INVESTIGATION OF THE SURFACE MODIFICATION OF ALUMINUM HYDROXIDE FILLER AND OPTIMUM MODIFIER DOSAGE LEVEL

The adsorption of a dicarboxylic anhydride (DAA) onto aluminium hydrox ide has been studied. Diffuse reflectance Fourier transform infrared s pectroscopy (DRIFT) investigations have shown that chemical adsorption of both acid groups of the hydrolysed DAA, via carboxylate salt linka ges with the substrate, can only occur at elevated temperatures. Optim um DAA dosage on BA Chemicals SF7-E aluminium hydroxide was determined using sedimentation volume measurements, rheological techniques and e xtraction studies. Good agreement between the methods was obtained and the optimum level compared well with a theoretical prediction based o n computer generated models of the. possible adsorbates. The effect of DAA level on the dispersion of the filler in polypropylene was also s tudied. Brabender Plasticorder mixing torque and extent of filler disp ersion reached limiting values at the optimum DAA level. In the partic ular case investigated, it was considered most likely that the optimum DAA dosage corresponded to a coverage that was approximately one mole cule in thickness.