The features and applications difference between PA6, PA66, PA610, PA12.

Introduction:
Nylon (Polyamide, PA for short) is a plastic composed of polyamide resins. Such resins can be made from diamines and dibasic acids through condensation, or from lactams formed after dehydration of amino acids through ring-opening polymerization. Unlike PS, PE, PP, etc., PA does not soften gradually with the increase in heat temperature but softens in a narrow temperature range near the melting point, which is obvious, melting point: 215-225°C. Once the temperature is reached, flow occurs.
There are many varieties of PA, mainly PA6, PA66, PA610, PA11, PA12, PA1010, PA612, PA46, PA6T, PA9T, MXD-6 aromatic amide, etc.
The appearance of nylon engineering plastics are presented as horny, tough, shiny surface, white (or cream) or slightly yellow, transparent or translucent crystalline resin, it is easy to be painted in any color. The molecular weight of nylon as an engineering plastic is generally 15-30,000. Their density is slightly greater than 1, density: 1.14-1.15g/cm3. tensile strength: >60.0Mpa. elongation: >30%. Bending strength: 90.0Mpa. notched impact strength: (KJ/m2) > 5. nylon shrinkage of 1% to 2%. The dimensional change of moisture absorption after molding needs to be noted. Water absorption 100% Relative moisture absorption can absorb 8% when saturated. Use temperature can be -40 ~ 105 ℃ between. Melting point: 215-225℃. Suitable wall thickness 2-3.5mm. mechanical properties of PA such as tensile and compressive strength change with temperature and moisture absorption, so water is relatively PA plasticizer, after adding glass fiber, its tensile and compressive strength can be increased by about 2 times, temperature resistance is also increased accordingly, PA's own wear resistance is very high, so it can be operated non-stop without lubrication, if you want to get special lubrication effect, you can add sulfide in PA. If you want to get a special lubrication effect, you can add sulfide to PA.
Advantages:
1. High mechanical strength, good toughness, high tensile and compressive strength. The specific tensile strength is higher than that of metal, and the specific compressive strength is comparable to that of metal, but it is not as rigid as metal. Tensile strength is close to yielding strength, more than twice as high as ABS. The absorption ability of impact and stress vibration is strong, and the impact strength is much higher than the general plastic and better than acetal resin.
2. Outstanding fatigue resistance, the parts can still maintain the original mechanical strength after repeated bending. Common escalator handrails, new bicycle plastic wheel rims, and other occasions where the role of periodic fatigue is very obvious are often used PA.
3. High softening point, heat-resistant (such as nylon 46, high crystalline nylon heat deflection temperature, can be used at 150 degrees for a long time. PA66 after glass fiber is reinforced, its heat deflection temperature reaches 250 degrees or more).
4. Smooth surface, small coefficient of friction, wear-resistant. It is self-lubricating, has low noise, and can be used without lubricant when the friction is not too high; if it is necessary to use a lubricant to reduce friction or help heat dissipation, water oil, grease, etc. can be chosen. Thus, it has a long service life as a transmission part.
5. Corrosion resistance, very resistant to alkali and most salt liquid, also resistant to weak acid, oil, gasoline, aromatic compounds, and general solvents, inert to aromatic compounds, but not resistant to strong acids and oxidizers. It can resist the erosion of gasoline, oil, fat, alcohol, weak alkali, etc., and has a good anti-aging ability. It can be used as a packaging material for lubricants, fuels, etc.
6. Self-extinguishing, non-toxic, odorless, good weather resistance, inert to biological erosion, good antibacterial, anti-mildew ability.
7. Excellent electrical properties. Good electrical insulation, nylon volume resistance is very high, high breakdown voltage, in a dry environment, can be used as frequency insulation materials, even in a high humidity environment still has good electrical insulation.
8. Lightweight, easy to dye, easy to shape. It has low melt viscosity and can flow quickly. Easy to fill the mold, high solidification point after filling the mold, can be quickly shaped, so the molding cycle is short, high production efficiency.
