Almost 10 times lighter than cork(average density not more than 20 kg/m 3 );
Coefficient of thermal conductivity 0.03 W/(m×K).
It chars, but does not burn in an open flame at 500 ° C, and when introduced into the composition flame retardants do not ignite in an oxygen environment.
It has significant water absorption and sensitivity to aggressive chemicals. During storage and operation, it is protected with cellophane or polyethylene film.
Used as heat and sound insulating material in construction, in the manufacture of refrigeration units, storage facilities and vessels for the transport of liquid oxygen, as a filler for hollow structures in transport engineering.
Carbamide glue
adhesive based on urea-formaldehyde resins and melamine-formaldehyde resins (so-called urea resins), as well as their mixtures.
in large quantities used in the woodworking industry in the manufacture of plywood, furniture, etc.; used for bonding phosphorus and metal.
is an aqueous solution of carbamide resin. Often the adhesive contains hardener (oxalic, phthalic, hydrochloric acids or some salts) and filler (bean or cereal flour, starch, wood flour, gypsum, etc.).
For example, glue K-17 consists
from 100 parts (by weight) of resin MF-17, 7 - 22 parts of a 10% aqueous solution of oxalic acid, 6-8 parts of wood flour.
can be cured both when heated and at normal temperature (only in the presence of a hardener).
Polyamides
hard translucent and opaque plastics softening at temperature 150-180°C. Differ in high chemical firmness, durability, resistance to friction, elasticity. Polyamides ignite poorly, burn with a bluish flame, emitting the smell of burnt bone.
Proteins (proteins), such as silk, which was replaced by nylon, are also polyamides.
The structure of polyamides
A distinctive feature of polyamides is the presence of a repeating amide group in the main molecular chain.–C(O)–NH–. There are aliphatic and aromatic polyamides. Known polyamides containing in the main chain as aliphatic and aromatic fragments.
Polyamide macromolecules consist of flexible methylene chains and polar amide groups regularly arranged along the chain.
acetic acid amide (acetamide)
Amides are functional derivatives of carboxylic acids in which the hydroxyl -OH in the carboxyl group -COOH is replaced by the amino group -NH2.
Methods for obtaining polyamides
1. polycondensation (this reaction is called polyamidation) dicarboxylic acids (or their diesters)
and diamines.
Polycondensation is carried out mainly in the melt, less often in a solution of a high-boiling solvent or in the solid phase.
To obtain polyamides of high molecular weight from dicarboxylic acids and diamines, polyamidation is carried out at equimolar
ratios of starting materials.
In this way, polyamides are obtained, which are used in the production of fibers of the anid type (NYLON).
2. Polycondensation of diamines, dinitriles and water in the presence of catalysts. For example, oxygen compounds of phosphorus and boron, in particular mixtures of phosphorous and boric acids.
The process is carried out at 260-300 °C. Initially, under pressure, periodically releasing the released ammonia from the reaction zone. Finished at atmospheric pressure.
Nitriles are organic compounds of the general formula R-C≡N, which are formally derivatives of hydrocyanic acid HC≡N.
3. Polymerization of lactam amino acids.Mainly caprolactam. The process is carried out in the presence of water, alcohols, acids, bases and other ring-opening substances, or in the presence of catalysts, in solution or melt at high temperature.
caprolactam
Lactam - cyclic amide
Capron and enanth are thus obtained.
Getting capron
Hydrolysis of caprolactam
polycondensation
NH2 -(CH2) 5 - COOH + NH2 -(CH2) 5 - COOH + ... →
NH2 -(CH2) 5 - CO - NH -(CH2) 5 - CO - ... + n H2 O Simplified scheme
In industry, it is obtained from caprolactam. The process is carried out in the presence of water, which plays the role of an activator, at a temperature of 240-270°C and a pressure of 15-20 kgf/cm2 in a nitrogen atmosphere.
