Dicarboxylic acids with different chain lengths can be used to modify the properties of polymers or plastics. Because of the longer carbon chain, the melt points and thus process temperatures are drastically reduced and the recrystallisation properties are improved. As a consequence of this, curing times are shortened, e. g. in hotmelt adhesive applications. Longer-and thus more water-repellent-side chains reduce water absorption and thus enhance washfastness. Furthermore, they improve the flexibility and elasticity of the polymeric materials produced from them. Last but not least, C-18 dicarboxylic acids increase the transparency of the polyamides compared with their shorter-chain homologues.