Design of Poly(cyclotriphosphazene)-Functionalized Zirconium Phosphate Nanoplatelets To Simultaneously Enhance the Dynamic Mechanical and Flame Retardancy Properties of Polyamide 6

Abstract

To obtain polyamide 6 (PA6) composites with improved flame retardancy and thermomechanical properties, highly cross-linked supramolecular poly(cyclotriphosphazene)functionalized α-zirconium phosphate (f-ZrP) nanoplatelets were synthesized and melt-blended with PA6 in a twin-screw extruder. The performance enhancements of composites were investigated through measuring the dynamic mechanical property and observing cone calorimeter data, toxic gas evolution, and UL-94 rating. The thermomechanical performance of PA6 was increased by 37.2% after composite formation with f-ZrP. As for the fire retardancy performance, compared to neat PA6, the composite containing 10 wt % f-ZrP showed 41.7 and 30.4% decrease in the peak heat and total heat release rates, respectively, and the UL-94 rating of the composite was V-0. Moreover, the thermogravimetric analysis combined with infrared spectroscopy revealed that the addition of f-ZrP to the PA6 led to decrease in the evolution of the volatile compounds and toxic gases, with the formation of highly cross-linked P−N-containing dense char with microspheres, providing a strong barrier to the inhibition of the heat and flammable volatile components transferring between the flame zone area and substrate during the combustion test. Finally, based on the obtained results, the possible mechanisms for improved mechanical and fire retardancy properties of the composites were proposed.

Superior flame retardancy, antidripping, and thermomechanical properties of polyamide nanocomposites with graphene‐based hybrid flame retardant

“…This is mainly attributed to the possible internal crosslinking between the polymer matrix and PSGO hybrid nanofiller; the degree of crosslinking increases with increasing PSGO content in the PA6 composite, and thus strengthening the storage energy 22,41 . The tan δ plots (Figure 5b) clearly show two peaks corresponding to the α and β for pristine PA6 and its FR composites, as explained in our previous work 42 . The β transition peak is observed at approximately −75°C owing to the damping of carbonyl group of PA6, which is in part of formation of hydrogen bonds with absorbed water.…”

“…22,41 The tan δ plots (Figure 5b) clearly show two peaks corresponding to the α and β for pristine PA6 and its FR composites, as explained in our previous work. 42 The β transition peak is observed at approximately À75 C owing to the damping of carbonyl group of PA6, which is in part of formation of hydrogen bonds with absorbed water. The α transition appeared at a higher temperature with a high peak intensity and was considered as the glass transition temperature (T g ).…”

Terminal group effects of DOPO-conjugated flame retardant on polyamide 6: Thermal stability, flame retardancy and mechanical performances

“…However, the effect of active terminal group in the molecules on the flame retardant efficiency have not been considered. Numerous researches have proved that active terminal groups such as epoxide or amino groups in flame retardants or flame retardant synergists have strong interaction with amino or carboxyl end-groups of polymer molecules by coupling reaction ( Liang et al, 2019 ; Xu et al, 2019 ) or hydrogen bonding ( Malkappa et al, 2020 ; Chen et al, 2017 ). The strong interaction between flame retardants and polymer matrix can improve the interfacial compatibility and promote the uniform dispersion of the flame retardants, which will be beneficial for improving the flame retardancy and thermomechanical or mechanical performance ( Zhou et al, 2021b ).…”