Abstract:

Micron-sized silicon particles were chemically surface-modified with coupling agent KH570, and the grafted particles PAN/SiO2 were obtained. The graft polymerization of acrylonitrile(AN) on the surfaces of particles PAN/SiO2 was performed in a solution polymerization system. The transformation reaction of nitrile groups of the grafted PAN to amidoxime groups(AO) was conducted with hydroxylamine hydrochloride as reagent in the presence of Na2CO3, resulting in functional composite particles of PAO/SiO2, on which poly(amidoxime) macromolecules were chemically anchored. The two kinds of particles were characterized with FTIR, TGA and SEM methods. The effects of the main factors on the graft polymerization of AN and on the amidoxime transformation reaction of the grafted PAN were examined. The experimental results show that in the graft polymerization process, the suitable amount of initiator used is 1.5% of monomer mass, and the appropriate reaction temperature is 75 ℃. As the graft polymerization is carried out for 5 h under the proper conditions, the grafted particles PAN/SiO2 with a grafting degree of 0.14 g/g can be obtained. The amidoxime transformation reaction can not be carried out completely due to the steric hindrance of amidoxime groups. The optimal reaction conditions for the amidoxime transformation reaction of the grafted PAN are as follows:pH value in a range of 6~7, reaction temperature 70 ℃ and reaction time 4 h. Under the appropriate conditions, the functional particles of PAO/SiO2 with a nitrile group conversion ratio of 78% can be obtained.

Key words: acrylonitrile, graft copolymerization, Poly (amidoxime), silica gel, Functional particle