Polyamide resins are linear condensates with high molecular weight and high crystallinity that contain repeating amide chains. They may be built from a single repeating monomer containing carboxylic acid and reactive amine groups, or they may be the result of a reaction between diamines and diacids.
Engineering polymers with strong wear resistance, good impact strength, and extraordinary hardness are polyamides. The creation of internal hydrogen bonds between the various polymer chains as a result of the amide bonding is what gives them their exceptional mechanical characteristics.
Fig 1. Polyamide resins.
Polyamide resins have good resistance to attack by aliphatic and aromatic hydrocarbons and moderate resistance to many halogenated hydrocarbons. Since they are resistant to diluted bases, they tolerate the majority of oils and greases well. Their resistance to weak acids is lower.
Polyamide resins are either reactive or non-reactive. Reactive polyamides are primarily employed as curing agents for epoxy resins found in adhesives and surface coatings. Hot-melt adhesives and printing inks are the two principal applications for non-reactive polyamides.