Stabilization of polycarbonate

The inhibiting activity of several organo-phosphorus stabilizers in thermal oxidation of polycarbonate (PS) prepared from 4,4′-dihydroxydiphenyl-2,2-propane was investigated by DTA and TGA according to absorption kinetics of oxygen, molecular weight variation and by UV spectroscopy. Many phosphites examined efficiently inhibit processes of degradation of PC in air at fairly high degrees of polymer conversion. With low degrees of conversion none of the stabilizers studied have a marked effect on DTA and TGA curves, absorption kinetics of oxygen and molecular weight variation. However, these stabilizers vary markedly in their effect on yellowing of PC in the initial period of oxidation. Some views are expressed concerning the possible mechanism of action of organo-phosphorus stabilizers.