Equilibrium adsorption of polyvinylpyrrolidone and its role on thermoregulating microcapsules synthesis process

The adsorption of polyvinylpyrrolidone (PVP) by the thermoregulating microcapsules has been studied. The mass ratio of PVP has been changed from 1 to 20, with respect to the lowest amount of PVP value (4.08 g). The results confirmed that a large amount of PVP was adsorbed by the polymeric shell. Experimental data were perfectly fitted by Langmuir model, obtaining at a confidence level of 95% values of 192.9 ± 0.4 g/kg and 0.18 ± 0.11 m³/kg for the maximum adsorption capacity and the equilibrium constant, respectively. It was found that utilizing PVP, at a concentration of 5.03 wt% of the total mass provided optimum conditions for synthesizing thermoregulating microcapsules containing Rubitherm®RT27 from poly(styrene-divinylbenzene) (P(St-DVB)), with the best thermal and physical properties. Finally, the robustness of the process was checked at a large scale by using a reactor that maintains geometrical similarities with that used at laboratory scale. The thermal properties, the encapsulation efficiency, and the microcapsule yield were similar, but at pilot plant scale, narrower particle size distributions were obtained.