Improving Reaction to Fire Properties of Thermoplastic Polyurethane with Intumescent Flame Retardants and MoS۲

Two-dimensional molybdenum disulfide (MoS۲) is used as a promising flame retardant and smoke suppressant nano additive in polymer composites due to its high thermal stability and layered structure. In this study, thermoplastic polyurethane (TPU) was melt-blended with MoS۲ (۱wt. %) and a halogen-free intumescent flame retardant (IFR) system. The IFR system consisted of ammonium polyphosphate (APP), Melamine polyphosphate (MPP), and pentaerythritol (PER), with a total amount of ۲۵ wt. %. The TPU/IFR/MoS۲ composite exhibited outstanding flame-retardant properties, achieving a UL-۹۴ V-۰ rating and a limiting oxygen index (LOI) value of ۳۴%. Reaction-to-fire performance of the TPU/IFR/MoS۲ composite was evaluated by cone calorimeter test (CCT). The CCT results indicated high flame-retardant efficiency and considerable smoke suppression performance, along with a significant decrease in the peak heat release rate (PHRR: ۶۵.۹%), peak smoke production rate (PSPR: ۶۵.۶%), and peak CO production (PCOP: ۶۰.۷%) compared to the neat TPU. The significant improvement in fire performance of TPU composite was mainly attributed to the effects of the physical barrier of MoS۲ and catalytic carbonization of the IFR system. These resulted in forming an intumescent compact carbonized layer during the combustion, effectively restricting dripping. The continuous structure of the residual char was revealed by FESEM. Thermogravimetric analysis (TGA) indicated improved thermal behavior of the TPU composite in high temperatures. This work provides an effective method to improve the reaction to fire of TPU composites by incorporating traditional IFRs and MoS۲, resulting in enhanced fire safety.

Keywords:

Reaction to fire- , Intumescent flame retardant , MoS۲ , Thermoplastic polyurethane , Heat release rate