Characterization and Reaction Mechanism of Graft Copolymer of Acrylamide onto Mechanically-Activated Starch

The mechanically-activated cassava starch acrylamide graft copolymers (C30-St-g-PAM) were synthesized by inverse emulsion polymerization with mechanically-activated 30 min cassava starch and acrylamide as raw materials. The structures of C30-St-g-PAM were characterized with Fourier transform infrared spectroscopy (FT-IR),differential scanning calorimetry (DSC),X-ray diffraction (XRD) and scanning electronic microscope (SEM). Meanwhile,the graft copolymerization mechanism in the inverse emulsion was discussed. The results show that polyacrylamide (PAM) is successfully grafted onto the mechanically-activated starch; C30-St-g-PAM are found to have a porous mesh-like structure with the graft-copolymerization reaction occurring at both crystalline regions and loose amorphous regions of the starch particle,which is not in agreement with the mechanism of surface control reaction. The aggregation phase of starch is changed from semicrystalline state to amorphous aggregation state due to the graft reaction of starch and acrylamide. However,the thermal stability of C30-St-g-PAM is higher than that of C-St-g-PAM. The size distribution is 15 μm～ 30 μm.