The results of positron lifetime measurements as a function of volume fraction QV of CaCO, particles on the high density polyethylene/CaCO, (HDPE/CaCO,) polymer composites with and without addition of a coupling agent are presented. It is observed that, first, positronium (Ps) is formed and annihilates in the free-volume hole of HDPE and the free-volume concentration decreases with increasing @"; second, the positron lifetime T~ and its intensity I, are strongly affected by the structure of the interface layer between CaCO, particle and HDPE matrix. An interesting correlation between positron parameters and the tensile strength of the composites is found.

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Positron lifetimes in polypropylene/ethylene‐propylene‐diene monomer blend (PP/EPDM, with the EPDM volume content of 40%), pure PP, and EPDM are measured in the temperature range of 95 to 370 K. We observe the γ and glass transitions in all samples and the transition temperatures Tγ and Tg are determined. The blend has two lower Tg values compared with pure EPDM and PP. At room temperature, the measured concentration and size of free volume in the blend versus EPDM volume fraction φv are smaller than those calculated by the rule of simple mixing. The different free‐volume properties and Tg values of blend, PP, and EPDM indicate the existence of interfacial interaction between PP and EPDM phases in PP/EPDM blend.

Positron annihilation lifetime spectra are measured in uniaxially drawn polyethylene (PE) at room temperature as function of deformation ϵ from 0 to 190%. The positron annihilation parameters are very sensitive to the microstructural changes of PE during the drawing process. In the elastic stage (ϵ = 0 to 20%), the amount and size of voids in amorphous regions and the size of defects in crystalline regions increase drastically with increasing deformation and reach a maximum at the yield point. In the strain softening stage (ϵ = to 40%), the fractional free volume f is nearly constant. When ϵ < 40%, i.e. in the plastic stage, the fractional free volume f continuously decreases, which shows that the degree of crystallinity increases owing to the orientation of chains and strain‐induced crystallization. continuously decreases, which shows that the degree of crystallinity increases owing to the orientation of chains and strain‐induced crystallization.

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