Papers by Author: Victor P. Shantarovich

Abstract: Positron annihilation lifetime spectroscopy (PALS) is a recognized instrument for the studies of size-distribution of nanopores (intrinsic free volume holes FVH) in polymers, particularly membrane materials. The limits of this application in the case of “alien” pores, produced by swelling of poly (hexafluoro propylene) PHFP in the gas (CO₂) in super-critical (sc-) state are discussed. The obtained conclusions are controlled by measurements of low temperature gas (N₂) sorption (LTGS) and by comparison of the data with the results on permeation of various gases through the PHFP membrane. Attention is payed to relaxation with time of the newly created FVH in the PHFP membrane.

Abstract: The structure of isotactic polypropylene (PP) and its blends with ethylene-propylene-diene terpolymer EPDM (0-100%) containing the unvulcanized and the vulcanized rubber phase were studied using positron annihilation lifetime (PAL) spectroscopy technique and thermostimulated luminescence (TSL). Cross-linking in the polymer blends is one of the effective ways to create novel materials with effective industrial properties. Meanwhile, composition of such systems is very complicated since it contains microphases of the dispersed components, cross-linked or not, elements of the cross-linking agents, which have some distribution between the blend components. This distribution, heterogeneity and also variation of elementary free volumes due to cross-linking are the points of interest in the study of polymer blend structures.

Abstract: Membrane materials and polymer sorbents, polymers with highly developed free volume and specific surface, are of great technical importance. Positron annihilation lifetime (PAL) studies of these materials and some additional experiments give a chance to learn about the character of size distributions of elementary free volumes (EFV) of these materials. Particularly to answer the question whether the distributions of o-Ps lifetimes are of Gaussian type, as it is suggested in a number of publications, or they have some asymmetry or even some multi-component character, also to check some ideas on the ways of o-Ps trapping. In this aspect, large scale of o-Ps lifetimes (pore sizes) in these materials is very important, since enables comparison with the results of auxiliary techniques.