反应详情

5 g of 30% aqueous CaCl2 (calcium chloride) solution was added into 100 g of cationic styrene-butadiene latex, BUTONAL® NX1118 from BASF Corporation. The latex remained as a stable dispersion. After mixing, 5 g of 35% aqueous (NH4)2HPO4 (ammonium biphosphate) solution was added under agitation. The latex pH remained below 4.5 during and at the end of (NH4)2HPO4 addition. This procedure was expected to produce approximately 2 wt % of calcium phosphate (Ca-phosphate) nano-crystals in the latex polymer. A thin latex film of approximately 250 μm was prepared by diluting the latex dispersion from 65% solids to 45% solids with water, spreading the dispersion on a polytetrafluoroethylene plate, and drying at room temperature. Masking tape was applied at four corners of the plate to keep the latex dispersion wetting the plate. After completely drying, the film was cut to expose a thin cross-section, and the cross-section was observed under the optical microscope. The presence of fine nano-crystals was apparent in the entire polymer film as shown in FIG. 2.

1. additionAfter mixing