Dynamic mechanical behavior of poly(vinyl‐methyl ether)‐poly(styrene) blends

Abstract

AbstractThe dynamic mechanical behavior of 10 and 20% poly(vinyl methyl ether)‐polystyrene blends has been studied in the frequency range 10−5 Hz to 5 Hz and temperature range 100–450 K. Isochronal plots of modulus G′ and loss factor, tan ϕ, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process at intermediate temperatures but below Tg may be inferred from the breadth of the G″ frequency curves in the transition zone of both blends. This process, at 280 < T < 300 K, is independent of PVME concentration and seems to be associated with the local modes of motions of PS chains. The rheological behavior of the blends shows them to be compatible up to 20% PVME. Their G′ and G″ data cannot be shifted along a frequency axis to produce a satisfactory master curve. The departure from thermorheological simplicity is much more clearly observed in the tan ϕ than in the modulus‐frequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near Tg. A molecular model of the growth of microshear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior.