I already know that polyamides are made through condensation polymerisation with a carboxylic acid and an amine. But how exactly does the mechanism work? If the reaction takes place in acid for nucleophilic acyl substitution, the amine group would get an extra proton and as a result the nucleophilic acyl substitution can't happen, like it would for an carboxylic acid and an alcohol to form polyesters.
Commercially the diacid/diamine mixture is heated (>250C) to overcome the amine protonation and remove water or by formation of the di-acyl chloride followed by reaction with the diamine. Reference here 1.
Nylon 6 is also formed by adding a little NaH to caprolactam, mechanism here 2