A comprehensive understanding of the process, performance, modification and application of PA6
Concerns concerning nylon have persisted over time; now, we'll discuss polyamide-6.
01 Description of polyamide-6
Usually referred to as nylon (Nylon), polyamide (also known as polyamide, PA) is a heterochain polymer with amide groups (-NHCO-) in the main chain. It comes in two categories: aliphatic and aromatic. largest engineering thermoplastic substance.
Polyamide's primary chain is made up of several amide groups that are repeated. When it is used as a plastic, it is referred to as nylon, and when it is used as a synthetic fiber, it is also referred to as nylon. Diamines, dibasic acids, and amino acids may all have variable numbers of carbon atoms, which can be used to create a range of different polyamides. There are several polyamide kinds available right now, including polyamide-6, polyamide-66, and polyamide-610 is the most widely used.
An aliphatic polyamide with good qualities, polyamide-6 has a low density, high strength, wear resistance, poor acid and basic resistance, modest organic solvent resistance, and is simple to form and process. It finds widespread application in the production of films, technical plastics, and textiles. A potent polar amide group, which is readily capable of forming hydrogen bonds with water molecules, is present in the molecular chain portion of PA6. High water absorption, poor dimensional stability, low impact strength in dry state and low temperature, and weak resistance to strong acid and strong alkali are all drawbacks of the product.
02 Process of Synthesis
1. Monomer synthesis
1) The phenol process, which involves hydrogenating phenol to produce cyclohexanol, dehydrating cyclohexanone, oximating cyclohexanone oxime, and then converting cyclohexanone oxime to caprolactam in an equal quantity of oleum. The following is the reaction formula:
2) Air oxidation of cyclohexane produces cyclohexanol and cyclohexanone. After separation, cyclohexanol is dehydrogenated to produce cyclohexanone, and cyclohexanone is then oximated to produce cyclohexanone oxime. Caprolactam is produced by transposition in an equivalent quantity of oleum. The following is the reaction formula:
3) Cyclohexane is nitrosylated using nitrosyl chloride in the presence of light to produce cyclohexanone oxime hydrochloride, which is subsequently converted in sulfuric acid to produce caprolactam. The following is the reaction formula:
4) The toluene method: Caprolactam is produced by reacting nitrosyl sulfuric acid with benzoic acid in the presence of oleum after benzoic acid has been oxidized by toluene and hydrogenated to produce cyclohexanecarboxylic acid. The following is the reaction formula:
High temperature hydrolysis of the caprolactam monomer yields aminocaproic acid, which is subsequently polymerized to produce polyamide-6.
1) The ring-opening process converts caprolactam into amino acids.
2) Self-condensation of amino acids
3) The caprolactam is electrophilically attacked by the nitrogen on the amino group to break the ring, and the growth
3. spinning technique
Currently, domestic nylon 6 mostly uses the melt spinning method, and the resulting chips are removed, melt spun, stretched into the desired final fibers as-spun, and then post-processed.
03 Nylon 6's product performance and modification
High tensile and compressive strength, excellent toughness, and high mechanical strength. It is superior to acetal resin because it has a lot stronger impact resistance than regular plastics and a significant capacity to absorb impact and stress vibration.
Outstanding fatigue resistance allows the workpiece to continue to retain its initial mechanical strength even after repeated bending.
Heat resistance and a high softening point.
The surface is smooth, has a low coefficient of friction, and is resistant to wear. It is quiet when utilized as a moving mechanical component and self-lubricating. When the amount of friction is not too great, it can be used without lubrication.
Corrosion-resistant, extremely resistant to alkalis and the majority of salt solutions, as well as to mild acids, motor oils, gasoline, aromatic compounds, and general solvents. However, it is not resistant to strong acids or oxidants. It has strong anti-aging properties and can withstand the erosive effects of alcohol, gasoline, oil, fat, mild alkali, etc.
Self-extinguishing, non-toxic, odorless, weather-resistant, immune to biological deterioration, and highly resistant to germs and mildew.
It may be utilized as a power frequency insulating material in dry environments and has outstanding electrical insulation even in environments with high humidity. It also has great electrical performance, good electrical insulation, high volume resistance of nylon, and high breakdown voltage.
Due to the low melt viscosity, the components flow swiftly, are lightweight, and are simple to shape and colour. The molding cycle is fast and the production efficiency is good because the material is simple to fill the mold with, has a high freezing point after filling the mold, and can be swiftly formed.
