AbstractWe show that the subglass secondary relaxation temperature at which a polymer changes from brittle (crazing) to ductile (yielding) behavior is a function of the characteristic ratioC∞(which is a measure of the intrinsic flexibility and rigidity of a coiled chain). At 1 Hz frequency, the correlation is given by {Tβ}/{Tα} =Tb/Tg= 0.135 + 0.082C∞, where {Tβ} is the secondary relaxation temperature, which corresponds toTbthe brittle—ductile transition temperature, and {Tα} is the primary relaxation temperature, which corresponds to the glass transition temperatureTgat the given frequency. The ratio {Tβ}/{Tα} orTb/Tgcan be predicted from chemical stru
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