Nylon 1,6 (aka polyamide 1,6) is a type of

polyamide A polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are proteins, such as wool and silk. Artificially made polyamides can be made throug ...

nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...

. Unlike most other

s, nylon 1,6 is not a

condensation polymer In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Natural proteins as well as s ...

, but instead is formed by an acid-catalyzed synthesis from

adiponitrile Adiponitrile is an organic compound with the chemical formula (CH2)4(CN)2. This viscous, colourless dinitrile is an important precursor to the polymer nylon 66. In 2005, about one million tonnes of adiponitrile were produced.M. T. Musser, "Adipi ...

formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...

, and water. The material was produced and studied by researchers at

DuPont Dupont, DuPont, Du Pont, duPont, or du Pont may refer to: People * Dupont (surname) Dupont, also spelled as DuPont, duPont, Du Pont, or du Pont is a French surname meaning "of the bridge", historically indicating that the holder of the surname re ...

in the 1950s. Synthesis can be performed at room temperature in open beakers.

Synthesis of nylon 1,6

Nylon 1,6 is synthesized from

, formaldehyde, and water by acid

catalysis Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

. Adiponitrile and formaldehyde (aqueous, paraformaldehyde, or trioxane) are combined with an acid (typically

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

) in a reactor. The reaction can be performed at room temperature. However, the reaction is exothermic, and especially at high ratios of formaldehyde to adiponitrile, cooling may be required. CH₂O + NC-(CH₂)₄-CN + H₂O → NH-CH₂-NH-OC-(CH₂)₄-CO-sub>n Addition of water to the reaction mixture readily precipitates the nylon 1,6 product, which can then be isolated and washed with water to afford high purity

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

Properties and applications

The DuPont evaluations of the 1950s era indicated that polyamide-1,6 was less acid stable than

nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing six carbon at ...

, and melts over 300–325 °C, with some decomposition. However, films were reported to have been successfully pressed at 275–290 °C. Molecular weight determined to be ~22,000–34,000 via an osmotic pressure method. The polymer was believed to be significantly branched and cross-linked owing to side reactions occurring during the acid catalyzed polymerization, but this was not conclusively established. Similar to other formaldehyde-based thermoset resins, thermal behavior of the polymer is a function of the CH₂O/ADN ratio employed in the synthesis. Picture of nylon 16 on filter

Melting point was found to increase with increasing synthesis CH₂O/ADN ratio, along with apparent increase in cross-linking, and reduction in crystallinity. Additionally, spectral features of ¹H-NMR of nylon 1,6 samples were found to trend with CH₂O/ADN synthesis ratio as well. Collectively, these properties parallel those of other formaldehyde-based thermoset resins, and it is interesting that nylon 1,6 is a rare example of a polyamide

thermoset In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and ...

resin rather than a

thermoplastic A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains as ...

material. Nylon 1,6 has been reported to exhibit a high moisture absorbance owing to the significant density of amide residues in the polymer, >130% of its weight (compare to ~2–2.5% for

and

nylon 6 Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the compari ...

References

{{Reflist Polyamides