cross linked curve 2 on the other hand is given for the same sheet after being cross linked by irradiation curves 1 and 2 have a bell shaped trend and have been plotted for a given frequency they present respectively maxima for the temperatures tg 1 and tg 2 called vitreous transition temperatures to which losses tg u03b4 1 and tg u03b4 2 correspond for each curve at temperatures less than the vitreous transition temperature the amorphous zones of the corresponding material are rigid above this temperature these zones are viscous or fluid for the purpose of comparison t a represents the ambient temperature it can be seen that though the vitreous transition temperature tg increases when crosslinking is carried out on the other hand the losses tg u03b4 decrease there is also shifting of the curve tg u03b4 f t rightwards of the diagram this shift causes in some temperature zones and at certain frequencies a reduction of the dielectric losses but increases in others however the loss maximum decreases when the cross linking rate increases the temperature tg increases with the frequency this leads to optimizing the losses depending on the frequency range and the temperature range corresponding to the use for irradiation doses such that there is cross linking of the amorphous zones and non destruction of the crystalline zones it may be arranged for the remanent polarization to be little affected as.