The term “polymer materials” is a general term. It combines three broad groups of synthetic plastics, namely: polymers; plastics and their morphological variety - polymer composite materials (PCMs) or, as they are also called, reinforced plastics. What is common to the listed groups is that their obligatory part is the polymer component, which determines the basic thermal deformation and technological properties of the material. The polymer component is an organic high-molecular substance obtained as a result of a chemical reaction between the molecules of the original low-molecular substances - monomers.

Polymers It is customary to call high-molecular substances (homopolymers) with additives introduced into them, namely stabilizers, inhibitors, plasticizers, lubricants, antiradicals, etc. Physically, polymers are homophase materials; they retain all the physical and chemical features inherent in homopolymers.

Plastics are polymer-based composite materials containing dispersed or short-fiber fillers, pigments and other bulk components. Fillers do not form a continuous phase. They (dispersed medium) are located in a polymer matrix (dispersed medium). Physically, plastics are heterophasic materials with isotropic (identical in all directions) physical macroproperties.
Plastics can be divided into two main groups - thermoplastic and thermoset. Thermoplastics are those that, once formed, can be melted and molded again; thermosetting, once formed, no longer melts and cannot take another shape under the influence of temperature and pressure. Almost all plastics used in packaging are thermoplastic, for example, polyethylene and polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, nylon (nylon), polycarbonate, polyvinyl acetate, polyvinyl alcohol and others.
Plastics can also be categorized based on the method used to polymerize them into polymers produced by polyaddition or polycondensation mechanisms. Polyaddition polymers are produced by a mechanism that involves either free radicals or ions, whereby small molecules are rapidly added to the growing chain without the formation of companion molecules. Polycondensation polymers are produced by reacting functional groups in molecules with each other so that a long chain polymer, and typically a low molecular weight co-product, such as water, is formed during each reaction step. Most packaging polymers, including polyolefins, polyvinyl chloride and polystyrene, are polyaddition polymers.

The polymerization reaction is the sequential addition of molecules of unsaturated compounds to each other to form a high-molecular product - a polymer. Alkene molecules that undergo polymerization are called monomers. The number of elementary units repeated in a macromolecule is called the degree of polymerization (denoted by n). Depending on the degree of polymerization, substances with various properties. Thus, short chain polyethylene (n = 20) is a liquid with lubricating properties. Polyethylene with a chain length of 1500-2000 links is a hard but flexible plastic material from which films can be made, bottles and other glassware, elastic pipes, etc. Finally, polyethylene with a chain length of 5-6 thousand links is a solid substance from which cast products, rigid pipes, and strong threads can be prepared.

If a small number of molecules take part in the polymerization reaction, then low-molecular substances are formed, for example, dimers, trimers, etc. The conditions for the occurrence of polymerization reactions are very different. In some cases, catalysts and high pressure are required. But the main factor is the structure of the monomer molecule. Unsaturated (unsaturated) compounds enter into the polymerization reaction due to the cleavage of multiple bonds.

Polymerization is a chain reaction, and in order for it to begin, it is necessary to activate the monomer molecules with the help of so-called initiators. Such reaction initiators can be free radicals or ions (cations, anions). Depending on the nature of the initiator, radical, cationic or anionic polymerization mechanisms are distinguished.

Chemical and physical properties plastics are determined by their chemical composition, average molecular weight and molecular weight distribution, processing (and use) history, and the presence of additives.

Polymer composite materials are a type of plastic. They differ in that they use not dispersed, but reinforcing, that is, reinforcing fillers (fibers, fabrics, tapes, felt, single crystals), which form an independent continuous phase in the PCM. Certain varieties of such PCMs are called laminated plastics. This morphology makes it possible to obtain plastics with very high deformation-strength, fatigue, electrical, acoustic and other target characteristics corresponding to the highest modern requirements.

The structural formulas of polymers are briefly written as follows: the formula of the elementary unit is enclosed in brackets and the letter n is placed at the bottom right. For example, the structural formula of polyethylene (-CH 2 -CH 2 -) n. It is easy to conclude that the name of the polymer is composed of the name of the monomer and the prefix poly-, for example polyethylene, polyvinyl chloride, polystyrene, etc.

The most common polymers with a hydrocarbon structure are polyethylene and polypropylene.

Polyethylene is produced by polymerization of ethylene. Polypropylene is produced by stereospecific polymerization of propylene (propene).
Stereospecific polymerization is the process of obtaining a polymer with a strictly ordered spatial structure.

Many other compounds are capable of polymerization - ethylene derivatives having general formula CH 2 =CH-X, where X are various atoms or groups of atoms.

Types of polymers

Polyolefins are a class of polymers of the same chemical nature (chemical formula -(CH 2) - n) with a diverse spatial structure of molecular chains, including polyethylene and polypropylene. By the way, all carbohydrates, for example, natural gas, sugar, paraffin and wood, have a similar chemical structure. In total, 150 million tons of polymers are produced annually in the world, and polyolefins make up approximately 60% of this amount. In the future, polyolefins will be around us much more than they are today, so it's useful to take a closer look at them.
The complex of properties of polyolefins, including resistance to ultraviolet radiation, oxidizing agents, tearing, puncturing, shrinkage during heating and tearing, varies within very wide limits depending on the degree of orientational stretching of molecules during the production of polymer materials and products.
It should be especially emphasized that polyolefins are environmentally cleaner than most materials used by humans. The production, transportation and processing of glass, wood and paper, concrete and metal uses a lot of energy, the production of which inevitably pollutes the environment. When disposing of traditional materials, harmful substances are also released and energy is consumed. Polyolefins are produced and utilized without the release of harmful substances and with minimal energy consumption, and when polyolefins are burned, a large amount of clean heat is released with by-products in the form of water vapor and carbon dioxide.

