Encapsulation of reactive components in polyurethane systems

Identifier:  TDX:3821

Handle: https://hdl.handle.net/20.500.11797/TDX3821

Authors:  Bouvier, Quentin

Abstract:
Nowadays polyurethanes are widely used in the coating and adhesive industry. Many different technologies exist to apply coatings and adhesives on substrates and technologies in which crosslinking or adhesion could be controlled are of greatest interest. Indeed, this would offer new possibilities for complex coating/adhesive systems. For this purpose, special reagents called blocked polyisocyanates have already been developed; they are derivatives of isocyanates which can only be activated via thermal trigger. In a similar approach, the encapsulation and controlled release of polyurethane formulation components would offer new perspectives toward enhanced technologies. First, the nanoencapsulation of metal-based catalysts into polycaprolactone nanocapsules was successfully performed by emulsion-solvent diffusion and nanoprecipitation. Improved encapsulation efficiency was obtained when the nanocapsules were loaded with a mixture of the catalyst and glyceryl trioctanoate, as well as when the nanocapsules were synthesized with charged outer surfaces. Implementation of these nanocapsules into polyurethane coatings showed that they are suitable for the preparation of thermoresponsive coatings. Then, the encapsulation of polyisocyanates was successfully achieved, either in polyurea microcapsules by interfacial polycondensation, or in polycaprolactone nanocapsules by nanoprecipitation. The encapsulation process and the long-term stability of the microcapsules was greatly improved by working on the polyurea shell properties, however, the microcapsules still remain fragile over time and could not be used industrially. The nanoencapsulation of polyisocyanates showed the isocyanate-water side-reaction is particularly challenging to avoid and it suggested that water-free encapsulation technique, such as spray congealing, should be investigated.