Big encyclopedia of oil and gas. Atactic polypropylene: properties and applications

Polypropylene (PP) - a colorless polymer related to thermoplastics - synthetic materials that change their ductility when heated. Melting point 160-170 C, density 900-910 kg / m 3, elongation without failure 200-400%, insoluble in organic solvents. It is resistant to hot water (in the flesh up to 130 ° C) and aggressive environments, except for strong oxidizing agents (concentrated nitric and sulfuric acids). In thin films it is almost transparent (96%).

For material high toughness, resistance to repeated bends, good wear resistance. Material conducts heat poorly, does not conduct electric current. Thin films, fibers and filaments are obtained from the granular material by extrusion. Distinguish two main methods of film extrusion: blown and flat slit extrusion. The first method allows you to get a film sleeve, which can be folded or cut. If the incision passes in one or more places along the sleeve, then the so-called half-sleeve is obtained. By cutting the sleeve along on both sides, a web can be obtained. In the second method (flat-gap extrusion), a film web is obtained. The film may be non-oriented and oriented.

The orientation of the films (the orientation of the molecules in the material) is achieved by stretching them in the heated state during extrusion. Of the oriented films, the biaxially oriented (BOPP) film is most widely used.

This film has a tensile strength of 3-4 times greater than that of non-oriented material.

Such films have frost resistance up to –50 ° C, high strength, wear resistance and at the same time elasticity. Biaxially Oriented Films, precisely because of their ability to withstand significant mechanical loads, they are used for packaging on automatic lines of various food products and other industrial goods. As a disadvantage of BOPP films, weldability is worse than that of films from non-oriented PP.

Non-oriented film is obtained mainly by blown sleeve extrusion, and biaxially oriented using flat-slot extrusion.

Differences between propylene and polyethylene

The differences between polypropylene and polyethylene and other types of plastics are in a lower density category, with a high level of resistance to environmental influences (that is, to light, temperature and oxygen). The strength of this material is higher, so the abrasion resistance also increases. A change in the mechanical properties is observed during the aging of the material. From this polypropylene protect the stabilizers that are introduced to protect the material, not only during use, but also during manufacture. An important quality of polypropylene is water resistance. Resistance to aggressive environments, as well as environmental factors is confirmed by many experiments.

The melting point of this material is significantly higher than that of polyethylene, so it is subject to heat treatment with steam and hot water without loss of properties. Polypropylene is also characterized by low conductivity of electricity. A feature of the material is also frost resistance.

All these polypropylene properties allow you to successfully use it as a packaging material. High strength and durability, as well as resistance to environmental factors, allows it to be used as packaging for food.

Polypropylene differs in molecular structure - it can be isotactic, syndiotactic and atactic polypropylene. The chemical and physical properties of different types of material are different. The main properties possessed by polypropylene can be reflected in the following table.

Polymers and materials, household items, equipment made from them are an important part of industry and human life as a whole. Natural resources, unfortunately, have been greatly depleted during their use. Therefore, people had to learn how to synthesize artificial materials, which have a number of important technical characteristics. One of these is polypropylene. The chemical formula of this compound, the features of its properties and the structure of the molecule will be considered during the article.

Polymers - General Description

This class of compounds includes those that have a very high value. Indeed, polymers are complex organic compounds consisting of multiple repeating monomer units, which can be from several tens to hundreds, thousands and millions.

Among all polymers, the following groups can be distinguished:

Natural origin - proteins, nucleic acids, ATP molecules and so on.
Artificial - those that are based on natural, but have been chemically modified in order to improve technical characteristics. For example, artificial rubbers.
Synthetic - those that are created only through chemical reactions, synthesis in the laboratory and industrial plants. Here, synthetic fabrics and fibers, polyethylene, polyvinyl chloride, polypropylene and others can serve as examples.

All designated polymer groups are an important industrial raw material for the production and production of various equipment, household items, dishes, toys, furniture and other things.

Representatives of the most important synthetic polymers

The chemical formula of one of the most important representatives of synthetic polymers is written as (-CH 2 -CH 2 -) n. This is polyethylene. Areas of its use are known. These are household needs (household film), and industrial, and food industry (packaging material). However, although it is the most common, it is by no means the only representative that is extremely important for humans. You can also name polymers such as:

polyvinyl chloride;
polypropylene;
polyisobutylene;
polystyrene;
teflon;
polyvinyl acetate and others.

It is in the construction business, as well as for the manufacture of dishes, such a material as polypropylene plays an important role. Therefore, we will further consider precisely its features from a chemical point of view.

Polypropylene Formula

From the point of view of the science of chemistry, the composition of a given substance can be expressed by different types of formulas. The first option is a molecular form of recording. In this case, the polypropylene formula looks like this: (C 3 H 6) n. The last n means the degree of polymerization, that is, the number of structural starting units in the macrochain.

Such a record allows us to conclude about the qualitative and quantitative composition of the molecule. Polypropene consists of carbon and hydrogen atoms, and their number in the monomer unit is 3/6, respectively, and in the general chain it depends on the exponent n. If we talk about the structure of the compound itself, about the order of the bonds of atoms in the molecule, then another kind of recording of the substance is necessary.

Polypropylene: structural formula

The type of record, which shows the order of the atoms in a molecule, is called the structural formula. For the substance we are considering, it will have the following form: (-CH 2 -CH-CH 3 -) n. Obviously, the generally accepted valency of atoms in organic chemistry persists in this case as well. The formula of polypropylene or polypropene shows which monomer unit underlies the compound. It is formed from (alkene) propene or propylene. Its empirical formula: C 3 H 8.

Starting Monomer

The monomer formula for producing polypropylene is as follows: (—CH 2 —CH — CH 3 -). If this fragment is repeated several hundred times, then we will get a whole macromolecule which is the material under consideration. In addition, we have already indicated that in general the usual alkene, propene, should be considered the starting material for. He is the monomer of polypropylene. will be written as CH 3 —CH \u003d CH 2. When a double bond is broken during the polymerization, the desired fragment is formed. The same monomer unit, which, repeating itself, forms a polymer macromolecule.

Physical and chemical properties

The formula of polypropylene (-CH 2 -CH-CH 3 -) n allows us to judge its physical and chemical characteristics. We list the main ones.

