Basic properties of polyamide and application in various fields

Heat-resistant polymers containing high molecular weight synthetic compounds of the amide group (CO-NH or CO-NH2) are called polyamides. The amide bond in the macromolecules of these polymers is repeated from two to ten times.

All polyamides are rigid materials. They have increased strength due to crystallization. Their density varies from 1.01 to 1.235 g/cm³. The surface of polyamide materials is smooth, resistant to fading and changing shape.

They are excellently painted with any dyes and are resistant to many chemicals.

Areas of application of polyamide

Polymers are used in various fields.

In the light and textile industries for the manufacture of:

• synthetic (nylon, nylon) and mixed fabrics;
• carpets and rugs;
• artificial fur and various types of yarn;
• socks and stockings.

In rubber production:

• for creating cord threads and fabrics;
• ropes and filters;
• conveyor belts and fishing nets.

In construction:

• for the production of various fittings and pipes;
• as antiseptic coatings for concrete, ceramic and wooden surfaces;
• to protect metal products from rust.

In mechanical engineering, aircraft and shipbuilding for the manufacture of parts for shock-absorbing mechanisms, rollers and bushings, various devices, etc.

They are found in adhesives and varnishes.

They are used in the food industry for the manufacture of individual equipment parts that come into contact with products.

In the medical industry, artificial veins and arteries are created from them, and various types of prostheses are made. Surgeons use polyamide threads to apply sutures during surgery.

Historical reference

Above we wrote about the date of synthesis of PA. But for the first time, the compound, which included the base of the Styrene resin, was made in the thirties of the nineteenth century by scientists Ostromyslensky and Staudinger. Using the light polymerization of styrax, the last chemist established fiber production in Germany in 1911. But this material was not very popular in the world due to the high cost of oil and gas resources. The picture changed during World War II. Then a weapon with napalm was required, which could not be extinguished with water for a long time. For this purpose, they began to use styrene rubber as a lubricant. Subsequently, the United States used this property to wage a scorch war in Vietnam.

A little history

Polyamides were first synthesized in America back in 1862 from petroleum products. It was poly-c-benzamide. And thirty years later, American scientists synthesized another variety - poly-e-capramide.

But the production of synthetic polyamide products was organized only in the late 30s of the last century. These were the fibers from which nylon and nylon fabrics . In our country, the production of polyamide fibers began after the Great Patriotic War, in 1948.

Main characteristics

Polymer fabric has the following properties:

• • Plasticity, in which it bends easily and at the same time restores its original shape, that is, it cannot be deformed.
• • Durability. Easily copes with heavy physical activity.
• • Heat resistance. Does not change its qualities when exposed to high and low temperatures.
• • Immunity to chemicals (alkalis, acid). In addition, it does not oxidize under the influence of oxygen and water, like metal.
• • Long-term operation, during which the products do not change their physical properties.
• • Ability to reduce the coefficient of friction.
• • Immunity to the conductivity of electrical charge.
• • Ability to withstand constant loads.
• • Does not change its qualities due to temperature changes.
• • Withstands steam influence at 140 degrees.
• • In severe frost it is not susceptible to breaking, that is, it retains its elasticity.
• • It is not affected by alcohol, solvent, oil and gasoline.
• • Dissolves in concentrated formic, sulfuric and trifluoroacetic acids. It is also affected by phenol, cresol, chlorine and trifluoroethanol.

To change the basic properties, various additives are used, such as mineral fillers and optical fiber. All methods are suitable for processing: milling, drilling, turning, welding and grinding. Can be painted well. The downside is poor air permeability, which negatively affects the production of clothes for small children. It is also impossible to operate products at temperatures below 40 degrees, this can lead to brittleness and crumbling. People suffering from allergies are strictly prohibited from using knitwear made from this fiber.

Brands produced by industry

At the present stage, the chemical industry produces several types of polyamides. The largest group is represented by aliphatic polyamides. They are divided into the following groups: Crystallizing homopolymers:

• polyamide 6 (PA 6), known as caprolon;
• polyamide 66 (PA6.6) or polyhexamethylenadinamide;
• polyamide 610 (PA 6.10) whose name is polyhexamethylene sebacinamide;
• polyamide 612 (RA 6.12);
• polyamide 11 (PA11) - polyundecanamide;
• polyamide 12 (PA12) - polydodecanamide;
• polyamide 46 (RPA46) and polyamide 69 (PA69).

