Why plastic. Plastic. Polyamides - PA

Today, plastic is one of the most commonly used materials. The variety of its types and properties allows it to be used in various fields of production. What types of plastics are there? What are their properties? How exactly are they used? We will consider the details in this article.

Types of plastics

So, the types of material under consideration are divided into a number of different categories, taking into account the following features:

rigidity;
fat content;
chemical composition.

However, even these points do not reflect the main criterion that most clearly demonstrates the nature of a particular polymer. It's about how the plastic behaves when heated. Considering this point, the following types of plastics are distinguished:

thermosets;
thermoplastics;
elastomers.

To determine which category a material belongs to, it is necessary to evaluate its size, shape, chemical composition, and the arrangement of the molecules.

Reaktoplasts

For the type of plastics under consideration, the following behavior is characteristic when heated: after they have been heated once (for example, during the production process), they acquire an absolutely solid state and become insoluble. They can no longer be softened with any subsequent heating. This process is called irreversible curing by experts.

The macromolecular structure of thermosets is initially linear. However, during the heating process, the properties of the plastic change. So, its molecules, figuratively speaking, are stitched together. In this case, a special spatial structure (mesh) is formed. This is what allows the material in question to become absolutely inelastic and extremely hard. Moreover, it is unable to re-enter a viscous state.

Due to these features, thermosetting plastics cannot be recyclable, they cannot be welded or formed a product when reheated (since the material will simply collapse due to the disintegration of molecular chains).

In what areas is the use of this kind of plastics appropriate? As a rule, it is their heat resistance that is used. Therefore, these materials are used to make:

details of the crankcase in the engine compartment;
body parts (external, oversized).

Thermoplastics

The classification of plastics distinguishes one more type of them - thermoplastics. Their peculiarity is that these materials melt under the influence of high temperatures, but when cooled, they quickly return to their original state. The molecular chains of this type of plastic are either slightly branched or linear. When the product is exposed to low temperatures, it is fragile and hard. This is due to the fact that the molecules are located extremely tightly to each other, which almost completely limits their movement. As soon as the temperature rises slightly, the molecules are able to move, which significantly weakens the bond between them. In the course of the described process, the material becomes more plastic. If the temperature continues to increase, then the intermolecular bonds finally weaken, and now they slide relative to each other. During this time, the plastic becomes viscous and incredibly elastic. If the temperature is lowered, then all these processes will be reversed.

If the temperature is controlled in such a way as to prevent overheating, which provokes the disintegration of the molecular chain, then the processes described above can be repeated an infinite number of times. Using these properties of this category of plastics, they are repeatedly processed into a variety of products. This allows for less environmental pollution, because plastic waste in the soil decomposes from one to four hundred years.

Moreover, due to the features described above, thermoplastics can be easily soldered or welded. Any mechanical damage can be corrected by correct temperature exposure.

The use of plastics of this type is widespread in the automotive industry (manufacture of wheel covers, bumpers, panels, lamp housings, frames, exterior mirrors, bumper grilles, etc.).

Basic thermoplastics:

polyvinyl chloride;
polyvinyl acetate;
polyoxymethylene;
polypropylene;
polyamide;
copolymers of butadiene, styrene and acrylonitrile;
polycarbonate;
polystyrene;
polyethylene;
polyvinyl acetate.

Elastomers

The main characteristic of this category of plastics is elasticity. In practice, this is manifested by the fact that in the event of a forceful impact, such a material exhibits incredible flexibility, and after its termination, in a short time it takes its previous shape. Moreover, this property is retained by elastomers in an extremely wide temperature range. Experts call it the limits of -60 and +250 degrees. Macromolecules of elastomers are similar to those of thermosets - spatially reticular. However, the distance between them is much greater, due to which these plastics are able to exhibit such properties.

Among other things, this network structure makes the plastics of this group soluble and completely infusible, but they tend to swell.

Materials that belong to the category in question:

silicone;
polyurethane;
rubber.

These materials have found practical application in the automotive industry, where all three of their types are successfully used. This plastic is used to make seals, tires, spoilers, and so on. Also, mixtures are formed from the listed three types of materials. They are called blends. Their properties differ depending on what ratio of components is used in this case.

PET

Polyethylene terephthalate is the material from which disposable bottles are made. They are disposable, because when reused, the material in question is capable of releasing substances that are extremely toxic to the human body into the water, which negatively affect the hormonal balance. Therefore, if you pour liquid into a bottle that is no longer new, remember that such dangerous elements as different types of alkalis and many bacteria will enter your body along with the drink, for which PET is an ideal breeding ground.

By itself, this type of plastic is lightweight, tough and very durable. Perhaps this can explain its unconditional popularity throughout the world. It is also especially heat-resistant (it does not deform or collapse if exposed to temperatures ranging from -40 to +200 degrees). Neither mineral salts, nor oils, nor diluted acids, nor alcohols, nor even the vast majority of organic compounds can cause any harm to the material. At the same time, it is unstable to the action of certain types of solvents and strong alkalis. When the material burns, a highly smoky flame arises. Extinguishes spontaneously when removed from fire.