The polymer is formed by the interaction amino - and carboxyl groups of the molecules of the original substances or due to the connection of open lactam molecules.
To produce stable polyamides and control their molecular weight, processes are often carried out in the presence of molecular weight regulators, most often acetic acid.
They attach to the reactive end groups of the growing chain and block them, stopping further growth molecules.
In the names of aliphatic polyamides after the word "polyamide" (in foreign literature - "nylon") put numbers indicating the number of carbon atoms in the substances used for the synthesis of polyamide.
Polyamide based hexamethylenediamide and adipic
acid is called polyamide-6,6, or nylon-6,6
the first digit indicates the number of carbon atoms in the diamine, the second in dicarboxylic acid.
Polyamides- high-molecular compounds related to heterochain polymers, the main chain of which contains amide bonds, through which monomeric residues are interconnected. An example of polyamides is nylon. Therefore, consider polyamides using polymers and nylon as examples.
Polymers
Polymers - chemical compounds with a high mol. mass (from several thousand to many millions), whose molecules (macromolecules) consist of a large number of repeating groups (monomeric units). The atoms that make up the macromolecules are connected to each other by the forces of the main and (or) coordination valences.
Classification of polymers
By origin, polymers are divided into natural (biopolymers), such as proteins, nucleic acids, natural resins, and synthetic, such as polyethylene, polypropylene, phenol-formaldehyde resins. Atoms or atomic groups can be located in a macromolecule in the form of: an open chain or a sequence of cycles extended into a line (linear polymers, such as natural rubber); branched chains (branched polymers, e.g. amylopectin), three-dimensional mesh (cross-linked polymers, e.g. cured epoxy resins). Polymers whose molecules consist of identical monomer units are called homopolymers (for example, polyvinyl chloride, polycaproamide, cellulose).
Macromolecules of the same chemical composition can be built from units of different spatial configurations. If macromolecules consist of the same stereoisomers or of different stereoisomers alternating in a chain at a certain periodicity, the polymers are called stereoregular.
Polymers whose macromolecules contain several types of monomer units are called copolymers. Copolymers in which links of each type form sufficiently long continuous sequences that replace each other within the macromolecule are called block copolymers. One or more chains of another structure can be attached to the internal (non-terminal) links of a macromolecule of one chemical structure. Such copolymers are called graft copolymers.
Polymers in which each or some of the stereoisomers of a link form sufficiently long continuous sequences that replace each other within one macromolecule are called stereoblock copolymers. Depending on the composition of the main (main) chain, polymers are divided into: heterochain, the main chain of which contains atoms of various elements, most often carbon, nitrogen, silicon, phosphorus, and homochain, the main chains of which are built from identical atoms. Of the homochain polymers, the most common are carbon chain polymers, the main chains of which consist only of carbon atoms, for example, polyethylene, polymethyl methacrylate, polytetrafluoroethylene. Examples of heterochain polymers are polyesters (polyethylene terephthalate, polycarbonates), polyamides, urea-formaldehyde resins, proteins, some organosilicon polymers. Polymers whose macromolecules, along with hydrocarbon groups, contain atoms of inorganic elements are called organoelement. A separate group of polymers is formed by inorganic polymers, such as plastic sulfur, polyphosphonitrile chloride.
properties and the most important characteristics polymers
Linear polymers have a specific set of physicochemical and mechanical properties. The most important of these properties are: the ability to form high-strength anisotropic highly oriented fibers and films, the ability to large, long-term developing reversible deformations; the ability to swell in a highly elastic state before dissolution; high viscosity solutions. This set of properties is due to the high molecular weight, chain structure, and flexibility of macromolecules. With the transition from linear chains to branched, sparse three-dimensional networks and, finally, to dense network structures, this set of properties becomes less and less pronounced. Highly cross-linked polymers are insoluble, infusible and incapable of highly elastic deformations.
