2. time-temperature superposition was applied to the maximum in dielectric loss factors meas­ ured on poly(vinyl acetate).+ data collected at different temperatures were shifted to match at tg = 28°c. the shift factors for the frequency (in hertz) at the maximum were found to obey the wlf equation in the following form: log w +6.9 = [19.6(t- 28))/[42 +(t- 28)]. esti­ mate the fractional free volume at tg and a for the free volume from these data. recalling from chapter 11 that the loss factor for the mechanical properties occurs at wr = 1, estimate the relaxation time for poly(vinyl acetate) at 40°c and 28.5°c.