The optimization of synthesizing graft copolymer of starch with vinyl monomers

Abstract

The graft copolymerization of acrylamide (AM)/acrylic acid (AA) onto starch (St-g-pAA and St-g-p (AA-co-AM) was carried out using an orthogonal test method. The combined effects of different reaction conditions on the water absorbency of the graft copolymers were optimized through mathematical statistical methods of range and square variance analysis. The maximum water absorbency was obtained when the ratio of dried starch to distilled water was 1∶8 (w/w), the ratio of starch to monomer 1∶6 (w/w), the initiator concentration 4.40×10⁻³ mol/L, the crosslinker concentration 10.86×10⁻² mol/L, and the basicity to AA 0.70 (mol/mol). Both the graft copolymers have an excellent water absorption capacity in distilled water and in 0.9 wt% NaCl solution. It was also found that in distilled water the water absorbency of St-g-pAA was higher than that of St-g-p(AA-co-AM), while in 0.9 wt% NaCl solution, the situation was just the reverse. The correlation between the water absorbency and the nature of the solution and the properties of the copolymers, which is related to the properties of the monomers, was discussed. The grafting of AA and AM onto starch was confirmed by the IR spectra of St-g-pAA and St-g-p (AA-co-AM).

Keywords

starch / acrylic acid / acrylamide / graft copolymerization / water absorbency / orhogonal test

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