HDPE

HDPE, low pressure polyethylene is a good quality plastic that neither initially nor subsequently releases hazardous compounds into the contents of the container. This is the most preferable option for storing water, since the liquid will be safe for consumption for a certain time. The abbreviation HDPE is nothing more than a designation for food grade plastic.

It is used for the manufacture of various products: some plastic bags, milk packaging, children's toys, sports and tourist bottles, designed for reusable use, packaging for detergents.

Sufficiently dense and tough, but relatively fragile material.

Pvc

Plastic parts in this category are highly toxic. They are able to secrete at least two dangerous substances that, by their effect on the body, negatively affect the hormonal balance of a person. The plastic is flexible and soft enough. Typically, it is used for the manufacture of packaging for children's toys and vegetable oil, as well as blister packs in which a variety of types of goods can be stored. Also, with the help of this plastic, computer cables are sheathed, plumbing parts and plastic pipes are produced.

It is not re-processed on the territory of the Russian Federation, which means that its use causes significant harm to the environment.

The material in question is incredibly elastic, and also does not burn too well (this is characterized by the fact that at the moment the plastic is removed from the flame it spontaneously extinguishes). The combustion process is also very interesting: the flame has a greenish-blue glow, and the plastic itself is very smoky, a very pungent and pungent smell of smoke is released. The burnt plastic looks like a black substance, very much like coal (it quickly turns into soot under light pressure).

LDPE

This abbreviation stands for High Density Low Density Polyethylene. The scope of the considered plastic is great. It is used to make disposable bags and liquid bottles. In the second case, it is absolutely safe, since it does not emit any poisonous or harmful chemical compounds into the water that is stored in it. However, it is better not to use the bags that are made of it in principle. In any products that are in them, they release substances that can seriously damage the functioning of the cardiovascular system.

PP

You also often find polypropylene in everyday life. This type of plastic is usually either white or translucent. You have often seen packaging made from it. Often they sell yoghurts or syrups. When heated, polypropylene does not deform or collapse. Since it does not melt when heated, this type of plastic is considered heat-resistant. It is relatively safe for food storage.

PS

Polystyrene is the material most commonly used to make disposable tableware and, paradoxically, is the worst suited for this purpose. Why? This is due to the fact that polystyrene actively releases toxic chemical compounds under the influence of high temperatures. Despite the fact that it is cheap, very light (products made from it are comfortable to hold in the hand and easy to transport) and strong enough to withstand a certain volume of liquid and other substances, it should never be used as a container for storing hot food. ... If it is impossible to avoid the use of disposable tableware, it is preferable to choose all the same paper products.

Other types

The classification of plastics includes all other types of plastics in this group. That is, those that, for certain reasons, cannot be included in the categories described above.

Sometimes one of the types of PVC is mistakenly attributed to them, since, not knowing all of its features, they cannot correctly evaluate it and attribute it to the required group of materials. This type of plastic can be distinguished by the following signs:

the seam located at the bottom of the product is distinguished by two symmetrical beads that are noticeable to the eye;
products, in particular bottles, made of PVC, as a rule, are blue or bluish in color;
if such plastic is bent, then a white stripe can be clearly seen along the fold line.

Use after processing

Plastic molding is a complex process. However, their processing is not so easy either. So, recycled plastics are used in dentistry, for the manufacture of packaging for food products, in construction, they produce bottles for various liquids, clothes and shoes.

Conclusion

Different types of plastics have different properties and can be used in a wide variety of industries. Undoubtedly, its use greatly simplifies our life. However, it is important to use it wisely so as not to harm your own body. For this, it is important to navigate the types of plastics, to know their inherent characteristics and be able to distinguish them from each other.

Be careful. Whenever possible, use only those types of plastic that are safe for your health and the health of your loved ones. And the information contained in this article will help you in this matter.

Plastics are extremely important for the development of various sectors of the national economy, primarily mechanical engineering. They are an independent structural material and possess a number of valuable technical properties that metals and other natural materials do not have.

The introduction into mechanical engineering of new synthetic materials with high mechanical strength and resistance to the action of petroleum products makes it possible to manufacture whole units from plastics, which leads to a reduction in the consumption of metals and reduces the weight of products.

Plastics called materials obtained on the basis of artificial and natural resins, and their mixtures with various fillers.

Under normal conditions, plastics are hard or elastic materials. Under the influence of temperature and pressure, plastics can pass into a plastic state, take and maintain the shape given to them.

Plastics in their composition are simple if they consist of pure binder resins, or complex (composite), if they contain, in addition to the binder, other components: fillers, plasticizers, lubricants, stabilizers, dyes, catalysts or accelerators.

Binder(resin) determines the basic properties of plastics. In the manufacture of plastics, artificial resins are most widely used - products of the processing of coal, oil and other materials. Plastics obtained on the basis of artificial resins are referred to as polymeric compounds. Natural resins (amber, shellac) and products of processing of natural materials (asphalt, rosin, etc.) are used much less frequently.

