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GLASS PLASTIC - THE BEGINNING

P 26.02.2019

 

Composite materials, their main features, production units, terms.

- Production of products from fiberglass and carbon fiber, artificial stone is a relatively new industry. Despite the fact that we know about the “epoxy” since the Soviet Union, and the first polyester resins began to be used for the manufacture of yachts in the 30s of the 20th century (more than 80 years ago!), This amazing achievement of mankind is all still not deep enough into our daily lives.

 - In everyday life, people often confuse "epoxy" and "polyester", I will clarify: these are two parallel branches of composites. Roughly speaking, at the molecular level, the curing of epoxides is the adhesion of short chains, or mono-molecules of 2 or more substances (POLYCONDENSATION REACTION) with the formation of solid plastics. Polyesters, on the other hand, are long hydrocarbon molecules floating in styrene, adding a hardener cross-linking them (POLYMERIZATION REACTION), resulting in the formation of hard plastic. Despite the fact that here and there the final product - plastic - these are different plastics, they differ in their manufacturing characteristics and final properties. The technology of epoxides and polyesters is so different that in one enterprise they are engaged, as a rule, either only with epoxides, or only with polyesters.

 - Modern high-quality epoxides have greater strength than polyesters, epoxy resins are more expensive, are used for the manufacture of lightweight and superior strength steel products with a reinforcing material - carbon cloth, casting a very durable artificial stone. In technology, they are more demanding on the temperature and dosages of the hardener. Most epoxides are toxic (especially in case of a violation of the dosage of the hardener — the main substance); therefore, to manufacture worktops, sinks and other public goods on their basis, special permission is required for a particular technological process and type of epoxy resin.

 - Polyesters are cheaper to purchase, so large items are made from them, such as: hulls of yachts, rigid superstructures on cars, lining objects, etc. The manufacturing process allows for temperature fluctuations and curing agent dosage without degrading the quality of the final product. According to the strength characteristics, fiberglass is most suitable as a reinforcing material for polyesters. In the production of artificial stone, lower strength of polyesters is compensated for by the good flowability of the resin (and epoxies, as a rule, are much thicker), which makes it possible to bring the percentage of filler to 75-83%. At the same time, the filler - aluminum hydroxide, marble chips, quartz sand - gives strength to the artificial stone. The vast majority of polyesters (there are a few exceptions, for example epoxy vinyl ester resin) are non-toxic, therefore they are widely used for the manufacture of public goods. Some types of polyester resin are even used for the production of food containers, laboratory glassware and medical equipment.

- Boat and boat hulls, tuning kit (bumper, spoilers, fairings, sills, linings) on domestic and foreign cars, rigid superstructures on cars (for example, “Daewoo Lanos” pickup and Tavria pickup), sleeping bags and high roofs ( for example, on the Kamaz and Maz vehicles), baths, shower trays and much, much more includes a range of fiberglass products manufactured directly in our Russian-speaking space.

 - The main attractiveness of polyester composites lies in their availability and the ability to produce finished products without expensive equipment, literally “on the knee”.

 - Of course, large-scale projects require a serious professional base, which can be implemented in a more or less large-scale production. It includes several important divisions:

    

 

1. DESIGNERS - DESIGNERS. The first tend to draw something beautiful. The latter then “struggle” with this beauty, trying to technologize what the designers “have pondered”. As a result of hard teamwork, a concept and a digital model of the future product emerges.

 

    

2. MODEL SHOP - highly skilled workers who are engaged in the manufacture of layouts of future products in full size. This is the initial stage of the physical existence of an idea on the way from the model to the finished product. Here, according to the drawings, or without them (if the enterprise cannot afford a designer, the designer), they make a model: bumper, spoiler, hull of the yacht, bath, etc., which will give rise to a series of products that have not yet existed. From here they begin to be!

 - The work of a fashion designer is similar to the work of a sculptor, the more, the less virtualized the stage of virtual modeling. In the absence of the first division at the enterprise, the modeler makes sketches and technical drawings of the product, manually makes the primary blockhead and brings its surface to readiness for forming an impression on it - the matrix.

 - In the case of a three-dimensional model and its physical copy produced on a 3 - 5-axis milling machine, the modeler performs a purely technical fine-tuning of surfaces to the required quality by impregnating the model with polyester resin, puttying with car putty, embroidering, coating with polyester primer putty grinding and polishing.

