PA is nylon. Baidu Encyclopedia has its purpose
1. Automobile manufacturing:
it is used to manufacture fuel filter screen, fuel filter, tank, trap, oil storage tank, engine cylinder cover, radiator water cylinder and balance rotating shaft gear. It can also be used in automobile electrical accessories, terminal posts, etc. In addition, it can also be used as driving and control components
2. Electrical and electronic industry:
it can be used to manufacture electric rice cookers, electric vacuum cleaners, high-frequency electronic food heaters, terminals, switches and resistors of electrical products
3. Medical instruments and precision instruments:
used for medical blood transfusion tubes, blood collection devices, infusion sets, etc. PA monofilament can be used as surgical suture and wig; In addition, the digital rotary disc, terminal, transmission gear of electronic typewriter, belt filter of printing machine, etc
4. Other aspects:
it is used to make disposable lighter body, alkaline dry battery pad, motorcycle driver’s helmet, office machine shell, corner wheel, seat and backrest of office chair, skates, fishing line, etc. PA film has excellent gas barrier performance, oil resistance, low-temperature impact resistance and penetration resistance. It can be used for the packaging of frozen food such as meat, ham sausage and so on. Polyamide can also be used as bars and plates, gears or other transmission devices.
nylon (nylon, polyamide, PA for short) refers to the plastic composed of polyamide resin. This kind of resin can be prepared by polycondensation of binary amine and binary acid, or by ring opening polymerization of lactam formed after dehydration of amino acid. Unlike PS, PE and PP, PA does not soften gradually with the increase of heating temperature, but softens in a narrow temperature range close to the melting point. The melting point is obvious, and the melting point is 215-225 ℃. Once the temperature is reached, flow occurs.
there are many varieties of PA, mainly including PA6, PA66, PA610, PA11, PA12, PA1010, pa612, PA46, PA6T, PA9T, mxd-6 aromatic amides, etc. PA6, PA66, PA610, PA11 and PA12 are the most commonly used.
nylon engineering plastics appear as horny, tough, bright surface, white (or milky white) or yellowish, transparent or translucent crystalline resin, which is easy to be painted into any color. The molecular weight of nylon as an engineering plastic is generally 15000-30000. Their density is slightly greater than 1, and the density is 1.14-1.15g/cm3. Tensile strength: ＞ 60.0mpa. Elongation: ＞ 30%. Bending strength: 90.0mpa. Notch impact strength: (kJ /m2) ＞ 5. The shrinkage of nylon is 1% ~ 2%. Pay attention to the dimensional change of moisture absorption after molding. The water absorption rate is 100%, and it can absorb 8% when it is saturated The service temperature can be – 40 ~ 105 ℃. Melting point: 215-225 ℃. The appropriate wall thickness is 2-3.5mm. The mechanical properties of PA, such as tensile and compressive strength, change with temperature and moisture absorption, so water is relatively the plasticizer of PA. after adding glass fiber, its tensile and compressive strength can be increased by about 2 times, and the temperature resistance can be improved accordingly. The wear resistance of PA itself is very high, so it can be operated continuously without lubrication. If you want to get special lubrication effect, sulfide can be added to pa.
the main advantages of PA performance are:
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 equal to that of metal, but its rigidity is lower than that of metal. The tensile strength is close to the yield strength, which is more than twice that of ABS. It has strong absorption capacity for impact, stress and vibration, and its impact strength is much higher than that of ordinary plastics, and better than acetal resin.
2. The fatigue resistance is outstanding, and the parts can still maintain the original mechanical strength after repeated bending for many times. PA is often used in places with obvious periodic fatigue effect, such as common escalator handrails and new bicycle plastic rims
3. High softening point and heat resistance (such as nylon 46, high crystalline nylon has high thermal deformation temperature and can be used for a long time at 150 ℃. After PA66 is reinforced by glass fiber, its thermal deformation temperature reaches more than 250 ℃).
4. Smooth surface, small friction coefficient and wear resistance. As a movable mechanical component, it has self lubrication and low noise. It can be used without lubricant when the friction effect is not too high; If lubricants are really needed to reduce friction or help heat dissipation, water, oil, grease, etc. can be selected. Thus, as a transmission component, its service life is long
5. Corrosion resistant, very resistant to alkali and most salt liquids, also resistant to weak acids, engine oil, gasoline, aromatic hydrocarbons and general solvents, inert to aromatic compounds, but not resistant to strong acids and oxidants. It can resist the corrosion of gasoline, oil, fat, alcohol, weak alkali and so on, and has good anti-aging ability. It can be used as packaging material for lubricating oil, fuel, etc.
6. It is self extinguishing, non-toxic, odorless, good weather resistance, inert to biological erosion, and has good antibacterial and mildew resistance.
7. Excellent electrical performance. Nylon has good electrical insulation, high volume resistance and high breakdown voltage. It can be used as power frequency insulation material in dry environment, and has good electrical insulation even in high humidity environment
8. The parts are light in weight, easy to dye and easy to form. Due to its low melting viscosity, it can flow quickly. It is easy to fill the mold. After filling, the freezing point is high and can be shaped quickly. Therefore, the molding cycle is short and the production efficiency is high.
main disadvantages of PA performance;
1. Easy to absorb water. High water absorption, saturated water can reach more than 3% To some extent, it affects the dimensional stability and electrical properties, especially the thickening of thin-walled parts; Water absorption will also greatly reduce the mechanical strength of plastics. When selecting materials, the influence of the use environment and the matching accuracy with other components should be taken into account. Fiber reinforcement can reduce the water absorption of the resin and make it work under high temperature and high humidity. Nylon has good affinity with glass fiber. It is often used to make comb, toothbrush, clothes hook, fan bone, net bag rope, fruit outer packing bag and so on. Non toxic, but not long-term contact with acid and alkali. It should be noted 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. Poor light resistance. In the long-term high-temperature environment, it will oxidize with oxygen in the air, turn brown at the beginning, and then break and crack.
