Synthesis and characterization of partially silane-terminated polyurethanes reinforced with acid-treated halloysite nanotubes for transparent armour systems

In the present work, nanocomposites based on the partially silane-terminated polyurethanes reinforced with sulfuric acid-treated halloysite nanotubes were synthesized and evaluated as a potential candidate for transparent blast resistant configurations. The polyurethane must present high tensile ductility at high strain rates to be able to contain fragments and increase the survivability of the system. Gas-gun spall experiments were conducted to measure the dynamic tensile strength (spall strength) and fracture toughness of the nanocomposite and neat polyurethane. The nanocomposite presented a 35% higher spall strength and 21% higher fracture toughness compared to the neat polyurethane while maintaining transparency. The recovered samples following the spall tests were analysed via scanning electron microscope fractographies. The nanocomposite and neat polyurethane samples were chemically characterized via Fourier transform infrared spectroscopy and melting behaviour via differential scanning calorimetry. The improved properties can be attributed, in large part, to the presence of more rigid spherulitic structures, and a rougher fracture surface constituting of several micro-cracks within the nanocomposite.