Apparently decomposition of free PVP occurs at about 600K in oxygen, but if you just want to dry it and want to prevent oxidation completely I would suggest much lower  temperatures and using vacuum, inert gas,  desicant and/or azeotropic distillation, depending on application etc.

polymer can oxidize very even when they are exposed far below their decomposition temperature (as measured by TGA).

For example, decompotion temperature of PP or PE is ca 300°C bu they oxidize within 1 min or less at 200°C.

regards

thanks ,

                Actually we are using PVP for inorganic nanofibers solutions and old PVP in our store and freshly purchased showing different viscosity of resultant solutions. So we were curious if  drying without oxidation can help in this however drying at 120 C did not reduced much weight of PVV, Can you please suggest more, thx