Plastics: classification, main characteristics, production and processing technologies

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

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 that the mass is able to maintain the shape given to it.

General description of plastics

Plastic masses began to be produced about 50-60 years ago. To date, these products have become widespread both in everyday life and in industry and other branches 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, and the chemical industry can no longer do without such products.

Plastic masses 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 do not have the disadvantages inherent in all these materials. They do not corrode like metal, rot like wood, and cannot be broken like glass.

General Usage Information

Plastic masses 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 in the need to transport pesticides, fertilizers, agricultural products. To date, the production of a gas-exchange film structure is already underway. Such membranes will be used to store products in an environment with a controlled amount of gas. For rural activities, reflective films are even being 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 compound or just a polymer, as well as natural (pitch, asph alt) or synthetic additives. To date, the most widespread and important are synthetic plastics, which are obtained by polymerization or polycondensation.

The process of polymerization of plastics is a reaction of combining identical molecules thatcalled monomers. In this case, no simple substances are released. And the resulting polymer will have a molecular weight equal to the mass of the two constituents that form it. It should be noted that several monomers can participate in the plastics production technology at the same time. 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. In this case, some simple substances will be released. 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 macromolecular compounds

The processing of these compounds is carried out by exposure to high temperature and pressure. Once prepared, such compounds will be in 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 formation.

Supplements

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 for 20-60%, and the rest of the mass fraction is occupied byspecial fillers. The main purpose of fillers is to change various properties: increasing fire resistance, increasing strength, increasing hardness and mechanical strength. For example, a filler such as carbon black is added to rubber.

Another additive found in plastic containers, for example, and in many other solid containers, are plasticizers. However, the more plasticizer is added, the greater will be the coefficient of plasticity. Thus, it is possible to obtain a durable, but rather plastic material.

Another important component is the stabilizer. It is added to the composition in order to avoid the 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 technology for the production of such compounds implies the presence of another component, which is called the IUD.

Navy is the most important additive that holds many different elements together, and also gives plasticity. In addition, HMS also promotes moldability, electrical insulation and anti-corrosion performance. If we talk about the general classification of plastics, then 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 anda large number of different additives that are evenly distributed in the binder, usually in the 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 quartz 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).

Speaking in more detail about plasticizers, they can be characterized as follows: these are low-volatile components, which are most often represented by some kind of liquid. Their introduction into the composition increases not only elasticity. A molded product with an increase in plasticizers in the composition improves frost resistance and elasticity.

There is another type of additives - hardeners. Their concentration is usually very low, and the main task is to convert polymers into a three-dimensional structure. In fact, this causes some plastics to become infusible.

Flaws

It is worth noting some of the shortcomings that this material still has. Any types of plastics have a significantly lower heat resistance than metal products. The bulk of plastic products can be operated at temperatures not exceeding 150 degrees Celsius. Despite their long service life, plastic products alsosubject to aging. This defect will manifest itself in darkening of the product, oxidation, reduction in strength characteristics, hardness.

Obtaining polyethylene

You can consider the technology for the production of plastics based on polyethylene. This is one of those substances that is obtained by polymerization, and it is in great demand in the market.

To obtain polyethylene in its usual form, three polymerization methods are used:

1. The first method is 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%.
2. The second variant of polymerization, 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 are used as catalysts in an oil environment in the absence of the slightest moisture and oxygen.
3. 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 manufacture and subsequent curing, two more types of plastics can be distinguished. The main distinguishing feature is the conditions of hardening or without it. According to this parameter, thermoplastic and thermosetting plastics stand out.

As for the first category of products, they are heatedwill undergo certain changes, passing from a solid state to a plastic, viscous and fluid state. This type of product will solidify back when cooled. Thermoplastic products include polyethylene, polystyrene, fluoroplasts and other types.

Thermosetting plastic, when heated to a temperature of 150-300 degrees, will undergo irreversible changes. Such masses will become solid, insoluble and infusible under pressure or without it. They contain hardeners as an additive. An example is epoxy.

Production in Russia

One of the oldest and largest enterprises for the manufacture of this product is the Nelidovsky 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 facility producing Isonel polyethylene foam (PPE). The area is 24,500 square meters. Next comes a much smaller area of shop number 2 - 7500 square meters. meters, where extruded sheet plastics are made. The site for vacuum forming products occupies another 3 thousand square meters. meters. In addition, the plant is engaged in the processing of plastics.