title: Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces.
abstract: Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites. Ligand engineering was used to synthesize bimodal ligands onto 15nm silica nanoparticles consisting of long epoxy compatible, poly(glycidyl methacrylate) (PGMA) chains, and short, π-conjugated, electroactive surface ligands. Surface initiated RAFT polymerization was used to synthesize multiple graft densities of PGMA chains, ultimately controlling the dispersion of the filler. Thiophene, anthracene, and terthiophene were employed as π-conjugated surface ligands that act as electron traps to mitigate avalanche breakdown. Investigation of the synthesized multifunctional nanoparticles was effective in defining the maximum particle spacing or free space length (Lf) that still leads to property enhancement, as well as giving insight into the effects of varying the electronic nature of the molecules at the interface on breakdown strength. Optimization of the investigated variables was shown to increase the AC dielectric breakdown strength of epoxy composites as much as 34% with only 2wt% silica loading.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29205, United States. Electronic address: bellmh@ufl.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Bell
authors.affiliation: Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: krentz.tim@gmail.com.
authors.forename: Timothy
authors.initials: T
authors.lastname: Krentz
authors.affiliation: Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: nelsoj@rpi.edu.
authors.forename: J
authors.initials: J
authors.lastname: Keith Nelson
authors.affiliation: Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: schadl@rpi.edu.
authors.forename: Linda
authors.initials: L
authors.lastname: Schadler
authors.affiliation: Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: wkcoke.work@gmail.com.
authors.forename: Ke
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: brenec@rpi.edu.
authors.forename: Curt
authors.initials: C
authors.lastname: Breneman
authors.affiliation: ABB AB, Corporate Research, Västerås SE-721 78, Sweden. Electronic address: su.zhao@se.abb.com.
authors.forename: Su
authors.initials: S
authors.lastname: Zhao
authors.affiliation: ABB AB, Corporate Research, Västerås SE-721 78, Sweden. Electronic address: Henrik.hillborg@se.abb.com.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hillborg
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29205, United States. Electronic address: benice@sc.edu.
authors.forename: Brian
authors.initials: B
authors.lastname: Benicewicz
keywords: Dielectric breakdown strength; Epoxy; Ligand engineering; Nanodielectric; RAFT polymerization; Surface modification