The main varieties of nylon are nylon 6 and nylon 66, which are absolutely dominant, followed by nylon 1 1, nylon 12, nylon 6 10, nylon 6 12, and nylon10/kloc-. There are many kinds of modified nylon, such as reinforced nylon, monomer cast nylon (MC nylon), reactive injection molding (RIM) nylon, aromatic nylon, transparent nylon, high impact (super toughness) nylon, electroplated nylon, conductive nylon, flame retardant nylon, blends and alloys of nylon and other polymers, etc. , to meet different special requirements, widely used.
Nylon is the most important engineering plastic, and its output ranks first among the five general engineering plastics.
Nylon, especially polyamide fiber (nylon) is a saying.
Nylon was developed by the outstanding American scientist carothers and his research team. It is the first synthetic fiber in the world. The appearance of nylon has brought a new look to textiles. Its synthesis is a major breakthrough in synthetic fiber industry and an important milestone in polymer chemistry.
From 65438 to 0928, DuPont, the largest chemical industry company in the United States, established the Institute of Basic Chemistry, and Dr. carothers, who was only 32 years old, was hired as the director of the Institute. He is mainly engaged in the research of polymerization. He first studied the polycondensation of bifunctional molecules, and synthesized long-chain polyester with high molecular weight through esterification and condensation of dihydric alcohol and dicarboxylic acid. In less than two years, carothers has made great progress in preparing linear polymers, especially polyesters, and increased the relative molecular weight of polymers to 65,438+00,000 ~ 25,000. He called polymers with relative molecular weight higher than 65,438+00,000 polymers. In 1930, carothers' assistant found that the melt of high polyester prepared by polycondensation of diol and dicarboxylic acid can be drawn out like cotton candy, and this fibrous filament can continue to be drawn even after cooling, and the drawn length can reach several times. After cooling and stretching, the strength, elasticity, transparency and gloss of the fiber are greatly increased. The peculiar properties of this polyester make them think that it may have great commercial value, and it is possible to spin fibers from molten polymers. However, continuous research shows that obtaining fiber from polyester is only of theoretical significance. Because high polyester melts below 100℃, it is particularly soluble in various organic solvents, but slightly stable in water, so it is not suitable for textile.
Subsequently, carothers conducted in-depth research on a series of polyester and polyamide compounds. After many comparisons, he chose1polyamide 66, which was first synthesized from hexamethylenediamine and adipic acid on February 28th, 935 (the first 6 represents the number of carbon atoms in diamine and the last 6 represents the number of carbon atoms in diacid). This polyamide is insoluble in common solvents, and its melting point is 263℃, which is higher than the common ironing temperature. The stretched fiber has the appearance and luster of silk, which is close to natural silk in structure and performance, and its wear resistance and strength exceed that of any fiber at that time. Considering its performance and manufacturing cost, it is the best choice among known polyamides. Then, DuPont solved the industrial source of raw materials for producing polyamide 66. 1938, 10 year1October 27th, officially announced the birth of the world's first synthetic fiber, and named polyamide 66 nylon. Nylon later became "the general name of all polyamides synthesized from coal, air, water or other substances, which has wear resistance and flexibility, and its chemical structure is similar to that of protein".
Polyamide (nylon)
Polydecylamine sebacate (nylon 10 10)
Polyundecylamide (nylon 1 1)
Polydecanamide (nylon 12)
Polycaprolactam (nylon 6)
Polydecanoyl ethylenediamine (nylon 6 10)
Polydodecyl ethylenediamine (nylon 6 12)
Polyhexamethylene adipate (nylon 66)
Polyoctanamide (nylon 8)
Poly (9- amino nonanoic acid) (nylon 9)
Nylon 6 and nylon 66
* Structure: nylon 6 is polycaprolactam and nylon 66 is hexamethylene adipate. Nylon 66 is harder 12% than nylon 6. Theoretically, the higher the hardness, the more brittle the fiber is and the easier it is to break. But in the use of carpets, this subtle difference is difficult to distinguish.
* Cleanliness and antifouling: It is the cross-sectional shape of the fiber and the antifouling treatment on the back that affect these two properties. However, the strength and hardness of the fiber itself have little effect on cleaning and antifouling.
