Polyamide (PA), commonly known as nylon, is a generic term for resins containing repeated amide groups - NHCO - on the molecular chain, which is obtained by condensation polymerization of binary acids and diamines or amino acids. Nylon is the basic resin with the most output [sensitive words], the most varieties, the most widely used and excellent comprehensive performance among the five general engineering plastics.
Nylon, as an important engineering plastic, is being continuously modified by physical and chemical methods to make it high-performance. At present, many fields have put forward new requirements for high temperature resistance of materials. In order to meet these requirements, people have done a lot of research in developing new high-temperature nylon.
Definition of high temperature nylon
High temperature nylon (HTPA) is a kind of heat-resistant polyamide, which can be used at 150 ℃ for a long time. Good performance in thermal, electrical, physical and chemical resistance. Especially at high temperature, it still has high rigidity and strength, and the dimensional accuracy and stability of [sensitive words].
Characteristics of High Temperature Nylon
1. High temperature resistance. The thermal deflection temperature is 280 ℃ (1.8 MPa), and the continuous use temperature is 180 ℃.
2. Creep properties. The high crystallinity of HTPA enables it to maintain excellent rigidity at high temperatures (greater than 120 ℃), with the same strength as aluminum, the same hardness as steel, and the same flexibility, ductility and impact resistance as rubber.
3. [Sensitive words] dimensional accuracy and stability. In the molecular structure of HTPA, the molecular chain segment contains aromatic rings, the molecular structure is more regular, and the chain is shorter, making it harder to move.
4. Chemical resistance. Polyamide materials have good resistance to most chemicals. Like other polyamide materials, HTPA is no exception, especially with excellent oil and grease resistance at high temperatures.
5. Moisture absorption. HTPA fiber reinforced products have low moisture absorption, and their water absorption is only half of that of the equivalent glass fiber reinforced PA46 products. This low hygroscopicity can save more drying costs for customers, and the dimensional stability of products is better.
6. Toughness. The excellent impact toughness of HTPA makes it a material choice with high requirements.
Types and properties of traditional high-temperature nylon
PA46
PA46 is an aliphatic polyamide polycondensated from butylene diamine and adipic acid. Compared with PA6 and PA66, PA46 has more amides on each chain with a given length and more symmetrical chain structure, which makes its crystallinity as high as 70% and gives it a very fast crystallization speed.
The melting point of PA46 is 295 ℃, and the HDT (thermal deformation temperature) of unreinforced PA46 is 160 ℃. After glass fiber reinforcement, its HDT can reach 290 ℃, and the long-term use temperature is 163 ℃.
The unique structure of PA46 endows other materials with unique properties that cannot be achieved. As the full owner of PA46 property rights, DSM is gradually industrializing its excellent performance through continuous modification. While ensuring its high temperature resistance, various special applications, such as super wear resistance, ultra-high rigidity and ultra-high fluidity, have been continuously developed.
In terms of high temperature resistance, DSM launched its new high-performance STAN YL Diablo on Chinaplas in 2008. It has long-term thermal stability, and can work normally at 230 ℃ for more than 3000 hours, while its mechanical properties decline by less than 15%.
PA6T
PA6T is a typical representative of semi aromatic nylon, which is polycondensated from hexamethylene diamine and terephthalic acid. The melting point of pure PA6T is as high as 370 ℃. At this temperature, nylon has degraded and cannot be thermoplastic molded. Therefore, PA6T in the market is a copolymer or composite with a lower melting point after copolymerization with other monomers.
PA6T introduces a large number of benzene rings on the basis of fat chain. Compared with traditional PA6 and PA66, PA6T has higher Tg, lower water absorption, dimensional stability and high heat resistance. Because PA6T needs to introduce other monomers for copolymerization to reduce the melting processing temperature, different monomer ratios become the key to the modification of PA6T. Therefore, it can be said that the high temperature resistance modification of PA6T has great development space.
Shanghai Jieshijie Company has also successfully issued PA6T series of high temperature resistant nylon, which has been put into production.
PA9T
PA9T is independently developed by Kuraray Company of Japan, which is polycondensation of nonanediamine and terephthalic acid. Although both are semi aromatic nylon, PA9T does not need to reduce its melting point by copolymerization modification like PA6T before processing. The melting point of pure PA9T is 306 ℃. The high glass transition temperature (125 ℃) and high crystallinity of PA9T endow it with good toughness under high temperature environment.
At the same time, it also has chemical resistance that other PA materials cannot match, second only to PPS, and its water absorption rate is only 0.17%, which is the [sensitive word] of all PAs. The comprehensive performance of PA9T is undoubtedly one of the better traditional heat-resistant nylon. With the continuous expansion of production scale, its cost will be close to that of ordinary PA, so PA9T is a variety with great development potential.
[Sensitive words] High temperature nylon
PA66
Although PA66 has relatively low Tm and Tg compared with traditional high temperature nylon, which seems to limit its application in the high temperature field, French Rhodia believes that it can still be used as a high-end application material. At the K Show in Germany in 2007, Rodier introduced TECHNYL Heat Performance (HP), an alternative PPA material in high temperature environment. This PA66 can meet the performance requirements in the rising temperature environment in the automobile hood.
It is said that this material also maintains the processing performance of nylon 66 at the cost level of nylon 66. This technology has brought new development to PA66 material in the field of high temperature resistance, but only Rhodia has mastered this technology at present.
PA4T
As the world's leading manufacturer of high-temperature nylon (PA46), DSM Company has a global [sensitive word] industrial solution for butylamine. Butylenediamine is the key raw material for PA46 synthesis, and such technical advantages also enable DSM to take the lead in developing PA4T products with this raw material.
This first new polymer in the 21st century has excellent spatial stability, lead-free welding compatibility, high melting point, high hardness and mechanical strength when the temperature rises, and shows ultra-low water absorption compared with the original PA46 product of DSM, even PA9T.
The comprehensive and excellent performance of PA4T will make it occupy an important share in the future high temperature resistant applications such as electronics, electrics and automobiles. The invention of PA4T is also the embodiment of higher requirements for performance materials in the miniaturization of the market and the centralization of electronic products.
