Basic Introduction to High Temperature Nylons

High temperature nylon refers to a nylon material that can be used in an environment above 150°C for a long time. The melting point is generally 290°C to 320°C. The heat distortion temperature with normal glass fiber modification is greater than 290°C. It maintains excellent mechanical properties in a wide temperature range and high humidity environment.

At present, mature industrialized high-temperature nylon varieties include PA46, PA6T, PA9T and PA10T, which can be broadly classified into aliphatic nylon, semi-aromatic nylon, fully aromatic nylon and alicyclic nylon.

PA46 is exclusively produced and sold by DSM. The brand name is Stanyl. It is an aliphatic polyamide formed by polycondensation of butanediamine and adipic acid. DSM is the only solution for the industrialization of butanediamine raw materials in the world. The chemical structure of PA46 is as follows:

Although the molecular structure of PA46 is similar to that of PA66, the number of amide groups in each chain of a given length of PA46 is more, and the chain structure is more symmetrical; the highly symmetrical chain structure results in high crystallinity (about 70%) , And the crystallization speed is fast, so the melting point is higher (295℃), the heat distortion temperature is also high, and the long-term use temperature can reach 163℃.

These characteristics make PA46 have technical advantages over other engineering plastics such as PA6, PA66 and polyester in terms of heat resistance, mechanical strength at high temperature, wear resistance, etc. The production cycle is short and the processing is more economical.

DSM’s PA46 has been used in the actuators of more than 200 million vehicles worldwide, such as electronic throttle control (ETC) actuators, exhaust gas recirculation systems (EGR), turbines, general purpose actuators (GPA), variable gas-feeding system and so on.

PPA is a kind of semi-aromatic polyamide made by polycondensation of benzene ring-containing dibasic acid (usually terephthalic acid) and aliphatic diamine. The main varieties are PA4T, PA6T copolymer, PA 9T, PA10T, PA11T, PA12T, etc.

Among them, PA6T copolymer is the most common, followed by PA9T and PA10T.

The melting point of pure PA6T is 370°C, which is higher than the decomposition temperature of general nylon (350°C). Therefore, pure PA6T must be copolymerized with other nylons and then the melting point is reduced to the normal processing temperature (320°C) before it can be used in injection molding.

Common copolymerization combinations include 6T/6I, 6T/66, 6T/6I/66, 6T/DT, 6T/6, etc. Some data divide DuPont HTN into a single type of high temperature nylon, but in fact 51G, 52G and 54G are 6T copolymers. Only 53G is classified as a high-performance nylon due to its low benzene ring content.

PA6T copolymer has an average melting point of 320°C and a high heat distortion temperature (about 290°C). It has excellent solder resistance, low water absorption, and excellent fluidity. It is used in automobile parts, mechanical parts and electrical/electronic parts. All have a wide range of applications.

PA9T was first successfully developed and industrialized by KURARAY (Kuraray Co., Ltd.). Its trade name is Genestar. It is obtained by polymerization of nonanediamine and terephthalic acid. Its melting point is 306°C. It does not require modification before processing to lower its melting point. It has good toughness in high temperature environments, but its long-term heat resistance is not good.

The water absorption rate of PA9T is 1/10 of PA46 and 1/3 of PA6T, so it will not have any abnormalities such as dimensional changes, declination in physical properties, or swelling and foaming due to water absorption in the applications for various purposes. And it has safer stability in high temperature environment.

Therefore, as a rising star, PA9T has shown strong market potential as soon as it is launched, and is mainly used in three fields: electrical and electronic industry, automobile industry and fiber industry. Since the production technology of nonanediamine has been monopolized by Kuraray, the only producer of PA9T is Kuraray, and the price is higher.

PA10T is made of terephthalic acid and decane diamine as monomers, polycondensed and polymerized. It has excellent heat resistance. Its melting point is 316℃, It has good chemical corrosion resistance, low water absorption and good dimensional stability. After modified with glass fiber its resistance temperature against the lead-free solder exceeds 280℃, and the overall performance is excellent.

Compared with other short-chain high-temperature nylons such as PA46, PA4T, PA6T, PA6I, MXD6 etc., PA10T has a longer diamine flexible long chain, which makes macromolecules gain a certain flexibility, a higher crystallization rate and crystallinity. Rapid forming is suitable for some small electronic components, such as LED reflective brackets, connectors, etc.

In addition, due to the excellent properties such as rigidity and corrosion resistance brought by the benzene ring structure in its molecular backbone, PA10T modified products can also be applied to some chemical reagents and/or heat-resistant environments, such as water treatment, nano injection molding of NMT, engine surroundings, etc.

The commercialization of PA10T products has filled the gap in our country’s independent research and development of new high-temperature nylon materials. The main domestic manufacturers include Shanghai Jieshijie and Jinfa Technology.

PA4T was the first synthetic high-temperature nylon since the 21st century. It was launched by DSM, who holds the world’s only industrialization solution for butanediamine. Similar to PA6T, it has a high melting point (430°C), and is generally copolymerized with other nylons, such as nylon 66 or nylon 6.

This first new polymer in the 21st century has excellent dimensional stability, lead-free soldering compatibility, high melting point, high hardness and mechanical strength under the condition of temperature rise. Compared with PA46 or even PA9T, it shows ultra-low water absorption.

PA5T: The melting point of PA5T will be lower than that of PA6T. The main reason for restricting its development is that the industrialization of pentanediamine is still in the research stage.

PA12T: PA12T is a product of homopolymerization of twelve carbodiamine and terephthalic acid.

Fully aromatic nylon was first developed by DuPont of the United States in the 1960s. There are two common types:

One is poly-metaphenylene isophthalamide. The trade name is Nomex, also known as Aramid 1313. It has excellent heat resistance, outstanding strength, rigidity, high melting point, and high viscosity. It is mainly used for H-class electrical insulation materials and preparation of high-performance fibers (HT-1 fiber);

The second is Kevlar (Kevlar). Its full name is poly-p-phenylene terephthalamide, also known as aramid 1414, softening point 550℃~580℃, long-term use temperature>180℃. With the properties of high strength, high modulus, high temperature resistance, and corrosion resistance it’s mainly used to prepare fibers, such as in bulletproof vests and in mobile phone protective covers.

Cycloaliphatic nylon is polymerized by cycloaliphatic diacid and aliphatic diamine, such as Asahi Kasei PA6C, its related patents show that it is polymerized by 1,4-cyclohexanedicarboxylic acid and hexamethylene diamine. Due to its similar structure to PA6T, it is also a semi-alicyclic polyamide copolymerized with other polyamides (also known as “PA6C copolyamide”).

Besides some university in China has done more research on PA12C.