* Melting point and elasticity: the melting point of nylon 6 is 220℃, and that of nylon 66 is 260℃. However, this is not the difference of carpet temperature conditions. The lower melting point makes nylon 6 have better resilience, fatigue resistance and thermal stability than nylon 66.
* Color fastness: Color fastness is not the characteristic of nylon, but the dye in nylon, not nylon itself, which fades under light.
* Abrasion resistance and dust resistance: Clemson University in the United States conducted an experiment with BASF Zeftron500 nylon 6 carpet and DuPont Antron XL nylon 66 carpet at Tampa International Airport for two and a half years. The carpet is in a state of extremely high human flow. The results show that BASF Zeftron500 nylon is slightly better than DuPont Antron XL in color retention and pile wear resistance. There is no difference in dust-proof performance between the two yarns.
Modification of nylon
Because nylon has many characteristics, it is widely used in automobiles, electrical equipment, mechanical parts, transportation equipment, textiles, paper-making machinery and so on.
With the development of miniaturization of automobiles, high performance of electronic and electrical equipment and lightweight of mechanical equipment, the demand for nylon will be increasing. In particular, as a structural material, nylon requires high strength, heat resistance and cold resistance. The inherent shortcomings of nylon are also an important factor limiting its application. Especially PA6 and PA66, compared with PA46, PAl2 and other varieties, have strong price advantages, although some properties can not meet the requirements of the development of related industries. Therefore, it is necessary to improve some properties of a certain application field through modification to expand its application field. It is mainly modified in the following aspects.
① Improve the water absorption of nylon and the dimensional stability of the product.
② Improve the flame retardancy of nylon and meet the requirements of electronics, electric power, communication and other industries.
③ Improve the mechanical strength of nylon, reach the strength of metal material and replace metal.
④ Improve the low temperature resistance of nylon and enhance its ability to resist environmental strain.
⑤ Improve the abrasion resistance of nylon, so as to adapt to occasions with high abrasion resistance requirements.
⑥ Improve the antistatic performance of nylon to meet the requirements of mine and its mechanical application.
⑦ Improve the heat resistance of nylon to adapt to the field of high temperature conditions such as automobile engines.
⑧ Reduce the cost of nylon and improve the competitiveness of products.
In a word, through the above improvements, the high performance and functionalization of nylon composite materials have been realized, and then the products of related industries have been promoted to develop in the direction of high performance and high quality.
The latest development of modified polyamide products
As mentioned above, glass fiber reinforced PA was studied in 1950s, but it was industrialized in 1970s. Since 1976, DuPont Company of the United States developed super-tough PA66, large companies in various countries have developed new modified PA products in succession. The United States, Western Europe, Japan, the Netherlands, Italy and other countries have vigorously developed reinforced PA, flame-retardant PA and filled PA, and a large number of modified PA have been put on the market.
In 1980s, the successful development of compatilizer technology promoted the development of PA alloys, and thousands of alloys such as PA/PE, PA/PP, PA/ABS, PA/PC, PA/PBT, PA/PET, PA/PPO, PA/PPS, PA/I, CP (liquid crystal polymer) and PA/PA were successively developed all over the world.
In 1990s, new varieties of modified nylon were increasing. During this period, the modified nylon was commercialized, forming a new industry and developing rapidly. At the end of 1990s, the world output of nylon alloy reached 65,438+65,438+10,000 tons/year.
In product development, high-performance nylon PPO/PA6, PPS/PA66, toughened nylon, nano nylon and halogen-free flame retardant nylon are the main directions; In application, the development of automobile parts and electrical components has made great progress. For example, high fluidity modified nylon for automobile intake manifold has been commercialized. Plasticization of this complex structure is of great significance not only in application, but also in prolonging the life of parts and promoting the development of engineering plastics processing technology.
Development trend of modified nylon
As the largest and most important variety of engineering plastics, nylon has strong vitality, mainly because it has achieved high performance after modification. Secondly, the demand for high-performance products in automobile, electrical appliances, communications, electronics, machinery and other industries is growing. The rapid development of related industries has promoted the process of high performance of engineering plastics. The future development trend of modified nylon is as follows.
① The market demand for high-strength and high-rigidity nylon is increasing, and new reinforcing materials such as inorganic whisker reinforcement and carbon fiber reinforced PA will become important varieties, mainly used in automobile engine parts, mechanical parts and aviation equipment parts.
② Nylon alloying will become the mainstream of the development of modified engineering plastics. Nylon alloying is an important way to realize high performance of nylon, and it is also the main means to manufacture nylon special material and improve nylon performance. By mixing other polymers, the water absorption of nylon is improved, and the dimensional stability, low temperature brittleness, heat resistance and wear resistance of the product are improved. Therefore, it is suitable for different requirements of vehicle models.
③ The manufacturing technology and application of nano nylon will develop rapidly. The advantages of nano nylon are that its thermal properties, mechanical properties, flame retardancy and barrier properties are higher than those of pure nylon, and its manufacturing cost is equivalent to that of back-penetrated nylon. Therefore, it has great competitiveness.
④ The flame-retardant nylon used in electronics, electrical appliances and electrical appliances is increasing day by day, and the green flame-retardant nylon is paid more and more attention by the market.
⑤ Antistatic, conductive nylon and magnetic nylon will become the first choice materials for electronic equipment, mining machinery and textile machinery.
⑥ The research and application of processing AIDS will promote the functionalization and high performance of modified nylon.
⑦ The application of comprehensive technology and the refinement of products are the driving forces to promote its industrial development.
Polyamide fiber is a kind of pseudofiber with C9-NH group on the macromolecular chain. Commonly used aliphatic polyester polyamide 6 and polyamide 66 are the main varieties, and their trade names in China are nylon 6 and nylon 66. . ? Nylon fibers are mainly filaments, and a small amount of short fibers are mainly used for blending with cotton, wool or other chemical fibers. Nylon filaments are widely used in deformation processing to make elastic yarns as raw materials for weaving or knitting. Polyamide fibers are generally spun by melt method. The strength of nylon 6 and nylon 66 fibers is 4 ~ 5.3 cn/dtex, the high-strength polyester can reach above 7.9 cn/dtex, the elongation is 18% ~ 45%, and the elastic recovery rate at 10% elongation is above 90%. According to the measurement, the abrasion resistance of nylon fiber is 20 times that of cotton fiber, 20 times that of wool and 50 times that of viscose. Fatigue resistance ranks first among all kinds of fibers. It is widely used to process blended products such as socks and improve the wear fastness of fabrics. However, the low modulus and wrinkle resistance of nylon fiber are not as good as polyester fiber, which limits the application of nylon in the clothing field. The service life of nylon rope is three times that of viscose, and the impact absorption energy is large, so the tire can run on bad roads. However, due to the large elongation of nylon rope, when the car is parked, the tire deformation produces a flat point, and the car jumps badly at the beginning. So it can only be used for truck tires, not for passenger car tire cords.
The surface of nylon fiber is flat, the friction coefficient of fiber without oiling agent is very high, and nylon oil agent is easy to fail after being stored for a long time, so it is necessary to add oil agent again during textile processing.
The hygroscopicity of nylon fiber is higher than that of polyester fiber, and the moisture regain of nylon 6 and nylon 66 is 4.5% under standard conditions, which is second only to vinylon in synthetic fibers. Good dyeing performance, can be dyed with acid dyes, disperse dyes and other dyes.
Edit this history of nylon:
People are no strangers to nylon. Nylon products abound in daily life, but few people know its history. Nylon is the first synthetic fiber in the world.
At the beginning of the twentieth century, it was considered inconceivable for enterprises to engage in basic scientific research. 1926 DuPont, the largest industrial company in the United States, is interested in basic science and suggests that it carry out basic research to discover new scientific facts. 1927, the company decided to pay $250,000 a year as research expenses and began to hire chemical researchers. By 1928, DuPont established the Institute of Basic Chemistry, and Dr. Wallace H. carothers (1896 ~ 1937), who was only 32 years old, was hired as the head of the Department of Organic Chemistry of the Institute.
American organic chemist Carothers. 1896 was born in Wilmington, Iowa, USA on April 27th. 1937 died in Philadelphia, USA on April 29th. 1924 After receiving his doctorate from the University of Illinois, he taught and studied organic chemistry in this university and Harvard University successively. 1928 was employed to do organic chemistry research in the laboratory of DuPont company in Wilmington, USA. He presided over a series of studies on obtaining high molecular weight substances by polymerization. In 1935, adipic acid and hexamethylene diamine were used as raw materials to prepare polymer. Because both components contained six carbon atoms, it was called polymer 66 at that time. He melted the polymer, extruded it with a needle and stretched it under tension, which is called fiber. This kind of fiber, polyamide 66 fiber, 1939 was named nylon after industrialization, and it was the earliest industrialized synthetic fiber variety.
The synthesis of nylon laid the foundation of synthetic fiber industry, and the appearance of nylon made textiles look brand-new Nylon stockings woven from this fiber is transparent and more durable than silk stockings. 1939,10mesh On the 24th, DuPont made a sensation when it publicly sold nylon stockings at its headquarters, and it was regarded as a rare thing to snap up. People once praised this fiber as "as thin as spider silk, as strong as steel wire and as beautiful as spun silk". To 1940,
From the outbreak of World War II until 1945, the nylon industry turned to military products such as parachutes, aircraft tire fabrics and military uniforms. Because of its characteristics and wide application, nylon developed very rapidly after the Second World War. Various products of nylon, from stockings and clothes to carpets and fishing nets, have appeared in countless ways and become one of the three major synthetic fibers.
A hot air balloon made of nylon can be made very big.
Edit the characteristics of this paragraph
1. DuPont Tactel nylon makes the fabric soft and comfortable, and its good hygroscopicity can balance the humidity difference between the air and the body, thus reducing the pressure on the body, which has an adjustment effect.
2. Extremely light and easy to maintain.
3. Machine washable, the drying time is three times faster than that of cotton cloth, and it only needs to be slightly ironed or non-ironed, which is not easy to deform and has obvious wrinkle resistance.
4. Because of its excellent resilience, it can be restored to its original state after stretching.
Edit the modification of nylon in this paragraph.
PA has strong polarity, strong hygroscopicity and poor dimensional stability, but it can be improved by modification.
? Glass fiber reinforced nylon
When 30% glass fiber is added to PA, the mechanical properties, dimensional stability, heat resistance and aging resistance of PA are obviously improved, and the fatigue strength is 2.5 times that of unreinforced PA. The molding process of glass fiber reinforced PA is basically the same as that of unreinforced PA, but the fluidity ratio is worse than that before reinforcement. Therefore, the injection pressure and speed should be appropriately increased, and the barrel temperature 10-40℃ should be increased. Because the glass fiber will be oriented along the flow direction in the injection molding process, the mechanical properties and shrinkage will be enhanced in the orientation direction, which will lead to the deformation and warping of the product. Therefore, when designing the mold, the position and shape of the gate should be reasonable, which can technically improve the temperature of the mold. After the product is taken out, it will be slowly cooled in hot water. In addition, the greater the proportion of glass fiber, the greater the wear of plasticizing parts of injection molding machine, and it is best to use bimetallic screw and barrel.
? Flame retardant PA
Due to the addition of flame retardants to PA, most of the flame retardants are easy to decompose at high temperature, releasing acidic substances, which have corrosive effects on metals. Therefore, plasticized parts (screws, rubber shoes, rubber shoes, rubber shoes, flanges, etc. ) Hard chromium plating is required. In the process, try to control the barrel temperature not to be too high and the injection speed not to be too fast, so as to avoid the discoloration of the product and the decline of mechanical properties caused by the decomposition of rubber due to too high temperature.
? Transparent pa
It has good tensile strength, impact strength, rigidity, wear resistance, chemical resistance, surface hardness and other properties, and has high light transmittance, which is similar to optical glass. The processing temperature is 300-365,438 05℃. In the molding process, the barrel temperature should be strictly controlled. If the melt temperature is too high, the product will change color due to degradation, and if the temperature is too low, the transparency of the product will be affected due to poor plasticization. The mold temperature should be kept as low as possible. If the mold temperature is high, the transparency of the product will be reduced due to crystallization.
? Weather resistance PA
Adding additives such as carbon black to absorb ultraviolet rays into PA greatly enhances the self-lubricating property of PA and the abrasion of metal, which will affect the blanking and abrasion of parts during molding. Therefore, the combination of screw, barrel, rubber-passing head, rubber-passing ring and rubber-passing ring with strong feeding ability and high wear resistance must be adopted.
? polyamide
Polyamide (PA, commonly known as nylon) is the first resin developed by DuPont, USA, and 1939 is industrialized. In 1950s, in order to meet the requirements of lightweight and cost reduction of downstream industrial products, injection molding products replacing metals were developed and produced. The main chain of polyamide contains many repeated amide groups, which are called nylon when used as plastics and nylon when used as synthetic fibers. Polyamide can be made of diamines and diacids, and can also be synthesized from omega-amino acids or cyclic lactams. According to the number of carbon atoms contained in diamines and diacids or amino acids, many different polyamides can be prepared. At present, there are dozens of polyamides, among which polyamide -6, polyamide -66 and polyamide -6 10 are the most widely used.
The chain structures of polyamide -6, polyamide -66 and polyamide -6 10 are [NH(CH2)5CO], [NH(CH2)6NHCO(CH2)4CO] and [NH(CH2)6NHCO(CH2)8CO] respectively. Polyamide -6 and polyamide -66 are mainly used for spinning synthetic fibers, which are called nylon -6 and nylon -66. Nylon 6 10 is a kind of thermoplastic engineering plastic with excellent mechanical properties.
PA has good comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance and self-lubrication, and has low friction coefficient, certain flame retardancy and processability. It is suitable for reinforcing and modifying filled glass fiber and other fillers, improving performance and expanding application range. There are many varieties of PA, such as PA6, PA66, PAll, PA2, PA46, PA6 10, PA6 12, PAl0 10/0, and there are also many new varieties of semi-aromatic nylon PA6T and special nylon developed in recent years. Using metal sodium and sodium hydroxide as main catalysts and n-acetylcaprolactam as cocatalyst, δ-caprolactam can be directly polymerized by negative ion ring opening in the model, and nylon -6 plastic products can be made, which is called cast nylon. This method is convenient for manufacturing large plastic parts.
Polyamide is mainly used in synthetic fibers, and its most prominent advantage is that its wear resistance is higher than all other fibers, which is 10 times higher than cotton and 20 times higher than wool. Adding some polyamide fibers to blended fabric can greatly improve its wear resistance. When stretched to 3-6%, the elastic recovery rate can reach100%; Can withstand tens of thousands of bends without breaking. The strength of polyamide fiber is 1-2 times higher than cotton, 4-5 times higher than wool and 3 times higher than viscose fiber. However, polyamide fiber has poor heat resistance and light resistance and poor retention, so the clothes made are not as crisp as polyester. In addition, both nylon -66 and nylon -6 used in clothing have the disadvantages of poor hygroscopicity and dyeability. Therefore, new varieties of polyamide fibers, nylon -3 and nylon -4, have been developed. They have the characteristics of light weight, excellent wrinkle resistance, good air permeability, good durability, dyeability and heat setting, so they are considered to be very promising.
Because of its non-toxicity, light weight, excellent mechanical strength, wear resistance and good corrosion resistance, polyamide is widely used to replace copper and other metals in manufacturing bearings, gears, pump blades and other parts in machinery, chemical industry, instrumentation, automobile and other industries. Polyamide has high strength after melt spinning and is mainly used as synthetic fiber and medical suture.
In civil use, nylon can be blended or spun into various medical and knitwear. Nylon yarn is mostly used in knitting and silk industry, such as knitting single stockings, elastic stockings and other wear-resistant nylon stockings, nylon scarves, mosquito nets, nylon lace, elastic nylon coats, various nylon yarns or interwoven yarns, etc. Nylon staple fiber is blended with wool or other chemical fiber wool products to make various wear-resistant and durable clothing materials.
In industry, nylon is widely used to make cord, industrial cloth, cable, conveyor belt, tent, fishing net and so on. Mainly used in military fabrics such as parachutes in the field of national defense.
A polymer whose repeating structure in polyamide molecular chain is amide group.