Physical properties of this polymer: density 0.91 g / cm 3, solid, abrasion resistant, not subject to corrosion. The color is white, opaque. The smell is absent. In water, organic solvents at ordinary temperatures, insoluble. When the indicator is above 100 0 C it dissolves in hydrocarbon compounds. It begins to soften after 140 0 С, at 170 0 С it melts. It has heat and frost resistance.
Chemical properties. From the point of view of activity, polypropene can be attributed to practically inert substances. It is able to interact only with especially strong oxidizing agents: fuming nitric, chlorosulfonic acids, oleum, active halogens (fluorine, chlorine). It does not interact with water at all, even at elevated temperatures. It reacts with oxygen only when irradiated with ultraviolet light; the process is accompanied by polymer destruction. In organic solvents swells and dissolves with increasing temperature.

The indicated properties can be attributed to the technical characteristics of the material itself, which is used in industry. However, not all polypropylene is the same. There are special stabilizing additives with the help of which various varieties of the polymer under consideration are created.

Material Specifications

Several basic properties that polypropylene possesses can be identified. Its characteristics are as follows:

When heated, it is able to melt, previously softened.
It does not have conductive properties.
Shockproof, durable for wear.
Resistant to abrasion.
Ages when exposed to the sun and oxygen, but the process is quite slow.
Like a polymer, it has a small molecular weight.
It has white color, is translucent, has no taste or smell.
When burned, it does not emit harmful substances, emits a light floral aroma.
It is flexible, durable, resistant to various kinds of pollution.
It has heat and frost resistance.

All the indicated properties of polypropylene as a material make it possible to use it for various needs. It is easy to use, convenient to care for and use in the practical activities of any sector of the national economy.

In total, three main varieties of this material can be distinguished:

attactic;
syndiotactic;
isotactic.

The main difference in them is, specifically, the location of methyl groups in the chain. Also on specifications stabilizing additives, the number of monomer units in the macrostructure influence.

This material is produced either in the form of crystalline granular structures, or in the form of fibers, sheets.

Areas of use

Polypropylene material is used for the production of various films, packaging containers, food containers. It is from it that ordinary plastic cups and other items of disposable tableware are made. This material is used for the manufacture of durable, resistant to chemical agents polypropylene plumbing pipes.

It is also used to create soundproof materials. Adhesive tape is also one of the varieties of polypropylene.

Attactic material is used for the manufacture of:

mastic;
adhesives;
putty;
sticky tapes;
road surfaces and stuff.

A large number of polypropylene sheets, fibers are spent on the manufacture of toys, stationery, household and household items.

It is a waxy mass of white color (thin sheets are transparent and colorless). Chemically and frost-resistant, insulator, insensitive to shock (shock absorber), softens when heated (80-120 ° C), freezes when cooled, adhesion is extremely low. Sometimes it is identified in the popular consciousness with cellophane - a similar material of plant origin.

Getting

For processing comes in the form of granules from 2 to 5 mm. Polyethylene is obtained by polymerization of ethylene:

Production of high pressure polyethylene

High pressure polyethylene (LDPE), or Low density polyethylene (LDPE) is formed under the following conditions:

temperature 200-260 ° C;
pressure 150-300 MPa;
the presence of an initiator (oxygen or organic peroxide);

in autoclave or tubular reactors. The reaction proceeds according to a radical mechanism. The polyethylene obtained by this method has a weight average molecular weight of 80,000-500,000 and a crystallinity of 50-60. The liquid product is subsequently granulated. The reaction is in the melt.

Obtaining medium pressure polyethylene

Medium pressure polyethylene (PESD) is formed under the following conditions:

temperature 100-120 ° C;
pressure 3-4 MPa;
the presence of a catalyst (Ziegler-Natta catalysts, for example, a mixture of TiCl 4 and R 3);

the product falls out of solution in the form of flakes. Obtained by this method, polyethylene has a weight average molecular weight of 300,000-400,000, a crystallinity of 80-90%.

Obtaining low pressure polyethylene

Low-pressure polyethylene (HDPE) or High density polyethylene (HDPE) is formed under the following conditions:

temperature 120-150 ° C;
pressure below 0.1 - 2 MPa;
the presence of a catalyst (Ziegler-Natta catalysts, for example, a mixture of TiCl 4 and R 3);

The polymerization proceeds in suspension by the ion-coordination mechanism. The polyethylene obtained by this method has a weight average molecular weight of 80,000-3,000,000, and a crystallinity of 75-85%.

It should be borne in mind that the names "low pressure polyethylene", "medium pressure", "high density", etc. have purely rhetorical meaning. So, polyethylene obtained by the 2nd and 3rd methods has the same density and molecular weight. The pressure in the polymerization process at the so-called low and medium pressures is the same in some cases.

Other methods for producing polyethylene

There are other methods for the polymerization of ethylene, for example, under the influence of radioactive radiation, but they have not received industrial distribution.

Polyethylene Modifications

The range of ethylene polymers can be significantly expanded by obtaining copolymers of it with other monomers, as well as by obtaining compositions by compounding one type of polyethylene with another type of polyethylene, polypropylene, polyisobutylene, rubbers, etc.

On the basis of polyethylene and other polyolefins, numerous modifications can be obtained - grafted copolymers with active groups that improve the adhesion of polyolefins to metals, tintability, reduce its combustibility, etc.

Modifications of the so-called “cross-linked” PE-S (PE-X) polyethylene stand out. The essence of crosslinking is that the molecules in the chain are connected not only sequentially, but also side bonds are formed that connect the chains to each other, due to this the physical and, to a lesser extent, chemical properties of the products change quite strongly.

There are 4 types of crosslinked polyethylene (according to the method of production): peroxide (a), silane (b), radiation (c) and nitrogen (d). The most widespread was PEX-b, as the fastest and cheapest in production.

Molecular structure

High pressure polyethylene macromolecules ( n≅1000) contain C 1 -C 4 side hydrocarbon chains, the medium-pressure polyethylene molecules are almost unbranched, it contains a larger proportion of the crystalline phase, therefore this material is denser; low-pressure polyethylene molecules occupy an intermediate position. The large number of lateral branches explains the lower crystallinity and, accordingly, lower density of LDPE compared to HDPE and PED.