Polymers can exist in crystalline and amorphous states. Necessary condition crystallization - the regularity of sufficiently long sections of the macromolecule. In crystalline polymers, various supramolecular structures (fibrils, spherulites, single crystals) can appear, the type of which largely determines the properties of the polymer material. Supramolecular structures in non-crystallized (amorphous) polymers are less pronounced than in crystalline ones.
Non-crystallized polymers can be in three physical states: glassy, highly elastic and viscous. Polymers with a low (below room) transition temperature from a glassy to a highly elastic state are called elastomers, and those with a high temperature are called plastics. Depending on the chemical composition, structure, and mutual arrangement of macromolecules, the properties of polymers can vary over a very wide range. So, 1,4.-cispolybutadiene, built from flexible hydrocarbon chains, at a temperature of about 20 ° C is an elastic material, which at a temperature of -60 ° C passes into a glassy state; polymethyl methacrylate, built from more rigid chains, at a temperature of about 20 ° C is a solid glassy product, turning into a highly elastic state only at 100 ° C. Cellulose, a polymer with very rigid chains connected by intermolecular hydrogen bonds, cannot exist at all in a highly elastic state up to the temperature of its decomposition. Large differences in the properties of polymers can be observed even if the differences in the structure of macromolecules are at first sight small. Thus, stereoregular polystyrene is a crystalline substance with a melting point of about 235 °C, while non-stereoregular polystyrene is not able to crystallize at all and softens at a temperature of about 80 °C.
Polymers can enter into the following main types of reactions: the formation of chemical bonds between macromolecules (the so-called crosslinking), for example, during the vulcanization of rubbers, leather tanning; decomposition of macromolecules into separate, shorter fragments, reactions of side functional groups of polymers with low molecular weight substances that do not affect the main chain (the so-called polymer-analogous transformations); intramolecular reactions occurring between functional groups of one macromolecule, for example, intramolecular cyclization. Cross-linking often proceeds simultaneously with degradation. An example of polymer-analogous transformations is the saponification of polytylacetate, leading to the formation of polyvinyl alcohol. The rate of reactions of polymers with low molecular weight substances is often limited by the rate of diffusion of the latter into the polymer phase. This is most clearly manifested in the case of cross-linked polymers. The rate of interaction of macromolecules with low molecular weight substances often depends significantly on the nature and location of neighboring units relative to the reacting unit. The same applies to intramolecular reactions between functional groups belonging to the same chain.
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Preparation of capron To obtain capron, some derivatives of amino acids are used, for example, caprolactam (a product of the intramolecular interaction of the carboxyl group and the amino group of the 6-aminohexanoic acid molecule). Caprolactam in the presence of water turns into 6-aminohexanoic acid, the molecules of which react with each other: O H 2 N -CH 2 - (CH 2) 4 -C + H -N -CH 2 - (CH 2) 4 -C + ... OH OH O H O H 2 N -(CH 2) 5 -C -N -(CH 2) 5 -C - ... + nH 2 O
Physical and Chemical properties Physical features: the polymer is a resin - an elastic, thermoplastic, wear-resistant transparent material; easily dyed with fabric paints; due to the presence of numerous hydrogen bonds between the amide groups of neighboring macromolecules, it has high strength; Chemical features: melts with strong heating. When burned, it forms a hard, shiny ball of dark color, spreading an unpleasant odor; In reactions to decomposition products, compounds containing amino groups are formed, which turn red litmus paper blue; It dissolves only in concentrated HNO 3, H 2 SO 4 and in molten phenol. Pink nylon
Types of materials based on nylon and their application By passing under pressure the melt of nylon through spinnerets with the smallest holes, fibers are obtained that are superior in strength to natural ones. A cord fabric is made from the bottom, with the help of which carcasses for auto and aircraft tires, fishing nets, nylon threads (tights, stockings, stockings) are made. Nylon fabrics are resistant to abrasion and do not wrinkle when deformed. However, they are destroyed by acids and cannot withstand high temperatures, so they cannot be ironed with a hot iron. Also, nylon resin is obtained from nylon, from which plastics are made. It is used for the manufacture of various machine parts, gears, bearing shells, which have exceptionally high strength and wear resistance. Towing cable (aviation capron) Capron 70%
Polycondensation reactions leading to the production of polyamides Interaction of diamines with dicarboxylic
acids,
diesters of dicarboxylic acids with
diamines
dicarboxylic acid dichlorides with
diamines
acid dinitriles with aldehydes
dicarboxylic acids with diisocyanates
Properties of polyamides
Polyamides are hard, horn-shaped polymers with highmelting point (for example, 2180 C for nylon, 2640
C for nylon).
