Accurate dynamic mechanical measurements have been performed on semicrystalline isotactic polypropylene over wide ranges of temperature and frequency. A mechanical model has been used to analyze experimental results in order to separate the behavior of amorphous and crystalline phases. The two main α and β relaxation processes have been analyzed. The β relaxation, related to the glass‐rubber transition of the amorphous fraction, has been studied with the help of a physical model. The behavior is similar to that of a wholly amorphous polymer, with two characteristics: a high rubbery plateau, indicating a crosslinking effect by the crystalline phase, and a strong effect of interfaces in shear strain. Experimental data suggest the α relaxation originates within the crystalline phase and that it can be attributed to diffusion of defects. The amorphous phase plays an important role in this process, because it has to adapt itself by cooperative movements to respect the compatibility of deformations of the two phases. The formalism developed here rationalizes experimental results obtained with samples having different thermal histories.

SynopsisT h e dynamic mechanical behavior of monodisperse atactic polystyrene (mol. wt. 98,OOO) has been measured in the frequency range, 10 ' to 10 Hz arid temperature range 359-374K. The time-temperature superposition of the entire data in the frequency range of overlap seems less satisfactory in both the real and imaginary components of the complex shear modulus, G" and G", respectively. The lack of adequate superposition becomes pronounccd in the tan Q (C;"/G') plots. The tan $I plots provide a more discerning criteria for the superposition than the G ' or G "spectra.An analysis based on an earlier model for anelastic deformation shows that of the several changes that may occur in the dynamic mechanical behavior on heating of polystyrene, the predominant ones are both an increase in the size of the microshear domains and the correlations of movement of segments near entanglements. These decrease the contribution to the modulus OIL heating near Tg so that the time-temperature superposition is vitiated.

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SynopsisThe dynamic mechanical behavior of 10 and 20% poly(viny1 methyl ether)-polystyrene blends has been studied in the frequency range Hz to 5 Hz and temperature range 100-450 K. Isochronal plots of modulus G' and loss factor, tan @, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process a t intermediate temperatures but below TR may be inferred from the breadth of the G" frequency curves in the transition zone of both blends. This process, a t 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 C' 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 Q than in the modulusfrequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near T#. A molecular model of the growth of micrashear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior. poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) and PPO-PPS blends showed a similar behavior of the fl process in that the temperature of the P-relaxation peak remained nearly constant with increased concentration of PPO in the blend, and the dielectric measurements substantiated these results.The purpose of this study was to investigate whether the blend of PVME, which plasticizes PS, in contrast with PPO, which antiplasticizes PS, shows a