Disadvantages:
1. Easy to absorb water. Water absorption is large, saturated water can reach more than 3%. To a certain extent, affect the dimensional stability and electrical properties, especially the thickening of thin-walled parts have a greater impact; water absorption will also greatly reduce the mechanical strength of plastic. The selection of materials should take into account the use of the environment and other components with the impact of the precision. The fiber reinforcement can reduce the resin water absorption so that it can work at high temperatures and high humidity. Nylon and glass fiber affinity is very good. It is commonly used to make combs, toothbrushes, coat hooks, fan bones, net bag ropes, fruit outer packaging bags, etc. Non-toxic, but not long-term contact with acid and alkali. It is worth noting that after adding glass fiber, the tensile strength of nylon can be increased by about 2 times, and the temperature resistance can be improved accordingly.
2. Light resistance is poor. In the long-term high-temperature environment, it will oxidize with the oxygen in the air, and the color will turn brown at the beginning, then the surface will be broken and cracked.
3. Strict requirements for injection molding technology: the presence of trace moisture will cause great damage to the quality of molding; it is difficult to control the dimensional stability of the product due to thermal expansion; the existence of sharp corners in the product will lead to stress concentration and reduce mechanical strength; wall thickness if uneven will lead to the distortion and deformation of the parts; the high precision of the equipment required for the post-processing of the parts.
4. It will absorb water and alcohol and swell, so it is not resistant to strong acid and oxidizer, and cannot be used as acid-resistant material.
Features and applications:
PA6 is a translucent or not too distant milky white crystalline polymer. Burning into a blue background yellow flame, burning plant smell. Melting temperature is lower than PA66, processing performance is better than other PA. Manufactured parts have a high impact strength rate, load dispersion, good flexibility, thermoplastic, lightweight, good toughness, resistance to cyclohexanone and aromatic solvents and durability good working temperature 80-1000C, low-temperature embrittlement temperature -20 to -300C, melting point: 215 ℃. Thermal decomposition temperature: >300℃. Density: 1.13g/cm3. Equilibrium water absorption: 3.5%. Suitable for use under light load conditions, with good wear resistance, self-lubrication, and solvent resistance. It has good vibration dissipation and noise reduction ability. It can be used as insulation for machines and instruments, instrument parts, wires, and cables; it can be made into gears and pump leaves after being reinforced with glass fiber. But PA6 water absorption is very large, the saturated water absorption rate of up to about 10%, affecting the performance; and because of the large dielectric constant, should not be used as a high-frequency low-loss material.
PA6 chemical-physical properties and PA66 are very similar, however, it has a lower melting point and a wide range of process temperatures. Its impact and dissolution resistance is better than PA66, but it is also more hygroscopic. The elasticity is greater than PA66, fatigue strength steel, heat resistance is lower than nylon 66 because many quality characteristics of plastic parts are subject to the influence of moisture absorption, so use PA6 to design products to take this into full consideration. In order to improve the mechanical properties of PA6, a variety of modifiers are often added. Glass is the most common additive, and sometimes synthetic rubber, such as EPDM and SBR, is added to improve impact resistance. For products without additives, the shrinkage of PA6 ranges from 1% to 1.5%. The addition of glass fiber additives can reduce the shrinkage to 0.3% (but slightly higher in the direction perpendicular to the process). The shrinkage of the molded assembly is mainly influenced by the crystallinity and moisture absorption of the material. The actual shrinkage is also a function of part design, wall thickness, and other process parameters.
PA6 is widely used for structural components due to its good mechanical strength and stiffness. Light loads, medium temperatures (80-100) without lubrication or with little lubrication. It is also used in the manufacture of bearings due to its good wear resistance properties.
PA66 has a high melting point among polyamide materials. It is a semi-crystalline - crystalline material. pa66 retains high strength and stiffness even at higher temperatures. pa66 remains hygroscopic after molding, the extent of which depends primarily on the composition of the material, wall thickness, and environmental conditions. It is important to consider the effect of moisture absorption on geometric stability when designing products. Nylon 66 offers the best balance of properties and is the most robust of all nylons.
