Double bond content determination
Fig. 5 demonstrates that the effects of reaction time on double
bond contents in modified PVDF membrane. It proved that the
double bonds were generated during the defluorination process.
As seen in Fig. 5, double bond contents increased firstly from the
reaction beginning to 5 min and then decreased slowly. This meant
that in alkali aqueous solution, double bond could be produced
quickly and its content increased with the prolonged reaction time.
But during the defluorination process, the formed double bonds
were attacked by excess hydroxyl group and dynamic equilibrium
was established afterwards. It was revealed in Fig. 5 that there
existed a slight decline of double bond contents after 15 min. The
phenomena were in the same tendency as the results reported
by Brewis [22].