Question

How is Nylon 6, 6 prepared?

Answer 1

Nylon-6,6 is prepared by the method of condensation polymerisation process. Hexamethylenediamine combines with adipic acid to give the macromolecule Nylon-6,6 with the elimination of water molecule.

\[\ce{\underset{\text{Adipic acid}}{nHOOC-(CH2)4-COOH }\underset{\text{Hexamethylediamine}}{+nH2N-(CH2)6 - NH2}->[553K][High pressure]}
\begin{array}{cc}
\phantom{.}\ce{H}\phantom{...........}\ce{H}\phantom{,,}\ce{O}\phantom{.,,......}\ce{O}\phantom{...}\\
|\phantom{............}|\phantom{...}||\phantom{.........}||\phantom{..}\\
\ce{[-N-(CH2)6-N-C(CH2)4-C -]n}\\
\text{Nylon 6,6}
\end{array}\]

Used in making sheets, bristles for brushes and in the textile industry.

Answer 2

Nylon -6,6 is synthesized by polycondensation of hexamethylenediamine and adipic acid. Equivalent amounts of hexamethylenediamine and adipic acid are combined with water in a reactor. This is crystallized to make nylon salt, an ammonium/carboxylate mixture. The nylon salt goes into a reaction vessel where polymerization process takes place either in batches or continuously.

n HOOC-(CH₂)₄-COOH + n H₂N-(CH₂)₆-NH₂ → [-OC-( CH₂)₄-CO-NH-(CH₂)₆-NH-]_n + (2n-1) H₂O

Removing water drives the reaction toward polymerization through the formation of amide bonds from the acid and amine functions. Thus molten nylon 66 is formed. It can either be extruded and granulated at this point or directly spun into fibers by extrusion through a spinneret (a small metal plate with fine holes) and cooling to form filaments.