good ones mechanical properties, resistant to abrasion and
are characterized by high tensile strength (700-750
kgf/cm2).
Polyamides of a regular structure are very resistant to
action of common solvents. Only strongly
polar compounds such as phenol, cresols,
formic acid, dissolve polyamides of such
type. Mixed polyamides dissolve at
heating in lower aliphatic alcohols
(methyl, ethyl) mixed with small
amounts of water (from 10 to 20%).
Industrial polyamides are insoluble in organic solvents, soluble in organic acids (sulphuric, acetic),
When heated in air, thermal-oxidative degradation occurs in polyamides. Moisture and UV acting at the same time, sharply
The properties of polyamides depend on the molecular weight and structure of the starting materials
Water absorption of polyamides
Grades of polyamides are designated by numbers. The first digit is the number of carbon atoms in the original diamine, the second is in the acid
Polycondensation of diamines and dicarboxylic acids proceeds as an equilibrium process
n H2N–R–NH2+ n HOOC– R1-COOH↔
H-(-HN–R–NH-CO–R1-CO-)OH
+H2O
The yield and molecular weight of polyamide depend
on the completeness and speed of water removal,equimolarity ratio
components
lack of monofunctional
connections
an excess of one of the components can
cause hydrolytic reactions
acidolysis, aminolysis and lead to a sharp
molecular weight reduction
In hexamethylene adipate (AG salt), hexamethylenediamine and adipic acid are combined strictly in an equimolar ratio
H2N–(CH2)6–NH2 + HOOC– (CH2)4-COOH →n H3N+–(CH2)6–N+H3 –-O C (O)– (CH2)4-C (O)O-
When the AG salt is heated in the melt, it polycondensates with the formation of polyamide
n H3N+–(CH2)6–N+H3 –-OC(O)–(CH2)4-C (O)O-→
H (-HN-(CH2)6NHCO(CH2)4-CO-)n-OH + (n-1)H2O
nylon 66
RAW
Hexamethylenediamine (CH2)6 (NH2)2 Tbp=9092C. (at 1.86 kPa), Тmelt = 39СAdipic acid HOOC– (CH2)4-COOH
white crystalline powder, soluble
in hot water, alcohol. Тmelt=151С
Sebacic acid HOOC– (CH2)8-COOH
white crystalline powder Tm=134
Aromatic diamines do not form salts with dicarboxylic acids because of their weak basicity. Therefore, the reaction in the melt is not
Obtaining polyamides at the phase boundary
-Сl-C+-R-C+-Cl-+H N–R –NH
2
1
2
Cl-C-R-CCl -HCl Cl-C-R-C
H2N-R1-N+H2
H2N–R1–NH
Benefits of an interface reaction
There is no need for strictequimolarity of starting materials - reaction
flows at the interface, so
equimolarity is regulated by the surface
section.
This results in a polymer with a very high degree
polymerization.
The reaction proceeds with high speed during
few minutes to completion.
You can use the whole variety of diamines and
dicarboxylic acids, regardless of their
high temperature resistance.
Phenylon
Aromatic polyamidederived from acid chloride
isophthalic acid and
metaphenylenediamine.
based on phenylone
heat resistant fibre.
