Since miniaturization in microelectronics and electrical engineering (cp. Moore’s law) significantly increases the energy density and heat development, one requirement of components is high thermal conductivity. Polymers, which have a very low thermal conductivity, correspondingly are in the focus of R&D activities. Aiming to enhance the thermal properties of epoxy resins, two strategies can be considered, the blending with aromatic species that tend to align in parallel due to π-π-stacking, and the compounding with (electrically insulating) nanoparticles. In this study, both strategies were combined in order to correlate the chain/segment mobility within a polymer resin with the extent of π-π-stacking of bisphenyl units; the steric hindrance due to nanoparticles and the temperature (above/below the glass-transition temperature of the resin) were focused on.<br/>The epoxy/amine resins (Figure 1) were prepared from two different diepoxy compounds, Bisphenol A diglycidyl ether BADGE and 1,2,7,8-diepoxyoctane DEO in order to investigate the effect of the segment mobility. For blending with different contents of bisphenyl units, two different primary diamines, isophorone diamine IPDA and o-dianisidine DAN, were used for the curing reaction in different ratios. As inorganic filler, pyrogenic silica nanoparticles were added in 5 wt.-% quantity. The π-π-stacking of bisphenyl units preferentially occurs in DEO-based resins above their glass-transition temperature (T = 90, 120 °C; Figure 1); in the BADGE counterparts, no significant influence of the temperature on their thermal conductivity can be observed. The addition of 5 wt.-% of nanoparticles reduces the extent of π-π-stacking, which unambiguously reveals the correlation of the molecular structures at the nano-level with the macroscopic properties.

Enhancing the thermal conductivity of crosslinked epoxy resins by the addition of bisphenyl units and silica nanoparticles

2019 Spring National Meeting

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