| Abstract: | Simultaneous formation of hydrofluoric acid (HF) in the radiation-induced polymerization of tetrafluoroethylene (TFE) was investigated. HF concentration in PTFE latex was determined mainly by conductometric titration with 0.01 and 0.001N NaOH. The amount of HF formed is almost independent of agitation speed and the amount of n-hexadecane added and is maximal at ca. 70°C corresponding to the rate of polymerization. The rate of HF formation increases with the initial pressure of TFE monomer and dose rate and decreases with polymerization or TFE consumption. This fact suggests that HF is formed mainly by TFE reactions and not by the degradation of PTFE. The mechanism of HF formation in this reaction system in the absence of oxygen is shown in the following two schemes: scheme I is the reaction of TFE with primary radicals (OH·, H·, e ) from the radiolysis of water; scheme II is the reaction of water with the species from the radiolysis of TFE. On the assumption that HF is formed only according to scheme I, the G value of HF formation G(HF)calc can be calculated as 11.25. All observed G values G(HF)obs are larger than G(HF)calc. When the polymerization is carried out at 20 kg/cm2 under various dose rates, G(HF)obs increases with the dose rate. When the polymerization is carried out at 3.0 × 104 rad/hr under various pressures, G(HF)obs decreases with the decrease in pressure from 20 to 2 kg/cm2 and is fairly close to G(HG)calc at 2 kg/cm2. This indicates that HF formation is due mainly to scheme II at high pressure (in the presence of enough TFE) and to scheme I as the pressure is lowered. |
