Synthesis of multihollow polyester particles in supra‐ and infra‐millimeter size ranges by double emulsion process

Multivesiculated particles (MVPs) are obtained from a double emulsion system, being currently used as opacifying agents by waterborne paint industry. They have high mechanical resistance and low density as a result of a rigid multialveolar structure formed by cross‐linked polyester. Depending on the particle sizes, different novel applications can be envisaged. This work studies how the conventional one‐step batch emulsification approach can be adapted for producing MVPs with average diameters ranging from tens of microns to a few millimeters. The Taguchi method was employed to identify the level of influence of several process variables on the final yield of small (<100 µm) or large (>1 mm) particles. Poly(vinyl alcohol) (PVA) concentration and molecular weight proved to be the most significant factors to obtain small particles. For large particles, the most significant factors were the PVA molecular weight and the stirring rate during the curing phase. Uniform vesiculation and low particle density could only be obtained by adjusting the stirring conditions during dispersion of the organic phase, due to limitations in water diffusion rate into large organic droplets. Large particles exhibited tendency to fracture due to residual stresses, but this problem was solved by using an organic‐soluble cure initiator. POLYM. ENG. SCI., 56:590–597, 2016. © 2016 Society of Plastics Engineers