FORMULATIONS PREPARED FROM POLYACRYLAMIDE AND STARCH

Acrylamide was polymerized in water with ammonium persulfate/triethanolamine initiation, and the resulting polymer gels were blended with excess starch in either-a ball mill or Sigma mixer to dewater the gel and to deposit polyacrylamide (PAA) onto the starch granules. Deposition of PAA occurred on only a minor fraction of the starch added. The major portion of added starch was free of significant amounts of PAA and could be separated by sieving from the coarser PAA-containing fraction. High molecular weight PAA (M(w) 19.3 x 10(6)) was reduced in molecular weight when the gel was either blended with starch or precipitated by high speed stirring with methanol. Lower molecular weight PAA (M(w) 2.5 x 10(6)) was not significantly affected by these processing conditions. Polymerization of acrylamide in the presence of starch yielded PAA of reduced molecular weight, suggesting that starch is acting as a chain transfer agent in these polymerizations. The conversion of monomer to polymer was also lowered in the presence of high concentrations of starch.