A dynamic mechanical thermal analysis study of high modulus polyethylene fibers

In the present work, a dynamic thermal mechanical analysis technique has been used to investigate the viscoelastic properties of high modulus polyethylene (HM-PE) as a function of frequency and temperature. The HM-PE specimens mainly were tested in the form of film, rather than fiber bundle. In this study, there are three relaxation processes in a temperature range from -170 to 150 degrees C, namely the alpha and gamma transitions occurring at around 80, -140 degrees C, respectively, for an experimental frequency of 1Hz, however, the beta transition is hardly visible, although some investigators revealed that HM-PE shows a weak, broad beta relaxation. These relaxations are generally recognized, furthermore, its molecular mechanism is given a better understanding. The structure and thermal relaxation properties of high modulus polyethylene fibers have been investigated by using differential scanning calorimetry (DSC). The measurements carried out by DMA revealed the significant influence of the constitution of the main and side chain on mechanical relaxation phenomena. Also, the HM-PE fiber bundle samples at different heat rate are studied by means of DMA. With the ramp temperature increases (from I to 6 degrees C/min), the glass transition region is found to be shift (and spread out) towards higher temperatures. The effect of heat rate on the thermal relaxation transitions of HM-PE fibers is explained.