Preparation of novel aramid film with ultra-high breakdown strength via constructing three-dimensional covalent crosslinked structure

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2019-11, Vol.375, p.122042, Article 122042
• Main Authors: Dai, Yu, Meng, Chenbo, Wu, Hang, Luo, Longbo, Liu, Xiangyang
• Format: Article
• Language: English
• Subjects: Aramid film; Composites; Crosslink; Electrical insulation; Nano-SiO2; Oligomers
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.122042

[Display omitted] •Crosslinked para-aramid film can be prepared by its reactive oligomers end-capped with CC groups.•Three-dimensional covalent crosslinking can be attained in aramid film by utilizing steric structure of SiO2.•Breakdown strength of the composite film reaches to nearly 624 kV mm−1 which is 70% higher than that of Kapton film.•The composite film owns excellent mechanical properties and dimensional stability. Electrical insulation materials with excellent thermal resistance and high breakdown strength have great application potential in energy storage devices. Herein, poly(benzimidazole-terephthalamide) (PABI) film with ultra-high breakdown strength was prepared by introducing three-dimensional covalent crosslinked structure, which was constructed by reactive PABI oligomers (PABI-O) and nano-SiO2 derivate (SiO2-Ac). PABI-O was end-capped with acryloyl chloride, and crosslinking reaction of CC groups from acryloyl chloride could take place above 300 °C. Then, SiO2-Ac grafted with large amounts of CC groups on its surface was prepared, and it was blended with PABI-O, which was followed by processing into films and annealing at 360 °C. Due to steric structure of SiO2-Ac and large amounts of CC groups on its surface, three-dimensional crosslinking can be attained in the composite film by radical addition reaction of SiO2-Ac and PABI-O. It is found that the three-dimensional crosslinked structure can increase path tortuosity in the electrical treeing breakdown, which endows the film with breakdown strength up to 624 kV mm−1 and shows 70% enhancement compared with that of Kapton film (a famous polyimide film). Moreover, the film exhibits excellent mechanical properties and dimensional stability. Tensile strength of the film is nearly 340 MPa, and the coefficient of thermal expansion (CTE) is only 5.06 ppm/°C at 20–250 °C.