PHYSICOCHEMICAL PROPERTIES OF CALCIUM POLYCARBOPHIL, A WATER-ABSORBING POLYMER

The physicochemical properties of calcium polycarbophil were examined. Calcium polycarbophil was decalcified rapidly under acidic conditions , affording polycarbophil. Polycarbophil absorbed about 10 times its o wn weight of water under acidic conditions, but the swelling ratio mar kedly increased at above pH 4 0 and reached 70 times the initial weigh t under neutral conditions. The swelling of polycarbophil was not affe cted by non-ionic osmolarity, but was affected by ionic strength, show ing a decrease with increase of ionic strength. Monovalent metal ions such as sodium and potassium ions in gastrointestinal fluid did not re duce the equilibrium swelling of polycarbophil but divalent ions such as calcium and magnesium ions did. However, calcium ion only slightly reduced the equilibrium swelling under sodium-rich conditions. The vis cosity (as an indicator of fluidity) of polycarbophil was larger than that of CMC-Na at every shear rate and polymer content examined.