Crystallizing copolymers:

• polyamide 6/66 (PA6.66) or PA 6/66;
• polyamide 6/66/10 (RA 6/66/10);
• thermoplastic polyamide elastomer (polyetherblockamide) - TPA (TPE-A) or REVA.

Amorphous

• polyamide MASM 12 (RA MASM12);
• polyamide RASM (RA RASM 12).

The second, no less common group is aromatic and semi-aromatic polyamides (PAA). They are divided into:

Crystallizing:

• polyphthalamides (synthesized from isophthalic and terephthalic acids), labeled: PA 6T; PA 6I/6T and PA 6T/6I; PA 66/6T and PA 6T/66; PA 9T HTN;
• polyamide MXD6 (PA MXD6).

Amorphous

• polyamide 6-3T (PA 63T; PA NDT/INDT).

Another group of polyamides is glass-filled. They belong to composite materials (modified polyamides), in which glass beads or structured threads are added to the resin. Common brands of glass-filled polyamides: RA 6 SV-30; RA6 12-KS; RA 6 210-KS; RA 6 211-DS, where

• SV - glass fiber, 30 - its percentage;
• KS - granule length less than 5 mm;
• DS - granule length from 5 mm to 7.5 mm.

The following are also used as modifiers:

• talc (deformation marks);
• molybdenum disulfate (increases wear resistance and reduces friction);
• graphite.

Trade organizations offer polyamides under various commercial names: nylon, Ultramid, Ultralon, Zutel, Duerthan, Sustamid, Akulon, Ertalon, Tekamid, Tekast, etc. But they all represent the brands listed above. For example, Tecamid 66 is Polyamide 66.

Products

We paid much attention to consumer goods produced by light industry. I would like to put emphasis on those things that are used for technical purposes. Polyamide material is successfully used in production:

• • Sliding bearings.
• • Various gaskets with unique performance properties.
• • Hub assemblies for automobiles and mechanical engineering machines, as well as for housing elements and brackets.
• • Spare parts for units of varying complexity, which are designed to reduce the susceptibility of shocks, vibrations, and sounds.
• • Seals that increase tightness in devices with high pressure.

This material is also used to produce parts:

• • warehouse hydraulic cart (wheels and rollers);
• • for pipes and profiles of different diameters (round, square, rectangular, decorative, external and internal plugs);
• • furniture fittings (plastic bumpers, guides, supports);
• • bearings.

Properties of polyamide material grades

The properties of polyamides of different brands are similar to each other. These are materials with increased strength and wear resistance. Synthetic filtered polyamide fabrics can be processed with hot steam (t=140°). At the same time, their elasticity is completely preserved. Parts, fittings and pipes made from polyamides can withstand high shock loads.

The structural thermoplastic Polyamide 6 is a product of anionic polymerization of caprolactam GOST 7850-74E, and is resistant to hydrocarbon products, fuels and lubricants and mechanical damage. Due to this, it is widely in demand in the oil refining industry, the production of automobiles and hand tools. Its disadvantage is its high moisture absorption, which limits its use in the manufacture of parts operating in humid environments. The advantage is that it does not lose its original properties after drying.

Polyamide 66 (Tecamide 66) is distinguished from Polyamide 6 (PA 6) by its greater density. This is a rigid material with increased hardness, strength and good elasticity. It is insoluble in alkalis and other solvents, technical oils, edible fats, fuels and lubricants, and is resistant to x-ray and gamma radiation.

Polyamide 12 has a high degree of slip and wear resistance. It can be used in conditions of ultra-high temperatures and high humidity. Used in the production of shock-absorbing parts, rollers and bushings, buffer strips and rope blocks, worm wheels, augers, etc.

Polyamide 11 differs from all other types in the lowest percentage of water absorption (0.9%), it practically does not age. It can be operated at sub-zero temperatures. The special property of maintaining its shape in a humid environment has made it an indispensable material in the engineering, aircraft and shipbuilding industries. In addition, it is physiologically inert and can be used in equipment for catering establishments. Low hygroscopicity makes Polyamide in demand in electrical engineering and energy as an insulating material. Polyamide 11 is one of the most expensive polymers.

Teamide 46 is a polyamide with a semi-crystalline structure and has the highest melting point (295°C). Used for the manufacture of parts operating at elevated temperatures. Its disadvantage is increased water absorption.

Filling polyamide with glass fiber modifiers improves their properties: they become stiffer, strength and heat resistance increase, and the coefficient of linear expansion decreases, reducing shrinkage. Polyamides become resistant to cracking from frost or elevated temperatures. Glass-filled polyamides are used in instrument making, the production of musical instruments (cases are made from them), in the manufacture of load-bearing parts of transformers, etc.

Video: “Machining of polyamide 6 (caprolon)”

Features of the composition

Polyamide has the following properties: matte rough or glossy smooth surface. Every texture has a positive and a negative.

pros

Modern polyamide material has many positive features:

• the highest strength - the thread can withstand a load of up to 1.5 kg. with a thickness slightly larger than a human hair;
• weightlessness - clothes made from the material are very light;
• good maintenance of the shape of the product - the density of polyamide allows things not to wrinkle and look well-groomed after folded;
• polyamide fire-resistant fabric does not ignite in fires, it can only melt at elevated degrees;
• perfectly allows air flow, allowing you to cool the body in hot weather;
• the fabric is gentle to the body, pleasant to touch;
• can be painted in any shade;
• polyamide is one of the materials that stretches well, allowing you to stretch the item to different body types;
• Manufacturers often say that a material that does not require special care is polyamide. It is enough to wash it in a washing machine with a powder that matches the color of the fabric and nothing will shrink;
• good reflection of light rays;
• do not deteriorate from thermal oxidizers;
• Polyamide dyed thread will not fade in the sun, from fungus and sea salt. Also, it does not rub during wear, even on bends;
• the fabric is water-repellent and quick-drying, so it is often added for winter and mid-season outerwear.

Minuses

Despite many advantages, there are negative properties:

• does not retain heat - due to its good throughput, the wind quickly blows away the heat. For winter clothes this is a negative property, and for summer clothes it is a positive property;
• at high temperatures from 40C it becomes hard and can break;
• fibers do not absorb moisture, which is why they become highly electrified. Moreover, static electricity accumulates over time and can “spark” when getting dressed;
• if you want to alter clothes or home textiles yourself, the fabric will crumble when cutting;
• instantly absorbs greasy and sweaty stains that are difficult to remove;
• may cause allergies in people with sensitive skin.

The material has many more advantages than disadvantages. Therefore, the material is very popular and is used for all seasons of the year in various forms.

Production technology

The production of polyamides is carried out in two ways:

• polymerization of caprolactam (for poly-e-capramides), which is carried out by converting the cyclic NC bond into a linear polymer;
• a chain reaction of polycondensation of hexamethylenediamine and adipic acid (for poly-c-benzamides), as a result of which polyamide chains are formed.

Both processes can be performed in continuous (the most common) and batch modes.

The continuous technological process of polymerization of caprolactam consists of the following stages:

1. Preparatory. At this stage, the AG salt is obtained from adipsic acid and hexamethylenediamine. To do this, adipsic acid is dissolved in methanol in a special apparatus equipped with a stirrer and heating. At the same time, caprolactam powder is melted in a melter equipped with a screw feeder;
2. At the second stage, polymerization occurs. This is done as follows: the prepared solution is introduced into the polymerization column. Columns are used in one of three types: L-shaped, vertical or U-shaped. Melted caprolactam also goes there. A neutralization reaction occurs and the solution boils. The resulting vapors enter the heat exchangers;
3. At the next stage, the polymer from the column in molten form is extruded into a special die and then sent for cooling. For this purpose, baths with running water or watering drums are provided;
4. When cooled, the polymer bundles and ribbons are supplied to the grinding machine by means of rollers or guides;
5. At the next stage, the resulting polyamide crumb is washed with hot water and filtered from low-grade impurities;
6. The technological process is completed by drying the polyamide crumbs in special vacuum-type dryers.

The continuous technological process of polycondensation (production of poly-c-benzamides) includes steps similar to the polymerization of caprolactam. The difference lies in the methods of processing raw materials.

