Effect of Aromatic Chain Extenders on Polyurea and Polyurethane Coatings Designed for Defense Applications

The present work describes the synthesis of new versatile polyurea (PU) and polyurethane (PUR) matrices, including different chain extenders, which facilitate the design of distinct, tunable properties, and high-performance derivatives. These polymers can be used for various defense and security applications, such as coatings for ballistic protection, CBRN protection, binders for energetic formulations, etc. Combining aliphatic and aromatic molecules in PU or PUR structures enables the synthesis of polymers with improved and controllable thermo-mechanical properties. Thus, for polyurea synthesis, we utilized two types of polymeric aliphatic diamines and three types of aromatic chain extenders (1,1'-biphenyl-4,4'-diamine, benzene-1,2-diamine, and 1,2-diphenylhydrazine). An analogous method was used to synthesize polyurethane films by employing one polymeric aliphatic polyol and three types of aromatic chain extenders (benzene-1,3-diol, benzene-1,4-diol, and benzene-1,2,3-triol). Subsequently, various analytic techniques (Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), single cantilever dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), frequency-dependent shear modulus survey, tensile tests, water contact angle measurements, and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX)) have been utilized to characterize the synthesized materials and to evaluate the influence of each chain extender on their final properties.