Plastics, or simply plastics, are high-molecular compounds made from natural or synthetic substances. The main feature of such substances is the possibility of transition to a plastic state under the influence of two factors - high temperature and pressure. In addition, it is also important that after this the mass is able to maintain the shape given to it.
General description of plastics
Plastics began to be produced about 50-60 years ago. To date, these products have gained enormous distribution both in everyday life, and in industry and other sectors of human activity. In addition, at present, plastic can successfully replace wood, glass, and even metal in some cases. It is worth noting that industries such as mechanical engineering, radio engineering, electrical engineering, the chemical industry can no longer do without such products.
Plastics are able to combine the strength of metal products, while having the weight of wood and the transparency of glass. With all these qualities, such substances have no drawbacks inherent in all these materials. They are not susceptible to corrosion like metal, rotting like wood, they cannot be broken like glass.
General usage information
Plastics can be used for the manufacture of film materials. They, in turn, are actively used during the cultivation of vegetables, for example. Great for creating a protected area in the ground, for growing berries, flowers and more.
In addition, plastic containers, containers and other containers also occupy one of the leading places when it is necessary to transport pesticides, fertilizers, and rural products. Today, a gas exchange film structure is already being produced. Such membranes will be used to store products in an environment with a controlled amount of gas. For rural activities, reflective films are even produced to mulch the soil.
Basic connections
If we give general information about plastics, we can say the following: the base consists of a high molecular weight compound or just a polymer, as well as natural (sands, asphalts) or synthetic additives. To date, the most common and important are synthetic plastics, which are obtained by polymerization or polycondensation.
The process of polymerization of plastic masses is a reaction of combining identical molecules called monomers. No simple substances are released. And the formed polymer will have a molecular weight equal to the mass of the two constituent components. It is worth noting that several monomers can participate in the technology for the production of plastics. In this case, the procedure will be called copolymerization.
If we talk about polycondensation, then the polymer will be obtained by combining several functional groups of different substances. This will release some simple substances. Based on this, it becomes clear that the total molecular weight of the finished polymer will not be equal to the total mass of the monomers involved in the formation.
Description of high molecular weight compounds
Processing of these compounds is carried out due to exposure to high temperature and pressure. Immediately upon receipt, such compounds will take the form of either a viscous liquid or a solid. In addition, it is worth saying that polymers are classified into three large groups - according to the chemical structure of the monomer used for the formation.
Additives
The structure and purpose of plastics depends on their properties. Therefore, it is worth saying that there are special additives that can change some qualities in the right direction.
Some finished products are 100% polymers - these are polyethylene or polyamides. Others consist of polymers only by 20-60%, and the rest of the mass fraction is occupied by special fillers. The main purpose of fillers is to change various properties: increase fire resistance, increase strength, increase hardness and mechanical strength. In rubber, for example, a filler such as soot is added.
Another additive that is part of plastic containers, for example, and in many other solid containers - plasticizers. However, the more plasticizer added, the greater the coefficient of plasticity. Thus, it is possible to obtain a strong, but sufficiently ductile material.
Another important component is the stabilizer. It is added to the composition in order to avoid decomposition of the finished product under the influence of high temperatures, sunlight and other external factors. In some cases, a little dye is added if you want to change the color of the product.
Detailed description of substances
The production technology of such compounds implies the presence of another component, which is called the IUD.
The IUD is an essential additive that holds many different elements together, and also gives plasticity. In addition, the Navy also contributes to the possibility of molding, gives electrical insulation and anti-corrosion characteristics. If we talk about the general classification of plastics, they can be unfilled and filled.
The first group is a mass of pure polymer, or with a very small amount of additives. The second group, on the contrary, contains both polymers and a large number of different additives that are evenly distributed in a binder composition, usually in resin.
As mentioned earlier, fillers are introduced to change or improve most qualities. By themselves, these components can be either organic or mineral compounds. They can be presented in the form of powder fillers - wood powder, mica or silica flour and others. And they can be represented by fibrous elements, for example, cotton. The last type of fillers is canvas (paper, mica, and others).
If we talk in more detail about plasticizers, then they can be characterized as follows: these are low-volatile components, which are most often represented by any liquid. Their introduction to the composition increases not only elasticity. A molded product with an increase in plasticizers in the composition improves the indicators of frost resistance, elasticity.
There is another type of additives - hardeners. Their concentration is usually very low, and the main task is to convert the polymers into a three-dimensional structure. In fact, this leads to the transformation of some plastics into a non-fusible state.
disadvantages
It is worth noting some of the disadvantages that this material still has. All types of plastics have a significantly lower rate of heat resistance than metal products. The bulk of plastic products can be operated at a temperature not exceeding 150 degrees Celsius. Despite their long service life, plastic products are also subject to aging. This defect will manifest itself in the darkening of the product, oxidation, a decrease in strength characteristics, hardness.
Polyethylene production
You can consider the technology of production of plastic mass based on polyethylene. This is one of those substances that are obtained by polymerization, and it is in great demand on the market.
To obtain polyethylene in its usual form, we use three polymerization methods:
- The first method is the polymerization under pressure of 1000-2000 atm with a temperature of 180 to 200 degrees Celsius. A small amount of oxygen is used as the initiator of the process - 0.005-0.05%.
- The second polymerization variant, on the contrary, takes place under the influence of either atmospheric or artificially created pressure of 2-6 atm and at a temperature of only 60-70 degrees. In this case, organometallic hydrocarbons in the oil medium are used as catalysts in the absence of the slightest moisture and oxygen.
- The last type of polymerization takes place under a pressure of 20-50 atm and with the participation of oxide catalysts with a temperature of 110-140 degrees Celsius.
Types of Plastics
During manufacturing and subsequent hardening, two more types of plastics can be distinguished. The main distinguishing feature is the hardening conditions or without it. According to this parameter, thermoplastic and thermosetting plastic is distinguished.
As for the first category of products, they will undergo certain changes when heated, passing from a solid state to a plastic, viscous and fluid. This type of product will solidify back upon cooling. Thermoplastic products include polyethylene, polystyrene, fluoroplastics and other types.
Thermoset plastic, when heated to a temperature of 150-300 degrees, will undergo irreversible changes. Such masses will turn into a solid, insoluble and non-melting state under pressure or without it. They contain hardeners as an additive. An example is epoxy resin.
Production in Russia
One of the oldest and largest enterprises for the manufacture of this product is the Nelidovo Plant of Plastics NZPM. The production facilities of this enterprise are located in the south-west of the Tver region.
The plant is located on 19 hectares of land, on which 25 industrial facilities are located.
The largest production area belongs to the construction of Izonel brand polyethylene foam (PPE). The area is 24,500 square meters. Following is a much smaller area of the workshop number 2 - 7500 square meters. meters where extrusion sheet plastics are made. The area for vacuum forming of products takes another 3 thousand square meters. meters. In addition, the plant is engaged in the processing of plastics.