Molecular Design of Novel Poly(urethane-urea) Hybrids as Helmet Pads for Ballistic and Blast Trauma Mitigation

Abstract : Polyurethane (PU) and poly(urethane urea) (PUU) based foams are currently being used as helmet pad materials. The U.S. Army still has a critical need for more efficient foam pad materials and designs that will provide warfighters with improved survivability against blast-induced traumatic brain injuries. Recent work has shown that tailoring the microphase-separated morphology is critical in controlling the high strain-rate mechanical deformation of bulk PU and PUU elastomers. In this work we focused on molecular influence and have successfully synthesized select model PU and PUU elastomers incorporating triptycene moieties. Adding triptycene-1,4 hydroquinone resulted in a 9C increase in the soft segment glass transition temperature compared to hydroquinone-containing PU. The 1,4-diaminotriptycene modified PUUs revealed improved tensile modulus and flow stress, which correlated well with the rubbery plateau modulus data determined from dynamic mechanical analysis and with the interdomain-correlation data from the small-angle X-ray scattering measurements.