Write a short note on: Nylon-$6,6$.

(N/A) Preparation: It is prepared by the condensation polymerization of hexamethylenediamine with adipic acid under high pressure and at high temperature $(553 \ K)$.
Chemical Reaction:
$nHOOC(CH_2)_4COOH + nH_2N(CH_2)_6NH_2$ $\xrightarrow{553 \ K, \text{high pressure}} [-NH(CH_2)_6NHCO(CH_2)_4CO-]_n + 2nH_2O$
Properties:
$1$. Nylon-$6,6$ is a fibre-forming solid.
$2$. It possesses high tensile strength due to strong intermolecular forces like hydrogen bonding.
$3$. These strong forces lead to close packing of chains,imparting a crystalline nature.
Uses:
It is used in making sheets,bristles for brushes,and in the textile industry.