Measurements of the dependence of track etch rate on the energy-loss of different ions have been presented. In this method,₁₈⁴⁰Ar,₁₀²²Ne,₈¹⁶O and₆¹²C-ions of different energies are used as energetic heavy ions for track formation in the detectors. The bulk etch rate and track etch rate are measured for different temperatures and hence the activation energies are determined. The variation ofV =V_t/V_b along the trajectory of the track has been shown for different temperatures. The maximum etched track length is compared with the theoretical range as well as with the range reported earlier. The experimental results indicate the absence of a well-defined threshold in the plastics studied.