Aromatic dicarboxylic acids are used as precursors (in form of acyl chlorides) to commercially important polymers, e.g. the fire-resistant material Nomex. Mixed with terephthalic acid, isophthalic acid is used in the production of PET resins for drink plastic bottles and food packaging. The high-performance polymer polybenzimidazole is produced from isophthalic acid. Also, the acid is used as an important input to produce insulation materials.