Learn more about the difference between nylon PA6 and PA66

- Mar 11, 2019-


Learn more about the difference between nylon PA6 and PA66

 

   PA6 and PA66 are mostly used in the clothing of civil silk, the cord fabric in the industrial yarn, the fishing net wire, the conveyor belt, and the high wear-resistant insulator in the plastic injection because of their thermoplasticity, light weight, good toughness, good chemical resistance and durability. Parts, as well as daily necessities and packaging films. At the same time, there are subtle differences between the two products, and there are also different application areas in terms of application due to differences in characteristics. Below we analyze the difference between the two from various aspects.

 

Physical properties

 

   Both PA6 and PA66 are translucent or opaque milky white crystalline polymers. However, there are large differences in the production of raw materials: PA6 raw material is caprolactam, which is obtained by ring-opening polymerization of caprolactam; the preparation of raw materials is mainly petroleum benzene, and some manufacturers are limited by the shortage of petroleum benzene to use hydrogenated benzene but the amount is extremely high. less. PA66 is obtained by polycondensation of hexamethylenediamine and adipic acid.

 

   PA6 has a lower melting point than PA66 and has a wide process temperature range. It has better impact resistance and solubility resistance than PA66, but it is also more hygroscopic. Because many of the quality characteristics of plastic parts are affected by hygroscopicity, more attention should be paid during use. The PA66 molecular arrangement is symmetrically distributed, and all the flag groups and amino groups can form hydrogen bonds. In addition, during the spinning process, the dynamic crystallization ability is about 20 times higher than that of PA6, so the splitting strength of the PA66 industrial knot has reached 9.7. g/d, and the strength of PA6 industrial yarn under the same conditions is only about 9.0g/d.

 

Application field

 

   PA6 engineering plastics have high tensile strength, good impact resistance, excellent wear resistance, chemical resistance and low friction coefficient. They can be modified by glass fiber, mineral filler modification and flame retardant. It makes it more comprehensive, mainly used in the automotive industry and electronic appliances. Glass is the most common additive, and sometimes synthetic rubbers such as EPDM and SBR are added to improve impact resistance. For products without additives, PA6 shrinks between 1% and 1.5%. The addition of a glass fiber additive reduces the shrinkage to 0.3% (but slightly higher in the direction perpendicular to the flow). The shrinkage of the molded assembly is mainly affected by the crystallinity and hygroscopicity of the material.

 

   PA66 has good comprehensive performance, high strength, good rigidity, impact resistance, oil resistance and chemical resistance, wear resistance and self-lubrication, especially hardness, rigidity, heat resistance and creep performance, and easy to obtain raw materials. Low cost, so it is widely used in various fields such as industry, clothing, decoration, engineering plastics. PA66 is more used for the production of industrial yarns such as cords because of its higher strength than PA6.

 

   The highest proportion of PA6 consumption is in the civil silk industry, and nylon filaments for clothing are about 58%. The tire frame nylon cord fabric market uses PA6 about 13%. Engineering plastics use PA6 accounted for 12%, including injection molding plastics and modified plastics. Fishing nets account for about 6% of PA6. The plastic film grade PA6 producing BOPA film accounts for 4%, and the staple fiber PA6 which produces carpet, sweater, non-woven fabrics and other products accounts for 4%, and other PA6 used for the production of PA rods and PA tapes account for 3%. Among the physical properties of PA6 itself, its shrinkage rate and molding shrinkage performance are poor, and it is not improved by the improvement of the production process. Rather, it is solved by adding excipients, auxiliaries, or by textile methods, and by composite use during the production process. For example, BOPA film, in order to reduce the impact of its shrinkage, it is necessary to use it in combination, relying on other films to reduce the overall shrinkage.

 

   The highest proportion of PA66 consumption is engineering plastics, accounting for 65% of total consumption, while industrial yarns account for 20%, and others account for 15% of total consumption. The downstream products of PA66 are mostly concentrated in engineering plastics, which are not suitable for spinning because of their rigidity and toughness. According to the segmentation of PA66 in China's consumption sector, the consumption of PA66 in nylon resin is about 320,000 tons, and the consumption of PA66 industrial yarn is about 110,000 tons. The application amount in other aspects is relatively small.

 

Differences in price and capacity

 

     The polymerization of PA6 is a ring-opening reaction. The ratio of input to output of caprolactam and slicing (or raw silk) is about 1:1.03; the polymerization of PA66 is a shrinkage reaction, and the ratio of input to output of 66 salt and slice (formed silk) is about 1.13-1.15. Generally speaking, PA66 is generally higher than PA6 by RMB 3000-4000/ton due to the difference in production process and raw materials.

 

    At the same time, because PA6 is more widely used, and the production process is easier to promote, domestic polymerization plants are about 40-50 large and small, and the production capacity in 2012 is maintained at 2.3 million tons. However, although there is a demand gap in PA66, it is lacked by raw material adiponitrile. Impact, slow development, only three domestic manufacturers. It is understood that the dependence of PA66 imports has been above 60% since 2005.

 

   Because China is a big clothing making country, plus the product in the process of use, first consider its cost performance. PA6 has better advantages in fiber textiles, making PA6 consumption much higher than PA66. At the same time, in the textile products such as industrial silk and cord fabric, the application ratio of PA6 is much higher than that of PA66 in terms of price and performance. But in terms of engineering plastics, PA66 has an advantage.



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