Functional epoxy composites for high voltage insulation involving c-BN and reactive POSS as compatibilizer

Abstract

Epoxy resins modified with only Polyhedral Oligomeric Silsesquioxanes (POSS) or cubic boron nitride (c-BN), as well as multiphase composites containing both, POSS and c-BN, were fabricated and investigated. Two different types of reactive liquid POSS with molecule sizes of approximately 2 nm, viz. Triglycidylisobutyl-POSS (TGIB-POSS) and Glycidyl-POSS were added in contents of 1 wt% to form single-phase and multiphase composites. Submicrometric c-BN, in contents of 5 wt%, was used for the respective single-phase composite as well as in the multiphase samples to create multifunctional nanostructured composites. All specimens were characterized by Broadband Dielectric Spectroscopy (BDS), dielectric breakdown experiments, Differential Scanning Calorimetry (DSC) and thermal conductivity measurements. The single-phase POSS composites have seen up to 15% improved dielectric breakdown strengths and enhanced thermal conductivities by up to 20%. The single-phase c-BN composite revealed the most distinct improvement in thermal conductivity of more than 25%, along with a reduction in dielectric breakdown strength of approximately 18%. Additionally, the dielectric and thermal properties of the multiphase composites containing 1 wt% POSS and 5 wt% c-BN, were found to be solely dictated by the submicrometric c-BN particles. SEM observations revealed a significantly improved dispersion of the c-BN particles in the presence of POSS for the multiphase composites, suggesting that POSS acts as a compatibilizer between organic epoxy matrix and inorganic filler particles.

Epoxy‐Based Nanocomposites for High‐Voltage Insulation: A Review

“…Interestingly, the appearance of this second glass transition is predicted by the Tsagaropoulos model for the interface (Section ), which attributes this glass transition to the loosely bound interfacial layer . The strongly bound first layer does not participate in the glass transition due to the impeded chain mobility . However, no other reports of this second glass transition have been found in literature for epoxy nanocomposites.…”

“…Aluminium nitride (AlN) and boron nitride (BN) are non‐oxide nanofillers that are used due to their intrinsic high thermal conductivities . The addition of cubic BN in epoxy modified with polyhedral oligomeric silsesquioxanes has led to improved dielectric breakdown strengths, enhanced thermal conductivities, and higher glass transition temperatures . Hexagonal BN and AlN in epoxy nanocomposites have also shown decreased permittivity for low filler contents .…”

Deposition of organic–inorganic hybrid polymer thin films with a silsesquioxane unit

“…27,28) POSS unit can also be introduced into common insulating polymers to improve their thermal and dielectric properties. 29) We explored the electrical properties of the BuPOSSMA films by J−V and impedance measurements. Figure 7 shows the J−V characteristics of the films deposited with I e of 0 mA (a), 10 mA (b), and 20 mA (c), respectively.…”

Effect of POSS‐grafted titanium dioxide on the electrical and thermal properties of LDPE/TiO2 polymer nanocomposite

“…In order to improve the dielectric and thermal properties of polymeric material, the incorporation of inorganic nanofillers into polymer matrix to form polymer nanocomposites or nanodielectrics has been found to be an interesting possibility . Indeed, this class of dielectric materials has shown significantly enhanced performances compared to the neat polymer such as higher dielectric BD strength, thermal conductivity, or surface resistance to partial discharge (PD) …”

“…The surface modification of TiO 2 was carried out using polyhedral oligomeric silsesquioxanes (POSS). As a hybrid material POSS features an inorganic silica‐like core and reactive organic side groups which are compatible with the polymer matrix . Thus, this leads to an intimate interaction between POSS molecules and the polymer, resulting in a restructuration of the polymer network on a nanometric scale.…”