A new approach on improving the fire resistance of polyamide 11 by incorporating sulfur‐based flame retardant

Abstract

In this work, a novel sulfur‐based flame retardant (SA‐M) was synthesized by the self‐assembly of melamine and sulfamic acid. The chemical structure of SA‐M was fully characterized. SA‐M, in company with Al2O3, was then introduced into polyamide 11 (PA 11) by melt compounding in order to improve the fire resistance of the polymer substrate. The observation by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) indicated the well dispersion of SA‐M in PA 11 matrix. The fire performance of PA 11 composites was evaluated by limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter tests, respectively. The results showed that the presence of 17.5% SA‐M and 2.5% Al2O3 increased the LOI value from 22.4% to 30.9%, upgraded the UL‐94 rating from no rating to V‐0, significantly eliminated the melt dripping, and decreased the peak heat release rate from 1024 to 603 kW/m2. The thermal behaviors were investigated by thermogravimeric analysis (TGA) and TGA‐Fourier transform infrared spectroscopy (FTIR). It was suggested that SA‐M took effects mainly in gas phase by diluting the combustible fuel, leading to the improvement of the fire resistance of PA 11.

The preparation of polyamide 11 composites with extremely long ignition time

“…The recorded FTIR spectra of volatile gases that are released from neat PA 11 and PA 11‐15PER samples are shown in Figure 3C–E. It can be seen from Figure 3C that neat PA 11 sample rarely decomposes until the temperature rises to 380°C when the corresponding peaks of CH (2923 and 2853 cm −1 ), CO 2 (2358 cm −1 ), and NH 3 (965 and 930 cm −1 ) can be detected as well as H 2 O (around 3750 and 1505 cm −1 ) 23 . When the temperature is further improved to 420°C, the peak intensity of CH becomes dominant, corresponding to the major degradation of PA 11 chains.…”

“One Stone Two Birds” Strategy of Synthesizing the Battery Material Lithium Sulfide: Aluminothermal Reduction of Lithium Sulfate

“…As the byproduct Al 2 O 3 of the aluminothermal method is a useful material for many applications (such as the catalyst support, polishing material, fire retardant, etc. ), − its value is taken into account for calculating the material cost of making Li 2 S. As shown in Table S3, the material cost of the aluminothermal method ($18.5/kg_Li 2 S) is a little higher than that ($8/kg_Li 2 S) of the conventional carbothermal method, but still much lower than the price of commercially available Li 2 S ($11,445/kg_Li 2 S), indicating still a large profit margin of our method. Moreover, the obtained byproduct Al 2 O 3 can even be directly used as a coating layer on the separator to mitigate the shuttle effect of lithium polysulfides and then enhance the battery performance.…”

Preparation and properties of wear‐resistant and flame‐retardant polyphenylsulfoneurea/monomer casting nylon copolymers

“…In addition, the overall heat release curve shifted downwards with a slower growth rate simultaneously, especially the slow HRR in the beginning of combustion might help slow down the spread of fire. It was believed that the flame‐retardant mechanism of sulfur compounds was to accelerate charring process in the condensed phase, and thus the formation of carbon served as a barrier to heat and mass transfer 25,26 . It was speculated that the sulfur base forms acidic substances during the combustion process, which might be the reason for promoting the formation of char.…”