Negative aspects of nylon 6:
High water absorption rate, more than 3% of saturated water may be absorbed easily. It somewhat affects electrical characteristics and dimensional stability; however, the thickening of thin-walled sections has a higher effect. Water absorption also significantly reduces the mechanical strength of plastics.
Poor light resistance causes it to oxidize with airborne oxygen in a prolonged high-temperature environment. The hue initially changes to brown, and the surface is fractured and shattered.
The requirements for injection molding technology are stringent, and the presence of trace moisture will significantly harm the molding quality. In addition, thermal expansion makes it difficult to control a product's dimensional stability, sharp corners will cause stress concentration and reduce mechanical strength, and uneven wall thickness will result in workpiece distortion and deformation. High equipment precision is also required.
It cannot be utilized as an acid-resistant material since it will absorb water and alcohol and expand. It is also not resistant to strong acids or oxidants.
Excellent qualities of PA6 include its light weight, high strength, resistance to wear, poor resistance to acids and bases, certain organic solvents, and ease of processing and molding. Although it is commonly employed in the production of fibers, engineered plastics, and films, PA6's molecular structure includes polarity. The product's drawbacks include rapid water absorption, poor dimensional stability, low impact strength in dry state and low temperature, poor resistance to strong acid and strong alkali, and more.
The shortcomings of conventional PA6 materials in some areas have restricted its growth in various domains, which has been hampered by the advancement of science and technology and the enhancement of living quality. PA6 should be altered in order to enhance performance and broaden its application area.
1. Blending adjustment
PP, PE, ABS, PET, PC, POM, PPO and other plastics or thermoplastic polyurethane elastomers, EPDM rubber and other elastomers, as well as other materials, are blended with nylon 6 to modify it through the process of mixing. a typical technique for modifying. The benefits of nylon 6 and other materials may be complimented by blending modification, which can significantly enhance the mechanical capabilities and dimensional stability of nylon 6 and lower water absorption.
2. Modification of filling reinforcement
Adding glass fiber, carbon fiber, whisker, wollastonite, calcium carbonate, talc, rare earth, mica, and silica to the matrix is a typical technique for physically altering PA6. The mechanical characteristics, flame retardancy, thermal conductivity, and dimensional stability of PA6 may all be greatly enhanced by adding different fillers.
3. Modification of copolymerization
As part of the modification of PA6 by copolymerization, amide and amide monomers as well as amide and non-amide monomers are copolymerized. The molecular chain may be altered by copolymerization modification, and additional functional groups or polymers can be grafted or blocked into the PA6 molecular chain to enhance all areas of its performance and create new PA6 copolymer products that adhere to strict specifications.
4. Modification of nanocomposite materials
Currently, carbon fibers, carbon nanotubes, graphene, montmorillonite, and inorganic nanoparticles are the principal nanomaterials employed to alter PA6. Utilizing melt blending and in-situ polymerization, nanomaterials and PA6 are combined and modified to improve the performance of PA6 in all areas. This is done by utilizing the special benefits of nanomaterials, such as their large specific surface area, good mechanical properties, electrical conductivity, and thermal conductivity.
04 application of a product
1. Sectioning at the fiber level
It may also be used to spin industrial yarn to create items like tire rope, sail line, parachute, insulation material, fishing net wire, safety belts, and civil silk for clothing like undergarments, socks, and shirts.
2. Slices of engineering plastic
Precision machines can be used to manufacture gears, shells, hoses, oil-resistant containers, cable sheaths, textile industry equipment components, etc.
3. sectioned a film after pulling it.
It may be utilized in the packaging sector for things like food and medical packaging.
4. Composite nylon material
For example, reinforced high-temperature-resistant nylon may be used to build impact drills, lawn mowers, and other appliances with unique demands. Other types of impact-resistant nylon include reinforced high-temperature-resistant nylon.
5. Automobile-related goods
There are currently numerous PA6 automotive products available, including radiator boxes, heater boxes, radiator blades, steering column covers, tail light covers, timing gear covers, fan blades, various gears, radiator water chambers, air filter shells, gas manifolds, control switches, intake ducts, vacuum connecting pipes, airbag housings, wipers, pump impellers, bearings, bushings, valve seats, door handles, and wheel covers, to name a few.