Kapton E is a mix of two dianhydrides, PMDA and biphenyltetracarboxylic acid dianhydride (BPDA), and two diamines, ODA and p-phenylenediamine (PPD). The BPDA component adds greater dimensional stability and flatness in flexible circuitry applications. Kapton E offers reduced coefficient of thermal expansion (CTE), reduced moisture absorption, and reduced coefficient of hygroscopic expansion (CHE) compared to Kapton H.[2]