Indicators characterizing the structure of the polymer chain of various types of polyethylene:
Indicator	LDPE	PESD	HDPE
The total number of CH 3 groups per 1000 carbon atoms:
The number of end groups of CH 3 per 1000 carbon atoms:
Ethical branches
The total number of double bonds per 1000 carbon atoms
including:
vinyl double bonds (R-CH \u003d CH 2),%
vinylidene double bonds (),%
trans-vinylene double bonds (R-CH \u003d CH-R ’),%
The degree of crystallinity,%
Density, g / cm³

Low Pressure Polyethylene (HDPE)

Physico-chemical properties of HDPE at 20 ° C:

Parameter

Value

Density, g / cm³

Breaking stress, kgf / cm²

tensile

with static bending

when cutting

elongation at break,%

bending modulus, kgf / cm²

tensile strength, kgf / cm²

elongation at the beginning of the course,%

At room temperature it is insoluble and does not swell in any of the known solvents. At elevated temperatures (80 ° C), soluble in cyclohexane and carbon tetrachloride. Under high pressure it can be dissolved in superheated water up to 180 ° C.

Over time, it destructs with the formation of transverse interchain bonds, which leads to an increase in fragility against the background of a slight increase in strength. Unstabilized polyethylene in air undergoes thermal oxidative degradation (thermal aging). Thermal aging of polyethylene proceeds according to a radical mechanism, accompanied by the release of aldehydes, ketones, hydrogen peroxide, etc.

Low pressure polyethylene (HDPE) is used in the construction of landfills for waste treatment, storage of liquid and solid substances that can pollute the soil and groundwater.

Recycling

Polyethylene (except for supermolecular) is processed by all methods known to plastics, such as extrusion, blown extrusion, injection molding, pneumatic molding. Extrusion of polyethylene is possible on equipment with an installed "universal" worm.

Application

Polyethylene film (especially packaging film, for example, bubble wrap or scotch tape),
Containers (bottles, cans, boxes, cans, watering cans, seedling pots)
Polymer pipes for sewage, drainage, water, gas supply.
Polyethylene powder is used as hot melt adhesive.
Armor (armored panels in body armor)
Hulls for boats, all-terrain vehicles

Details of technical equipment, dielectric antennas, household items, etc .; A small-tonnage brand of polyethylene - the so-called "ultra-high molecular weight polyethylene", characterized by the absence of any low molecular weight additives, high linearity and molecular weight, is used for medical purposes as a replacement for the cartilage tissue of the joints. Despite the fact that it compares favorably with HDPE and LDPE in its physical properties, it is rarely used because of the difficulty of its processing, since it has a low MFI and is processed only by casting.

nCH 2 \u003d CH (CH 3) → [-CH 2 -CH (CH 3) -] n

International designation - PP.

The parameters necessary to obtain polypropylene are close to those at which low-pressure polyethylene is obtained. Moreover, depending on the particular catalyst, any type of polymer or mixture thereof can be obtained.

Polypropylene is available in the form of a white powder or granules with a bulk density of 0.4-0.5 g / cm³. Polypropylene is available in stabilized, dyed and unpainted form.

Molecular structure

According to the type of molecular structure, three main types can be distinguished: isotactic, syndiotactic and atactic. Isotactic and syndiotactic are formed randomly;

Physical and mechanical properties

Unlike polyethylene, polypropylene is less dense (density 0.91 g / cm 3, which is the lowest value in general for all plastics), harder (resistant to abrasion), more heat-resistant (begins to soften at 140 ° C, melting point 175 ° C), almost does not undergo corrosion cracking. It has a high sensitivity to light and oxygen (sensitivity decreases with the introduction of stabilizers).

The tensile behavior of polypropylene to an even greater extent than polyethylene depends on the rate of application of the load and on temperature. The lower the tensile speed of polypropylene, the higher the value of the mechanical properties. At high tensile speeds, the tensile breaking stress of polypropylene is significantly lower than its tensile yield strength.

The indicators of the main physical and mechanical properties of polypropylene are given in the table:

Physico-mechanical properties of polypropylene of different grades are given in the table:

Physico-mechanical properties of polypropylene of various grades

Performance / Brand

01P10 / 002

02P10 / 003

03P10 / 005

04P10 / 010

05P10 / 020

06P10 / 040

07P10 / 080

08P10 / 080

09P10 / 200

Bulk density, kg / l, not less

Melt flow rate, g / 10 min

Elongation at break,%, not less than

Yield strength at break, kgf / cm², not less

Resistance to cracking, h, not less

Heat resistance according to the NIIPP method, ° C

Polyethylene (PE): physicochemical and consumer properties, consumption structure, areas of application of polyethylene

Polyolefins are the most common type of polymers produced by the polymerization and copolymerization reactions of unsaturated hydrocarbons (ethylene, propylene, butylene and other alpha olefins). About 50% of the world's ethylene is used to produce polyethylene.

The chemical structure of the polyethylene molecule is simple and represents a chain of carbon atoms, to each of which two hydrogen molecules are attached.
Polyethylene (PE) [–CH2 – CH2–] n exists in two modifications that differ in structure and, therefore, in properties. Both modifications are obtained from ethylene CH2 \u003d CH2. In one form, the monomers are linked in linear chains with a degree of polymerization (SP) of usually 5,000 or more; in the other, branches of 4-6 carbon atoms are randomly attached to the main chain. Linear polyethylenes are produced using special catalysts; polymerization proceeds at moderate temperatures (up to 150 0С) and pressures (up to 20 atm.).
Polyethylene is a thermoplastic polymer, opaque in a thick layer, crystallizes in the temperature range from minus 60 ° C to minus 369 ° C; it is not wetted by water, at room temperature it does not dissolve in organic solvents, at a temperature above 80 ° C it first swells and then dissolves in aromatic hydrocarbons and their halogen derivatives; PE is resistant to the action of aqueous solutions of salts, acids, alkalis, but at temperatures above 60 ° C, sulfuric and nitric acids quickly destroy it. Short-term treatment of PE with an oxidizing agent (for example, a chromium mixture) leads to surface oxidation and wetting by water, polar liquids and adhesives. In this case, PE products can be glued.
Ethylene can be polymerized in several ways, depending on which the polyethylene is divided into: high pressure polyethylene (LDPE) or low density (LDPE); low pressure polyethylene (HDPE) or high density (HDPE); as well as linear polyethylene.
LDPE is polymerized in a radical way under pressure from 1000 to 3000 atmospheres and at a temperature of 180 degrees. The initiator is oxygen.
HDPE is polymerized at a pressure of at least 5 atmospheres and a temperature of 80 degrees using Ziegler-Natta catalysts and an organic solvent.
Linear polyethylene (also called medium pressure polyethylene) is obtained at 30-40 atmospheres and a temperature of about 150 degrees. Such polyethylene is, as it were, an “intermediate” product between HDPE and LDPE, with regard to properties and qualities.
Not so long ago, technology began to be applied where so-called metallocene catalysts were used. The meaning of the technology is that it is possible to achieve a higher molecular weight of the polymer, which, accordingly, increases the strength of the product.
According to their structure and properties (despite the fact that the same monomer is used), LDPE, HDPE, linear polyethylene are different, and, accordingly, are used for various tasks. LDPE is a soft material, HDPE and linear polyethylene have a rigid structure.
Differences also appear in density, melting point, hardness, and strength.
Comparative characteristics of high and low pressure polyethylene (LDPE and HDPE)