Polyethylene
About 60% of all plastics used for packaging are polyethylene, which is used so widely mainly due to its low cost, but also due to its excellent properties for many applications.

High-density polyethylene (HDPE - low pressure) has the simplest structure of all plastics, it consists of repeating ethylene units:
-(CH 2 -CH 2)- n high density polyethylene.

Low density polyethylene (LDPE - high pressure) has the same chemical formula, but differs in that its structure is branched:
-(CH 2 -CHR)- n low density polyethylene,
where R can be -H, -(CH 2) n, -CH 3, or a more complex structure with secondary branching.

Polyethylene, due to its simple chemical structure, easily folds into crystal lattice, and therefore tends to have a high degree of crystallinity. Chain branching interferes with this ability to crystallize, resulting in fewer molecules per unit volume, and therefore lower density.

LDPE - high-density polyethylene. Plastic, slightly matte, waxy to the touch, processed by extrusion into blown film or flat film through a flat die and chilled roller. LDPE film is strong in tension and compression, resistant to impact and tear, and durable at low temperatures. Has the peculiarity - quite low temperature softening (about 100 degrees Celsius).

HDPE - low-density polyethylene. HDPE film is rigid, durable, and less waxy to the touch compared to LDPE films. It is obtained by extruding a blown hose or extruding a flat hose. The softening temperature of 121°C allows for steam sterilization. The frost resistance of these films is the same as that of LDPE films. Resistance to tension and compression is high, and resistance to impact and tear is less than that of LDPE films. HDPE films are an excellent barrier to moisture. Resistant to fats and oils.
The “russling” T-shirt bag in which you pack your purchases is made of HDPE.
There are two main types of HDPE. The older type, produced first in the 1930s, polymerizes at high temperatures and pressures, conditions that are energetic enough to produce appreciable rates of chain reactions that result in the formation of both long and short chain branches. . This type of HDPE is sometimes called high-density polyethylene (HDPE, HDPE, due to the high pressure), if there is a need to distinguish it from linear low-density polyethylene, a “younger” type of LDPE.

At room temperature, polyethylene is quite soft and flexible material. It retains this flexibility well in cold conditions, so it is suitable for packaging frozen food products. However, at elevated temperatures, such as 100°C, it becomes too soft for some applications. HDPE has a higher brittleness and softening point than LDPE, but is still not suitable for hot fill containers.

About 30% of all plastics used for packaging are HDPE. It is the most widely used plastic for bottles due to its low cost, ease of molding, and excellent performance for many applications. In its natural form, HDPE has a milky white, translucent appearance, and is thus not suitable for applications where exceptional transparency is required.

One disadvantage of using HDPE in some applications is its tendency to undergo environmental stress cracking, defined as the failure of a plastic container under conditions of simultaneous stress and contact with the product, which alone does not cause failure. Environmental stress cracking in polyethylene is related to the crystallinity of the polymer.

LDPE is the most widely used packaging polymer, accounting for approximately one third of all packaging plastics. Due to its low crystallinity, it is a softer, more flexible material than HDPE. Due to its low cost, it is the preferred material for bags and bags. LDPE offers better clarity than HDPE, but still lacks the crystal clarity desired for some packaging applications.

Polypropylene
It has excellent transparency (with rapid cooling during the formation process), high melting point, chemical and water resistance. PP allows water vapor to pass through, which makes it indispensable for “breathable” food packaging (bread, herbs, groceries), as well as in construction for hydro-windproofing. PP is sensitive to oxygen and oxidizing agents. It is processed by extrusion blowing or through a flat die with pouring onto a drum or cooling in a water bath. It has good transparency and gloss, high chemical resistance, especially to oils and fats, and does not crack when exposed to environment.

Polyvinyl chloride
IN pure form rarely used due to fragility and inelasticity. Inexpensive. Can be processed into film by blown extrusion or flat-slit extrusion. The melt is highly viscous. PVC is thermally unstable and corrosive. When overheated and burned, it releases a highly toxic chlorine compound - dioxin. Widespread in the 60s and 70s. Being replaced by more environmentally friendly polypropylene.

It's amazing how diverse the objects around us and the materials from which they are made are. Previously, around the 15th-16th centuries, the main materials were metals and wood, a little later glass, and almost always porcelain and earthenware. But today’s century is the time of polymers, which will be discussed further.

Concept of polymers

Polymer. What is it? You can answer from different points of view. On the one hand, this modern material, used to make many household and technical items.

On the other hand, we can say that it is a specially synthesized synthetic substance obtained with predetermined properties for use in a wide specialization.

Each of these definitions is correct, only the first from a household point of view, and the second from a chemical point of view. One more chemical determination is the following. Polymers are compounds based on short sections of a molecular chain - monomers. They are repeated many times, forming a polymer macrochain. Monomers can be both organic and inorganic compounds.

Therefore, the question: “polymer - what is it?” - requires a detailed answer and consideration of all properties and areas of application of these substances.

Types of polymers

There are many classifications of polymers according to various signs(chemical nature, heat resistance, chain structure, etc.). In the table below we briefly consider the main types of polymers.

Classification of polymers

Principle	Species	Definition	Examples
By origin (appearance)	Natural (natural)	Those that occur naturally, in nature. Created by nature.	DNA, RNA, proteins, starch, amber, silk, cellulose, natural rubber
	Synthetic	Obtained in laboratory conditions by humans, have no relation to nature.	PVC, polyethylene, polypropylene, polyurethane and others
	Artificial	Created by man in laboratory conditions, but based on	Celluloid, cellulose acetate, nitrocellulose
From a chemical point of view	Organic nature	Most of all known polymers. It is based on a monomer of organic matter (consists of C atoms, possibly including N, S, O, P and others atoms).	All synthetic polymers
	Inorganic nature	The basis is elements such as Si, Ge, O, P, S, H and others. Properties of polymers: they are not elastic, do not form macrochains.	Polysilanes, polydichlorophosphazene, polygermanes, polysilicic acids
	Organoelement nature	A mixture of organic and inorganic polymers. The main chain is inorganic, the side chains are organic.	Polysiloxanes, polycarboxylates, polyorganocyclophosphazenes.
Main chain difference	Homochain	The main chain is either carbon or silicon.	Polysilanes, polystyrene, polyethylene and others.
	Heterochain	The main skeleton is made up of different atoms.	Examples of polymers are polyamides, proteins, ethylene glycol.

