molecular masses and molecular mass distributions were studied. The structure of virgin and oxidized PP spec-
imens was examined using X-ray diffraction, DSC, and IR spectroscopy. It was shown that the thermal oxida-
tion of the polymers results in the annealing of crystals and conformational reorganization of interlamellar tie
chains in amorphous regions. The contribution of both processes depends on the initial molecular structure and
is associated with the kinetics of oxygen uptake and buildup of polymer oxidation products. The PP sample in
which conformational G
T transitions in interlamellar tie chains prevail and the chains are enriched in stretched conformers is oxidized at a lower rate than the sample with a prevalent annealing of crystallites. In
turn, the thermooxidative degradation of tie chains facilitates the annealing and thickening of crystallites.