About high temperature nylon PA
About high temperature nylon PA
1.Nylon PA introduction
Polyamide (PA) commonly known as nylon, by diacid and binary amine or by amino acid polycondensation, is the molecular chain containing repeated amide group -NHCO- resin general name. Nylon is the base resin with the largest yield, the largest variety, the widest use and excellent comprehensive performance among the five general engineering plastics.
Nylon, as an important engineering plastic nowadays, is being continuously modified by physical and chemical methods to make it high performance. At present, many fields have put forward new requirements for the high temperature resistance of materials. In order to meet these requirements, people have done a lot of research in the development of new high temperature nylon.
2. High temperature nylon definition
High temperature nylon (HTPA) is a kind of heat-resistant polyamide, can be used for a long time at 150℃ environment engineering plastic. It has good performance in heat, electricity, physics and chemical resistance. Especially in the high temperature still has high rigidity and high strength and excellent dimensional accuracy and stability.
3. High temperature nylon characteristics
1. High temperature resistance. The thermal flexural temperature is 280 ° C (1.8MPa) and the continuous service temperature is 180 ° C.
2. Creep performance. The high crystallinity of HTPA allows it to maintain excellent rigidity at high temperatures (above 120 ° C), with aluminum-like strength, steel-like hardness, and rubber-like flexibility, ductility, and impact resistance.
3, excellent dimensional accuracy and stability. In the molecular structure of HTPA, the molecular chain segment contains aromatic ring, the molecular structure is more regular, the chain is short and it is not easy to move.
4, chemical resistance. Polyamides have good resistance to most chemicals. Like other polyamide materials, HTPA is no exception, especially at high temperature oil and grease resistance is very good.
5, moisture absorption. HTPA fiber reinforced product has low hygroscopicity, and its water absorption rate is only half of that of the same volume glass fiber reinforced PA46 product. This low moisture absorption can save customers more drying costs, and the product size stability is better.
6. Toughness. HTPA’s excellent impact toughness makes it a material of choice for high demand fabrication.
4. The traditional high temperature nylon types and properties
4.1 PA46
PA46 is an aliphatic polyamide formed by polycondensation of butyldiamine and adipic acid. Compared with PA6 and PA66, PA46 has more amides in each chain of a given length and more symmetric chain structure, which makes its crystallinity up to 70% and gives it a very fast crystallization rate.
The melting point of PA46 is 295℃, the HDT(thermal deformation temperature) of the unenhanced PA46 is 160℃, and the HDT can be as high as 290℃ after the strengthening of the glass fiber, and the long-term service temperature is 163℃.
The unique structure of PA46 gives unique properties that no other material can achieve. As the full owner of the property rights of PA46, DSM is gradually putting its excellent performance into industrialization through continuous modification. While ensuring its high temperature resistance, a variety of special applications such as ultra-wear resistance, ultra-high rigidity, ultra-high mobility have been continuously developed.
In terms of high temperature resistance, DSM launched its new high performance STANYLDiablo on Chinaplas in 2008. It has long-term heat stability and can work normally at 230℃ for more than 3000h, while the mechanical performance is reduced by less than 15%.
4.2 PA6T
PA6T is a typical representative of semi-aromatic nylon, which is formed by condensation of hexandiamine and terephthalic acid. The melting point of pure PA6T is as high as 370℃. At this temperature, nylon has been degraded and cannot be thermoplastically formed. Therefore, the PA6T in circulation in the market are copolymers or complexes with reduced melting point after copolymerization with other monomers.
PA6T introduces a large number of benzene rings on the basis of the fatty chain. Compared with the traditional PA6 and PA66, PA6T has higher Tg, low 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 ratio becomes the key to the modification of PA6T, so it can be said that the high-temperature modification of PA6T has a great development space.
4.3 PA9T
PA9T was developed by Kuraray Company in Japan. It is a polycondensation of nonendiamine and terephthalic acid. Although PA9T is semi-aromatic nylon, it does not need to be modified by copolymerization to reduce the melting point before processing like PA6T. The melting point of pure PA9T is 306℃. The high glass transition temperature (125℃) and high crystallinity of PA9T give it good toughness at high temperature.
At the same time, it also has the incomparable chemical resistance of other PA materials, second only to PPS, and its water absorption rate is only 0.17%, which is the lowest among all PA. The comprehensive performance of PA9T is undoubtedly a better one of the traditional heat-resistant nylon, and with the continuous expansion of the production scale, its cost will be close to the cost of ordinary PA, so PA9T is a variety with great development potential.
5. The latest high temperature nylon
5.1 PA66
Although PA66 has relatively lower Tm and Tg than conventional high temperature nylon, which seems to limit its use in the high temperature field, Rhodia believes that it can still be used as a high-end material. At the 2007 K Show in Germany, Rhodia introduced TECHNYL Heat Performance(HP), a PPA replacement material for high temperature environments. This PA66 is capable of meeting the performance requirements of rising temperatures in the hood of a car.
The material is also said to maintain the processing properties of nylon 66 at the cost level of nylon 66. This technology brings a new development in the field of high temperature resistance of PA66 materials, but only Rhodia has mastered this technology.
5.2 PA4T
As the world’s leading high temperature nylon (PA46) manufacturer, DSM has the world’s only butylenediamine industrial solution. Butylenediamine is the key raw material for the synthesis of PA46, and such technical advantages also lead DSM company to develop PA4T product using this as raw material.
This new polymer, the first of the 21st century, has excellent spatial stability, lead-free welding compatibility, a high melting point, high hardness and mechanical strength in the presence of rising temperatures, and exhibits ultra-low water absorption compared to DSM’s original PA46 products, even PA9T.
The comprehensive and excellent performance of PA4T will enable it to occupy an important share in the future applications of high temperature resistance such as electronics and automotive. The invention of PA4T also reflects the higher requirements of market miniaturization and centralization of electronic products on performance materials.
5.3 PA10T
The results show that pure PA10T has a high melting point of 319.1℃, and its excellent heat resistance makes PA10T show potential commercial value.
Domestic plastic modification leading enterprises commercialized this technology, so that it has excellent heat resistance, ultra-low water absorption, better dimensional stability, resistance to lead-free solder temperature up to 280℃, excellent chemical resistance and injection processing performance.
And it is said that nearly half of the raw materials of PA10T resin come from castor beans, which belong to bio-based environmental protection materials, excellent comprehensive performance, showing a strong market competitiveness.
The commercialization of PA10T products has filled the gap in China’s independent research and development on high temperature nylon new material.
5.4 Other PPA materials
PPA(semi-aromatic nylon) is prepared by condensation polymerization of aliphatic diamines or diamines with aromatic rings. In addition to the above mentioned PA4T, PA6T, PA9T, PA10T and other materials, there are PAMXD6, PA12T and many other PPA varieties. Because of the aromatic ring structure in the chemical structure of these nylons, the thermal deformation temperature is increased in different degrees. Dupont used dimethyl terephthalate (DMT) and dodecylamine (DDMD) to synthesize PA12T, with a melting point of 296.6℃, which has a strong application value.
Six, high temperature nylon application
HTPA is an ideal engineering plastic for heat-resistant parts in the automotive, mechanical, electronic/electrical industries because it can provide thermal deformation temperatures in excess of 270 ° C. At the same time, HTPA is also an ideal choice for parts that must maintain structural integrity under short-term high temperature.