AbstractDielectric properties of phenolic‐formal resins are studied between 0.06 and 300 kHz. The resins are prepared from novolac and 1,3‐dioxalane with a strong acid as catalyst. The high dielectric losses are attributed to proton jumps felicitated by water molecules which are produced in the curing reaction. The activation energy of the dielectric relaxation is 0.77 e.v. Curing often continues for weeks after preparation, which is reflected by a gradual increase of the frequency of maximum loss. Drying the samples causes the loss maximum to return to lower frequenc
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