Excipients give plastics certain physical and mechanical properties and, in many cases, reduce the cost of plastic parts.

Organic substances are used as fillers: wood flour, wood veneer, paper, fabrics, cotton wool, shavings, sawdust, etc., as well as minerals: quartz flour, talc, kaolin, asbestos, fiberglass, fiberglass, etc.

Plasticizers provide plastics with plasticity, increase fluidity. They are used as dibutyl phthalate, tricresyl phosphate, camphor, etc.

Lubricants prevent adhesion of the manufactured product to the mold. These include stearin, wax, etc.

Stabilizers increase thermal stability and bind by-products. Inorganic (water, phosphates) and organic (amino acids) substances serve as stabilizers.

Dyes(nigrosine, mummy, etc.) give the plastics the required color.

Plastics

This article was written in the early 70s by a prominent Soviet chemist, prof. Elena Borisovna Trostyanskaya, the author of many works, textbooks and books on the chemistry of polymers and plastics. However, over the past 30 years, the article has not lost its relevance at all. Of course, some of the plastics production figures quoted here are out of date. It should also be noted that among the leaders among plastics, along with polyethylene and polystyrene, polypropylene has now entered.

Plastics, plastics, plastics - materials containing in their composition a polymer that is in a viscous-flow or highly elastic state during the formation of products, and in a glassy or crystalline state during operation. Depending on the nature of the processes accompanying the molding of products, plastics are divided into thermosets and thermoplastics. The number of thermosetting plastics includes materials, the processing of which into products is accompanied by a chemical reaction of the formation of a reticulated polymer - curing; in this case, the plastic irreversibly loses its ability to pass into a viscous-flow state (solution or melt). When molding products from thermoplastics, no curing occurs, and the material in the product retains the ability to re-enter a viscous-flow state.

Plastics usually consist of several mutually compatible and non-compatible components. Moreover, in addition to the polymer, the composition of the plastic may include fillers of polymer materials, plasticizers that lower the pour point and viscosity of the polymer, stabilizers of polymer materials that slow down its aging, dyes, etc. Plastics can be single-phase (homogeneous) or multi-phase (heterogeneous, composite) materials. In homogeneous plastics, the polymer is the main component that determines the properties of the material. The rest of the components are dissolved in the polymer and can improve one or another of its properties. In heterogeneous plastics, the polymer acts as a dispersion medium (binder) in relation to the components dispersed in it and constituting independent phases. To distribute the external effect on the components of a heterogeneous plastic, it is necessary to provide strong adhesion at the interface between the binder and the filler particles, achieved by adsorption or chemical reaction of the binder with the filler surface.

Filled plastics

The filler in plastic can be in gas or condensed phases. In the latter case, its elastic modulus can be lower (low modulus fillers) or higher (high modulus fillers) the elastic modulus of the binder.

Gas-filled plastics include foams, which are the lightest of all plastics; their apparent density is usually from 0.02 to 0.8 g / cm 3 .

Low-modulus fillers (they are sometimes called elasticizers), which are used as elastomers, without lowering the heat resistance and hardness of the polymer, give the material increased resistance to alternating and shock loads (see Table 1), prevent the growth of microcracks in the binder. However, the coefficient of thermal expansion of elasticized plastics is higher and deformation resistance is lower than that of monolithic binders. The elasticizer is dispersed in a binder in the form of particles with a size of 0.2-10 microns. This is achieved by polymerizing the monomer on the surface of synthetic latex particles, curing the oligomer in which the elastomer is dispersed, and mechanically grinding the mixture of the rigid polymer with the elastomer. The filling should be accompanied by the formation of a copolymer at the interface between the particles of the elasticizer and the binder. This provides a cooperative reaction of the binder and elasticizer to external influences under the operating conditions of the material. The higher the elastic modulus of the filler and the degree of filling the material with it, the higher the deformation resistance of the filled plastic. However, the introduction of high-modulus fillers in most cases contributes to the appearance of residual stresses in the binder, and, consequently, to a decrease in the strength and solidity of the polymer phase.

The properties of a plastic with a solid filler are determined by the degree of filling, the type of filler and binder, the strength of adhesion at the contact boundary, the thickness of the boundary layer, the shape, size and mutual arrangement of the filler particles. Plastics with small-sized filler particles, evenly distributed over the material, are characterized by isotropy of properties, the optimum of which is achieved at a degree of filling that ensures the adsorption of the entire volume of the binder by the surface of the filler particles. With an increase in temperature and pressure, part of the binder is desorbed from the filler surface, so that the material can be molded into products of complex shapes with brittle reinforcing elements. Small filler particles, depending on their nature, to various limits, increase the elastic modulus of the product, its hardness, strength, give it frictional, antifriction, heat-insulating, heat-conducting or electrically conductive properties.

To obtain low density plastics, fillers in the form of hollow particles are used. Such materials (sometimes called syntactic foams), in addition, have good sound and thermal insulation properties.

