Major developments in the area of blast mitigation using polyurea coatings as retrofit or existing structures are discussed.

The increasing usage of polyurea coatings has attracted the attention of researchers worldwide. Commercial polyurea formulations contain chain extenders as an essential ingredient, which increases the possibility of intermolecular H-bonding by bringing the urea linkages closer. In this work, we establish the effect of increasing chain length of chain extender on the material properties of the polymer. Different types of chain extender were blended with a long chain diamine and subsequently reacted with an MDI-based isocyanate prepolymer through a reactive spray processing technique. Polyurea coatings containing aromatic chain extenders were found to exhibit higher tensile strength as compared to their aliphatic analogues. Increasing the chain length of the aliphatic chain extender led to a reduction in the mechanical strength. A suitable combination of aromatic and aliphatic chain extender of short length was found to force the macromolecule to orient in such a fashion so as to result in optimal H-bonding. This manifested in terms of improved processability, as confirmed by chemorheological investigations. Fourier transform infrared spectroscopy was used to understand the Hbonded internal structure of the polymer. Optimum H-bonding resulted in improved mechanical properties of the spray-coated polyurea.The structure-property relationship of polyurea can be adjusted primarily by three factors: choice of the monomer pairs, polymer composition, and its final macromolecular architecture. 11 In view of the above, it is possible to design formulations by varying the isocyanates and amines to result in coatings displaying a range of properties. Much like the diisocyanates, aliphatic or aromatic amines and chain Additional Supporting Information may be found in the online version of this article.

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