Abstract
The results of this investigation of the temperature and frequency dependence of the deformation and mechanical loss of elastomeric network polymers in the temperature range from −90 to +120° C may be understood on the basis of the conceptions of three types of relaxation processes in these materials: orientation of the units of the chain molecules, overcoming of the secondary crosslinks (entanglements) in the movement of the segments, and the process of destruction of the polysulfide bonds, which comprise quite a small part of the total number of the chemical crosslinks. The first process is connected with the glass-transition and leads to the occurrence of a low-temperature maximum of mechanical losses, while the third leads to a high-temperature maximum. The first and third relaxation processes are apparently characterized by narrow spectra of relaxation times, which may be substituted for approximately by the corresponding averaged relaxation times. For the second process the spectrum of relaxation times is probably very wide and it is not possible to make the analogous substitution; this also explains the absence of a third mechanical loss maximum and the occurrence of a well marked frequency dependence of the deformation amplitude in the high-elastic range. The models of a network polymer considered for low and high temperatures give a qualitative description of all the main mechanical properties of these materials.