The key difference between PA6 and PA66 is that PA6 is derived from a diamine, whereas PA66 is derived from diamine and diacid.
There are various types of polyamides having a wide range of properties, depending on their applications. We can denote polyamides as PA. Nylon is a type of polyamide. There are different types of nylon, such as nylon 6 and nylon 66, denoted by PA6 and PA66.
What is Nylon?
Generally, the most characteristic feature of nylon fibers is their strength and light weight. Furthermore, this material possesses very high abrasion resistance, unlike many other synthetic fibers. Nylon is extremely elastic and second only to spandex yarn and rubber. This material is resilient, which makes it resistant to wrinkles. The silky luster of nylon gives an appearance similar to cotton and wool. A tightly woven nylon fabric may feel light, but it traps moisture, air, and heat. Therefore, it is ideal for making fabrics of umbrellas and raincoats. Insects and mildew do not affect nylon.
However, there are some drawbacks of using nylon; e.g. exposure to sunlight can reduce the properties of nylon, the attraction of lint and dirt and static buildup. The major applications areas of nylon include consumer electronics, automotive industry, packaging etc. There are two types of nylons: the monaidic (-[RNHCO]n-), and the dyadic (-[NHRNHCOR’COn]-). The type of nylon is often abbreviated as ‘nylon x’ or ‘nylon xy’, where x and y represent the number of carbon atoms in the monomer(s) from which they are synthesized. We can denote these types as PA6 and PA66, respectively.
What is PA6?
PA6 is one of the most important monadic nylons, mainly useful as a fibre-forming polymer and as an engineering plastic. We can synthesize PA6 via melt polymerization of either Ɛ-aminocaproic acid or Ɛ- caprolactam. This material absorbs moisture up to a certain extent, and the Tg (glass transition temperature) of the PA6 reduces along with increasing moisture content.
The zig-zag molecular conformation and the anti-parallel arrangement of PA6 chains result in more hydrogen bonds between amide groups. The tensile properties of this material also reduce with increasing moisture content. The tenacity of fibres can be improved by melt spun and hot drawing of fibres. When compared to PA66, PA6 has high impact strength. Cast PA6 is useful in manufacture hug gears and bearings, fuel tanks, building shutters, and various parts of paper production machinery and construction equipment. Fiberglass reinforced PA6 resins are useful in producing automotive radiator shrouds, air ducts, structural components, fuel cells, and reservoirs.
What is PA66?
PA66 is a dyadic nylon we can produce by high-temperature melt polymerization of adipic acid and hexamethylenediamine. This material is one of the most important and highly useful nylons in the world, owing to its superior balance of properties and relatively low price. The melting point of PA66 is around 260- 265 °C, and Tg is about 50 °C when dry.
Similar to PA6, this material consists of zig-zag chain conformation, resulting in intramolecular hydrogen bonds. Glass-fiber filled PA66 has excellent specific stiffness and toughness, which enable it to be useful in applications such as molded industrial drills and pump housing products. The tensile strength of PA66 is greater than that of nylon 6. The applications of molded PA66 include lawnmower blades, tractor hood extensions, bicycle wheels, skate wheels, skis for snowmobiles, bearings, electrical connections, and motorcycle crankcases. PA66 fibers are important in the clothing, fabric and rug industries.
What is the Difference Between PA6 and PA66?
PA 6 and PA66 are two types of polyamides. The key difference between PA6 and PA66 is that PA6 is derived from a diamine, whereas PA66 is derived from diamine and diacid.
The following infographic summarizes the differences between PA6 and PA66 in tabular form for side by side comparison.
Summary – PA6 vs PA66
PA6 and PA66 denote nylon 6 and nylon 66, respectively. The key difference between PA6 and PA66 is that PA6 is derived from a diamine, whereas PA66 is derived from diamine and diacid.
1. “Nylon 6.” Science Direct, Available here.
1. “Polycaprolactam” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia
2. “Nylon 6,6” By D.328 07:44, 13 December 2005 (UTC) – drawn by D.328 (JChemPaint) (CC BY-SA 3.0) via Commons Wikimedia