CONCLUSIONS
The glass transition temperature of the starting isocyanate trimers highly influences the properties of the final urethane coatings:
- the IPDI trimer gives harder coatings, with lower water permeabilities than the corresponding HDI based materials.
Considering each class of materials (from IPDI or HDI), the fluorine content plays a relevant role:
- the higher the fluorine percentage, the lower the water absorption into the coatings.
The chain length of the polyols used for the synthesis of the prepolymers is a variable which exhibits great influence on the coating properties:
- coatings containing shorter PFPE segments show better barrier properties.