 - It should be noted here: the terms “MODEL” and “MASTERMODEL” are often confused. A model is a mock-up of a finished product made of pressed cardboard, or foam plastic, putty, boards, and other materials. It is needed to translate the FORM-FORMING SURFACE of the future product from the virtual to the real, physical form. The model is designed for the manufacture of a single matrix. When removing the molded matrix from it, it usually breaks and goes to the trash. Mastermodel is a cast from the active matrix, made of gelcoat and fiberglass, besides the shaping surface of the product itself, it also has technological allowances for trimming, flanging, characteristic of the matrix. Can withstand a large number of removals and not deteriorate. It is made for reproduction of the same matrices in case of the need for production at the plant of this product in quantities of more than 1-2 pieces per day.

 - Some people still use the term “MASTERFORM” in connection with fiberglass. Usually they imply a model, mastermodel, or matrix. But there is no such term in the composite field, it exists in metallurgy and has no relation to our region.

 - In order not to be confused, you need to remember: the model looks like a product, but is made from easily processed materials; The matrix (form) is the inverse cast of the model (negative): where the convexity on the model is concavity on the matrix, it is made of gelcoat and fiberglass. When molding, or casting in the matrix, it turns out the finished product made of fiberglass or artificial stone. Mastermodel (or REPLICATOR) is a positive fiberglass for reproduction of matrices.

 - In the model production there is also the term “PRIMARY BOLVAN” - this is a blank for machining, glued together from pieces of foam, or MDF: angular, roughly repeating the contours of the future product. When a milling machine removes all unnecessary from it, it turns out just "BOLVAN." This is a blank, which more precisely repeats all the contours of the future product, but still needs to be worked out with empathetic human hands, which is called the “DOLODIS BOLVAN”. After refinement, he begins to be, in fact, a model. We begin to call the dummy model somewhere between sanding P40 and P400 sandpaper, when we (modelmers) like its surface.

 - The attractiveness of fiberglass technology lies in the fact that, if necessary, you can completely eliminate the first two points of production. At first, you can use other people's products purchased in the store for the manufacture of their matrices and the production of finished products from them. The need for design and physical modeling appears only when your company is already firmly “standing on its feet” and you want to create something new.

    

3. EQUIPMENT - workshop, where the finished model is delivered. Here, flanging is attached to them (technological bends, which serve to stiffen the edge of the matrix, - protect the edge of the matrix from chipping the gelcoat, - joining the detachable parts of the matrix, if such are provided for in the design), cover their surface with a release compound (so that the future matrix does not stick to the surface of the model, and easily removed from it).

 - Since the manufacture of the matrix is very similar to the molding of the finished product from fiberglass, molders work here, but it must be the best specialists. Because the quality of work here should be the highest. After all, the matrix serves up to 10 years (maybe more, just the products go out of fashion, they are replaced by others, with a new design), the better it is made, the less will be the hassle of repairing and finishing the surface of finished products.

 - Specialists for the manufacture of dies called equipment, because the matrix - it is a snap for the manufacture of final products.

 - The model prepared as described above is coated with a matrix gelcoat (high-quality polyester plastic with additives, fillers and dyes, similar to paint). This layer no longer belongs to the model; this is the beginning of a new matrix.

 - Then a glass mat (nonwoven and a cloth glued together with special impregnation consisting of multidirectional glass filaments) is placed on the hardened gelcoat; impregnate it with polyester resin with a hardener previously added to it. Thanks to the impregnation of which the glass mat threads are glued, when soaked with resin, it becomes plastic, taking any shape of the surface on which it is laid. Impregnation also gives the resin an additional TIKSOTROPNY (left alone from the mechanical effects of the resin - thickens). This is a very useful feature when you need to apply laminate to a sheer, or ceiling surface. After some time, the LAMINATE (glass mat impregnated with resin with a hardener) hardens. It is sanded to remove the “spikes” (some threads after laying are not in the plane of the molding). Then another layer is formed - until the planned thickness is reached (usually 6-10 mm). In the final, an amplifying framework is glued to the matrix in order to prevent its deformation in structurally less rigid places. The frame also acts as a support for convenient placement of the matrix on the table, or on the floor when molding products.

 - After that, the matrix is removed from the model using wooden, or plastic wedges and compressed air. This process is called REFORMING. The toolkit grinds the removed matrix with a set of pieces of emery paper, with a consistently decreasing grain (from P400 to P2000). The final stage of processing the mat is polished. Using the polishing wheel, the surface of the matrix is processed with fine-abrasive pastes, which remove the thinnest layer of the surface and bring it to a mirror shine.

