Development and Application of Semi Aromatic Nylon Special Engineering Plastics

1、 Structure and properties of semi aromatic nylon
Semi aromatic nylon can be divided into homopolymer semi aromatic nylon and co polymer semi aromatic nylon according to resin type. The composition of homopolymer semi aromatic nylon is determined, and it generally has a high crystallinity, making it particularly suitable for fiber manufacturing. The following table shows the structure and melting point of common homopolymer semi aromatic nylon.

We can see that the melting point of PA MXD6 is only 238 ℃, and its heat resistance is low. It is mainly used for gas barrier and resin blending modification. PA6I is an amorphous polymer with poor temperature resistance but high light transmittance, which can be used as a transparent material. In addition, common homopolymer semi aromatic nylons are synthesized from aromatic dicarboxylic acids and aliphatic diamines, such as PA6T and PA10T. The rigidity of aromatic rings and the hydrogen bonding effect of amide bonds together endow semi aromatic nylon with excellent heat resistance, with a significant increase in melting point compared to aliphatic nylon, especially for resin varieties with carbon atom numbers ≤ 6 in the fatty chain.
From the perspective of structure and performance, in addition to PA TMDT, semi aromatic nylon exhibits a decrease in resin water absorption with the increase of diamine carbon chains, but a decrease in melting point and poor melt fluidity. The blending modification of PA6I and PA6 can reduce water absorption and improve the dimensional stability of formed products. At the same time, it can also be added to other polymer materials reinforced with glass fibers to reduce surface floating fibers and improve product appearance. The performance of semi aromatic nylon varies significantly due to its structure, and therefore its applications may also vary.
The following table compares the structure and performance of commonly commercialized semi aromatic nylon resins.

The industrialization of semi aromatic nylon in China started relatively late. Since 2000, some domestic universities, such as Zhengzhou University, Sichuan University and Zhejiang University, have begun to devote themselves to the development of synthetic technology and industrial transformation of semi aromatic nylon, so that China gradually has the independent production capacity of semi aromatic nylon special engineering plastics. In 2023, the semi aromatic nylon trial of Weifang Dongsheng Hengni Technology Co., Ltd. was completed and officially promoted to the market.
2、 Application of semi aromatic nylon
1. Application in electronic appliances
Semi aromatic nylon is currently widely used in the field of electronics and electrical appliances. This is mainly due to the excellent heat resistance and thin-wall formability of semi aromatic nylon. It is required that the thermal deformation temperature of glass fiber reinforced products under the load of 1.8MPa should reach more than 280 ℃, so that precision parts that have been "reflowed" can be produced, such as Electrical connector that are suitable for lead-free solder surface mount technology (SMT) and precision parts of halogen-free flame-retardant low-voltage electrical appliances.
2. Application in the LED industry
With the deepening of energy-saving and environmental protection concepts, light-emitting diode (LED) technology has rapidly developed due to its low energy consumption, high brightness, and high stability. Semi aromatic nylon is mainly used in LED brackets in the LED industry, specifically as black material for LED display screens and white material for medium and low power LED lighting. The black material is a mineral filled type with more than 50%, requiring the resin to have good stability and high fluidity, while there is basically no requirement for the color of the resin. The white material is titanium dioxide whitening and mineral enhanced, requiring the resin to have good stability and high heat resistance. The resin color is required to be white, and there is no obvious yellowing at high temperatures.
3. Application in the automotive industry
For most application scenarios in the automotive industry, their long-term use temperature will not exceed 100 ℃, and most semi aromatic nylon products will not experience deformation due to long-term use.
After years of development, semi aromatic nylon has become one of the main varieties in the field of special engineering plastics and has been widely used in various fields such as electronics and automobiles. After more than ten years of early accumulation, the domestic semi aromatic nylon industry has achieved substantial breakthroughs from scratch, providing strong support for the development of high-tech fields such as electronic appliances, LED industry, and automotive industry in China.
However, on the one hand, the accumulation of original technology in this field in China still needs to be further strengthened, and there is still a certain gap in the quality of domestic resins compared to similar foreign products; On the other hand, foreign chemical giants will not easily give up any opportunities and are constantly disrupting the domestic market through methods such as price reductions for low-end products and low price shocks for sub branded materials.
At the same time, the market continuously puts forward stricter requirements for the price, temperature resistance, stability, and flowability of semi aromatic nylon, and alternative competition from high-performance materials such as PPS, PCT, and LCP is also becoming more intense. Domestic production enterprises should unite and collaborate, integrate resources, increase investment, compete with foreign manufacturers with technology and production strength, and contribute to China's transformation from a manufacturing powerhouse to a manufacturing powerhouse.