3. Strict requirements for injection molding technology: the existence of trace moisture will cause great damage to the molding quality; The dimensional stability of products is difficult to control due to thermal expansion; The existence of sharp corners in products will lead to stress concentration and reduce the mechanical strength; If the wall thickness is not uniform, it will lead to distortion and deformation of the workpiece; The equipment requires high precision during post-processing.
4. It will absorb water and alcohol and swell. It is not resistant to strong acid and oxidant. It can not be used as acid resistant material.
usage nylon is mainly used in automobile industry, electrical and electronic industry, transportation industry, machinery manufacturing industry, wire and cable communication industry, film and daily necessities Manufacturing all kinds of bearings, gears, round gears, cams, bevel gears, oil pipes, oil reservoirs, protective covers, support frames, wheel covers, deflectors, fans, air filter housings, radiators, water chambers, brake pipes, hood, door handles Bearing, gear, pulley pump impeller, blade, high-pressure sealing ring, gasket, valve seat, bushing, oil delivery pipe, oil reservoir, rope, transmission belt, grinding wheel adhesive, battery box, electrical coil, cable joint, various rollers, pulley, pump impeller, fan blade, worm gear, thruster, screw, nut, oil resistant sealing gasket, oil resistant container, shell, hose, cable sheath Shearing machine, pulley sleeve, shaper slider, electromagnetic distribution valve seat, cold aging equipment, gasket, bearing cage, various oil pipelines, pistons, ropes, transmission belts on automobiles and tractors, zero fog materials for textile machinery industrial equipment, daily necessities and packaging films, etc. Wait. In addition, the output of packaging tape and food film (high-temperature film for cooked food and low-temperature film for cool drinks) is also quite large.
molding and post-treatment
except transparent nylon, other nylon are crystalline plastics with high melting point, narrow melting temperature range and poor thermal stability. PA is easy to absorb moisture. During the molding process, the viscosity of wet nylon decreases sharply and is mixed with bubbles. There is silver wire on the surface of the product, and the mechanical strength of the product decreases. Therefore, the material must be dried before processing. It can be dried at 80-110 ℃ for 6 hours. During molding, the allowable water content of nylon 6 and nylon 66 is 0.1%, nylon 11 is 0.15%, nylon 610 is 0.1-0.15%, and the maximum shall not exceed 0.2%. Note that PA plastic is easy to cause discoloration when it is dried above 90 ℃. PA has good fluidity and is easy to overflow. Self locking nozzle should be used and heated. At the same time, due to the fast condensation speed of the solution, the shortage of products caused by material blocking the nozzle, runner and gate should be prevented. The die overflow value is 0.03, and the melt viscosity is sensitive to the changes of temperature and shear force, but it is more sensitive to temperature. To reduce the melt viscosity, start with the barrel temperature. The forming shrinkage range and shrinkage rate are large, the directionality is obvious, and shrinkage cavity and deformation are easy to occur. PA recycled materials should be used no more than three times to avoid discoloration of products or sharp decline of mechanical and physical properties. The application amount should be controlled below 25%. Too much will cause fluctuation of process conditions. The mixture of recycled materials and new materials must be dried. When starting the machine, first turn on the temperature of the nozzle, and then heat the feeding cylinder. When the nozzle is blocked, do not face the nozzle hole, so as to prevent the sudden release of the solution in the feeding cylinder due to pressure accumulation and danger. Empty the screw during shutdown to prevent breaking the screw during the next production. The use of a small amount of release agent can sometimes improve and eliminate defects such as bubbles. The release agent of nylon products can be zinc stearate and white oil, or mixed into paste. When using, it must be small and uniform to avoid surface defects of products. The post-treatment of nylon products is to prevent and eliminate the residual stress in the products or the dimensional change caused by moisture absorption. There are two post-treatment methods: heat treatment and wet adjustment. a). Common methods of heat treatment: in high boiling liquids such as mineral oil, glycerol and liquid paraffin, the heat treatment temperature should be 10-20 ℃ higher than the service temperature. The treatment time varies depending on the product wall thickness. The thickness below 3mm is 10-15 minutes, the thickness is 3-6mm, and the time is 15-30 minutes. The products after heat treatment should be cooled slowly to room temperature to prevent the stress in the products from regenerating due to sudden cooling. b). Humidity regulation treatment humidity regulation treatment is mainly carried out for products with high environmental humidity. There are two methods: one is boiling water humidity regulation, and the other is potassium diacetate aqueous solution humidity regulation (the ratio of potassium acetate to water is 1.25:1, and the boiling point is 121 ℃). Boiling water humidity regulation is simple. As long as the products are placed in the environment with humidity of 65%, they can reach the equilibrium moisture absorption, but it takes a long time, The treatment temperature of potassium acetate aqueous solution is 80-100 ℃, and the treatment time mainly depends on the product wall thickness. When the wall thickness is 1.5mm, it is about 2 hours, 3mm is 8 hours and 6mm is 16-18 hours