Obtaining polyamides from heterocyclic compounds by polymerization reaction
R A ↔ –R–A–+ H2O ↔ N+H3-(CH2)nCOO- →
C(O)
(CH2)n
NH
→H(-HN-R-CO-)nOH
RAW
Caprolactam - lactam ε - aminocaproicacids
White crystalline solid
powder or melted pieces T pl \u003d 70C.
Highly soluble in water and organic
solvents. Hygroscopic, store in
closed container. Used to get
polyamide - capron:
n caprolactam + H2O → H (-HN-R-CO-) 5OH
capron
PA 6 (nylon 6, capron) - hydrolytic polymerizationcaprolactam in the presence of water and AG salt. White,
horn-like, amorphous-crystalline. Resistant to
the action of gasoline, oil, solvents, water Thr. - up to -30С,
Tplasticity=160C. High physical and mechanical properties,
dielectric properties, wear resistance. Non-toxic and
physiologically inert - used for prosthetics.
The disadvantage is high water absorption (up to 10%, in the atmosphere -
up to 3%), which worsens the properties of the material.
PA-6 - structural material of general technical
appointments in the aviation industry, medicine,
electrical engineering (insulation). Produced in the form of granules.
Film PA-6
Amino acids with more CH2 methylene groups than aminocaproic acid (more than 5) do not form cyclic compounds
(lactams), and polycondensationtheir general form is:
Representatives of polyamides derived from amino acids
enantH-[-NH-(CH2) 6-CO-]n-OH
pelargon
H-[-NH-(CH2) 8-CO-] n-OH
undecane
H-[-NH-(CH 2) 10-CO-] n-OH
(polyamide-11)
PA-6 block (caprolite, nylon 6)
Polymerization in an autoclave at 200C andatmospheric pressure, catalysts
physical and mechanical own block PA-6
outperform PA-6 synthesized
hydrolytic polymerization.
Production of overall thick-walled
products by mechanical processing
blocks. Processed by milling,
drilling, turning. Responsible details
in aircraft and mechanical engineering.
Produced in blocks
PA-66
PA-66 linear polar, amorphous - crystallinepolymer, white horn-like. Resistant to
solvents, gasoline, oil. PA-66 vs.
other aliphatic polyamides has the most
high strength, hardness, abrasive
stability, heat resistance.
Structural material in mechanical engineering,
automotive industry, chemical industry By
in relation to organic and inorganic media
similar to PA-6 and 66. Less hygroscopic than PA-66.
Strength, rigidity, abrasion resistance PA-610
somewhat lower than that of PA-66, however, the stability of these
properties are higher for PA-610 due to lower water absorption
under operating conditions
PA-610
construction material inengineering, automotive, chemical
industry, as well as for the production
chemical fibers and films. Temperature
operation of products - from -60 to 170C.
The cost of PA-610 is higher due to the high
cost of sebacic acid. Issued
in the form of granules, processed by molding under
pressure, pressing, extrusion.
Properties of polyamides
Physical and mechanical properties of polyamidesdetermined by the number of hydrogen bonds per
unit of length of a macromolecule, which
increases in the series PA-12, PA-610, PA-6, PA-66.
Increase in the linear density of hydrogen bonds
in the macromolecule increases the temperature
melting and vitrification of the material, improves
heat resistance and strength characteristics,
but at the same time water absorption increases,
the stability of properties and dimensions decreases
materials, the dielectric properties deteriorate
characteristics.
Application
Polyamides are structural(engineering) polymeric materials. AT
different from general purpose polymers,
structural polymers are characterized
increased strength and heat resistance,
and, accordingly, more expensive than household
polymer materials. They are used
when creating products that require
durability, wear resistance, reduced
combustibility and able to withstand
cyclic loads.
The following main types of polyamides are presented on the Russian market: polyamide 6, polyamide 66, polyamide 610, polyamide 12,
polyamide 11. Most widely used inworld and in Russia represented
group of polyamides PA-6
