engleski

Component compatibility influences radiation stability of low temperature cured gels based on PDMS

Transparent low-temperature cured gels were prepared using PDMS-DGE, a selected amine (DAP, DETA, and TAEA) and up to 30% of an organic liquid component – ethanol, t-butanol, or benzene. A mixture of the components was kept at 50 °C long enough to ensure completion of reaction that involves opening of diglycidyl ether (DGE) group and formation of an isopropanol-amine link. Hansens solubility parameters (HSP) were used to explain the influence of compatibility of PDMS, amine used for curing, and a liquid component. The properties and radiation stability (D = 50 kGy, γ-radiation) of obtained gels were studied using impedance spectroscopy, Soxhlet extraction, thermal analysis and ATR-FTIR spectroscopy. Even though amine segments are a minor component of a polymer gel-network, they had major influence on gel properties while liquid component was of secondary importance. The most stable were the gels prepared with a branched triamine, TAEA, regardless of the liquid components. Diamines DAP and particularly DETA produced soft and less stable gels. Influence of liquid components depended on the difference of its solubility parameters to that of both PDMS and the amine used for curing. In ATR-FTIR spectra of most of the irradiated gels amide absorption was observed. It indicates degradation at the isopropanol- amine link. However, no overall degradation was observed in those gels. So called “dangling chains” may have formed and remain entangled in the gel-network. Additionally, free-radicals formed in the PDMS segment of polymer network likely crosslinked thus compensating for degradation at isopropanol-amine links what contributed to stability specially of PDMS-TAEA gels.

Polysiloxane ; Chemical gels ; Hansens solubility parameters ; DSC ; ATR-FTIR spectroscopy ; Impedance spectroscopy

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