Positron lifetimes in polytetrafluroethylene (PTFE) and polyethylene (PE) have been measured as a function of residual deformation [MATH]. For PTFE, the variation of o-Ps intensity shows a three-stage processes : the elastic region ([MATH]), plastic-f low region ([MATH]) and strain-strengthening region ([MATH]). The changes of free-volume hole size and concentration suggest the separation, scission and orientation of segments. For PE, the o-Ps parameters are sensitive to the elastic and plastic regions. Particularly, the hole concentration decreases linearly with [MATH], which indicates the crystallization during deformation

No abstract

Positron lifetimes in polypropylene/ethylene-propylene-diene monomer blend (PP/EPDM, EPDM volume content = 40%), pure PP and EPDM have been measured in the temperature range of 95-370K. We observed the Υ - and glass transitions in all samples and the transition temperatures TΥ and Tg are determined. The blend has two lower TgS compared with pure EPDM and PP. At room temperature, the measured freevolume concentration in blend versus EPDM volume fraction Φv is smaller than that calculated by the simple mixing . The different free-volume properties and TgS between blend, PP and EPDM indicate the existence of interfacial interaction between PP and EPDM phases in blend