The effect of solvents on the structural-dynamic characteristics of films and nonwoven materials based on polyurethane, the styrene-acrylonitrile copolymer, and their blends

Abstract

A structural-dynamic analysis combining thermophysical measurements and studies of segmental mobility via the ESR microprobe method is applied to films and nonwoven materials based on polyurethane, the copolymer of styrene and acrylonitrile, and blends of these polymers. The effect of solvents—such as tetrahydrofuran, ethyl acetate, and acetone—on the structures and molecular dynamics of films and matrixes based on PU and styrene-acrylonitrile copolymer ultrathin fibers is studied. It is shown that a solvent weakly affects the molecular dynamics of chains in the film and nonwoven polyurethane materials and has a strong effect on the molecular mobility in the films based on the styrene-acrylonitrile copolymer and blends with a high content of the copolymer. For the nonwoven material, this effect is insignificant. It is found that in both film and nonwoven materials mesomorphic structures are formed. An analysis of the dependences of the correlation time of probe rotation, τ, on the temperature and the polymer ratio reveals the presence of breaks at the melting temperatures of mesomorphic structures PU. This effect is the most pronounced at a 50: 50 mass ratio of the components for both film and nonwoven materials as a result of phase inversion. The spin-probe studies show that the oxidizer ozone influences the amorphous phase of the studied polymers. Measurements of the dynamics of probe rotation for film and nonwoven materials after ozonation demonstrate that, for both PU-based films and nonwoven materials, ozone has practically no effect on the molecular dynamics, whereas for the blends of these polymers and the styrene-acrylonitrile copolymer these changes in τ are significant.