The main reason for the differences in the properties of PE is the branching of macromolecules: the more branches in the chain, the higher the elasticity and less crystallinity of the polymer. Branches impede denser packing of macromolecules and prevent the crystallinity from reaching 100%; Along with the crystalline phase, there is always an amorphous phase containing insufficiently ordered sections of macromolecules. The ratio of these phases depends on the method of producing PE and the condition of its crystallization. It determines the properties of the polymer. LDPE films are 5-10 times more permeable than HDPE films.
The mechanical parameters of PE increase with increasing density (degree of crystallinity) and molecular weight. In the form of thin films, PE (especially low-density polymer) has greater flexibility and some transparency, and in the form of sheets it acquires greater rigidity and opacity.
Polyethylene is resistant to shock loads. Among the most important properties of polyethylene, frost resistance can be noted. They can be operated at temperatures from -70 ° C to 60 ° C (LDPE) and up to 100 ° C (HDPE), some brands retain their valuable properties at temperatures below -120 ° C.
Polyethylenes, being saturated hydrocarbons, are resistant to many aggressive environments (acids, alkalis, etc.) and organic liquids.
A significant disadvantage of polyethylene is its rapid aging. The aging period is increased due to special additives - antioxidants (phenols, amines, gas soot).
The viscosity of the LDPE melt is higher than the HDPE, so it is easier to process into products.
By its electrical properties, PE, as a non-polar polymer, refers to high-quality high-frequency dielectrics, the dielectric constant and the dielectric loss tangent change little with a change in the frequency of the electric field, temperature in the range from minus 80 ° С to 100 ° С and humidity. However, the catalyst residues in HDPE increase the dielectric loss tangent, especially when the temperature changes, which leads to some deterioration in the insulating properties.
PEHD Low Pressure Polyethylene
Light elastic crystallizing material with heat resistance of individual grades up to 110 0С. Allows cooling to -80 0C. Melting point grades: 120-135 0С. Glass transition temperature: approx. -20 0С. Gives a shiny surface.
It is characterized by good impact strength and greater heat resistance compared to LDPE.
Properties are highly dependent on the density of the material. An increase in density leads to an increase in strength, stiffness, hardness, and chemical resistance. At the same time, with increasing density, impact resistance at low temperatures, elongation at break, and permeability to gases and vapors decrease.
High creep is observed under prolonged loading. It has a very high chemical resistance (more than that of LDPE). It has excellent dielectric characteristics. Biologically inert. Easy to recycle.

Indicators (23 0С)	Values \u200b\u200bfor unfilled stamps
Density	0.94-0.97 g / cm3
Heat resistance according to Vika (in a liquid medium, 50 0С / h, 50Н)
Tensile Strength (50 mm / min)
Tensile modulus (1 mm / min)
Tensile Elongation (50mm / min)
Charpy impact strength (notched specimen)
Ball indentation hardness (358 N, 30 s)
Surface resistivity	10 ^ 14-10 ^ 15 Ohm
Water absorption (24 hours, humidity 50%)

HDPE (high density) polyethylene is used mainly for the production of containers and packaging. Abroad, about a third of the polymer produced is used for the manufacture of containers by blow molding (containers for food products, perfumes and cosmetics, automotive and household chemicals, fuel tanks and barrels). It is worth noting that, compared with other areas that are outpacing, the use of HDPE for the production of packaging films is growing. PE ND is also used in the production of pipes and piping components, where such advantages of the material are used as durability (service life - 50 years), ease of butt welding, low cost (on average 30% lower compared to metal pipes).
High pressure polyethylene

Other designations: PE-LD, PEBD (French and Spanish designation).
Lightweight elastic crystallizable material with heat resistance without load up to 60 ° C (for individual grades up to 90 ° C). Allows cooling (various grades in the range from -45 to -120 ° C).
Properties are highly dependent on the density of the material. An increase in density leads to an increase in strength, stiffness, hardness, and chemical resistance. At the same time, with increasing density, impact resistance at low temperatures, elongation at break, crack resistance, and permeability to gases and vapors decrease. It is prone to cracking when loaded. It does not differ in dimensional stability.
It has excellent dielectric characteristics. It has a very high chemical resistance. Not resistant to fats, oils. Not resistant to UV radiation. Differs in the increased radiation resistance. Biologically inert. Easy to recycle.
Brand Assortment Features
(minimum and maximum values \u200b\u200bfor industrial brands)

Application examples

LDPE (low density) polyethylene is used mainly in the production of food, technical, agricultural films and for insulation of pipelines. In recent years, the consumption and production of linear low-density polyethylene has been growing most actively abroad, which in a number of foreign countries has largely displaced LDPE from the main market segments (film production).
LLDPE Linear Polyethylene

Other designations: PE-LLD, L-LDPE
Lightweight elastic crystallizable material. Heat resistance up to 118 0С. It has greater resistance to cracking, impact strength and heat resistance than low density polyethylene (LDPE). Biologically inert. Easy to recycle. Provides less warpage and greater dimensional stability than LDPE.
Brand Assortment Features
(minimum and maximum values \u200b\u200bfor industrial brands)

