U.S. patent application 20180215983 (applicant Encapsys LLC, Appleton, Wis.):
"The invention discloses a microencapsulated phase change material having a specific Thermal Efficiency Index (TEI). The composition of the invention comprises particles of a microencapsulated phase change material, the particles comprising a core and a shell that encapsulates the core, the shell comprising a polyurea obtained by polymerizing an isocyanate and an amine, prepared by (i) providing a water phase with an emulsifier, (ii) providing an internal phase of a core material and a multifunctional isocyanate soluble or dispersible in the internal phase, (iii) adding the internal phase to the water phase under high speed agitation to form an emulsion comprising droplets of the internal phase dispersed in the water phase and forming a first shell at an interface of the internal phase droplets and water phase mixture, and (iv) adding a multifunctional amine monomer to the emulsion thereby forming additional polyurea shell over the first shell at an interface of the internal phase droplets and water phase mixture. The resulting particles have a Thermal Efficiency Index greater than 0. Microcapsules according to the invention are highly effective at delivering enhanced thermal performance as compared to conventional microcapsules."