What is the difference between PA66 and PA6?
PA66 (polyamide 66 or nylon 66), polyamide resin, English name is polyamide, referred to as PA. Commonly known as nylon (Nylon), it is a general term for polymers containing amide groups in the macromolecular main chain repeating units. It is the variety with the largest output, the most varieties and the widest application among the five major engineering plastics. The main varieties of nylon are nylon 6 and nylon 66, which occupy an absolute dominant position. Nylon 6 is polycaprolactam, while nylon 66 is polyhexamethylene adipamide. Nylon 66 is 12% harder than nylon 6; followed by nylon 11, nylon 12, nylon 610, nylon 612, and nylon 1010, nylon 46, nylon 7, nylon 9, nylon 13. New varieties include nylon 6I, nylon 9T and special nylon MXD6 (barrier resin), etc. There are many modified varieties of nylon, such as reinforced nylon, monomer cast nylon (MC nylon), reaction injection molding (RIM) nylon, aromatic nylon, transparent nylon, high impact (super tough) nylon, electroplated nylon, conductive nylon, flame retardant nylon, nylon and other polymer blends and alloys, etc., which meet different special requirements and are widely used as substitutes for traditional materials such as metal and wood. Compared with PA6, PA66 is more widely used in the automotive industry, instrument housings and other products that require impact resistance and high strength. PA66 plastic raw materials are translucent or opaque milky white crystalline polymers with plasticity. Density 1.15g/cm3. Melting point 252℃. Brittle temperature -30℃. Thermal decomposition temperature greater than 350℃. Continuous heat resistance 80-120℃, equilibrium water absorption rate 2.5%. It can resist corrosion from acids, alkalis, most inorganic salt aqueous solutions, halogenated alkanes, hydrocarbons, esters, ketones, etc., but is easily soluble in polar solvents such as phenol and formic acid. It has excellent wear resistance, self-lubrication, and high mechanical strength. However, it has high water absorption, so its dimensional stability is poor. PA66 is the highest mechanical strength and most widely used variety in the PUS DuPont's raw material packaging in Asia A series. Because of its high crystallinity, its rigidity and heat resistance are high.
PA6, also known as nylon 6, is a translucent or opaque milky white particle with the characteristics of thermoplasticity, light weight, good toughness, chemical resistance and durability. It is generally used in automotive parts, mechanical parts, electronic and electrical products, engineering accessories and other products. Its name is determined by the specific number of carbon atoms in the synthetic monomer, such as: nylon-6, 66, 1010, 610, etc. It has high crystallinity and obvious melting point; high surface hardness, wear resistance, low friction coefficient, self-lubrication and soundproofing. It has good low-temperature performance and certain heat resistance (can be used below 100 degrees). It is non-toxic, odorless, and mildew-proof. It has self-extinguishing properties and good weather resistance, but poor dyeability. It was invented by Carothers, a famous chemist from DuPont, the largest chemical industry company in the United States, and his research team. The nylon series is the most important engineering plastic. This product is widely used, covering almost every field. It is the most widely used variety among the five major engineering plastics. Its main characteristics include good aging resistance, good mechanical vibration reduction ability, good sliding properties, excellent wear resistance, good machinability, no creep when used for precise and effective control, good wear resistance, and good dimensional stability.
The chemical and physical properties of PA6 nylon plastic are very similar to those of PA66. However, it has a lower melting point and a wide process temperature range. It has better impact resistance and solubility resistance than PA66, but it is also more hygroscopic. Because many quality characteristics of plastic parts are affected by hygroscopicity, this should be fully considered when designing products using PA6. In order to improve the mechanical properties of PA6, various modifiers are often added. 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, the shrinkage rate of PA6 is between 1% and 1.5%. Adding glass fiber additives can reduce the shrinkage to 0.3% (but slightly higher in the direction perpendicular to the process). The shrinkage of molding and assembly is mainly affected by the crystallinity and hygroscopicity of the material. The chemical and physical properties of PA6 nylon plastic are very similar to those of PA66, however, it has a lower melting point and a wide processing temperature range. It has better impact resistance and solvent resistance than PA66, but it also absorbs more moisture. Because many quality properties of plastic parts are affected by hygroscopicity, this should be fully considered when designing products using PA6. In order to improve the mechanical properties of PA6, various modifiers are often added. Glass fiber 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%. Adding glass fiber additives can reduce the shrinkage to 0.3% (but slightly higher in the direction perpendicular to the process). The shrinkage of molding and assembly is mainly affected by the crystallinity and hygroscopicity of the material. The actual shrinkage is also a function of the plastic part design, wall thickness and other process parameters.