Application examples

Packaging. Containers (including for food), containers.
Savilen: TU 6-05-1636-97
Sevilen - a copolymer of ethylene with vinyl acetate - is a high molecular weight compound related to polyolefins. Get it by a method similar to the method of production of low density polyethylene (high pressure).
Sevilen surpasses polyethylene in transparency and elasticity at low temperatures, has increased adhesion to various materials.
The property of sevilen mainly depends on the content of vinyl acetate (5-30 wt.%). With an increase in the vinyl acetate content, crystallinity, tensile stress, tensile strength, heat resistance decrease, while coc density, elasticity, transparency, and adhesion increase.
Sevilen with a vinyl acetate content of up to 15% (grades 11104-030, 11306-075) is processed by the same methods as low density polyethylene, but extrusion and injection molding are carried out at a lower temperature.
From sevilen grades 11104-030, 11306-075 it is possible to produce blown products, hoses, gaskets, toys. Weatherproof, transparent films are obtained from the same grades of sevilen, which, in comparison with polyethylene films, have a lower melting point.
The high adhesive properties of sevilen and good compatibility with waxes make it possible to use it as a coating of paper and cardboard in the manufacture of containers. For these purposes, sevilen with a vinyl acetate content of 21-30 weight is used. % (grades 11507-070, 11708-210, 11808-340).
An important area of \u200b\u200buse of sevilen is the preparation of hot melt adhesives on its basis. Hot melt adhesives do not contain solvents; at room temperature they are solids. They are used in molten form at a temperature of 120 - 200C.
Sevilen containing 21-30% by weight of vinyl acetate (grades 11507-070, 11708-210, 11808-340) is used to produce hot melt adhesives. Glues-melts based on sevilen are widely used in printing, furniture, footwear and other industries.
Savilen combines well with various fillers, which leads to the widespread distribution of filled products.
Table of quality indicators of the brands of Savilen TU 6-05-1636-97

The name of indicators	Savilen 11104-030	Savilen 11205-040	Savilen 11306-075	Savilen 11407-027	Savilen 12206-007	Savilen 12306-020
Density, g / cm2
The melt flow rate, g / 10 min, within: at t \u003d 190 0С
The spread of the melt flow rate within the batch,%
Mass fraction of vinyl acetate,% within
Number of inclusions no more
Tensile strength, MPa (kgf / cm2), not less
Elongation at break%, not less than
Adhesive strength, N / mm (kgf / cm), not less
Resistance to thermooxidative aging, h, at least, for formulations 02, 03, 06
Resistance to thermooxidative aging, h, not less, for formulations 05.07				not standardized	not standardized	not standardized
Overgrowing Method		extrusion molding	extrusion, casting, compounding	extrusion	extrusion molding	extrusion molding

The complex of physicomechanical, chemical and dielectric properties of PE determines its consumer properties and makes it widely applicable in many industries (cable, radio engineering, chemical, light, medicine, etc.).
PE consumption structure,%

Electrical wire insulation. The high dielectric properties of polyethylene and its mixtures with polyisobutylene, low permeability to water vapor allow it to be widely used for insulation of electric wires and cable manufacture, used in various communication equipment (telephone, telegraph), signaling devices, telemetry control systems, high-frequency installations, for winding wires engines operating in water, as well as for insulation of submarine and coaxial cables.
A cable with insulation made of polyethylene has advantages over rubber insulation. It is lightweight, more flexible and has greater electrical strength. A wire coated with a thin layer of polyethylene may have an upper layer of plasticized polyvinyl chloride, which forms a good mechanical protection against damage.
In the production of cables, LDPE is used, crosslinked with small amounts (1-3%) of organic peroxides or irradiated with fast electrons.
Films and sheets. Films and sheets can be made of PE of any density. Upon receipt of thin and elastic films, LDPE is more widely used.
Films are produced in two ways: by extruding the molten polymer through an annular slit, followed by blowing or extruding through a flat slit, followed by drawing. They are produced with a thickness of 0.03-0.30 mm, a width of up to 1400 mm (in some cases up to 10 m) and a length of up to 300 m.
In addition to thin films, sheets of a thickness of 1-6 mm and a width of up to 1400 mm are made from PE. They are used as a lining and electrical insulating material and processed into technical household products by vacuum molding.
Most of the products made of LDPE serve as packaging material, competing with other films (cellophane, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyethylene terephthalate, polyvinyl alcohol, etc.), a smaller part is used for the manufacture of various products (bags, bags, boxes and liners for other types of containers).
Films are widely used for packaging frozen meat and poultry, in the manufacture of balloons and balloons for meteorological and other studies of the upper atmosphere, and corrosion protection of oil and gas pipelines. In agriculture, transparent film is used to replace glass in greenhouses and greenhouses. The black film serves to cover the soil in order to retain heat during the cultivation of vegetables, fruits and legumes, and also for lining silage pits, the bottom of reservoirs and canals. More and more polyethylene film is used as a material for roofs and walls in the construction of premises for storing crops, agricultural machinery and other equipment.
Household items are made from a plastic film: raincoats, tablecloths, curtains, napkins, aprons, scarves, etc. The film can be applied on one side to various materials: paper, fabric, cellophane, metal foil.
Reinforced plastic film is more durable than ordinary film of the same thickness. The material consists of two films, between which there are reinforcing threads of synthetic or natural fibers or a rare glass cloth.
From very thin reinforced films are made tablecloths, as well as films for greenhouses; from thicker films - bags and packaging material. Reinforced film reinforced with a rare glass cloth can be used for the manufacture of protective clothing and used as a wrapping material for various containers.
On the basis of PE films, sticky (adhesive) films or tapes can be made, suitable for repairing high-frequency communication cable lines and for protecting steel underground pipelines from corrosion. Polyethylene films and tapes with an adhesive layer contain on one side a layer of low molecular weight polyisobutylene, sometimes mixed with butyl rubber. They are produced with a thickness of 65-96 microns, a width of 80-I50 mm.
LDPE and HDPE are also used to protect metal products from corrosion. The protective layer is applied by flame and vortex spraying.
Pipes. Of all types of plastics, PE has found the greatest use for extrusion and centrifugal casting of pipes, characterized by lightness, corrosion resistance, insignificant resistance to fluid movement, ease of installation, flexibility, frost resistance, ease of welding.
The continuous method produces pipes of any length with an inner diameter of 6-300 mm and a wall thickness of 1.5-10 mm. Small diameter polyethylene pipes are wound on drums. By injection molding, the reinforcement for pipes is manufactured, which includes bent pipes bent at an angle of 45 and 90 degrees; tees, couplings, crosses, branch pipes. Pipes of large diameter (up to 1600 mm) with wall thicknesses up to 25 mm are obtained by centrifugal casting.
Due to their chemical resistance and elasticity, polyethylene pipes are used for transporting water, solutions of salts and alkalis, acids, various liquids and gases in the chemical industry, for the construction of internal and external water supply networks, in irrigation systems and sprinklers.
LDPE pipes can operate at temperatures up to 60 0С, and from HDPE pipes - up to 100 0С. Such pipes are not destroyed at low temperatures (up to - 60 0С) and when water freezes; they are not susceptible to soil corrosion.
Molding and injection molding. From plastic sheets obtained by extrusion or pressing, it is possible to make various products by stamping, bending according to the template or vacuum forming. Oversized products (boats, bathtubs, tanks, etc.) can also be made of polyethylene powder by sintering on a heated form. Individual parts of products can be welded using a jet of hot air heated to 250 0C.
By molding and welding, valves, caps, containers, parts of fans and pumps for acids, mixers, filters, various containers, buckets, etc. can be manufactured.
One of the main methods for processing PE into products is injection molding. Bottles from polyethylene ¬ from 25 to 5000 ml, as well as utensils, toys, electrical products, trellis baskets and boxes, are widely used in the pharmaceutical and chemical industries.
The choice of a particular technological process is determined primarily by the need to obtain a branded assortment with a certain set of properties. The suspension method is appropriate for the production of polyethylene pipe grades and grades of polyethylene intended for processing by extrusion method, as well as for the production of high molecular weight polyethylene. With the use of mortar technologies, LPEND is obtained for high-quality packaging films, polyethylene grades for the manufacture of products by casting and rotational molding methods. The gas-phase method produces a branded assortment of polyethylene intended for the manufacture of consumer goods.

