Preparation of TPU/GO/Mg-Al LDHs Hybrid Material With Enhancing Flame Retardancy and Smoke Suppression Performance

Flammability of Thermoplastic polyurethane (TPU) limits its application in automotive, wires and cables, sports and textile coatings. Endowing TPU with simultaneously improved flame retardancy and smoke-suppressant will be highly beneficial. Herein, a novel green and efficient condensed phase GO/Mg Al layered double hydroxides (LDHs) flame retardant for TPU was synthesized by the co-precipitation of Mg2+ and Al3+ and assembled with graphene oxide (GO) by electrostatic interaction. The unique two-dimensional layered structure of GO/LDHs has a large specific surface area, which can form a dense and uniform char layer during the combustion process, thus hindering mass and heat transfer between gaseous and condensed phases. The XRD, TEM, SEM and EDS results showed that Mg Al LDHs and GO/LDHs were successfully synthesized. The thermal, flame retarding and smoke suppression properties of TPU/GO/Mg Al LDHs were determinated by UL-94, limiting oxygen index (LOI), cone calorimeter (CCT) and smoke density (SDT). UL-94 testing results showed that all the TPU/GO/Mg Al LDHs samples had a vertical combustion rating of V-0. Compared with pure TPU (19.1. 0.2 %), the LOI value of all TPU/GO/Mg Al LDHs composites are above 27%. CCT results showed TGAL3 sample displayed the lowest peaks of heat release rate (pHRR) value of 142.9 +/- 9.3 Kwm(-2). The total heat release (THR) value of TGAL5 is almost 70% lower than that of pure TPU. In addition, compared to pure TPU, GO/Mg Al LDHs materials has excellent performance in smoke suppression. The digital photos and Raman spectra of char residue demonstrated that TPU/GO/Mg Al LDHs materials has a denser carbon layer after combustion. Apart from flame retarding and smoke suppression, the mechanical properties of TPU/GO/Mg Al LDHs can maintain more than 80% of the original TPU after addition of GO/LDHs. These results indicates that GO/LDHs composites is a kind of two-dimensional layered material with unique structure and excellent flame retardant and smoke suppression.