Enhancing the dielectric properties of highly compatible new polyimide/γ-ray irradiated MWCNT nanocomposites

Abstract

Novel polyimide/γ-ray irradiated MWCNTs (PI/γ-MWCNTs) nanocomposites with improved dielectric properties were fabricated by casting and curing processes. The interfacial interactions between the two domains, i.e. PI and MWCNTs, were enhanced by hydrogen bonding between the hydroxyl groups present on PI and modified CNTs. A PI matrix having pendant phenolic hydroxyl groups was derived from pyromellitic dianhydride (PMDA) and diamine monomer 4,4′-diamino-4′′-hydroxytriphenylmethane. MWCNTs (5-20 wt%) were dispersed in the synthesized PI matrix. Before addition to PI, the surface of MWCNTs was equipped with hydroxyl and carboxylic groups by irradiating with γ-rays under a dry oxygen environment. Surface examination of PI/γ-MWCNTs composite films by scanning electron microscopy (SEM) revealed that MWCNTs are uniformly dispersed and completely wrapped by PI matrix, most likely due to the hydrogen bonding. The influence of greater adhesion of MWCNTs with PI matrix on the dielectric, visco-elastic, and mechanical properties of final PI/γ-MWCNTs nanocomposites was explored using appropriate analytical techniques. The composite films exhibited high dielectric constant, a 7.6 folds improvement as compared to pristine PI. The storage modulus (E′) and glass transition temperature (Tg) demonstrated an improvement of 1.4 and 1.2 folds, respectively. Similarly, mechanical and thermal properties were also found to be improved remarkably. We believe that significant property enhancement of PI/γ-MWCNTs nanocomposites is the direct consequence of increased interface compatibility via hydrogen bonding between polymer matrix and carbon nano-filler.

Enhanced dielectric and mechanical properties in chlorine-doped continuous CNT sheet reinforced sandwich polyvinylidene fluoride film

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Progress of heat resistant dielectric polymer nanocomposites with high dielectric constant

“…Table 1 shows that the addition of fillers into PVDF, PI or PEN may reduce or increase the thermal resistance of the polymer. Generally, positive roles of fillers for improving thermal resistance of a polymer are (i) retarding the formation and escape of volatile by‐products during the pyrolysis [89], (ii) avoiding heat concentration upon external thermal exposure if fillers have good thermal conductivity and uniform dispersion in polymer, (iii) limiting the movement of polymer segments and thus increasing the energy for degrading macromolecular chains through physical interlock and chemical interaction with polymer [90].…”

Modified halloysite nanotube filled polyimide composites for film capacitors: high dielectric constant, low dielectric loss and excellent heat resistance

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