Qualifying carbon nanotube reinforced polyurethane foam as helmet inner liner through in-situ, static and low velocity impact testing

Helmet inner liner (HIL) is a critical component of helmets which ensures safety and comfort of the wearer. Efforts are made in this work to qualify polyurethane (PU) foams for HIL application. Processing temperature and weight fraction of carbon nanotubes (CNTs) nanofillers is varied to optimize the microstructure and hence average properties of PU foams. Experimental results show that PU foam processed at −5 °C and reinforced with 1.6 wt% of oxidized CNTs shows 40% higher specific elastic modulus and 11% better recovery under compression testing, absorbs 97% more energy per unit volume in comparison to EPS under low velocity impact in drop weight tests. The 34% higher thermal conductivity than EPS implies that it will provide better comfort by efficiently dissipating the heat generated in helmet. The superior combination of properties makes CNT reinforced PU foams a better alternative as HIL in comparison to currently used EPS foam.