Linking Nanoscale Chemical Changes to Bulk Material Properties in IEPM Polymer Composites subject to Impact Dynamics.

A synthesizable Interfacial Epoxy-Polyurea hybridized-Matrix (IEPM), comprised of chemical bonded nanostructures across an interface width ranging between 2 μm to 50 μm, is a candidate for dialing-in molecular vibrational properties and providing high-impact dynamics resistance to conventional Fiber(x)-Reinforced Epoxy (F/E), engendering an x-Hybrid-polymeric Matrix Composite system (x-HMC / IEPM-tc). Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) elucidate interfacial nanoscale morphology and chemical structure via reaction kinetics of curing epoxy (as a function of time, tc) and fast-reacting (pre-polymerized) polyurea. Nano-Infrared Spectroscopy (nano-IR) spectra reveal that simultaneous presence of characteristic epoxy and polyurea vibrational modes, within a nanoscale region, indicates chemical bonding, enabling IEPM reaction kinetics, as a function of tc, to control natural bond vibrations and type / distribution of interfacial chemical bonds and physical mixtures, likely due to the bond mechanism between -NCO in polyurea, and epoxide and -NH2 in epoxy hardener (corresponding to characteristic absorption peaks in nano-IR results), leading to enhanced IEPM quality (fewer defects/ voids). Dynamic Mechanical Analysis (DMA) and test results of ballistics-resistant panels, integrated with thin intermediate layers of x-HMC / IEPM-tc, confirm that lower tc significantly enhances loss modulus (∝ material damping) in impact dynamics environments.