External Effects on the Structure and Dynamics of Molecules in Oriented Polyolefins

Abstract Oriented polyethylene samples are investigated mechanically, thermally and by oxidation. A complicated character of changes in mobility of molecules on static loading of oriented polyolefins is studied. The influence of deformation, stretching, molecular mass and its distribution on the value and sign of this change is found. The regularities of structural changes in the course of ozone oxidation are revealed. It is shown that the initial stage of oxidation is followed by a considerable improvement of mechanical properties. At a greater extent of oxidation the dependence of molecular mobility on reversible deformation of highly oriented samples of medium molecular weight (MW) and narrow molecular weight distribution (MWD) is reversed. A relaxational transition is observed over the temperature range of from 40°C to 60°C for polyethylene and from 60°C to 70°C for polypropylene. After ozone oxidation at a temperature above 90°C and oxidation under load and subsequent annealing (at the temperature of...