In recent years, polyester resins have gained a lot of popularity.First of all, they are in demand as a major component in the manufacture of glass-reinforced plastics, durable and light construction materials.
Manufacturing pitches: the first stage
How to start the production of polyester resins?This process begins with a petroleum distillate - during this allocated different substances: benzene, ethylene and propylene.They are necessary to obtain anhydrides, polybasic acids, glycols.After cooking together all these components creates a so-called base resin, which at a certain stage must be diluted with styrene.The latter material, for example, can be 50% of the finished product.At this stage also allowed the sale of finished resin, but the stage of production is not yet as over: we should not forget about the saturation of different additives.It is through such components finished resin acquires its unique properties.
composition of the mixture can be changed by the manufacturer - a lot depends on where the concrete will be used polyester resin.Experts pick the most optimal combination of the result of such work are substances with very different properties.
production of resins: the second stage
It is important to cook the mixture was solid - usually waiting for the polymerization process comes to the end.If he stopped, and the material was in the sale - he is only partially polymerized.If it does not do, the polymerization continues, the substance is required to harden.For these reasons, the shelf life of the resin is very limited: the older the material is, the worse its final properties.Polymerization can also be slowed down - for this use refrigerators, there is no hardening.
to production stage is completed, and finished products, the resin is also necessary to add two important ingredients: catalysts and activators.Each of them performs its function: the mixture begins to heat generation, which contributes to the polymerization process.That is a source of external heat is required - everything happens without it.
course of the polymerization process is controlled - controlled proportions of components.Since due to the contact between the catalyst and activator can get an explosive mixture, the latter decided to enter into the resin only in the proceedings before using the catalyst is added, it is usually delivered separately.Only when the polymerization process is completely finished, the material hardens, it can be concluded that the production of polyester resins completed.
starting resin
What is the material in its original state?This honey-like, viscous liquid whose color can vary from dark brown to light yellow.When introduced into a number of hardeners, polyester resin is first thickens slightly, then takes on a gelatinous state.A little later, the consistency resembles a rubber, then - the substance hardens (becomes infusible, insoluble).
This process is commonly called curing, since it takes a few hours at ambient temperature.When the resin is in the solid state, it resembles a hard durable material that is easy to paint the different colors.Typically, it is used in combination with glass fiber (GRP), it performs the function of the structural element for the manufacture of various products - such polyester resin.Instructions when working with such mixtures is very important.Observe each of its point.
main advantages
polyester resin hardened state are remarkable structural materials.They are characterized by toughness, high strength, excellent dielectric properties, wear resistance, chemical resistance.We should not forget that in the operation of a polyester resin product is safe from an environmental standpoint.Certain mechanical properties of mixtures, which are used in conjunction with fiberglass, whose performance reminiscent of the parameters of structural steel (in some cases even exceed them).Manufacturing technology is cheap, simple, safe, because the substance is cured at ordinary room temperature, it does not even require the application of pressure.Release of volatile and other by-products does not take place, unless there is little shrinkage.So, to make a product, do not need expensive cumbersome installation is not necessary in the heat, allowing the company to quickly learn as a large-capacity and low-tonnage production.Do not forget about the low cost of polyester resins - this figure is two times lower than that of epoxy equivalents.
production growth
We can not ignore the fact that at present the production of unsaturated polyester resin is gaining momentum with each passing year - it is not only our country, but also the common foreign trends.If you believe the opinion of experts, this situation will continue for the foreseeable future.
Disadvantages pitches
course, polyester resins also have some disadvantages, as well as any other materials.For example, during the production of styrene is used as a solvent.It is flammable, is very toxic.At this point already created such brands which do not have in their composition styrene.Another obvious drawback: flammability.Unmodified unsaturated polyester resins burn just as solid wood.This problem is solved: the substance introduced in particulate fillers (low molecular weight organic compound with a content of fluorine and chlorine, antimony trioxide), sometimes used chemical modification - tetrachlorophthalic administered, hlorendikovuyu acid, certain multidimensional: vinilhloratsetat, chlorostyrene, and other compounds which contain chlorine.
resin composition
If we look at the composition of unsaturated polyester resins, there may be noted a multi-component mixture of chemical elements of different nature - each of them performs a specific task.The main components are polyester resins, they have different functions.For example, polyester - a main component.It is a product of a polycondensation reaction of polyhydric alcohols which are reacted with an anhydride or polybasic acids.
Speaking of polyhydric alcohols, there is demand diethylene glycol, ethylene glycol, glycerol, propylene glycol, dipropylene glycol.As used adipic anhydride, fumaric acid, phthalic and maleic anhydrides.Casting polyester resin is unlikely to be possible if the polyester in a state of readiness for processing has a low molecular weight (about 2,000).In the process of forming articles it turns into a polymer having a three-dimensional network structure, high molecular weight (after curing initiators is introduced).Such structure provides chemical resistance, high strength material.
solvent monomer
Another obligatory component - monomer solvent.This solvent serves a dual function.In the first case it is required to reduce the viscosity of the resin to a level that is needed for processing (as polyester itself too thick).
On the other hand, the monomer has been actively involved in the process of copolymerization with polyester, due to which provides optimum cure speed and high depth of cure of the material (when considered separately polyesters, their cure is quite slow).Hydroperoxide - the one component that is required for conversion to the solid state of the liquid - the only way all of its quality acquires polyester resin.Use of the catalyst is also necessary when working with unsaturated polyester resins.
Accelerator
This ingredient can be formulated into polyester both during manufacture and when the processing takes place (before the initiator).For most polymers, curing accelerators can be called optimal cobalt salt (cobalt octoate, naphthenate).Polymerization is necessary not only to accelerate, but also activate, although in some cases it slow.The secret is that if you do not use the accelerators and initiators, in the finished material are independently formed free radicals, due to which the polymerization will occur prematurely - straight during storage.To prevent such a phenomenon can not do without inhibitor (inhibitor) curing.
principle of action inhibitor
mechanism of action of this component is: it interacts with free radicals that arise periodically, resulting in the formation of radicals or inactive compounds that do not have a radical nature.Inhibitors usually function operate such substances: quinones, tricresol, benzophenone, some of the organic acids.The composition of the polyesters inhibitors administered in small amounts during manufacture.
Other additives
components described above - the main, precisely because they can work with a polyester resin as a binder with.However, in practice, in the process of forming articles sufficiently large amount of additives introduced into the polyesters, which, in turn, carry a variety of functions that modify the properties of the starting material.Among such components can be noted particulate fillers - they are administered specifically to reduce shrinkage, reduce the cost of the material, increase the fire resistance.It should also be noted fiberglass (reinforcing agents), the use of which is due to higher mechanical properties.There are other additives: stabilizers, plasticizers, dyes, and so forth.
glass mat
As the thickness, so the structure of glass is different.Glass mat - fiberglass, which cut into small pieces, their length varies between 12-50 mm.The elements are glued together by means of another temporary binder, which is usually acts powder or emulsion.Epoxy polyester resin used for making glass fiber mats, which consist of fibers arranged randomly, fiberglass also their appearance resembles an ordinary cloth.To achieve the greatest possible strengthening should use a different brand of fiberglass.
general, glass fiber mats have less strength, but they are much easier to handle.When compared with glass fiber, the material is better to repeat the form of a matrix.Because the fibers are short enough to have random orientation, the mat can hardly boast of great strength.However, it can be very easy to infiltrate the resin as it is soft, with loose and thick, is a bit like a sponge.The material is really soft, moldable give in without a problem.The laminate, for example, which make such mats differs excellent mechanical properties, has high resistance against weather conditions (even within the extended period).
which uses glass fiber mats
Matt finds application in the field of contact molding, to be able to produce products of complex shapes.Products made from this material are used in a variety of areas:
- in the shipbuilding industry (building canoes, boats, yachts, ryborezki, different internal structures and so on.);
- glass mat and polyester resin employed in the automotive industry (various machine parts, cylinders, vans, diffusers, tanks, dashboards, housing and other.);
- in the construction industry (certain elements of wood products, construction of bus stops, partitions, and so on. D.).
have different density glass mat is as thick.Separate the material by weight of one square meter, which is measured in grams.Are fairly thin material, virtually air (steklovual), there is also a thick, almost like a blanket (used to ensure that the product has acquired the desired thickness to obtain the desired strength).