 - The end of the preparation of the matrix for operation is the application of separation compositions. These are special polymeric substances that reduce the adhesion between the matrix and the future product. After processing by a separator, the forming (working) surface of the matrix is covered with the thinnest polymer film of a permanent (permanent) separator. It can only be damaged by scratching and removing it by polishing or grinding. With careful handling, the separated matrices give a lot of removals without FLASHING (copolymerization with the product), thanks to this layer. When reducing the anti-adhesion properties of the working part of the matrix (when the product is unformed, they begin to emerge from it with difficulty), the separation layer is updated.

  

4. FORMING - shop where the matrix is constantly working. Here they massively produce finished products.

 “In this workshop, MALAR works, which by means of a hand-held sprayer, or by machine, applies a layer of gel coat for the products on the surface of the matrix. The gelcoat gives the product surface color, beautiful appearance, durability and weather resistance.

 - The main number of personnel of the plant for the production of products from fiberglass are FORMERS. They are molded into gel-coated matrices of the required thickness.

 - In the state of laminate (impregnated with resin with hardener), glass mat of a certain density has a constant thickness. So, glass mat with a density of 450 grams per square meter, has a thickness of 0.8-1 mm. And, if we need to make a product with a thickness of 4 mm, we can make it by placing 4 layers of 450th glass mat in the matrix.

 - Sometimes in the manufacture of products using glass. It is a woven cloth, like burlap, only - from glass threads. It is shaped more difficultly than glass mat; it is prone to wrinkling; it takes the shape of irregularities worse. But - much stronger on a gap, than a nonwoven cloth (glass mat). Therefore, it is used in such products where tensile strength is important, for example, it is laid in the 3rd and last (7th - 8th) layers in the boat hull, - the last (3rd - 4th) layer in the car bumper .

 - Gelcoat for many products is allowed to apply and brush. In this case, the matrix gelcoat products are not painter, and molders themselves.

 - Please note: at the beginning of manufacturing the product, the gelcoat of the product is applied to the matrix, it no longer refers to the matrix. After its hardening, laminate is laid on it (fiberglass). The gelcoat of the product is separated from the matrix and copolymerized with the laminate. So The front layer of the product is in direct contact with the matrix (this is practically one surface with it, if we exclude a layer of separator several molecules thick), and the body of the product, “its thickness” is applied over it. When disassembling, what “looked” into the matrix will be outside. Those. the assumptions that when the matrix is formed on a model and the product is molded on a matrix, the dimensions of the final product all the time change by the thickness of the matrix and the product are incorrect.

 - In developed enterprises, large and relatively uncomplicated products are laminated using a special machine called CHOPPER. This device prepares the laminate directly during application: chopped ROVING (glass filament tow), resin and hardener are fed into the spray torch. All this is mixed in the air and falls on a layer of laminated surface. At such enterprises, the chopper is controlled by the OPERATOR ON THE LAMINATE APPLICATION. And molders roll laminated rollers, following the machine. This allows several times to speed up the molding process, especially for large products.

 - Competent work of molders, painter, operator is very important for the quality of the final product, therefore, great attention should be paid to the training of these specialists in the enterprise. Also, the company necessarily need to control the quality of the finished product.

  

5. CASTING SHOP. In terms of lower labor costs and lesser dependence of product quality on the “human factor”, the molding production is much more attractive. Here, for the manufacture of products requires a smaller number of specialists: painter, mixers, cutters of finished products. However, in the manufacture of products from artificial stone, high quality products can be achieved only with well-established technology. Errors in the dosages and the time of the technological operations are more pernicious here than on the molding.

We summarize the above:

 - Fiberglass and carbon fiber, artificial stone - is a composite material consisting of polyester (epoxy) resin and a reinforcing material (filler).

 - The unique properties of the resin lies in the fact that when mixed with a hardener, it turns from a liquid into a solid of sufficiently high strength. All this happens without any complicated devices, at room temperature and atmospheric pressure.

 - When applied to the surface of a special polymer composition - a separator, the applied polymer resin ceases to be glued to it. This property allows you to make casts (matrices) and inverse casts (products) from various objects, including those made from polymers.

 - These two properties generate a whole variety of products from epoxides and polyesters, all types of matrices and products (molded and molded).

 - All polymeric materials are divided into 3 main types:

 - Gelcoats - outer (front) layer of matrices and products, which has increased strength, aesthetics and weather resistance;

 - Resins - together with the reinforcing material (filler) make up the bulk (body) of both the matrices and products, increased strength and resistance to impact are required of the reinforcing components;

 - Fillers - gluing pastes and putties, used for finishing models, reinforcing problem areas of matrices and products, gluing parts of complex molded fiberglass products (deck and boat hull, etc.).

 - All polyester materials are cured by one type of hardener based on methyl ethyl ketone peroxide.

 - Epoxides have different hardeners for different grades and groups of materials.

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