The use of natural and synthetic organic fibers as fillers, as well as inorganic fibers (glass, quartz, carbon, boric, asbestos), although it limits the choice of molding methods and complicates the manufacture of products of complex configuration, but sharply increases the strength of the material. The strengthening role of fibers in fiberglass, materials filled with chemical fibers (so-called organofibers), carbon fiber (see Carbon fiber) and fiberglass is manifested already at a fiber length of 2-4 mm. With an increase in the length of the fibers, the strength increases due to their mutual interlacing and a decrease in stresses in the binder (with a high modulus filler), localized at the ends of the fibers. In cases where this is allowed by the shape of the product, the fibers are fastened together in threads and in fabrics of various weaves.

Fabric-filled plastics (PCBs) are laminates characterized by anisotropy of properties, in particular, high strength along the filler layers and low strength in the perpendicular direction. This disadvantage of laminated plastics is partly eliminated by the use of the so-called. three-dimensional woven fabrics, in which individual canvases (layers) are intertwined. The binder fills the looseness of the weaves and, hardening, fixes the shape given to the filler blank.

In products of simple shapes, and especially in hollow bodies of revolution, filler fibers are located in the direction of action of external forces. The strength of such plastics in a given direction is determined mainly by the strength of the fibers; the binder only fixes the shape of the product and evenly distributes the load along the fibers. The elastic modulus and tensile strength of the product along the fiber arrangement reach very high values (see Table 1). These figures depend on the degree of filling of the plastic.

For panel structures, it is convenient to use laminates filled with wood veneer or paper, including synthetic fiber paper (see Wood plastics, Getinax). A significant reduction in the mass of panels while maintaining rigidity is achieved by using materials of a three-layer, or sandwich, construction with an intermediate layer of foam or honeycomb.

The main types of thermoplastics

Among thermoplastics, polyethylene, polyvinyl chloride and polystyrene are most widely used, mainly in the form of homogeneous or elasticized materials, less often gas-filled and filled with mineral powders or synthetic organic fibers.

Polyethylene-based plastics are easily molded and welded into products of complex shapes, they are resistant to shock and vibration loads, chemically resistant, have high electrical insulating properties (dielectric constant 2.1-2.3) and low density. Products with increased strength and heat resistance are obtained from polyethylene filled with short (up to 3 mm) fiberglass. With a filling degree of 20%, the tensile strength increases 2.5 times, with bending - 2 times, impact strength - 4 times and heat resistance - 2.2 times.

Rigid plastic based on polyvinyl chloride - vinyl plastic, including elasticized (impact-resistant), is molded much more difficult than polyethylene plastics, but its strength to static loads is much higher, creep is lower and hardness is higher. Plasticized polyvinyl chloride-plasticate finds wider application. It is easily formed and reliably welded, and the required combination of strength, deformation stability and heat resistance is achieved by selecting the ratio of plasticizer and solid filler.

Plastics based on polystyrene are molded much easier than from vinyl plastic, their dielectric properties are close to those of polyethylene plastics, they are optically transparent and are not much inferior to vinyl plastic in terms of strength to static loads, but they are more fragile, less resistant to solvents and flammability. Low impact strength and fracture due to the rapid growth of microcracks - properties that are especially characteristic of polystyrene plastics are eliminated by filling them with elastomers, i.e., polymers or copolymers with a glass transition temperature below -40 ° C. Elasticized (impact-resistant) polystyrene of the highest quality is obtained by polymerizing styrene on particles of styrene-butadiene or nitrile-butadiene latex.

The material, called ABS, contains about 15% of a gel fraction (block and graft copolymers of polystyrene and these copolymers of butadiene), which constitutes the boundary layer and connects the elastomer particles with a polystyrene matrix. The frost resistance of the material is limited by the glass transition temperature of the elastomer, the heat resistance is limited by the glass transition temperature of polystyrene.

The heat resistance of the listed thermoplastics is in the range of 60-80 ° C, the coefficient of thermal expansion is high and amounts to 1 x 10 -4 , their properties change sharply with a slight change in temperature, deformation resistance under load is low. Thermoplastics belonging to the group of ionomers, for example, copolymers of ethylene, propylene or styrene with monomers containing ionic groups (usually unsaturated carboxylic acids or their salts), are partially devoid of these disadvantages. Below the pour point, due to the interaction of ionic groups between macromolecules, strong physical bonds are created, which are destroyed when the polymer softens. Ionomers successfully combine the properties of thermoplastics, favorable for molding products, with properties characteristic of reticulated polymers, i.e., with increased deformation resistance and stiffness. However, the presence of ionic groups in the polymer reduces its dielectric properties and moisture resistance.

Plastics with higher heat resistance (100-130 ° C) and less abrupt change in properties with increasing temperature are produced on the basis of polypropylene, polyformaldehyde, polycarbonates, polyacrylates, polyamides, especially aromatic polyamides. The range of products made from polycarbonates, including those filled with fiberglass, is rapidly expanding.

