Polyamide (PA) refers to a class of polymer compounds containing amide groups (-CONH-). It is widely used in textiles, automobiles, electronics, machinery and other fields, and the most well-known ones are PA6 and PA66.

History of PA66

Polyamide 66 (PA66) was first developed by American chemist John R. R. in the 1940s and was quickly commercialized. PA66 quickly became a leader among various engineering plastics due to its excellent mechanical properties, heat resistance and chemical stability. Especially in the automotive industry, PA66 is widely used in the manufacture of engine hoods, car shells, fuel pipes and other parts.

PA66 is synthesized by polycondensation reaction of hexanedioic acid and hexamethylene diamine, and there is a repeating amide group (-CONH-) in the molecular structure. It is this structure that makes PA66 have very high strength, heat resistance and chemical corrosion resistance, becoming an important representative of high-performance materials.

Characteristics of PA66

Translucent or opaque milky white crystalline polymer

Emits purple-white or blue-white light when exposed to ultraviolet light

High mechanical strength,

Good stress cracking resistance,

Excellent self-lubrication,

Good heat resistance, and is a self-extinguishing material,

Excellent oil resistance, but easily soluble in solvents such as phenol and formic acid,

Adding carbon black can improve weather resistance;

High water absorption, poor dimensional stability

Good molding and processing, can be used for injection molding, extrusion, blow molding, spraying,

Casting molding, machining, welding, bonding.

Comparison between PA66 and PA6

PA66 and PA6 are both polyamide materials. They are very similar in chemical structure and contain amide groups, but they have significant differences in some properties.

1. Differences in molecular structure

PA6 is formed by the condensation of hexamethylenediamine (1,6-hexamethylenediamine) and caprolactam (caprolactam), while PA66 is obtained by the condensation of adipic acid and hexamethylenediamine. Although both contain the same amide groups in their chemical structures, the molecular chains in PA66 are longer than those in PA6, resulting in a stronger polymer structure.

2. Differences in thermal properties

PA66 has a higher heat deformation temperature and melting point than PA6. The melting point of PA66 is about 265°C, while that of PA6 is about 225°C. This difference makes PA66 more stable in high temperature environments and suitable for applications with high temperature requirements, such as engine parts and heat-resistant electrical appliances.

3. Comparison of mechanical properties

PA66 has higher rigidity and strength than PA6. Due to its longer molecular chain, PA66 can withstand greater tensile stress, so PA66 has an advantage in applications requiring high strength and high rigidity. For example, in automotive manufacturing, PA66 is often used in parts that require wear resistance and impact resistance, such as car tires and dashboards.

4. Differences in water absorption

Water absorption is an important factor affecting the performance of polyamide materials. PA66 has a slightly higher water absorption rate than PA6, which means that the mechanical properties of PA66 may be reduced in a humid environment. Although PA66 can still maintain its performance, PA6 may be more stable in some specific applications.

5. Differences in processability

PA6 is easier to process than PA66, especially in injection molding and textile fiber production. PA6 has a lower melting point, so it can be processed at a lower temperature, reducing energy consumption. In contrast, the higher melting point of PA66 may require higher temperatures and more equipment requirements in some processing processes.

Application areas of PA66

Thanks to its excellent comprehensive performance, PA66 has been widely used in many industries. Here are some of the main application areas:

1. Automotive industry: Due to its high heat resistance and mechanical strength, PA66 is often used in the production of automotive parts, such as engine parts, cooling systems, oil pipes, and exterior parts.

2. Electrical and electronics: PA66's good electrical insulation makes it an important choice for electrical housings, electrical plugs, and cable insulation materials.

3. Textile industry: PA66 is also widely used in the textile industry, especially in the production of high-strength and high-wear-resistant fibers, such as nylon 6 and nylon 66 fibers.

4. Industrial manufacturing: PA66's wear resistance and chemical corrosion resistance make it a component material in industrial equipment, such as gears, bearings, and mechanical transmission parts.

Summary

PA66, as a high-performance engineering plastic, has been widely used in many fields due to its excellent properties such as high strength, high rigidity, heat resistance, and chemical resistance. Compared with PA6, although PA66 is slightly more complicated to process, it has incomparable advantages in applications with high temperature and high strength requirements. Whether in the field of automobile manufacturing, electronic appliances, or industrial machinery, PA66 has demonstrated its great potential and broad application prospects as an engineering plastic.