Meaning
Polymerized shells composed of multi-functional amines and isocyanates provide robust containment for active ingredients in self-healing coatings and adhesives. These specialized structures, known as polyurea microcapsules, protect the core material from moisture and premature reaction until triggered by stress. They are designed to survive the high-temperature and high-shear environments of polymer processing, ensuring the active agent remains intact.
This high level of stability makes them valuable for advanced composite materials, especially in demanding automotive applications.
Thermal Resistance
These microcapsules show excellent thermal stability, often withstanding temperatures up to two hundred and fifty degrees Celsius without rupturing. When polyurea microcapsules are mixed into thermoplastic melts, their resilient crosslinked shells prevent any leakage of the encapsulated compound. This resistance allows their use in standard compounding equipment for engineering plastics.
Activation Trigger
Mechanical shear or physical damage to the polymer matrix ruptures the shell, releasing the active liquid core to initiate repair or signaling. The thickness of the shell is engineered to balance processing survival against ease of activation in the final product. A shell that is too thick will not rupture, rendering the self-healing function useless.
Material Formulation
The synthesis of the shell is controlled by adjusting the ratio of amine to isocyanate monomer during the emulsion polymerization process. This adjustment determines both the capsule size and the shell porosity. Achieving the correct balance is essential to prevent the slow leaching of the core material over time.