Compared to PA6, PA66 is more widely used in the automotive industry, instrument housings, and other products that require impact resistance and high strength. PA66 is the highest mechanical strength and the most widely used variety in the PA series. Its high crystallinity, so rigidity, hardness, heat resistance are high, yield strength than PA6 and PA66, small coefficient of friction, good stress cracking resistance, especially creep resistance is one of the strongest varieties of thermoplastics; water absorption of 7%, working temperature 100-1200C. suitable for use under medium load conditions, can be made to contain chemical bottles, tubes, other uses similar to PA6. PA66 fatigue strength and steel are higher, heat resistance is better, low friction coefficient, good wear resistance, but moisture absorption, dimensional stability is not enough. To improve the mechanical properties of PA66, a variety of modifiers are often added. Glass is the most common additive, and sometimes synthetic rubber, such as EPDM and SBR, is added to improve the impact resistance.
PA66 is less viscous and therefore flows well (but not as well as PA6). This property can be used to process very thin components. Its viscosity is sensitive to temperature changes. the shrinkage of PA66 is between 1% and 2%, and the addition of glass fiber additives can reduce the shrinkage to 0.2% to 1%. The difference of shrinkage in the process direction and perpendicular to the process direction is large. PA66 is resistant to many solvents but is less resistant to acids and other chlorinated agents.
Using PA6 material, can achieve the translucent effect, but the temperature resistance is not ideal, such as the use of PA66, can not achieve the translucent effect, PA66 than PA6 heat-resistant performance is better, PA66 good rigidity, PA6 good toughness, the price of nylon 66 than nylon 6 expensive, feel softer than nylon 6, can do microfiber, do high-end clothing fabrics, now the market quality of down fabrics are used Nylon 66, feel smooth, light and soft, and have an anti-feather effect. But dyeing is more difficult, not easy to color, needs high-temperature dyeing, color fastness is not very good. Nylon 66 and nylon 6 belong to the same polyamide fiber, nylon 66 is made of adipic acid adipamide condensation, and nylon 6 is made of caprolactam condensation. From the molecular structure, these two fibers are very similar, so the physical and chemical properties of the two are also similar. The difference is that the hydride bonding between adjacent molecules of nylon 66 is more solid, so its melting point is as high as 260℃, about 40℃ higher than that of nylon 6, which is superior in heat resistance. The weaving and sewing properties of both are still good, but the higher melting point of nylon 66, better heat resistance, the elastic modulus is also better, more suitable for the manufacture of heat-resistant strain products, such as tire cord and heat-resistant water washing fabrics and woven fabrics. But this is the difference from the subtle aspects, in fact, the difference between the two in clothing textiles is not very big, the main difference in the use of industrial applications, especially in the use of a cord, nylon 66 is more excellent.
PA66 is often used for wear-resistant stressed transmission parts working without lubrication or with little lubrication under medium load, using temperature <100-120 degrees.
PA610 is easy to mold, performance between PA6 and PA66, higher hardness, wear resistance is slightly worse than PA6.PA610 strength, rigidity, and heat resistance are lower than nylon 66, but moisture absorption is small, has good wear resistance, it's earth yellow.
The application of PA610 is similar to PA6, PA610 is more suitable for use as a gear requiring more precision, parts with large changes in humidity in working conditions.
PA12 is a linear, semi-crystalline - crystalline thermoplastic material from butadiene. It has similar properties to PA11 but has a different crystal structure. PA12 is a good electrical insulator and, like other polyamides, does not suffer from moisture-related insulating properties. PA12 has a number of improved plasticizing and reinforcing properties. Compared to PA6 and PA66, these materials have lower melting points and densities, and have very high moisture recovery rates; PA12 is not resistant to strong oxidizing acids. It flows very well. Shrinkage ranges from 0.5% to 2%, depending mainly on material species, wall thickness, and other process conditions.
PA12 is commonly used in water meters and other commercial equipment, cable sleeves, mechanical cams, sliding mechanisms, and bearings, etc.