In organic synthesis, compounds containing the carbodiimide functionality are used as dehydration agents. Specifically they are often used to convert carboxylic acids to amides or esters.  Additives, such as N-hydroxybenzotriazole or N-hydroxysuccinimide, are often added to increase yields and decrease side reactions.
Polycarbodiimides can also be used as crosslinkers for aqueous resins, such as polyurethane dispersions or acrylic dispersion. Here the polycarbodiimide reacts with carboxylic acids, whose functional groups are often present in such aqueous resins, to form N-acyl urea. The result is the formation of covalent bonds between the polymer chains, making them crosslinked.