FLUORINATION RATES OF POLYOLEFINS AS A FUNCTION OF STRUCTURE AND GAS ATMOSPHERE

Polyolefins and fluoropolymers were reacted with elemental fluorine un der carefully controlled conditions in a thermobalance adapted to be c ompatible with fluorine gas. The fluorination reactions were monitored by measuring the mass increase as a result of hydrogen substitution b y fluorine. The mass increase was directly proportional to the square root of the fluorination time, which indicates that fluorine gas diffu sion to the unreacted surface is the rate determining step. The fluori nation rate was increased by increasing the fluorine concentration and the fluorination temperature. The fluorination rate is higher when ni trogen rather than helium is used as diluting gas. The fluorination ra te for the reaction in which CO2 is used as diluting gas is the same a s during fluorination with nitrogen as diluting gas, while the presenc e of oxygen dramatically decreased the fluorination rate. Oxygen is in corporated during fluorination with oxygen as diluting gas, while no f unctionalization was observed when CO2 was employed as diluting gas. T he effect of polymer structure on fluorination was studied. Poly(vinyl fluoride) gained mass during fluorination, while no reaction was obser ved for poly(vinylidenefluoride). The reaction rate for polypropylene was higher than that of polyethylene.