There are also polymers of linear, network and branched structure. The basis of polymers allows them to be thermoplastic or thermosetting. They also differ in their ability to deform under normal conditions.

Physical properties of polymer materials

The main two states of aggregation characteristic of polymers are:

• amorphous;
• crystalline.

Each is characterized by its own set of properties and has important practical significance. For example, if a polymer exists in an amorphous state, it means that it can be a viscous flowing liquid, a glass-like substance, or a highly elastic compound (rubbers). It finds wide application in the chemical industries, construction, technology, production of industrial goods.

The crystalline state of polymers is rather conditional. In fact this state interspersed with amorphous sections of the chain, and in general the entire molecule turns out to be very convenient for obtaining elastic, but at the same time high-strength and hard fibers.

Melting points for polymers are different. Many amorphous ones melt at room temperature, and some synthetic crystalline ones can withstand fairly high temperatures (plexiglass, fiberglass, polyurethane, polypropylene).

Polymers can be painted in a variety of colors, without restrictions. Thanks to their structure, they are able to absorb paint and acquire the brightest and most unusual shades.

Chemical properties of polymers

The chemical properties of polymers differ from those of low molecular weight substances. This is explained by the size of the molecule, the presence of various functional groups in its composition, and the total reserve of activation energy.

In general, several main types of reactions characteristic of polymers can be distinguished:

1. Reactions that will be determined by the functional group. That is, if the polymer contains an OH group, characteristic of alcohols, then the reactions in which they will enter will be identical to those of oxidation, reduction, dehydrogenation, and so on).
2. Interaction with NMCs (low molecular compounds).
3. Reactions of polymers with each other to form cross-linked networks of macromolecules (network polymers, branched).
4. Reactions between functional groups within one polymer macromolecule.
5. Disintegration of a macromolecule into monomers (chain destruction).

All of the above reactions occur in practice great value to obtain polymers with predetermined and convenient properties for humans. Polymer chemistry makes it possible to create heat-resistant, acid- and alkali-resistant materials that at the same time have sufficient elasticity and stability.

Use of polymers in everyday life

The use of these compounds is widespread. There are few areas of industry, national economy, science and technology that do not require polymer. What is it - polymer farming and widespread use, and what does it end with?

1. Chemical industry (production of plastics, tannins, synthesis of essential organic compounds).
2. Mechanical engineering, aircraft manufacturing, oil refineries.
3. Medicine and pharmacology.
4. Obtaining dyes and pesticides and herbicides, agricultural insecticides.
5. Construction industry (steel alloying, sound and thermal insulation structures, building materials).
6. Manufacturing of toys, dishes, pipes, windows, household items and household utensils.

The chemistry of polymers makes it possible to obtain more and more new materials, completely universal in properties, which have no equal among metals, wood or glass.

Examples of products made from polymer materials

Before naming specific products made from polymers (it is impossible to list them all, there is too much variety), first you need to understand what the polymer provides. The material that is obtained from the Navy will be the basis for future products.

The main materials made from polymers are:

• plastics;
• polypropylenes;
• polyurethanes;
• polystyrenes;
• polyacrylates;
• phenol-formaldehyde resins;
• epoxy resins;
• nylons;
• viscose;
• nylons;
• adhesives;
• films;
• tannins and others.

This is just a small list of the diversity that modern chemistry offers. Well, here it already becomes clear what objects and products are made from polymers - almost any household items, medicine and other areas ( plastic windows, pipes, dishes, tools, furniture, toys, films, etc.).

Polymers in various branches of science and technology

We have already touched upon the question of in what areas polymers are used. Examples showing their importance in science and technology include the following:

• antistatic coatings;
• electromagnetic screens;
• housings of almost all household appliances;
• transistors;
• LEDs and so on.

There are no limits to imagination regarding the use of polymer materials in the modern world.

Polymer production

Polymer. What is it? This is practically everything that surrounds us. Where are they made?

1. Petrochemical (oil refining) industry.
2. Special plants for the production of polymer materials and products made from them.

These are the main bases on the basis of which polymer materials are obtained (synthesized).

Polymers, or macromolecules, are very large molecules formed by the bonds of many small molecules, called constituent units, or monomers. The molecules are so large that their properties do not change significantly when several of these building blocks are added or removed. The term "polymer materials" is a general one. It combines three broad groups of synthetic plastics, namely: polymers; plastics and their morphological variety - polymer composite materials (PCMs) or, as they are also called, reinforced plastics. What is common to the listed groups is that their obligatory part is the polymer component, which determines the basic thermal deformation and technological properties of the material. The polymer component is an organic high-molecular substance obtained as a result of a chemical reaction between the molecules of the original low-molecular substances - monomers.

Polymers are usually called high-molecular substances (homopolymers) with additives introduced into them, namely stabilizers, inhibitors, plasticizers, lubricants, antiradicals, etc. Physically, polymers are homophasic materials; they retain all the physicochemical features inherent in homopolymers.

Plastics are polymer-based composite materials containing dispersed or short-fiber fillers, pigments and other bulk components. Fillers do not form a continuous phase. They (dispersion medium) are located in a polymer matrix (dispersion medium). Physically, plastics are heterophasic materials with isotropic (identical in all directions) physical macroproperties.

Plastics can be divided into two main groups - thermoplastic and thermoset. Thermoplastics are those that, once formed, can be melted and molded again; thermosetting, once formed, no longer melts and cannot take another shape under the influence of temperature and pressure. Almost all plastics used in packaging are thermoplastics, such as polyethylene and polypropylene (members of the polyolefin family), polystyrene, polyvinyl chloride, polyethylene terephthalate, nylon (nylon), polycarbonate, polyvinyl acetate, polyvinyl alcohol, and others.

Plastics can also be categorized based on the method used to polymerize them into polymers produced by addition to polycondensation. Addition polymers are produced by a mechanism that involves either free radicals or ions, whereby small molecules are rapidly added to the growing chain without producing companion molecules. Polycondensation polymers are produced by reacting functional groups in molecules with each other so that a long chain of polymer is formed in stages, and typically produces a low molecular weight co-product, such as water, during each reaction step. Most packaging polymers, including polyolefins, polyvinyl chloride and polystyrene, are addition polymers.

The chemical and physical properties of plastics are determined by their chemical composition, average molecular weight and molecular weight distribution, processing (and use) history, and the presence of additives.

Polymer reinforced materials are a type of plastic. They differ in that they use not dispersed, but reinforcing, that is, reinforcing fillers (fibers, fabrics, tapes, felt, single crystals), which form an independent continuous phase in the PCM. Certain varieties of such PCMs are called laminated plastics. This morphology makes it possible to obtain plastics with very high deformation-strength, fatigue, electrical, acoustic and other target characteristics that meet the highest modern requirements.

The polymerization reaction is the sequential addition of molecules of unsaturated compounds to each other to form a high-molecular product - a polymer. Alkene molecules that undergo polymerization are called monomers. The number of elementary units repeated in a macromolecule is called the degree of polymerization (denoted n). Depending on the degree of polymerization, substances with different properties can be obtained from the same monomers. Thus, short chain polyethylene (n = 20) is a liquid with lubricating properties. Polyethylene with a chain length of 1500-2000 links is a hard but flexible plastic material from which films can be made, bottles and other glassware, elastic pipes, etc. Finally, polyethylene with a chain length of 5-6 thousand links is a solid substance from which cast products, rigid pipes, and strong threads can be prepared.

If a small number of molecules take part in the polymerization reaction, then low-molecular substances are formed, for example, dimers, trimers, etc. The conditions for the occurrence of polymerization reactions are very different. In some cases, catalysts and high pressure are required. But the main factor is the structure of the monomer molecule. Unsaturated (unsaturated) compounds enter into the polymerization reaction due to the cleavage of multiple bonds. The structural formulas of polymers are briefly written as follows: the formula of the elementary unit is enclosed in brackets and the letter n is placed at the bottom right. For example, the structural formula of polyethylene is (-CH2-CH2-)n. It is easy to conclude that the name of the polymer is composed of the name of the monomer and the prefix poly-, for example polyethylene, polyvinyl chloride, polystyrene, etc.

Polymerization is a chain reaction, and in order for it to begin, it is necessary to activate the monomer molecules with the help of so-called initiators. Such reaction initiators can be free radicals or ions (cations, anions). Depending on the nature of the initiator, radical, cationic or anionic polymerization mechanisms are distinguished.

The most common hydrocarbon polymers are polyethylene and polypropylene.

Polyethylene is produced by the polymerization of ethylene: Polypropylene is produced by the stereospecific polymerization of propylene (propene). Stereospecific polymerization is the process of obtaining a polymer with a strictly ordered spatial structure. Many other compounds are capable of polymerization - ethylene derivatives having the general formula CH2 = CH-X, where X are various atoms or groups of atoms.

Types of polymers:

Polyolefins are a class of polymers of the same chemical nature (chemical formula -(CH2)-n) with a diverse spatial structure of molecular chains, including polyethylene and polypropylene. By the way, all carbohydrates, for example, natural gas, sugar, paraffin and wood, have a similar chemical structure. In total, 150 million tons of polymers are produced annually in the world, and polyolefins make up approximately 60% of this amount. In the future, polyolefins will be around us much more than they are today, so it's useful to take a closer look at them.

The complex of properties of polyolefins, including resistance to ultraviolet radiation, oxidizing agents, tearing, puncturing, shrinkage during heating and tearing, varies within very wide limits depending on the degree of orientational stretching of molecules during the production of polymer materials and products.

It should be especially emphasized that polyolefins are environmentally cleaner than most materials used by humans. The production, transportation and processing of glass, wood and paper, concrete and metal uses a lot of energy, the production of which inevitably pollutes the environment. When disposing of traditional materials, harmful substances are also released and energy is consumed. Polyolefins are produced and utilized without the release of harmful substances and with minimal energy consumption, and when polyolefins are burned, a large amount of clean heat is released with by-products in the form of water vapor and carbon dioxide. Polyethylene

About 60% of all plastics used for packaging are polyethylene, mainly due to its low cost, but also due to its excellent properties for many applications. High-density polyethylene (HDPE - low pressure) has the simplest structure of all plastics, it consists of repeating ethylene units. -(CH2CH2)n- high density polyethylene. Low density polyethylene (LDPE - high pressure) have the same chemical formula, but differs in that its structure is branched. -(CH2CHR) n- low density polyethylene Where R can be -H, -(CH2)nCH3, or a more complex structure with secondary branching.

Polyethylene, due to its simple chemical structure, easily folds into a crystal lattice, and therefore tends to have a high degree of crystallinity. Chain branching interferes with this ability to crystallize, resulting in fewer molecules per unit volume, and therefore lower density.

LDPE - high-density polyethylene. Plastic, slightly matte, waxy to the touch, processed by extrusion into blown film or flat film through a flat die and chilled roller. LDPE film is strong in tension and compression, resistant to impact and tear, and durable at low temperatures. It has a peculiarity - a rather low softening temperature (about 100 degrees Celsius).

HDPE - low-density polyethylene. HDPE film is rigid, durable, and less waxy to the touch compared to LDPE films. It is obtained by extruding a blown hose or extruding a flat hose. The softening temperature of 121°C allows for steam sterilization. The frost resistance of these films is the same as that of LDPE films. Resistance to tension and compression is high, and resistance to impact and tear is less than that of LDPE films. HDPE films are an excellent barrier to moisture. Resistant to fats and oils. The “rustling” T-shirt bag (“rustling”) in which you pack your purchases is made of HDPE.

There are two main types of HDPE. The "older" type, produced first in the 1930s, polymerizes at high temperatures and pressures, conditions that are energetic enough to allow a significant occurrence of chain reactions that lead to the formation of branches, both long and short. chains. This type of HDPE is sometimes called high-density polyethylene (LDPE, HDPE, due to the high pressure), if there is a need to distinguish it from linear low-density polyethylene, a “younger” type of LDPE. At room temperature, polyethylene is a fairly soft and flexible material. It retains this flexibility well in cold conditions, making it suitable for frozen food packaging. However, at elevated temperatures such as 100°C, it becomes too soft for some applications. HDPE has a higher brittleness and softening point than LDPE, but is still not suitable for hot fill containers.

About 30% of all plastics used for packaging are HDPE. It is the most widely used plastic for bottles due to its low cost, ease of molding, and excellent performance for many applications. In its natural form, HDPE has a milky white, translucent appearance, and is thus not suitable for applications where extreme transparency is required. One disadvantage of using HDPE in some applications is its tendency to undergo environmental stress cracking, defined as the failure of a plastic container under conditions of simultaneous stress and contact with the product, which alone does not cause failure. External stress cracking in polyethylene is related to the crystallinity of the polymer.

LDPE is the most widely used packaging polymer, accounting for approximately one third of all packaging plastics. Due to its low crystallinity, it is a softer, more flexible material than HDPE. It is the preferred material for films and bags due to its low cost. LDPE offers better clarity than HDPE, but still lacks the crystal clarity desired for some packaging applications.

PP - polypropylene. Excellent transparency (with rapid cooling during the shaping process), high melting point, chemical and water resistance. PP allows water vapor to pass through, which makes it indispensable for “anti-fog” packaging of food products (bread, herbs, groceries), as well as in construction for hydro-windproofing. PP is sensitive to oxygen and oxidizing agents. It is processed by extrusion blowing or through a flat die with pouring onto a drum or cooling in a water bath. It has good transparency and gloss, high chemical resistance, especially to oils and fats, and does not crack under environmental influences.

PVC - polyvinyl chloride. It is rarely used in its pure form due to its fragility and inelasticity. Inexpensive. Can be processed into film by blown extrusion or flat-slit extrusion. The melt is highly viscous. PVC is thermally unstable and corrosive. When overheated and burned, it releases a highly toxic chlorine compound - dioxin. Widespread in the 60s and 70s. Being replaced by more environmentally friendly polypropylene.

Polymer Identification

Consumers of polymer films often face the practical task of recognizing the nature of the polymer materials from which they are made. The basic properties of polymer materials, as is well known, are determined by the composition and structure of their macromolecular chains. Hence it is clear that to identify polymer films to a first approximation, an assessment of the functional groups included in the composition of macromolecules may be sufficient. Some polymers, due to the presence of hydroxyl groups (-OH), gravitate towards water molecules. This explains the high hygroscopicity of, for example, cellulose films and a noticeable change in their performance characteristics when moisturizing. In other polymers (polyethylene terephthalate, polyethylenes, polypropylene, etc.) such groups are absent altogether, which explains their fairly good water resistance.

The presence of certain functional groups in a polymer can be determined on the basis of existing and scientifically based instrumental research methods. However, the practical implementation of these methods is always associated with relatively large time costs and is due to the availability of appropriate types of rather expensive test equipment that requires appropriate qualifications for its use. However, there are quite simple and “fast” practical ways recognition of the nature of polymer films. These methods are based on the fact that polymer films made from various polymer materials differ from each other in their external signs, physical and mechanical properties, as well as in relation to heating, the nature of their combustion and solubility in organic and inorganic solvents.

In many cases, the nature of the polymer materials from which polymer films are made can be determined by external signs, when studying which special attention you should pay attention to the following features: surface condition, color, gloss, transparency, hardness and elasticity, tear resistance, etc. For example, non-oriented films made of polyethylene, polypropylene and polyvinyl chloride are easily stretched. Films made of polyamide, cellulose acetate, polystyrene, oriented polyethylene, polypropylene, and polyvinyl chloride do not stretch well. Cellulose acetate films are not tear-resistant, easily split in a direction perpendicular to their orientation, and also rustle when crushed. Polyamide and lavsan (polyethylene terephthalate) films are more tear-resistant and also rustle when crumpled. At the same time, films made of low-density polyethylene and plasticized polyvinyl chloride do not rustle when crushed and have high tear resistance. The results of studying the external features of the polymer film under study should be compared with the characteristic features given in Table. 1, after which some preliminary conclusions can be drawn.

Table 1. External signs

Type of polymer	Mechanical symptoms	Surface condition to the touch	Color	Transparency	Shine
	Soft, elastic, tear resistant	Soft, smooth	Colorless	Transparent
		Slightly oily, smooth, sweetly rustling	Colorless	Translucent
	Rigid, slightly elastic, tear resistant	Dry, smooth	Colorless	Translucent or transparent
	Rough, tear resistant	Dry, smooth	Colorless	Transparent
	Soft, tear resistant	Dry, smooth	Colorless	Transparent
	Tough, tear resistant		Colorless	Transparent
		Dry, smooth	Colorless or light yellow	Translucent
	Rigid, weakly resistant to tearing	Dry, smooth, very rustling	Colorless or with a bluish tint	Transparent
	Rigid, weakly resistant to tearing	Dry, smooth, very rustling	Colorless, with a yellowish or bluish tint	Highly transparent
	Hard, not tear resistant	Dry, smooth	Colorless	Highly transparent
Cellophane	Hard, not tear resistant	Dry, smooth	Colorless	Highly transparent

However, as is easy to understand from the analysis of the data given in table. 2, it is not always possible to unambiguously determine the nature of the polymer from which the film is made by external signs. In this case, it is necessary to try to quantitatively assess some physical and mechanical characteristics of the existing polymer film sample. As can be seen, for example, from the data given in table. 2, the density of some polymer materials (LDPE, HDPE, PP) is less than unity, and, therefore, samples of these films must “float” in water. In order to clarify the type of polymer material from which the film is made, the density of the existing sample should be determined by measuring its weight and calculating or measuring its volume. Experimental data on such physical and mechanical characteristics as tensile strength and relative elongation under uniaxial tension, as well as the melting temperature (Table 2). In addition, as can be seen from the analysis of the data given in table. 2, the permeability of polymer films with respect to various media also significantly depends on the type of material from which they are made.

Table 2. Physical and mechanical characteristics at 20°C

Type of polymers	Density kg/m3	Tensile strength, MPa	Elongation at break, %	Water vapor permeability, g/m2 in 24 hours	Oxygen permeability, cm 3 / (m 2 khatm) in 24 hours	CO 2 permeability, cm 3 / (m 2 khatm) in 24 hours	Melting point, 0 C
Cellophane

Besides distinctive features In the physical and mechanical characteristics, it should be noted that there are existing differences in the characteristic features of various polymers during their combustion. This fact allows the so-called thermal method of identifying polymer films to be used in practice. It consists in setting a film sample on fire and keeping it in open flame for 5-10 seconds, while recording the following properties: the ability to burn and its nature, the color and nature of the flame, the smell of combustion products, etc. Characteristic signs combustion is most clearly observed at the moment the samples are ignited. To establish the type of polymer material from which the film is made, it is necessary to compare the results of the test with data on the characteristic features of the behavior of polymers during combustion given in Table. 3.

Table 3. Combustion characteristics. Chemical resistance

Type of polymer	Flammability	Flame color	Smell of combustion products	Chem. acid resistance	Chem. alkali resistance
		Inside is bluish, without soot	Burning paraffin	Excellent
	Burns in flame and when removed	Inside is bluish, without soot	Burning paraffin	Excellent
	Burns in flame and when removed	Inside is bluish, without soot	Burning paraffin	Excellent
		Greenish with soot	Hydrogen chloride
	Difficult to ignite and go out	Greenish with soot	Hydrogen chloride	Excellent	Excellent
	Lights up and burns outside the flame	Yellowish with strong soot	Sweetish, unpleasant	Excellent
	Burns and self-extinguishes	Blue, yellowish at the edges	Burnt horn or feather
	Difficult to ignite and go out	Glowing	Sweetish	Excellent	Excellent
	Difficult to ignite and go out	Yellowish with soot	Burnt paper
	Burning in flames	Sparkling	Acetic acid
Cellophane	Burning in flames		Burnt paper

As can be seen from the data given in table. 3, by the nature of combustion and the smell of combustion products, polyolefins (polyethylene and polypropylene) resemble paraffin. This is quite understandable, since elementary chemical composition these substances are the same. This makes it difficult to distinguish between polyethylene and polypropylene. However, with a certain skill, you can distinguish polypropylene by the sharper smells of combustion products with hints of burnt rubber or burning sealing wax.

Thus, the results of a comprehensive assessment of individual properties of polymer films in accordance with the methods outlined above make it possible, in most cases, to fairly reliably establish the type of polymer material from which the studied samples are made. If difficulties arise in determining the nature of the polymer materials from which the films are made, it is necessary to conduct additional studies of their properties chemical methods. To do this, samples can be subjected to thermal decomposition (pyrolysis), and the presence of characteristic atoms (nitrogen, chlorine, silicon, etc.) or groups of atoms (phenol, nitro groups, etc.) prone to specific reactions that result in a very definite indicator effect. The above practical methods determinations of the type of polymer materials from which polymer films are made are to a certain extent subjective in nature, and, therefore, cannot guarantee their one hundred percent identification. If such a need nevertheless arises, then you should use the services of special testing laboratories, whose competence is confirmed by relevant certification documents.

Melt flow rate

The melt flow rate of a polymer material is the mass of polymer in grams extruded through a capillary at a certain temperature and a certain pressure drop in 10 minutes. The melt flow rate is determined using special instruments called capillary viscometers. At the same time, the dimensions of the capillary are standardized: length 8.000±0.025 mm; diameter 2.095±0.005 mm; the internal diameter of the viscometer cylinder is 9.54±0.016 mm. Non-integer values ​​of capillary sizes are due to the fact that for the first time the method of determining the melt flow index appeared in countries with the English system of measures. The conditions recommended for determining the melt flow rate are regulated by relevant standards. GOST 11645-65 recommends loads of 2.16 kg, 5 kg and 10 kg and temperatures that are multiples of 10°C. ASTM 1238-62T (USA) recommends temperatures from 125°C to 275°C and loads from 0.325 kg to 21.6 kg. Most often, the melt flow rate is determined at a temperature of 190°C and a load of 2.16 kg.

The value of the fluidity index for various polymer materials is determined at various loads and temperatures. Therefore, it must be borne in mind that the absolute values ​​of the fluidity index are comparable only for the same material. For example, you can compare the melt flow index of low-density polyethylene of different brands. Comparing the values ​​of the fluidity indicators of high- and low-density polyethylene does not make it possible to directly compare the fluidity of both materials. Since the first is determined with a load of 5 kg, and the second with a load of 2.16 kg.

It should be noted that the viscosity of polymer melts significantly depends on the applied load. Since the yield index of a particular polymer material is measured only at one load value, this indicator characterizes only one point on the entire flow curve in the region of relatively low shear stresses. Therefore, polymers that differ slightly in the branching of macromolecules or in molecular weight, but with the same melt flow rate, can behave differently depending on processing conditions. However, despite this, the melt flow indicator for many polymers sets the boundaries of the recommended technological parameters of the processing process. The significant spread of this method is due to its speed and accessibility. Extrusion film production processes require high melt viscosities; therefore, grades of raw materials with low melt flow rates are used.

Based on materials from the company "NPL Plastic"

Polymers are organic and inorganic substances that are divided into various types and types. What are polymers and what is their classification?

General characteristics of polymers

Polymers are high-molecular substances whose molecules consist of repeating structural units connected to each other by chemical bonds. Polymers can be organic or inorganic, amorphous or crystalline substances. Polymers always contain a large number of monomer units; if this amount is too small, then it is no longer a polymer, but an oligomer. The number of units is considered sufficient if the properties do not change when adding a new monomer unit.

Rice. 1. Polymer structure.

The substances from which polymers are made are called monomers.

Polymer molecules can have a linear, branched or three-dimensional structure. The molecular weight of common polymers ranges from 10,000 to 1,000,000.

The polymerization reaction is characteristic of many organic substances that contain double or triple bonds.

For example: polyethylene formation reaction:

nCH 2 =CH 2 —> [-CH 2 -CH 2 -]n

where n is the number of monomer molecules interconnected during the polymerization process, or the degree of polymerization.

Polyethylene is produced by high temperature And high blood pressure. Polyethylene is chemically stable, mechanically strong and therefore widely used in the manufacture of equipment in various industries. It has high electrical insulating properties and is also used as food packaging.

Rice. 2. Substance polyethylene.

Structural units are groups of atoms repeated many times in a macromolecule.

Types of polymers

Based on their origin, polymers can be divided into three types:

• natural. Natural or natural polymers can be found naturally occurring in nature. This group includes, for example, amber, silk, rubber, starch.

Rice. 3. Rubber.

• synthetic. Synthetic polymers are obtained in laboratory conditions and are synthesized by humans. Such polymers include PVC, polyethylene, polypropylene, polyurethane. these substances have nothing to do with nature.
• artificial. Artificial polymers differ from synthetic ones in that they are synthesized, albeit in laboratory conditions, but on the basis of natural polymers. Artificial polymers include celluloid, cellulose acetate, and nitrocellulose.

From the point of view of chemical nature, polymers are divided into organic, inorganic and organoelement. Most of all known polymers are organic. These include all synthetic polymers. The basis of substances of inorganic nature are elements such as S, O, P, H and others. Such polymers are not elastic and do not form macrochains. These include polysilanes, polysilicic acids, and polygermanes. Organoelement polymers include a mixture of both organic and inorganic polymers. The main chain is always inorganic, the side chains are organic. Examples of polymers include polysiloxanes, polycarboxylates, and polyorganocyclophosphazenes.

All polymers can be found in different states of aggregation. They can be liquids (lubricants, varnishes, adhesives, paints), elastic materials (rubber, silicone, foam rubber), as well as hard plastics (polyethylene, polypropylene).

Preface

All types of polymeric materials are substances in which each molecule is a chain of tens or hundreds of thousands of identical groups of atoms connected in series, and the same group of atoms is rhythmically repeated many times.

Contents

The main polymeric materials include resins and plastics. Depending on whether it is a thermoplastic polymer or a thermoset, the material can either soften and harden many times, or, with a single heating, turn into a solid state and permanently lose its ability to melt. The most commonly used modern polymer materials are dispersions, latexes and adhesives.

What are building polymer materials

What are polymer materials and how are they used in construction? All types of polymeric materials are substances in which each molecule is a chain of tens or hundreds of thousands of identical groups of atoms connected in series, and the same group of atoms is rhythmically repeated many times.

The main types of polymer materials are divided into thermoplastic and thermosetting. Thermoplastic polymers They are capable of repeatedly softening and hardening with changes in temperature, and also easily swell and dissolve in organic solvents. These include polystyrene, polyethylene and polyvinyl chloride (polyvinyl chloride) resins and plastics.

The main property of thermosetting polymer materials is the transition when heated to an insoluble solid state and the irreversible loss of the ability to melt. Such polymers include phenol-formaldehyde and urea-formaldehyde, polyester and epoxy resins.

Certain types of polymer materials in construction, under the influence of heat, light and atmospheric oxygen, change their properties over time: they lose flexibility, elasticity, in other words, they age.

To prevent aging of modern polymer building materials, special stabilizers (anti-aging agents) are used, which are various organometallic compounds of lead, barium, cadmium, etc. For example, Tinuvin P is used as a stabilizer.

What polymer materials are there and what their main characteristics are, you will learn on this page.

Polymer plastic materials and their properties

One of the main types of polymeric materials is plastics. They are a group organic materials, which are based on synthetic or natural resin-like high-molecular substances that can be molded under heat and pressure, stably maintaining their given shape.

Polymer plastic materials have good thermal insulation and electrical insulation qualities, corrosion resistance and durability. Average density plastics - 15-2200 kg/m3; compressive strength - 120-160 MPa. Plastics are endowed with good electrical and thermal insulation properties, corrosion resistance and durability. Some of them are transparent and have high adhesive properties, and also tend to form thin films and protective coatings. Due to their properties, these polymer materials are widely used in construction, mainly in combination with binders, metals and stone materials.

Plastics are made up of binder- polymer, filler, plasticizer and curing accelerator. Mineral dyes are also used in the production of colored plastics.

Organic and mineral powders, asbestos, wood and glass fibers, paper, glass and cotton fabrics are used as fillers in the manufacture of this type of polymer materials. wood veneer, asbestos cardboard, etc. Fillers not only reduce the cost of the material, but also improve certain properties of plastics: they increase hardness, strength, acid resistance and heat resistance. They must be chemically inert, low volatile and non-toxic. Plasticizers in the manufacture of plastics are zinc acid, aluminum stearate and others, which give the material greater plasticity. Catalysts (accelerators) are used in plastics to speed up curing. An example of a catalyst is lime or methenamine, which are used to cure phenol-formaldehyde polymer.

Synthetic polymer materials and their applications

According to the production method, synthetic polymer materials are divided into two classes: class A - polymers obtained by chain polymerization; class B - polymers obtained by polycondensation and stepwise polymerization.

The polymerization process is a combination of identical and different molecules. No by-products are formed during polymerization.

The polycondensation process is the combination of a large number of identical and different polyreactive molecules of low molecular weight substances, resulting in the formation of a high molecular weight substance. During the polycondensation process, water, hydrogen chloride, ammonia and other substances are released.

Silicone resins- This is a special group of high-molecular compounds. The peculiarity of these polymer building materials is that they have the properties of both organic and inorganic substances.

The physical and mechanical characteristics of these polymeric materials are virtually unaffected by temperature fluctuations compared to conventional resins, and they are also highly hydrophobic and heat resistant. Organosilicon resins are used to obtain various products, resistant to elevated temperatures (400-500°C).

The main area of ​​application of these synthetic polymeric materials is the production of concrete and mortars to increase their durability. They are also used in the form protective coatings on natural and artificial stone materials (concrete, limestone, travertine, marble, etc.). Impregnation has a protective effect for 6-10 years, after which it should be renewed.

For impregnation surfaces of products made of natural stone and others building structures water-repellent organosilicon liquids (HSLs) are used, which are dissolved before use organic solvents, as well as an aqueous 50% emulsion (milk- white), which is mixed with water in a ratio of 1:10 before use.

Polyvinyl acetate dispersion (PVA) is a product of polymerization of vinyl acetate in an aqueous medium in the presence of an initiator and a protective colloid. It is a viscous, white, homogeneous liquid, without screams or foreign inclusions.

Depending on the viscosity, PVA is produced in three grades: N - low-viscosity, S - medium-viscosity, B - high-viscosity. It is used in the production of polymer-cement mortars, mastics, and pastes, which are used in facing work.

Synthetic latex SKS-65GP- a product of co-polymerization of butadiene with styrene in a ratio of 35:65 (by weight) in an aqueous emulsion using nekal and sodium soap of synthetic fatty acids as an emulsifier. Latex SKS-65GP is used in the production of polymer concrete, emulsion paints, mastics and pastes used in facing work. Latex is also used in various coatings.

Physicochemical properties of this polymer building material latex SKS-65GP:

• dry matter content,%, not less than 47;
• content of unpolymerized styrene, %, not more than 0.08;
• hydrogen ion concentration (pH), not less than 11;
• surface tension, dynes/cm2, no more than 40;
• viscosity, s - 11-15;
• Ash content,%, no more than 1.5.

Synthetic latex SKS-ZOSHR is a product of joint polymerization of butadiene with styrene in an aqueous emulsion, used as a binder or adhesive material for facing work.

Physico-chemical properties of SKS-ZOSHR latex:

• dry matter content,%, not less than 33;
• gelatinization temperature, °C, not higher than 14;
• free alkali content, %, not more than 0.15.

Characteristics of polymer adhesive materials

Polymer adhesive materials are produced in the form of liquids, powders and films.

There are two types of liquid adhesives. The first type of adhesive compositions are rubbers, resins or cellulose derivatives dissolved in an organic volatile solvent (alcohol or acetone). After the solvent evaporates, a solid adhesive joint is formed. The second type of adhesive composition is aqueous solutions resins specially prepared for adhesives. When properly stored, such solutions do not thicken for several months. Liquid adhesives contain 40-70% solid adhesive.

From liquid adhesives the most common are melamine-formaldehyde, phenol-formaldehyde, urea-formaldehyde, rubber, epoxy, polyvinyl acetate, as well as adhesives with the addition of silicones.

CMC glue (sodium salt of carboxymethylcellulose) is used in the manufacture of mastics and solutions used in.

Carbinol glue (vinylacetylene carbolene) is a viscous transparent liquid of light orange color with high adhesive ability. That's why it is called universal. It is capable of gluing various materials, even such as concrete, stone, metal, wood. Hardened carbinol glue is resistant to oils, acids, alkalis, gasoline, acetone and water.

Concentrated nitric acid or benzoyl peroxide are used as catalysts to accelerate the hardening of carbinol glue. The latter is an explosive powder, so it should be stored away from fire.

Carbinol glue is produced on the basis of carbinol syrup (100 parts by weight) in two compositions: in the 1st one, benzoyl peroxide (1-3 parts by weight) is added as a hardener, in the 2nd - concentrated nitric acid (1-2 parts by weight). h.).

Carbinol glue is stored at a temperature of 20°C and in the dark, since under the influence of light it loses its adhesive ability.

Epoxy glue is a transparent viscous liquid of light brown color with high adhesive ability. It is used for gluing stone, concrete, ceramic tiles. The hardened seam of epoxy adhesive is resistant to acids, alkalis, solvents, water, as well as to high mechanical loads. Hardeners epoxy resin Polyethylene polyamine or hexamethylenediamine are used, and dibutyl phtholate is used as a plasticizer.