Relaxation in Filled Systems

In accordance with the concepts developed in (44) the ass transition temperature is dependent on the mobility of both very small and large stmctural ekments of the chains, even on the mobility of supetmrdecular structures. For this reason the j ass transition temperature cannot be consideted only as a temperature which determines the manifestation of segmental mobility. 

Obvioudy, tte presence of a loose temperature glass transition interval can be explained by tte fact that various mechanisms participate in the process of glass transition. Of interest from this point of vfew is the examination of the effect of fillers on such relaxation processes in which sufficiently large structural elements take part. Those phenomena were studied (33. 45-47) by calculating the average relaxatirai time proceeding from the data on the isothermic contraction of the volume of various filled systems by the method proposed in (48). 

The analyas of the data obtained for a number of sterns, containing both inorganic and polymeric fillers, shows that the average time of relaxation of the process of isothermic contraction t v increases in the presence of hard particles. However, from the point of view of understanding the mechanism of the processes which occur in the interface, it is mote cmrect to compare tte relaxation time at corresponding temperatures equidistant from the glass transient t nperature, rather than at equal temperatures. 

As is seen in Fig. S, which represents the relaxation time versus the difference between the temperature in the exj riment and Tg. the relaxation time in such a comparison for the system examined in the presence of a solid surface, is smaller than for an unfilled polymer. 

The increase of Tg in the surface layer explains the greater relaxation time in filled systems compared at equal temperatures. However, some of our research indicated a reduction of the density of padring of polymers in the surface layer, and an increase of the free volume (1). This effect reduces the aver relaxation time in 

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