• the process of obtaining AG salts is the same as during polymerization, but after isolation they crystallize and are fed into the reactor in the form of a powder rather than a solution;
• The polycondensation chain reaction occurs in an autoclave reactor. This is a horizontal cylindrical apparatus with a stirrer;
• polycondensation is carried out in a pure nitrogen environment at t=220°C and P=1.76 MPa. The duration of the process is from one to two hours. Then the pressure is reduced to atmospheric pressure for one hour, after which the reaction is carried out again at P = 1.76 MPa. The full production cycle of this type of polyamide takes place within 8 hours;
• after its completion, the molten polyamide is filtered, cooled and crushed into granules, which are dried with hot air in pneumatic dryers.

Types of polyamide fabric

Various questions are received about the types of polyamide fabric. Many people are surprised, what kind of canvas is this, which has 7 different types? Now we will talk about each type separately.

Nylon

This is the original and still in demand type of matter. It is used to produce underwear, tights and is added to textile and knitwear products (socks, blouses, sweaters). It is beautiful, light and does not take long to dry even in an unventilated area. But when wet, it can stretch, and also causes allergic reactions in people with delicate skin.

Caring for nylon is not difficult; you can use a washing machine with cold or warm water; hot water will ruin the fabric. The fabric does not wrinkle, so there is no need to iron it. But if the item was dried in a crumpled state, then you can walk over it with a warm iron. Nylon fiber is often added to cotton and satin to make fabrics lighter, cheaper and more resilient.

Jordan

It can be used in any clothes for adults and in clothes for children. The fabric is very soft, smooth, has a pleasant shimmer, repels liquids and conducts air currents. A variety of outerwear is made from fabric fabric, from off-season windbreakers to winter overalls.

Elastane

Used to add to other materials. It allows fabrics to stretch up to 8 times with a return to their original appearance, and become not susceptible to fading in the sun, damage from greasy and sweaty stains, sea water, and cosmetics.

Velsoft

Another type of polyamide fabric with high strength and hairiness. She is also not prone to fumbling, breathes and is very warm. It has the appearance of a voluminous fleecy material on which pellets do not form. After washing, the shape of the product is not lost, the size does not decrease and the color is not washed out. It can be one color or with a variety of images. The material is very soft, therefore it is in demand for home textiles (blankets, towels, bedspreads) and everyday adult and children's clothing.

Polyamide filter fabric

Very dense and difficult to tear compared to natural fabrics. It does not deteriorate from chemical reagents and stores solid, liquid and gaseous particles, preventing them from getting on the skin.

Taslan

Used for sewing clothes for adults. It weighs more than nylon, but is stronger and has excellent breathability due to its porous structure.

Nylon, tactel

Very famous types of polyamide from which hosiery products are made. Very durable and lightweight.

Anid

Anide is a type of nylon with better heat retention and coloring properties.

Advantages and disadvantages

Polyamide fabrics have the following positive qualities:

• Resistant to fire, moisture and sunlight.
• Doesn't shed.
• Most are well breathable.
• It does not require special care.
• Dries quickly.
• Strength and elasticity.
• The fabrics are light, pleasant to the skin, and do not deform.

But there are also some disadvantages:

• High electrification.
• Does not absorb dirt, but absorbs sweat and greasy stains well.
• Exposure to high temperatures during ironing makes the fabric brittle.
• The ability to cause an allergic reaction.

Previously, for many people the question “Polyamide - what kind of fabric?” - remained unanswered. But with the receipt of new samples of synthetics and the improvement of existing ones, almost everyone now knows why polyamide is used in clothing and what kind of material it is. Its application is quite wide, and it is in demand in production.

Where to buy polyamide: choose a reliable manufacturer and supplier

When a production need arises to purchase a batch of polyamide, the question arises of where to buy raw materials and how not to make a mistake in choosing a supplier. Buying polyamide from UCG means being confident in the quality of the material.

LG Chem: history of quality

We supply polymers from a time-tested company. LG Chem. is a petrochemical concern that has existed for more than 60 years. The company was one of the first to synthesize polymers on an industrial scale and today is one of the leaders on the market.

Among the raw materials produced is polyamide: price

material depends on its brand and the volume of material required. Korean innovation and traditional quality go hand in hand and are increasingly gaining the trust of customers around the world.