What is polyamide

Polyamide belongs to plastic polymers, which are distinguished by increased strength and rigidity. The substance is used for the manufacture of fibers, films and structural plastics.

Polyamide: properties and characteristics

To understand what polyamide is, it is worth learning about the properties of the material. Among the advantages is the ability to maintain elasticity at low temperatures. The operating temperature range is from -50°C to +100°C. The density of polyamide is 1.1-1.2 g/cm3. Other characteristics:

• Increased resistance to shock and deforming mechanical loads.
• Easy processing – amenable to shape and surface transformation by milling, drilling, polishing, grinding, turning.
• Ability to manufacture products of any shape by high-frequency welding.
• Easy painting and surface decoration – the possibility of printing.
• Resistance to alcohols, weak alkalis and acids, oils and other chemicals.
• Increased tensile strength – over 43 MPa.
• Durability – the service life of plastic products exceeds 50 years.

Other advantages include corrosion resistance, resistance to biological damage by fungi and mold. Nylon polyamide fibers are characterized by increased elasticity. A nylon thread with a diameter of 0.1 mm can withstand a weight of 550 grams.

The melting point of polyamide is 180-260°C. The melting point increases with an increase in the number of amide groups in the molecule. Increased water absorption, compared to other plastics, leads to instability of shape and size, which worsens the consumer properties of polyamide. To solve the problem, reinforcing components are added to the composition, mainly based on glass. As a result, the strength of the material and impact strength increase.

Polyamide: production technology

The material is made from methylene and dicarboxylic acids with the addition of amides (diamines). Other components of the composition are lactams and amino acids. Obtaining polyamide involves combining raw material components taken in different proportions. Polyamide-6, which is known as caprolon, is made by melting caprolactam in the presence of water and acids that contribute to the creation of new molecular bonds. Catalysts, mainly aminocaproic acid, are added to accelerate the reaction.

Polyamide production is characterized by low cost, which makes it possible to reduce the cost of production. Plastics are cheaper than many other structural materials, in particular metal and ceramic composites. During the production of plastic, various technologies are used – polymerization in autoclaves under high pressure or in the open air in special reactors. The finished material in the form of granules is used for further processing and manufacturing of products.

Polyamides: types

Depending on the production technology and the addition of additional components, different types of polyamide are obtained. The marking next to the name of the material indicates a number that reflects the number of carbon atoms in the molecular structure. The properties of plastics with different molecular structures differ slightly. Amorphous polyamides have lower vapor permeability and water absorption than crystalline ones.

Polyamide: scope

Construction plastic acts as a cheap substitute for metal. Polyamide material is 6-7 times lighter than metal. Reducing the mass of components leads to a reduction in the weight of the finished product, which simplifies transportation and logistics (loading, unloading, warehousing).

Polyamide plastic is intended for the manufacture of elements of household appliances, cars and bicycles, furniture. The material is used to make bearings, housings of household and medical equipment, terminal blocks, door handles, furniture rollers. The material is suitable for the manufacture of medical products, withstands disinfection treatment with hot steam at a temperature of 140°C.

The reduced coefficient of friction during contact with any metals determines its wide application in the mechanical engineering, machine tool industry and in the production of household appliances. The use of plastic parts in a friction pair with metals slows down wear and extends the service life of the latter by 2 times. An additional plus is reduced noise during the operation of a mechanical metal unit. What is made of polyamide:

• sliding bearings;
• friction pair liners;
• sliders, bushings and couplings;
• pulleys of lifting mechanisms;
• fan blades;
• worm wheels and gears.

Wheel hubs, brackets and other products requiring increased resistance to impact loads are made of polyamide. Plastic guides for friction units can withstand loads of up to 20 MPa in the presence of lubrication or on a dry surface. Many polyamide plastics are food grade and do not emit harmful substances when in contact with food, water and drinks.

Polyamide and polyethylene: comparison

Both materials belong to the group of thermoplastic polymers. They are distinguished by improved strength, elasticity and durability. However, different raw materials and differences in production technology determine different properties.

Polyamides actively absorb moisture (water absorption rate is 0.7-11% depending on the type), which leads to a change in consumer properties. Polyamide plastics are not suitable for the manufacture of containers that are intended for storing water supplies. Unlike polyamide, polyethylene has a low water absorption rate of 0.01%. The material is used to make water tanks – drinking and technical, which are used to store supplies, arrange irrigation and water supply systems.

The advantage of polyamide is its wider range of application. With the help of plasticizing additives, it is possible to change the properties of the finished material, which allows manufacturing products taking into account needs. Polyamides are used in the production of parts for the automotive and aviation industries, for the manufacture of clothing fabrics, artificial leather, carpets and other floor coverings.

Polyethylene is mainly intended for the manufacture of packaging, pipes, medical prostheses and instruments. Industrial tanks are made of polyethylene, which are suitable for the transportation and storage of chemicals, agricultural products, drinking and technical water, fuels and lubricants. Among the advantages of polyethylene is its low price compared to polyamide. As a result, even large-sized products, for example, tanks for transporting liquid and bulk substances with a capacity of more than 10 thousand liters, are an economically advantageous purchase.

Both materials are used in the production of pipes and other building materials. When choosing products, you should consider the needs and purposes of use. Thus, polyethylene pipes are not suitable for installation of hot water supply systems. The recommended operating temperature is no more than 60-90°C. For polyamide pipes, the maximum value is 105°C, for some types it reaches 160°C.