Abstract:

Objective Poplyphenylene sulfide (PPS) fiber has outstanding performance and cost advantage, and can be used for making heat protection fabrics. However, when it burns, the release of heat and smoke is likely to cause damage to human body. The loose charcoal layer of its combustion will lead to high thermal and smoke release, which will cause harm to the human body. This paper is proposed to improve the structure of PPS burning charcoal layer to achieve low release of heat and smoke, and explores the applications of PPS in engineering thermal protection fabrics.
Method Based on the obstruction effect of graphene (G) and its application in the field of flame retardancy, graphene was introduced to the PPS matrix and melting spinning was adopted to prepare PPS/G fiber. In the study, the crystallinity and orientation structures of the fiber were explored by differential scanning calorimeter and an X-ray diffractometer, and the mechanical properties of the fiber were also investigated. The PPS/G fiber was made into fabrics, cone is adopted to study the heat and smoke release of combustion, and the Raman maps and SEM images of the burning charcoal layer were adopted to clarify the changing mechanism of combustion behavior.
Results PPS/G fibers were prepared by introducing graphene into the PPS matrix, and its microstructure and physical images suggested the characteristics of smoothness and uniformity, indicating that graphene can be well dispersed in the PPS matrix and that the fiber forming process is relatively stable. The mechanical properties of PPS/G fibers were positively influenced by graphene, and the breaking strength and elongation at break were both improved prominently (Fig.3). When the content of graphene was 0.5%, the breaking strength of the fiber was increased to 4.63 cN/dtex, while when the content of graphene was 0.3%, the elongation at break was increased to 22.01%. The improvement of mechanical properties is very beneficial for the application of fiber. In the aspect of combustion performance, the addition of graphene has a significant inhibitory effect on smoke release and heat release. The doped of graphene reduced the peak heat release rate (PHRR) of PPS from 67 kW/m² to 28 kW/m², the total heat release (THR) was reduced from 3.38 MJ/m² to 1.28 MJ/m², and the total smoke production was reduced from 1.055 m² to 0.358 7 m² (Fig.5). All these can be attributed to the change of combustion residual carbon. On the one hand, the quality of combustion residual carbon was significantly improved, at 800 ℃, the residual carbon content of PPS/G fiber was significantly higher than that of pure PPS (Fig.4). On the other hand, the change in structure of carbon residue was obvious. The compactness of the residual carbon is significantly increased, and the carbon layer of PPS/G fabric exhibited a non-porous nature (Fig.6). It is found that the graphitization degree of carbon layer was also significantly increased (Fig.7). The conversion of carbon content and structure is beneficial to inhibit the heat and smoke release, which is the key to the change of PPS/G fabric combustion performance.
Conclusion With the addition of graphene, the barrier effect of carbon layer in PPS/G combustion was effectively increased, and the heat release and smoke release of PPS fabric were significantly reduced. However, for the demand of thermal protection fabric, the blending and other processes need to be further explored to achieve higher heat blockage and smoke inhibitory effects. New solutions that meet the advantages of price and heat protection need to be further sought.

Key words: nanofiber, composite fiber, thermal protection fabric, polyphenylene sulfide, graphene, heat release, smoke release