Fabrication of high-temperature aromatic polyamides with ultra-high breakdown strength via complex-assisted chain arrangement

Abstract

• Highly orientated polyamides were prepared via complex-assisted chain arrangement. • The breakdown strength of the polyamide increased from 460 to 641 kV/mm. • Cross-linking enhanced breakdown strength to 706 and 572 kV/mm at 25 and 150 °C. • Breakdown strength of the cross-linked polymer is higher than that of commercial film. • The polymer films presented excellent mechanical properties and dimensional stability. Improving the breakdown strength ( Eb ) of high-performance polymer films is critical for their use as high-temperature insulation films. In this study, we demonstrated HCl can complex with the benzimidazole units of heterocyclic aramid polymers, temporarily suppressing the intermolecular hydrogen-bonding interactions. Moreover, the weak interchain interactions led to improved mobility and extended the conformation of the macromolecular chain. Therefore, after HCl decomplexation, the macromolecular chains presented higher orientations and degrees of order during subsequent high temperature annealing, resulting in an increase the Eb of the films from 460 to 641 kV/mm at 25 °C. The Fourier-transform infrared spectroscopy and theoretical calculation results indicated that the hydrogen-bonding interactions were restored and enhanced after HCl decomplexation via annealing. In addition, trace amounts of O 2 were used to catalyze the cross-linking reaction between phenyl groups based on the high electron density of the benzimidazole moieties. Owing to the chemical cross-linking reaction, the Eb of the films further increased to 706 and 572 kV/mm at 25 °C and 150 °C, respectively, whereas the tensile strength of the films reached 337.4 MPa.