Polymer networks such as epoxy resins, polyesters, and polyamides are used as insulating materials in high-voltage engineering. Poly(2-oxazoline)s, which may be considered as ‘pseudo’-polyamides, can be synthesized by the cationic ring-opening polymerization of 2-oxazolines; the monomers can be obtained from the reaction of ethanol amine with carboxylic acids such as decanoic acid from coconut oil (yielding 2-nonyl-2-oxazoline) and undec-10-enoic acid from castor oil (yielding 2-dec-9′-enyl-2-oxazoline). The corresponding copolymers can be crosslinked by UV-induced thiol-ene click reactions. Poly(2-oxazoline)s with a high degree of crosslinking exhibit the same range of permittivity, loss factor, and conductivity like polyamides. The permittivity of crosslinked poly(2-oxazoline)s increases with temperature and decreases with the network density, indicative of a correlation with the flexibility of the material: The changes of the loss factor can be explained by interfacial polarization within the material. Lower degrees of crosslinking by, e.g., hydrolyzable glycol dimercaptoacetate consequently yield poly(2-oxazoline)-based networks that cannot be considered as insulators. Dielectrics based on those poly(2-oxazoline)s can be obtained by compounding with 10 wt.-% of nano-scaled particles such as alumina, silica, or boron nitride; the enhancement of the dielectric properties can be referred to interfacial interaction between the nanoparticles and the polymer matrix.

High-voltage insulators based on polymers and nanocomposites derived from natural resources

256th National Meeting (2018)

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