What Are The Differences In Nylon

Nylon,  also known as polyamide, is the first of the five engineering plastics, with broad application space. It is widely used from clothes, backpacks, nylon tubing to aerospace and automation. However, nylon materials are actually a huge family of materials. According to different molecular structures, nylon family can be divided into various types, each type has its unique performance and application fields. Here are some common nylon types:

PA6

The full name of PA6 is Polycaprolactam or Polyamide 6, which is formed by open loop polymerization of caprolactam. It is one of the most common nylon materials and has a wide range of use scenarios, such as automotive parts, electronics, pipeline connections and fiber textile.

It is cheap and has high strength, abrasion resistance, heat resistance and chemical resistance. Its melting point is about 215-225 ℃, and its low-temperature resistance is good, which can maintain sufficient stress in a wide range.

It is suitable for many processing and forming processes, but it is highly moisture absorption. If the humidity is too high during processing, the product size and final performance will be affected, so special attention shall be paid to drying before processing. When the humidity is greater than 0.2%, dry it in hot air or carry out vacuum drying.

PA66

PA66 also known as Polyamide 66, which is formed by condensation polymerization of adiamine and adipic acid. Its molecular structure is similar to PA6, but the number of hydrogen bonds is more and the molecular force is stronger. It is also one of the most common nylon materials with only second yield to PA6.   

Its overall performance is similar to that of PA6, but it has higher strength and rigidity, about 12% harder than PA6. The thermal property is also good, and the melting point is about 250-270 ℃. It crystallizes fast and therefore has better processability than PA6. In addition, it has good oil resistance, abrasion resistance, chemical resistance and self-lubrication.

However, it is also susceptible to water absorption and dimensional stability. Therefore, attention shall be paid to drying before processing, and drying shall be carried out when the humidity is high.

Due to its performance advantages, PA66 is more suitable for occasions requiring high strength, high rigidity, heat resistance and abrasion resistance, such as PA fiber resistance fuel in automobile engine compartment, brake system, air bag and mechanical pump parts.

PA11

PA11, fully known as Polyamide 11, is the earliest biological polyamide product. It is a long-chain flexible nylon produced by reaction of castor oil and methanol to generate ω - undecylic acid, and finally through polymerization reaction. Therefore, it is considered more environmentally friendly and sustainable.

It features light weight, corrosion resistance, smooth surface and large resistance, making it very suitable for making cable protective cover, military equipment, gas pipeline, clothing, etc. Its melting point is relatively low, about 200 ℃, but its toughness at low temperature is much better than that of PA6.

At the same time, compared with PA6 and PA66, PA11 has low water absorption, good dimensional stability and easy processing and molding.

However, although PA11 material has incomparable advantages, due to its high cost, its application range is significantly limited.

PA12

PA12 is fully called Polyamide 12, its characteristics are similar to PA11, but its crystal structure is different. It is a linear, semi-crystalline - crystalline thermoplastic material from butadiene. It has a low melting point, but good low-temperature toughness, good chemical and oil resistance, and the lowest shrinkage in nylon.

Similar to PA11, PA12 also has low water absorption, excellent dimensional stability and easy molding.

With the development of technology, there are many improved varieties of PA12 in terms of plasticized properties and enhanced properties. Modified PA12 can meet the requirements of low temperature impact resistance of air brake pipe, and is widely used in air brake pipe, sliding mechanism, photovoltaic backplane and bearing of automobile.

PA46

PA46, is fully known as Polyamide 46 and is prepared by polycondensation reaction of butanedipamide and adipic acid. It is a high performance engineering plastic known for its outstanding heat resistance, high strength, high rigidity and low water absorption.

The melting point of PA46 is usually above 290 ℃, much higher than that of general nylon materials. At the same time, PA46 exhibits extremely high tensile strength and bending modulus due to its high crystallinity and close molecular arrangement. It has the best abrasion resistance in high temperature nylon, so it can maintain a long service life at high temperature or under high stress and load.

PA46 has low water absorption. Although its melting point is high, its processability is still good due to its good mobility. It can be molded by common plastic processing methods such as injection molding and extrusion.

MXD6

MXD6 stand for Poly(meta-xylylene adipamide), which is synthesized by condensation reaction of m phenylenediamine and adipic acid. It has very outstanding gas barrier performance and its comprehensive physical property is superior to PA66 and close to PA46.

It is characterized by good toughness, tensile resistance, abrasion resistance, solvent resistance, small water absorption, excellent dimensional stability and non-combustion. Its light transmittance can reach 90%, and its mechanical property and electrical property are stable at high temperature.

MXD6 nylon stands out in packaging and automotive applications with its outstanding barrier properties and is well used in many high temperature products with hydrolysis and gas barrier requirements.