Particularly high are the chemical resistance, impact strength and dielectric properties of plastics based on polytetrafluoroethylene and tetrafluoroethylene copolymers (see. Fluoroplastics). In materials based on polyurethanes, wear resistance is successfully combined with frost resistance and long-term strength under conditions of alternating loads. Polymethyl methacrylate is used for the manufacture of optically transparent weather-resistant materials.

The absence of curing reactions during the molding of thermoplastics makes it possible to maximally intensify the processing process. The main methods of molding products from thermoplastics are injection molding, extrusion, vacuum molding and pneumatic molding. Since the melt viscosity of high molecular weight polymers is high, molding thermoplastics on injection molding machines or extruders requires specific pressures of 30-130 MN / m = (300-1300 kgf / cm 2 ).

Further development of the production of thermoplastics is aimed at creating materials from the same polymers, but with new combinations of properties, the use of elasticizers, powder and short-fiber fillers.

The main types of thermosets

After the end of molding products from thermosetting plastics, the polymer phase acquires a reticulated (three-dimensional) structure. Due to this, cured thermosetting plastics have higher indicators of hardness, modulus of elasticity, heat resistance, fatigue strength, and a lower coefficient of thermal expansion than thermoplastics; at the same time, the properties of cured thermosetting plastics are not so sharply dependent on temperature. However, the inability of the cured thermosetting plastics to pass into a viscous-flow state forces the polymer synthesis to be carried out in several stages.

The first stage ends with the production of oligomers (resins) - polymers with a molecular weight of 500-1000. Due to the low viscosity of the solution or melt, the resin can be easily distributed over the surface of the filler particles, even when the degree of filling reaches 80–85% (by weight). After the introduction of all the components, the fluidity of the thermosetting plastic remains so high that products from it can be molded by pouring (casting), contact molding, winding. Such thermosets are called premixes when they contain filler in the form of fine particles, and prepregs, if the filler is continuous fibers, fabric, paper. Technological equipment for molding products from premixes and prepregs is simple and energy costs are low, but the processes are associated with holding the material in individual molds for curing the binder. If the resin is cured by the polycondensation reaction, then the molding of the products is accompanied by a strong shrinkage of the material and significant residual stresses arise in it, and the solidity, density and strength are far from reaching the limiting values (with the exception of products obtained by winding with tension).

To avoid these disadvantages, in the technology of manufacturing products from resins cured by the polycondensation reaction, an additional stage is provided (after mixing the components) - the prevention of the binder, carried out during rolling or drying. At the same time, the duration of the subsequent holding of the material in the molds is reduced and the quality of products increases, however, filling the molds due to a decrease in the fluidity of the binder becomes possible only at pressures of 25-60 MN / m 2 (250-600 kgf / cm 2).

The resin in thermosetting plastics can be cured spontaneously (the higher the temperature, the higher the speed) or with the help of a polyfunctional low-molecular substance - a hardener.

Reactoplastics with any filler are made using phenolic-aldehyde resins as a binder, often elasticized with polyvinyl butyral, nitrile-butadiene rubber, polyamides, polyvinyl chloride (such materials are called phenoplasts), and epoxy resins, sometimes modified with phenolic or aniline-based resin-formaldehyde resins or epoxy resins ...

High-strength plastics with heat resistance up to 200 ° C are produced by combining glass fibers or fabrics with curing oligoesters, phenolic-formaldehyde or epoxy resins. In the manufacture of products that operate for a long time at 300 ° C, fiberglass or asboplastics with an organosilicon binder are used; at 300-340 ° C - polyimides in combination with silica, asbestos or carbon fibers; at 250-500 ° C in air and at 2000-2500 ° C in inert media - phenolic plastics or polyamide-based plastics filled with carbon fiber and subjected to carbonization (graphitization) after molding.

High-modulus plastics [modulus of elasticity 250-350 Gn / m 2 (25,000-35,000 kgf / mm 2 )) are produced by combining epoxy resins with carbon, boric or monocrystalline fibers (see also Composite materials). Monolithic and lightweight plastics, resistant to vibration and shock loads, waterproof and retaining dielectric properties and tightness under difficult loading conditions, are made by combining epoxy, polyester or melamine-formaldehyde resins with synthetic fibers or fabrics, paper from these fibers.

The highest dielectric properties (dielectric constant 3.5-4.0) are characteristic of materials based on quartz fibers and polyester or organosilicon binders.

Laminates are widely used in the building materials and shipbuilding industries.

The volume of production and structure of consumption of plastics

Plastic materials based on natural resins (rosin, shellac, bitumen, etc.) have been known since ancient times. The oldest plastic made from an artificial polymer - cellulose nitrate, is celluloid, the production of which was started in the USA in 1872. In 1906-10 in Russia and Germany, the production of the first thermosetting plastics - materials based on phenol-formaldehyde resin - was launched in pilot production. In the 30s. in the USSR, the USA, Germany, and other industrialized countries, the production of thermoplastics is organized - polyvinyl chloride, polymethyl methacrylate, polyamides, and polystyrene. However, the rapid development of the plastics industry began only after World War II (1939–45). In the 50s. in many countries the production of the largest-tonnage plastic - polyethylene - begins.

