A series of samples with different amounts of bentonite, cross linker, initiator,
starch and acrylic acid with 40% degrees of neutralization were prepared with
the following procedure: tapioca flour and water were mixed together with a
ratio of 1:20 and put into a four neck flask equipped with a magnetic stirrer,
thermometer and nitrogen line. The slurry was heated at 90°C for 30 minutes
and then chilled to a temperature of 60-65°C. The APS was added into the
mixture and stirred for 15 minutes. A mixture of partially neutralized AA, MBA
and bentonite was then added to the system. The total concentration of the water
in the reactor was 75 w-%. The system was heated slowly to 70°C until a gel
block product was obtained that could not be stirred anymore. Then the
resulting product was washed with ethanol and distilled water and dried at a
temperature of 70°C to a constant weight. The dried product was milled and
screened to achieve a particle size in the range of 20-80 mesh.