INFLUENCE OF PLASTICIZATION OF ISOPRENE RUBBER ON ITS MOLECULAR CHARACTERISTICS. PART 2

Abstract

The discussion of the mechanism of mechano-thermal plasticization of SKI-3 (P), which was based on an experiment and started in the first part of the work, is continued. In detail the change in the material balance of a mass portion of different fractions (F) of rubber: ultra-high molecular weight (SWMF), high molecular weight (WMF), middle (MMF) and low molecular weight (NMF) depending on the temperature T and the time t of P is under consideration. The equations describing the balance between the decrease in the portion of molecules of average molecular weight due to destruction with the formation of macroradicals and the increase due to recombination of the formed macroradicals are proposed for each F. It is shown that the main mass exchange occurs between neighboring fractions, for example, due to a high proportion of recombination in the MMF, there is a significant increase in the mass of the WMF. The character of the calculated dependence of the M_w of SKI-3 on t for different T coincides with the experimentally obtained in the first part of the work. For T = 30 °C it is a curve with a minimum, for T = 130 °C it is a curve with a maximum. At T = 80 °C, the calculated value, as well as the experimental value, changes little, that is, there is approximately equality of the contributions of destruction and recombination for all t. The conclusion made in the first part of the work that only the ratio of destruction and recombination processes affects on M_w of SKI-3 in the course of its P is confirmed.