Preparation, characterization, and water resistance of cationic acetylated starch-g-poly(styrene-butyl acrylate) surfactant-free emulsion

Cationic acetylated starch-g-poly(styrene-butyl acrylate) surfactant-free emulsion (CAS-g-poly(St-BA)) was synthesized by graft copolymerization of styrene (St) and butyl acrylate (BA) onto CAS using FeSO4H2O2 redox initiator. The maximum graft of 55.68% was derived when H2O2 concentration, monomer concentration, and St/BA ratio were 9%, 130%, and 1:1, respectively. The results obtained from FTIR, NMR (H1 NMR and C13 NMR), XRD, SEM, and thermogravimetric analysis (TGA-DTG) confirmed graft copolymerization of St and BA onto CAS. And it was demonstrated that film-forming properties of starch were greatly improved via grafting St and BA onto starch. It was also found that paper sized with CAS-g-poly(St-BA) exhibited higher ring crush index and bursting strength than paper sized with cationic potato starch (CS) and CAS, as well as much lower water absorption, which is further verified by contact angles results.