate the properties of polyester resins and anticipate ease of use depending on the purpose of the product, its size, operating conditions, cost estimates.

Resin storage

The resin has a maximum shelf life of 3 to 12 months (depending on type) from the date of manufacture at a temperature not exceeding 25°C and when stored out of direct sunlight.

Epoxy and polyester resins are thermosetting, due to this quality, they are not able to return to a liquid state after curing. Both compositions are made in liquid form, but are capable of possessing different properties.

What is epoxy resin?

Epoxy type resin is of synthetic origin, it is not used in its pure form, a special agent is added to solidify, that is, a hardener.

When combining epoxy resin with a hardener, strong and solid products are obtained. Epoxy resin is resistant to aggressive elements, they are able to dissolve when acetone enters. Cured epoxy resin products are distinguished by the fact that they do not emit toxic elements, and shrinkage is minimal.

The advantages of epoxy resin are low shrinkage, resistance to moisture and wear, and increased strength.

The solidification of the resin occurs at temperatures from -10 to +200 degrees.

Epoxy type resin can be hot cured or cold cured. With the cold method, the material is used on the farm, or in such enterprises where there is no possibility of heat treatment.

Polyester resin: production and work with them

The hot method is used to manufacture high-strength products that can withstand heavy loads.

The working time for an epoxy type resin is up to one hour, since then the composition will begin to harden and become unusable.

Epoxy Resin Application

Epoxy type resin serves as a high-quality adhesive material.

It is able to bond wood, aluminum or steel, and other non-porous surfaces.

Epoxy-type resin is used to impregnate fiberglass; this material is used in the automotive and aviation industries, electronics, and in the manufacture of fiberglass for construction.

Epoxy resin can serve as a waterproofing coating for floors or walls with high humidity. Coatings are resistant to aggressive environments, so the material can be used for finishing external walls.

After solidification, a durable and hard product is obtained, which can be easily polished. Fiberglass products are made from such material, they are used in the economy, industry, and as room decor.

What is polyester resin?

The basis of this type of resin is polyester; solvents, accelerators or inhibitors are used to solidify the material.

The composition of the resin has different properties. It depends on the environment in which the material is used. Frozen surfaces are treated with special compounds that serve as protection against moisture and ultraviolet radiation. This increases the strength of the coating.

Polyester-type resin has low physical and mechanical properties compared to epoxy material, and is also characterized by low cost, due to which it is actively in demand.

Polyester resin is used in construction, mechanical engineering, and the chemical industry. When combining resin and glass materials, the product hardens and becomes durable. This allows you to use the tool for the manufacture of fiberglass products, that is, canopies, roofs, shower cubicles and others. Also, polyester resin is added to the composition in the manufacture of artificial stone.

The surface treated with polyester resin needs additional coating; for this, a special gelcoat agent is used.

The type of this tool is selected depending on the coverage. When using polyester resin indoors, when moisture and aggressive substances do not get on the surface, orthophthalic gelcoats are used. At high humidity, isophthalic-neopentyl or isophthalic agents are used. Gelcoats are also available with different qualities, they can be resistant to fire or chemicals.

The main advantages of polyester resin

Polyester resin, in contrast to the epoxy composition, is considered more in demand.

It also has a number of positive qualities.

• The material is hard and chemical resistant.
• The resin has dielectric properties and wear resistance.
• When used, the material does not emit harmful elements, therefore it is safe for environment and health.

When combined with glass materials, the agent has increased strength, even exceeding steel.

For solidification, special conditions are not required, the process takes place at normal temperature.

Unlike epoxy, polyester resin has a low cost, so coatings are cheaper. The polyester-type resin has already started the curing reaction, so if the material is old, then it may have a solid appearance, and is unsuitable for work.

Polyester-type resin is easier to work with and the cost of the material saves on costs.

But to get a more durable surface or high-quality bonding, epoxy material is used.

Differences between polyester and epoxy resin, which is better?

Each material has a number of advantages, and the choice depends on the purpose of the product used, that is, under what conditions it will be applied, the type of surface also plays an important role.

Epoxy type resin has a higher cost than polyester material, but it is more durable. The adhesive property of epoxy exceeds any material in strength, this tool reliably connects various surfaces. Unlike polyester resin, the epoxy composition has less shrinkage, has high physical and mechanical properties, less moisture passes through, and is resistant to wear.

But unlike the polyester composition, epoxy hardens more slowly, which leads to a slowdown in the manufacture of various products, such as fiberglass.

Also, to work with epoxy requires experience or careful handling, further processing of the material is more difficult.

With exothermic curing, during the temperature increase, the material is able to lose viscosity, this makes it difficult to work. Basically, epoxy-type resin is used in the form of glue, as it has high adhesive qualities, unlike polyester material. In other cases, it is better to work with polyester-type resin, this will significantly reduce costs and simplify the work.

When using epoxy-type resin, it is necessary to protect hands with gloves, and respiratory organs with a respirator, so that when using hardeners, you do not get burns.

