Bimodal particle distribution for emulsions: The effect of interstitial functional particles

The location of hydroxyl functionality was investigated for thermosetting acrylic latexes. Large and small latex particles with and without hydroxyl functionality were synthesized and characterized. Such large and small latex particles with and without hydroxyl functionality were blended together and a melamine-formaldehyde (M-F) resin was added to crosslink the hydroxyl groups. Mechanical and thermo-mechanical properties were evaluated as function of blend ratio and functionality location. The packing of the latexes was dependent on small to large particle ratio. It was shown that the mechanical properties were also dependent on the location of the functionality. The higher concentration of hydroxyl groups in the small latex particles contributed more to the tensile properties of the latexes than the functionality of the large particles. The location of the M-F resin in the small latex particles resulted in a lowering of the volume fraction needed for a continuous network.