In 1973, the world production of polymers for plastics reached ~ 43 million tons. Of these, about 75% were thermoplastics (25% polyethylene, 20% polyvinyl chloride, 14% polystyrene and its derivatives, 16% other plastics). There is a trend towards a further increase in the share of thermoplastics (mainly polyethylene) in the total plastics production.

Although the share of thermosetting resins in the total production of polymers for plastics is only about 25%, in fact, the volume of production of thermosetting plastics is higher than that of thermoplastics, due to the high degree of filling (60-80%) of the resin.

The plastics industry is developing at a much faster rate than traditional materials of construction such as cast iron and aluminum.

The consumption of plastics in construction is constantly increasing. P This is due not only to the unique physical and mechanical properties of polymers, but also to their valuable architectural and construction characteristics. The main advantages of plastics over other building materials are lightness and relatively high specific strength. Thanks to this, the mass of building structures can be significantly reduced, which is the most important problem of modern industrial construction.

Plastics occupy one of the leading places among structural materials for mechanical engineering. Their consumption in this industry becomes commensurate (in terms of volume) with the consumption of steel. The feasibility of using plastics in mechanical engineering is determined primarily by the possibility of reducing the cost of production. At the same time, the most important technical and economic parameters of machines are also improved - weight is reduced, durability, reliability, etc. are increased. Gear and worm wheels, pulleys, bearings, rollers, machine tool guides, pipes, bolts, nuts, a wide range of technological equipment, etc. are made of plastics. ...

The main advantages of plastics, which determine their widespread use in aircraft construction, are lightness, the ability to change technical properties in a wide range. Thermoplastics are used in the production of glazing elements, antenna radomes, in decorative finishing of aircraft interiors, etc., foam and honeycomb plastics - as fillers for highly loaded three-layer structures.

The fields of application of plastics in shipbuilding are very diverse, and the prospects for their use are practically unlimited. They are used for the manufacture of ship hulls and hull structures (mainly fiberglass), in the production of parts for ship mechanisms, instruments, for interior decoration, their heat, sound and waterproofing.

In the automotive industry, the use of plastics for the manufacture of cabins, bodies and their large-sized parts is especially promising. the body accounts for about half of the mass of the car and ~ 40% of its cost. Plastic bodies are more reliable and durable than metal bodies, and their repair is cheaper and easier. However, plastics have not yet become widely used in the production of large-sized car parts, mainly due to insufficient rigidity and relatively low weather resistance. The most widely used plastics are used for interior decoration of car interiors. They are also used to manufacture engine, transmission and chassis parts. The great importance that plastics play in electrical engineering is determined by the fact that they are the basis or an indispensable component of all elements of the insulation of electrical machines, apparatus and cable products. Plastics are often used to protect insulation from mechanical stress and corrosive environments, for the manufacture of structural materials, etc.

Lit .: Encyclopedia of Polymers, t, 1-2, M., 1972-74; Technology of plastics, ed. V.V. Korshak, M., 1972; Losev I.P., Trostyanskaya EB, Chemistry of synthetic polymers, 3rd ed., M., 1971; Plastics for structural purposes, ed. E.B. Trostyanskaya, M., 1974.

Studying with children you always discover a lot of new things. While I was preparing material for classes on the world around me, I read a lot of interesting things about the Pole Star (I didn't even know what its peculiarity was) and the size of the Universe, the history of the Olympic Games, and finally I myself stopped confusing reptiles and amphibians :). But one topic touched me especially.

What is plastic made of

Now we are studying the section "economy". We study rather superficially, since we have already touched upon professions, bread production and similar issues. But, in order to remember, we watched several videos (thanks to Tatiana), including those about the manufacture of plastic.

And everything would be fine. The video is drawn quite clearly. But before that, Varvara and I got acquainted with the topic of pollution of the world's oceans, and many things shocked me. I just never thought about it! I've always felt sorry for throwing away glass, but I just didn't think about plastic. And many would prefer to grin at all and give up on it. After all, we can no longer give up plastic.

Where does the plastic go ...

Plastic is an unnatural material for nature and therefore practically does not decompose. The plastic will not be "digested" by the earth and will not return to the earth.

Polymers are made from a non-renewable natural resource - oil and gas.

Approximately 150 million tons of plastics are produced annually and this volume is increasing.

We will throw away almost 90% of what was produced immediately or within a few months (bags, bottles, packaging, lighters, etc.).

Plastic waste must not be stored or buried. Plastic absorbs toxic substances from water, these compounds seep into groundwater.

Plastic waste is dangerous to burn, and when burned, toxic gases are formed that are dangerous to humans and the atmosphere.

Plastic waste can be recycled, but only 5% is recycled, and items made from recycled plastic cannot be recycled a third time, they also will not naturally decompose. This is just a little respite and conscience relief. It's still better though.