To work with polyester-type resin, special knowledge and experience are not required, the material is easy to use, does not emit toxic elements, and is notable for its low cost.

Polyester resin can be used to treat various surfaces, but the coating needs additional treatment with a special tool. Polyester resin is not suitable for bonding various materials; it is better to use an epoxy mixture. Also, for the manufacture of decorative products, it is better to use epoxy resin, it has high mechanical properties and is more durable.

Much less catalyst is required to make a compound from polyester resin, which also helps to save money.

The polyester composition hardens faster than the epoxy material, within three hours, the finished product has elasticity or increased bending strength. The main disadvantage of polyester material is its combustibility, due to the content of styrene in it.

Polyester resin should not be applied on top of epoxy. If the product is made or patched with epoxy resin, then in the future it is better to use it for restoration.

A polyester-type resin, unlike an epoxy composition, can shrink significantly, it must be done immediately all the work in two hours, otherwise the material will harden.

How to properly prepare the surface for processing?

In order for the resin to adhere well, the surface must be properly treated, such actions are performed using an epoxy and polyester composition.

First, degreasing is performed, for this, various solvents or detergent compositions are used.

The surface must be free of grease or other contaminants.

After that, grinding is performed, that is, the top layer is removed, with a small area, sandpaper is used.

For surfaces large sizes use special grinding machines. Dust is removed from the surface with a vacuum cleaner.

During the manufacture of fiberglass products or when re-applying the agent, the previous layer is covered with resin, which has not had time to completely harden and has a sticky surface.

Results

Polyester resin is much easier to work with, this material helps to save on costs, as it has a low cost, it quickly hardens, and does not need complex processing.

Epoxy-type resin is characterized by high strength, adhesive ability, and is used when casting individual products.

When working with it, you must be careful, further processing is more difficult. During work with such compounds, it is necessary to protect the hands and respiratory organs with special means.

General requirements
All work with resin must be carried out in a room equipped with supply and exhaust ventilation, at a temperature of 18-25ºС and a humidity of not more than 65%.

Lowering the temperature below 18ºС is unacceptable.
All materials before use must be kept in the conditions of the production room (at room temperature) for at least 2 days.
Before work, it is recommended to test on a small amount of resin.
ATTENTION! Mixing accelerator and hardener alone may cause explosion or fire!!!
It is necessary to first thoroughly mix the accelerator with the resin, and only then add the hardener!!!
Operating procedure
1.

Initially, we add the cobalt Co accelerator (6%) to the resin, it has a dark color, in the amount of 2% (20 g per 1 kg of resin), mix thoroughly until smooth.

In this state, the resin can be stored for up to 6 months, retaining its properties, but it is better to mix the resin and the accelerator before use.

2. The hardener, a transparent liquid, is added right before use (casting / spreading), in an amount of 2% (20 grams per 1 kg of resin).

Do not mix the resin too vigorously, because. a lot of air bubbles can get into it, which then will need to be expelled from the resin. Mix the resin for about two minutes to ensure that the hardener is evenly distributed (otherwise the curing will not be uniform).

Gel time, i.e. the time until the resin loses fluidity is between 7 and 60 minutes and depends on the curing system, ambient temperature (the warmer the faster), humidity.

Low humidity speeds up curing time. If the ambient temperature is below 18ºC, then the curing time may increase. Increasing the amount of accelerator and hardener can lead to foaming and overheating of the composition.
Basically, the operating range lies in the interval of 30 - 45 minutes.
Resin cures faster when in a compact volume and slower when spread over a large area in a thin layer (you can improve pot life by using shallow, wide pans or paint cuvettes instead of cylindrical containers).

Another way to prolong the pot life is to remove the resin with the catalyst introduced into the refrigerator during breaks, put the container on ice or in a bucket of cold water.

Polymerization of the resin is accompanied by heating the composition to 70ºС, changing the color of the composition.
Resin during hardening can shrink up to 1.5%. Reducing the amount of accelerator and hardener reduces shrinkage, but increases cure time. It is not recommended to make a layer thicker than 5 mm, so that cracking does not occur.
If fiberglass or glass mat is impregnated with resin, then you should not lay more than three layers at a time.

It is necessary to let the resin stand up, but so that the surface is sticky, and then continue laying the glass materials. The thickness of the final product depends on the thickness and number of layers of glass material. To impregnate 1 m² of laminate, you need an amount of resin that is 2 times the surface density of the glass mat or equal to the surface density of the fiberglass (depending on which material you use).

It should be borne in mind that the resin rises quickly enough, so you need to knead at a time only the amount of resin that you have time to work out in 7-10 minutes. It is better to knead less and then knead more than to throw away the uncured resin.

Curing of the resin on average takes 1 - 3 hours, complete polymerization of the resin occurs within 24 hours, this time can be reduced if the product is placed in a drying chamber for 1 hour with heating up to 60ºС.
Polyester resin is NOT an adhesive and does not adhere well to almost any material other than glass.