in forming a coating film of a fluororesin , e . g . polytetrafluoroethylene , on a metallic or nonmetallic surface by a physical vapor deposition technique , problems attributed to the necessity of intensely heating or bombarding the fluororesin as the evaporating source or target material are solved by using a molecular weight reduced fluororesin not higher than 5000 in molecular weight . it is best to use a low molecular weight fluororesin powder obtained by heating a high molecular weight fluororesin in presence of a fluorine source and precipitating the molecular weight reduced polymer from the reaction gas .