[en] Complete text of publication follows. During crosslinking of unsaturated polyester resin phase separation may occur, as the crosslinked part becomes insoluble in unreacted resin. Radiation initiated reaction can be interrupted and the system be analysed at different reaction stages. Resin samples were irradiated to selected doses in cells of different width. Phase separation occurred at total dose above 4 kGy, liquid part was removed and analysed separately of gel part. DSC traces of residual reaction were recorded showing difference in shape. Gels had one distinct reaction peak, while unreacted resin and liquid parts had double partially overlapped peaks. Such behavior has been noted previously in the literature but it was attributed to effects of initiator. Radiation crosslinking enabled us to show that double reaction peaks are property of resin system itself. In most cases the high temperature peak of liquid phase corresponded to that of related gel. Low temperature process is assumed to be styrene-polyester reaction. At higher temperatures steric hindrances can be overcome to enable homopolymerization of polyester double bonds. As the radiation dose was increased, the onset temperature of the residual reaction in the liquid phase was approximately constant but it decreased at the doses where liquid phase became scarce before it disappeared. On the other hand onset temperatures of corresponding gels were almost constant. Reaction heats of the liquid phase were almost constant, the influence of sample width was insignificant. Gels of wider sample showed higher dependence of residual reaction heat on radiation dose