Fabrication of a hybrid from metal organic framework and sepiolite (ZIF-8@SEP) for reducing the fire hazards in thermoplastic polyurethane

Aluminum hypophosphite (AHP) is an effective flame retardant to thermoplastic polyurethane (TPU), but it also results in increase on smoke release caused by the presence of phosphorus groups. In this work, a novel synergistic flame retardant was fabricated from metal organic framework (ZIF-8) and sepiolite (SEP). For the compsosite of TPU/8.0AHP/1.0ZIF-8@SEP, limiting oxygen index (LOI) reached 27.5% and it satisfied the UL-94 V-0 grade. The heat release rate and the total heat release decreased by 78.9% and 39.1% compared with the control TPU respectively. The increased smoke production caused by AHP was partly adsorbed by ZIF-8@SEP, therefore, the sample of TPU/8.0AHP/1.0ZIF-8@SEP showed the lowest smoke release in cone calorimeter test. Unsimilar as other flame retardant, the using of 8.0AHP/1.0 ZIF-8@SEP just brought less than 2.0% loss on tensile strength and 7.8% drop on the elongation at break of TPU. Consequently, the ZIF-8@SEP was documented as excellent synergistic flame retardant for TPU and it brought limited damage on mechanical performance.