Plastics

Chains of polypropylene molecules.

Housewares, fully or partially made of plastic

Plastics (plastic masses) or plastics - organic materials based on synthetic or natural macromolecular compounds (polymers). Extremely widespread use of plastics based on synthetic polymers.

The name "plastics" means that these materials, under the influence of heating and pressure, are able to form and maintain a given shape after cooling or hardening. The molding process is accompanied by the transition of a plastically deformable (viscous flowing) state to a glassy state.

History

The first plastic was obtained by the English metallurgist and inventor Alexander Parks in 1855. Parks called it parkesin (later another name became popular - celluloid). Parkesin was first presented at the Great International Exhibition in London in 1862. The development of plastics began with the use of natural plastic materials (for example, chewing gum, shellac), then continued with the use of chemically modified natural materials (such as rubber, nitrocellulose, collagen, galalite) and finally came to fully synthetic molecules (bakelite, epoxy resin, polyvinyl chloride, polyethylene and others).

Parkesin was a trademark of the first artificial plastic and was made from cellulose treated with nitric acid and a solvent. Parkesin was often called artificial ivory. In 1866, Parkes created the Parkesine Company to mass produce the material. However, in 1868, the company went bankrupt due to poor product quality, as Parks tried to reduce production costs. Parkesin was succeeded by xylonite (another name for the same material), manufactured by Daniel Spill, a former Parks employee, and celluloid, manufactured by John Wesley Hyatt.

Types of Plastics

Depending on the nature of the polymer and the nature of its transition from a viscous flowing to a glassy state during the molding of plastic products, they are divided into

Thermoplastics ( thermoplastic plastics) - when heated, they melt, and when cooled, they return to their original state.
Reactoplasts ( thermosetting plastics) - they are distinguished by higher operating temperatures, but they break down upon heating and upon subsequent cooling do not restore their original properties.

Getting

The production of synthetic plastics is based on polymerization, polycondensation or polyaddition reactions of low molecular weight starting materials released from coal, oil or natural gas. In this case, high-molecular bonds are formed with a large number of starting molecules (the prefix "poly-" from the Greek "a lot", for example ethylene-polyethylene).

Processing methods

Injection / Injection Molding
Pressing
Vibroforming
Foaming
Casting
Welding

Mechanical restoration

Plastics, in comparison with metals, have an increased elastic deformation, as a result of which, when processing plastics, higher pressures are used than when processing metals. Apply any lubricant, as a rule, is not recommended; only in some cases, the final processing allows the use of mineral oil. Cool the product and tool with a stream of air.

Plastics are more fragile than metals, therefore, when processing plastics with cutting tools, it is necessary to apply high cutting speeds and reduce the feed. Tool wear in plastic processing is much greater than in metal processing, why is it necessary to use a tool made of high-carbon or high-speed steel or hard alloys. The blades of cutting tools should be sharpened, if possible, more sharply, using fine-grained circles for this.

Plastic can be machined on a lathe, can be milled. Band saws, circular saws and carborundum wheels can be used for sawing.

Welding

The plastics can be connected to each other mechanically by means of bolts, rivets, gluing, dissolving, followed by drying, and also by welding. Of the listed methods of joining only by welding, it is possible to obtain a joint without foreign materials, as well as a joint that will be as close as possible to the base material in terms of properties and composition. Therefore, the welding of plastics has found application in the manufacture of structures, which are subject to increased requirements for tightness, strength and other properties.

The process of welding plastics consists in forming a joint due to the contact of heated joined surfaces. It can occur under certain conditions:

Fever. Its value should reach the temperature of the viscous flow state.
Tight contact of the welded surfaces.
Optimum welding time is holding time.

It should also be noted that the temperature coefficient of linear expansion of plastics is several times higher than that of metals, therefore, during welding and cooling, residual stresses and deformations occur, which reduce the strength welded joints plastics.

The strength of the welded joints of plastics is greatly influenced by the chemical composition, orientation of macromolecules, ambient temperature and other factors.

