Dielectric relaxation and aging effect in interpenetrating network polymers of poly(urethane)‐poly(methyl methacrylate)

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Abstract
The permittivity and loss of poly(methyl methacrylate) (PMMA) network crosslinked with trimethylol‐1,1,1 propane and its interpenetrating network polymers with 10, 34, and 50% (by weight) poly(urethane) have been measured from 100 to 400 K over a frequency range of 12 to 1 × 105 Hz. Two relaxation processes, γ and β, are observed in the PMMA network, and a third process, αpu, in the 10% poly(urethane) IPN. At higher concentrations of poly(urethane), the γ process is removed from the temperature‐frequency range of our study. Crosslinking in pure PMMA slows the segmental motions involved in the β process and raises its activation energy. Physical aging of the 10 wt% poly(urethane)‐PMMA causes its γ process to become indiscernible and the αpu process to become better resolved. A discussion of these results in terms of local regions of segmental motion is provided.