"Biodegradable" plastics - In most marketing ploys, there is no perfectly safe plastic waste.

... to which cities

There are landfill cities in the world where technological and electronic waste is brought from Europe and the United States. Toxic substances in soil, water and air in these places exceed all conceivable norms. But we do not see this. We threw the trash in the bag, put the bag in the car, and we enjoy the cleanliness, convenience and disposable items. And people in dump cities rarely live to be 30 years old.

World ocean plastic porridge

But most of the waste travels on its own. In the world's oceans, there are five large "garbage dumpsters" where the world current carries plastic waste. The largest is the Pacific Garbage Patch, or, as it is called, the Eastern Garbage Continent. This is a spot of suspension of large and small plastic particles with an area of about 700 - 1.5 million square kilometers, containing more than one hundred million tons of garbage.

In some places, there is several times more plastic in water than plankton.

Plastic does not decompose, but disintegrates under the influence of water and sun, and every particle of it becomes toxic. Hundreds of thousands of marine animals suffer from poisoning. Some toxins cause hormonal disruptions.

Turtles die by swallowing plastic bags, which they mistake for jellyfish. The birds feed the chicks with plastic bottle caps.

Is it possible to live without plastic

And while scientists are looking for better and more commercially viable ways to recycle plastic and e-waste, we replenish it every day. And we can no longer refuse it.

For a child, all this information is not yet clear and difficult to perceive. But we discussed many questions about what we can do with our family, our home.

There are many exaggerations in the opening video. The absence of plastic will not take us back to the Stone Age, of course. We have always bought clothes only from cotton and linen, our furniture is wooden, but we cannot refuse household appliances, toothpaste and brushes, shampoo jars, switches and sockets, and hundreds of other things that fill our home.

My husband, for example, is very fond of throwing away. For him, the ease of buying and changing things is something like a symbol of convenience and wealth. And my suggestions, for example, not to throw out the bottle, but to pour water at home and take it with him, instead of buying again - he perceived only as miserly.

But! finally we agreed to do without small toys from kinder surprises and McDonald's! I have been fighting with them for a long time. As in general with frequent purchases of small cheap toys, most of which do not provide any benefit other than commercial income for their creators. A huge industry of pseudo-toys aimed at collecting, constant purchases, allowing us to "buy off" children.

We will try to pay more attention to alternatives: wooden and textile toys, tin and paper packaging (for example, eggs), do not forget to take bags with you to the store, instead of a dozen (!) Bags that are given here in supermarkets, try to extend the life of things and, in general, think carefully about every new thing that crosses the threshold of our house.

Yes, it will be a drop in the ocean, or rather, in the ocean with garbage. But this is not an excuse to do nothing at all.

The history of plastic is very exciting. Below are the dates of the most important events in plastic history over the past 150 years.

Notice how many plastics have familiar trade names, such as Teflon and Styrofoam.

What's more interesting is how many known types of plastics were actually discovered by accident!

The early years of plastic

1862 g - parkesin's discovery... Parkesin is the first man-made plastic that was created by Alexander Parks in London and was an organic material derived from cellulose. After heating and changing the shape, it was cooled and it retained the resulting shape;
1863 year – the discovery of cellulose or celluloid nitrate... The material was discovered by John Wesley Hyatt when he was trying to find a substitute for ivory in billiard balls. Celluloid came to be known as the material used in the first flexible film for photography and cinema;
1872 g - discovery of polyvinyl chloride (PVC)... For the first time, polyvinyl chloride was created by the German chemist Eugene Bauman, who never patented his discovery. In 1913, his compatriot Friedrich Klatte invented a new method for polymerizing vinyl chloride using sunlight. It was he who became the first inventor to receive a patent for polyvinyl chloride. However, PVC only became used after Waldo Semon improved the material in 1926.