Various types of plastic welding are used:

Welding with gas coolant with and without additives
Extrudable welding
Contact heat welding
Contact heat welding
High frequency electric field welding
Ultrasonic welding of thermoplastics
Friction welding of plastics
Radiation welding of plastics
Chemical welding of plastics

As with metal welding, plastic welding should strive to ensure that the material weld and the heat-affected zone in mechanical and physical properties differed little from the main material. Fusion welding of thermoplastics, like other methods of their processing, is based on the transfer of the polymer first to a highly elastic and then to a viscous flow state and is possible only if the surfaces to be welded of materials (or parts) can be transferred to a state of viscous melt. Moreover, the transition of the polymer to a viscous flow state should not be accompanied by decomposition of the material by thermal degradation.

When welding many plastics, harmful fumes and gases are released. For each gas there is a strictly defined maximum available concentration in air (MPC). For example, the maximum permissible concentration for carbon dioxide is 20, for acetone - 200, and for ethanol - 1000 mg / m³.

Plastic based materials

Furniture plastics

Plastic, which is used for the manufacture of furniture, is obtained by impregnating paper with thermosetting resins. Paper production is the most energy- and capital-intensive stage in the entire process of plastic production. 2 types of papers are used: the basis of plastic is kraft paper (thick and unbleached) and decorative (to give a plastic picture). Resins are divided into phenol-formaldehyde, which are used to impregnate kraft paper, and melamine-formaldehyde, which are used to impregnate decorative paper. Melamine formaldehyde resins are made from melamine, so they are more expensive.

Furniture plastic consists of several layers. The protective layer - overlay - practical transparent. It is made of high quality paper, impregnated with melamine-formaldehyde resin. The next layer is decorative. Then several layers of kraft paper, which is the basis of plastic. And the last layer is compensating (kraft paper impregnated with melamine-formaldehyde resins). This layer is present only in American furniture plastic.

Ready-made furniture plastic is a durable tinted sheet with a thickness of 1-3 mm. Its properties are close to getinax. In particular, it does not melt at the touch of a soldering iron tip, and, strictly speaking, is not a plastic mass, since it cannot be cast in a hot state, although it lends itself to a change in the shape of the sheet when heated. Furniture plastic was widely used in the 20th century for interior decoration of subway cars.

Plastic marking system

Identification of plastics.

To ensure the disposal of disposable items in 1988, the Plastic Industry Society developed a marking system for all types of plastic and identification codes. Plastic marking consists of 3 arrows in the shape of a triangle, inside of which is a figure indicating the type of plastic. Often, when marking products under the triangle, an alphabetic marking is indicated (in parentheses is indicated by Russian letters):

PET or PETE (PAT, PET) - Polyethylene terephthalate. Usually used for the manufacture of containers for mineral water, soft drinks and fruit juices, packaging, blisters, upholstery. Such plastics are potentially dangerous for food use.
PEHD or HDPE (HDPE) - High density polyethylene, low pressure polyethylene. Production of bottles, flasks, semi-rigid packaging. It is considered safe for food use.
PVC (PVC) - Polyvinyl chloride. It is used for the production of pipes, tubes, garden furniture, floor coverings, window profiles, shutters, containers for detergents and oilcloths. The material is potentially hazardous for food use, as it may contain dioxins, bisphenol A, cadmium.
Ldpe and PELD (LDPE) - Low density polyethylene, high pressure polyethylene. Production of tarpaulins, trash bags, bags, films and flexible containers. It is considered safe for food use.
PP (PP) - Polypropylene . It is used in the automotive industry (equipment, bumpers), in the manufacture of toys, as well as in the food industry, mainly in the manufacture of packaging. It is considered safe for food use.
PS (PS) - Polystyrene. It is used in the manufacture of insulation boards for buildings, food packaging, cutlery and cups, boxes and other packaging (cling film and foams), toys, dishes, pens and so on. The material is potentially hazardous, especially in the case of combustion, as it contains styrene.
OTHER or ABOUT - other. This group includes any other plastic that cannot be included in previous groups. It is mainly polycarbonate. Polycarbonate is not toxic to the environment, but may contain bisphenol A, which is harmful to humans. Used for the manufacture of solid transparent products, such as baby horns.

[Plastic waste and its processing

A suspension of plastic particles resembles zooplankton, and jellyfish or fish can take them for food. A large number of durable plastic (caps and rings from bottles, disposable lighters) is found in the stomachs of seabirds and animals, in particular, sea turtles and black-footed albatrosses. In addition to causing direct harm to animals, floating waste can be absorbed from water by organic pollutants, including PCBs (polychlorinated biphenyls), DDT (dichlorodiphenyltrichloromethylmethane) and PAHs (polyaromatic hydrocarbons). Some of these substances are not only toxic - their structure is similar to the hormone estradiol, which leads to hormonal failure in a poisoned animal.

Recycled plastic

Methods for processing plastic:

In December 2010, Ian Byens and his colleagues at the University of Warwick proposed a new technology for processing almost all plastic waste. The machine, using pyrolysis in a fluidized bed reactor at a temperature of about 500 ° C and without oxygen, decomposes pieces of plastic debris, and many polymers decompose into the initial monomers. Next, the mixture is separated by distillation. The final product is wax, styrene, terephthalic acid, methyl methacrylate and carbon, which are raw materials for light industry. The use of this technology saves money by abandoning waste disposal, and taking into account the receipt of raw materials (in case of industrial use) is a quickly recouped and commercially attractive way to dispose of plastic waste.

Plastics based on phenolic resins, as well as polystyrene and polychlorinated biphenyl can decompose with white rot fungi. However, this method is commercially ineffective for waste disposal - the process of destruction of plastic based on phenolic resins can last many months.

With incomplete combustion of polypropylene and polyethylene, carbon monoxide (CO) and water are formed, with full combustion, carbon dioxide (CO2) and water.

Physiological effect, toxicity

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The melting point of polypropylene ranges from 165 - 175 C, which, combined with a sufficiently high strength characteristics and excellent chemical resistance in many aggressive environments, significantly expands the possibilities of using it in the chemical industry as a structural and protective material.

Dependence of the crystallization temperature on the time of nucleation at the initial moment (/ and at the end (2 growth of spherulites in the polypropylene melt in the presence of shear (solid line and in the absence of shear (dashed line)

The melting point of polypropylene is about 165 C, however, under ordinary conditions, crystallization occurs at temperatures below 150 C. In this case, crystallization occurs at higher temperatures and the orientation of the polymer chains.

