Rheological Issues of Phase Change Materials Obtained by the Complex Coacervation of Butyl Stearate in Poly Methyl Methacrylate Membranes

The research started from the fact that the coacervation process represents the process of formation of macromolecular aggregates after separation from the phase that takes place in a homogeneous polymer solution as a result of the addition of a non-solvent. This process is very complex, and takes place in several stages of emulsification technology. The first step of the research created a sample through an encapsulation process of complex coacervation, followed by the creation of three different samples with specific emulsification technologies. Each resulting sample and step of emulsification went through rheological analysis, including the development of evolutions of the complex viscosity, loss module and respective storage module. When we analyzed the rheological properties of each sample at different emulsification stages, we reached the conclusion that, at the moment when the polymerization reaction develops the methyl methacrylate (MMA), the loss modules of the samples were stronger than the storage modules. In this context, the emulsification technology strongly influenced the process of forming the polymethyl methacrylate (PMMA) layer over the butyl stearate particles. In addition, in order to obtain the corresponding microcapsules, it was preferable for the butyl stearate particles covered with MMA to be vigorously stirred in a short period of time, under 250 s, because after that the polymerization process of the MMA on the surface of the particles begins. When producing microcapsules, it is very important that the whole process of emulsification be accompanied by rigorous stirring.