Abstract:Carboxymethyl starch-graft-acrylamide copolymer (CMSGAM) was prepared by using carboxymethyl starch (CMS) as the raw material and acrylamide (AM) as the monomer for grafting. The preparation process was optimized through single factor and orthogonal experiments by using the viscosity of the CMSGAM paste as the index. Characterization of the CMSGAM was performed using fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analyzer (TG). The physical and chemical properties of CMSGAM such as viscosity, transparency, salt resistance, coagulation and water retention were determined. The results showed that the optimum conditions for the preparation were: pH 7.5, reaction temperature 50 ℃, and reaction time 3 h. Under such conditions, the viscosity of CMSGAM paste was the highest (26000 MPa·s). In the FT-IR spectra, a absorption peak near 1667 cm-1 was found (which reflected the characteristic stretching vibration of carbonyl residue in the amide group), along with the absorption peak near 1455 cm-1 (which corresponded to the characteristic vibration of C-N bond in the amide group). The thermalgravimetric analysis revealed the thermal decomposition of the acrylamide group from 350 ℃ to 450 ℃, which proved the success of grafting the acrylamide group into the carboxymethyl starch. The SEM images showed a large number of pores and fractures on the CMS particles, indicating that the graft copolymerization reaction was severe and the structure of starch granule was destroyed. The viscosity and transparency of the CMSGAM paste increased more than 4 times, along with higher anticoagulation effect and thermal stability and minimally improved salt resistance, compared to the CMS paste.