The period before World War II

1908 g - opening cellophane®. In 1900, the Swiss textile engineer Jacques E. Brandenberger first came up with the idea of creating a transparent, protective material for packaging... In 1908 he developed the first machine for the production of transparent regenerated cellulose sheets. Jacques' first customer was the American candy company Whitman's, which decided to use cellophane to wrap the chocolate;
1909 g - opening bakelite... Bakelite (polyoxybenzylmethylene glycol anhydride) was one of the first plastics made from synthetic components. It was developed by the Belgian chemist Leo Beckeland, who lived in New York. Bakelite, a phenol-formaldehyde thermosetting resin, due to its low electrical conductivity and heat-resistant properties used in electrical insulators, housings for radios and telephones, and in products as diverse as dishes, jewelry, pipes and children's toys;
1926 year - vinyl or pvc opening... Vinyl was invented in the United States by Walter Simon, a researcher at B.F. Goodrich ". The material was first used in golf balls and heels. Vinyl today is the second most produced plastic in the world and is used in many products such as shower curtains, raincoats, wires, various appliances, floor tiles, paints and surface coatings;
1933 year - opening of polyvinylidene chloride (PVDC / PVDC) or Saran (Saran)... The material was accidentally discovered by Ralph Wiley in the laboratory of the American chemical company "Dow Chemical" and was first used by the military to coat fighters with it to protect them from salt sea water. Car manufacturers have also used PVC upholstery. After World War II, the company found a way to get rid of the green color and the unpleasant odor of saran, and thus it was approved for production as food packaging material... In 1953 it was marketed under the trade name "Saran Wrap" ®;
1935 H - opening of low density polyethylene (LDPE / LPDE)... This material was discovered by Reginal Gibson and Eric Fawcett in the laboratory of the British industrial giant Imperial Chemical Industries in two forms: low density polyethylene (LDPE) and high density polyethylene (HDPE / HDPE). Polyethylene is cheap, flexible, durable, and chemically resistant. LDPE is used for the production of films and packaging materials, including plastic bags. HDPE is most often used for the manufacture of containers, plumbing and auto parts;
1936 year - discovery of polymethyl methacrylate (PMMA) or acrylic... By 1936, American, British and German companies were producing polymethyl methacrylate, more commonly known as acrylic. Although acrylic is widely used these days in liquid form in paints and synthetic fibers, in solid form it is quite strong and more transparent than glass. The Plexiglas and Lucite brands sell acrylic as glass substitute;
1937 year - polyurethane opening... Polyurethane is an organic polymer that was invented by chemist Otto Bayer of the German company Friedrich Bayer & Company. Polyurethanes are used as resilient foam in upholstery, mattresses, earplugs, chemically resistant coatings, specialty adhesives, sealants and packaging. In solid form, polyurethane is used in materials for thermal insulation of buildings, in water heaters, in refrigerated transport, in commercial and non-commercial refrigeration. Polyurethanes are sold under the trade names Igamid® as plastics and Perlon® as fibers;
1938 H - first use of polystyrene... Polystyrene was first discovered in 1839 by the German pharmacist Eduard Simon, but it was not first used in the 1930s, when scientists at the world's largest chemical company, BASF, developed a commercial method for making polystyrene. Polystyrene is a tough plastic that can be made by injection molding, compression molding, extrusion, or blow molding. Material widely used in plastic cups, egg cartons, peanut cartons, and in building materials and electrical appliances;
1938 H - discovery of polytetrafluoroethylene (PTFE) or Teflon... The polymer was discovered by accident by chemist Roy Plunkett, who was then working for the American chemical company DuPont. PTFE was one of the most widely used plastics in war, and was (top secret!) Applied to metal surfaces as a protective coating. low friction to prevent scratches and corrosion. In the early 1960s, Teflon non-stick pans became very popular. PTFE was later used to synthesize the first Gore-Tex membrane tissues. By mixing Teflon with fluorine compounds, a material is obtained that is used to make dummy missiles to distract heat-seeking missiles;
1938 H - nylon and neoprene opening... Both materials were developed by Wallace Carothers when his research team at DuPont was trying to find a synthetic replacement for silk. Neoprene, a synthetic rubber, was first made in 1931. Further research on polymers led to the development of nylon, also known as "wonder fiber". In 1939, DuPont first announced and demonstrated nylon and nylon stockings to the American public at the New York World's Fair. Also nylon was previously used in the manufacture of fishing line, surgical thread and a toothbrush;
1942 year - opening unsaturated polyester or PET (also called polyester, lavsan and dacron). The material was patented by English chemists John Rex Winfield and James Tennant Dixon and was used for the manufacture of synthetic fibers that were sold in the post-war period. Because polyester is denser than other cheap plastics, it is used in soda and sour beverage bottles. And since polyester is also strong and abrasion resistant, it is used for the manufacture of mechanical parts, food trays, and other items. Polyester films from Mylar are used in audio and video cassettes.

Fluoroplastic has a fairly low coefficient of friction, good wear resistance, resistance to high temperatures, due to which it is successfully used in various industries.

Important discoveries after World War II

1951 year - opening high density polyethylene or polypropylene... Two American chemists Paul Hogan and Robert Banks, who work for the oil company Phillips Petroleum in the Netherlands, have found a way to produce crystalline polypropylene. Polypropylene is similar to its "cousin" polyethylene and its cost is relatively low, but unlike polyethylene, it is much stronger and is used in almost everything from plastic bottles to carpets and plastic furniture. It is used very actively in the automotive industry;
1954 year - opening of Styrofoam or Styrofoam... The English designation of expanded polystyrene "Styrofoam" and as a trade name was borrowed by the chemical company "The Dow Chemical Company". The foam was invented by accident by the scientist Ray McIntyre, who tried to make a flexible electrical insulator by combining styrene with isobutylene under pressure, which was a rather explosive compound. As a result of his experiment, bubble polystyrene foam was discovered, which is 30 times lighter than conventional polystyrene.

Take a look around the room where you are right now and count how many items are all or part of plastic. You will immediately see how ubiquitous plastic is. He is really everywhere!