Due to the heterogeneity of molecules and different crystallite sizes, the melting point of polypropylene varies from 160 to 175 C. The heat capacity of polypropylene is greatly influenced by the presence of impurities and contact with some metals, such as copper or its alloys. Therefore, when installing polypropylene pipelines for hot water supply, fittings containing copper elements should not be used.

It was shown that the introduction of chlorine causes an increase in the melting point of polypropylene.

Dependency properties.

In a wide temperature range - between the glass transition temperature of polyisobutylene and the melting point of polypropylene - the mixture exhibit highly elastic properties.

This small change in the chemical structure leads to the fact that the melting point of polypropylene exceeds the melting point of polyethylene by 30-50 ° C.

The dependence of the melting temperature on the amount of chlorine in the polymer. | Dependence of intrinsic viscosity on the amount of chlorine in the polymer.

For this purpose, it is proposed to carry out the polymerization of gaseous polypropylene under the action of complex catalysts: titanium trichloride of triethyl aluminum, supported on particles of a powdered polymer or at temperatures above the melting point of polypropylene, when the resulting polymer flows from the catalyst carrier.

The temperature in the screw is 80-100 С higher than in the melt-water or on the die, and the temperature at which the fiber is formed is 80-120 С higher than the melting point of polypropylene. With insufficiently careful stabilization of polypropylene during molding, thermooxidative destruction of the polymer occurs, and the intensity of this process is greater, the higher the molecular weight of the starting polymer.

To rationally heat the melt above the melting point of polypropylene, it is advisable to choose large distances between the holes of the die than when forming fibers from melts of polyamides or polyesters.

In the same works of Flory, it is suggested that for polypropylene, in which the spiral form of macromolecules, detected in the crystalline state, has great internal stability, the forces of intermolecular interaction do not play a decisive role in the initiation of crystallization processes. It is noted that the melting temperature of polypropylene (169 C) is very high compared to the melting temperature of polyethylene (137 C), whose molecules have the structure of a flat zigzag.

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Depending on the amount of the isotactic part contained in the polypropylene, as well as the molecular weight, the properties of this material can vary within wide limits. Of greatest industrial interest is polypropylene, the molecular weight of which is from 80 to 200 thousand, and the content of the isotactic part is from 80 to 98 percent.

In many of its properties, polypropylene resembles.

Physical and mechanical properties

The density of polypropylene, in contrast to the density of polyethylene, is lower (this indicator is 0.90 g / cm 3, and this is the least among all types of plastic), it is harder (greater resistance to abrasion), also has the highest value of heat resistance (it softening begins at a temperature of 140 degrees Celsius, it melts at 175 ° C), is practically not susceptible to corrosion cracking. Polypropylene is highly sensitive to oxygen and light (a decrease in sensitivity occurs during the introduction of stabilizers).

How polypropylene will behave during stretching is even more dependent on temperature and the speed at which the load is applied. The lower the tensile speed of a given material, the higher the rate of its mechanical properties. At high speeds, tensile, which destroys stress during tensile polypropylene, is significantly lower than its yield strength during stretching.

Physico-mechanical properties of various grades of this material can be seen in the table:

Chemical properties

Propylene is a hydrocarbon having three carbon atoms. During a stepwise polymerization reaction, a polymer is formed from it, in which methyl groups are also attached to the polymer chain.

Three types of polypropylene are formed - syndiotactic, isotactic and attactic. The differences between these polymers is the positioning of methyl groups in space. In isotactic type polypropylene, each of the methyl groups is positioned on one side of the polymer, in syndiotactic polypropylene they can be positioned on different sides, and in attactic - positioning is random.

Polypropylene is a material with chemical resistance. Only strong oxidizing agents, such as nitric fuming acid, chlorosulfonic acid, oleum and halogens, can exert a significant effect on it. Sulfuric acid at a concentration of 58%, as well as 30% hydrogen peroxide at room conditions have a negligible effect. The destruction of polypropylene occurs only as a result of prolonged contact with these reagents at a temperature of 60 degrees Celsius.

Polypropylene is a water-resistant material (up to a temperature of 130ºC), and is also resistant to aggressive environments (for example, alkalis and acids, some brands can be in contact with food products, used for the manufacture of goods and packaging, for example polypropylene tape, as well as used in medical biological industry); but it is affected by strong oxidizing agents (H2SO4, HNO3, chromium mixture).

In organic solvents, this material swells slightly at room temperature. At a temperature,exceeding 100ºC, polypropylene dissolves in aromatic hydrocarbons, such as toluene, benzene. Information on the resistance of this material to the effects of individual chemicals can be seen in the table.

Due to the presence of tertiary carbon atoms, this material is more sensitive to the influence of oxygen, especially at higher temperatures. This is the reason why polypropylene is more prone to aging when compared with polyethylene. Aging of the material proceeds more quickly and is accompanied by a rather sharp deterioration in the mechanical properties of polypropylene. For this reason, the material is used only in a stabilized form. Stabilizing substances are used to protect polypropylene from destruction both during processing and during operation. This material is less likely than polyethylene to undergo cracking resulting from the influence of aggressive media. It can withstand standard stress cracking tests that are carried out in various environments. At a temperature of 50 degrees Celsius, the indicators of resistance to cracking in a 20 percent aqueous OP-7 emulsifier solution for polypropylene, the melt flow rate of which is from 0.5 to 2.0 g / 10 min, which is in a state of stress, is over 2 thousand hours.

Polypropylene is a waterproof material. Even after six months of contact with water (at room temperature), its water absorption is not higher than 0.5%, and at a temperature of 60 degrees Celsius this indicator is less than two percent.

Thermophysical Properties

The melting point of polypropylene is higher than that of polyethylene, which means that its decomposition temperature is also higher. Pure isotactic-type polypropylene begins to melt at a temperature of 176ºC. The highest temperature of propylene use is from 120 to 140ºС. All polypropylene products can withstand boiling, and are able to undergo steam sterilization, and their mechanical properties or shape does not change.

Polypropylene has greater heat resistance than polyethylene, but is inferior to this material in frost resistance. The temperature of its frost resistance or brittleness is from -5 to -15ºС. To increase the frost resistance of isotactic polypropylene, ethylene units can be introduced into its macromolecule (for example, during the copolymerization of ethylene with propylene).

The indicators of the main polypropylene thermophysical properties are listed in the table: