Tricalcium Phosphate Containing Sodium Hexametaphosphate as Polymer Suspension Stabilizer
Tricalcium phosphate as hydroxyapatite is used as a suspension stabilizer in styrene polymerization process. Particle size of TCP plays an essential role in the particles’ size distribution and geometrical form of polystyrene products. As the particle size of TCP is reduced, there will be much better chance to engulf the styrene particles. The higher the number of TCP particles surrounding each styrene particle, the lesser will be their tendency to form a large particle after collision. Therefore, there will be higher percentages of spherical polystyrene with small particle size and narrower size distribution in the product. Experimental results have indicated that the addition of sodium hexametaphosphate (SHMP) to the reaction mixture of lime and phosphoric acid, after drying the product by spray dryer, lead to decrease the size of TCP particles from ca. 5 μm (without SHMP) to ca. 1.5 μm (with SHMP). In this study, the role of TCP containing SHMP as polymer suspension stabilizer and consequently the beads size of polystyrene is investigated in laboratory scale. The results show that despite addition of SHMP to the reaction mixture of lime and phosphoric acid decreases the TCP particles size and the mean bead size of the product of polystyrene become larger than the product prepared by TCP without SHMP.