Abstract
Polyamide 6 (PA6) is a widely-used polymer that could find applications in various sectors, including home textiles, transportation or construction. However, due to its organic nature, PA6 is flammable, and flame-retardant formulations have to be developed to comply with fire safety standards. Recently, it was proposed to use ammonium sulfamate as an effective flame retardant for PA6, even at low loading content. However, processing issues could occur with this additive considering large-scale production. This paper thus studies the use of another sulfamate salt—guanidine sulfamate (GAS)—and evidences its high efficiency when combined with melamine polyphosphate (MPP) as a flame retardant for PA6. A decrease of the peak of the heat release rate by 30% compared to pure PA6 was obtained using only 5 wt% of a GAS/MPP mixture in a microscale calorimeter. Moreover, PA6 containing the mixture GAS/MPP exhibits a Limiting Oxygen Index (LOI) of 37 vol% and is rated V0 for the UL 94 test (Vertical Burning Test; ASTM D 3801). The mechanisms of degradation were investigated analyzing the gas phase and solid phase when the material degrades. It was proposed that MPP and GAS modify the degradation pathway of PA6, leading to the formation of nitrile end-group-containing molecules. Moreover, the formation of a polyaromatic structure by the reaction of MPP and PA6 was also shown.
Highlights
The organic nature of polymers, like polyamide 6 (PA6), is an issue in terms of flammability for certain applications
The first part of this paper aims at investigating, at the lab scale, the influence of the guanidine sulfamate (GAS)/melamine polyphosphate (MPP) ratio on the fire performance of PA6/GAS/MPP evaluated according to micro-scale combustion calorimetry (MCC)
The total heat release (THR) is only slowly affected by the substitution of GAS by MPP, and the differences between the samples remain in the range of the error
Summary
The organic nature of polymers, like polyamide 6 (PA6), is an issue in terms of flammability for certain applications. In order to comply with these requirements, fire retardants (FR) are usually added to the polymer when melted during extrusion. Ammonium sulfamate was effectively added to PA6 fibers to improve their fire behavior; it was shown that the FR loadings and processing parameters might be issues regarding the matrix degradation, because of the high temperature usually involved in PA6 processing [3]. This was attributed to the release of ammonia from AS, leading to aminolysis of the PA6 during processing. This could limit the use of AS as a flame retardant for PA6 at an industrial scale
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