A novel impact hardening polymer with negative Poisson's ratio for impact protection

Although lots of impact protective materials reported exhibited better impact protective performance thanking to their excellent mechanical performance, their applications were still seriously impeded due to absence of soft-stiffness switch smartness. Herein, a novel impact hardening polymer (IHP) with negative Poisson's ratio was synthesized via a condensation polymerization, followed by a simple thermal annealing to achieve a perfect soft-stiffness switch characteristic and self-healing capacity. Its soft-stiffness switch ability sigma, defined as G'(max)/G'(min) in rheological analysis, can reach 9000, which is never reported so far. The result of laser speckle scatter measurement elucidates that IHP has negative Poisson's ratio, which is the root cause why IHP exhibits soft-stiffness switch capacity. Finally, 3D composite anti-impact fabrics were prepared by dip-coating IHP dispersion onto a 3D porous polyester fabric. Not only the impact protective performance of anti-impact fabrics finished with the IHP is significantly improved, but also the flexibility and hand feeling of anti-impact fabrics finished with the IHP are obviously very good because the IHP is flexible without impact. (C) 2015 Elsevier Ltd. All rights reserved.