Fully bio-based fire-safety viscose/alginate blended nonwoven fabrics: thermal degradation behavior, flammability, and smoke suppression

Suppression of Smoldering of Calcium Alginate Flame-Retardant Paper by Flame-Retardant Polyamide-66

“…The Ca-Alg fiber affected the thermal-oxidative degradation process of FR-PA and greatly reduced the R max (at 429 °C) of FR-PA. This may be related to the fact that calcium ions in Ca-Alg fibers catalyze specific chemical reactions during thermal oxidative degradation, such as carbonization, dehydration, and cyclization, thus reducing the rate of thermal degradation [ 18 , 19 , 29 , 49 ]. In the high-temperature region (500–800 °C), the R max (about at 552 °C) of composite paper was lower than that of Ca-Alg paper, T max s occurred earlier, and the char residues increased.…”

“…In the third stage of thermal degradation (350–600 °C, T max is 420 °C) of the FR-PA/Ca-Alg (30/70) composite paper, the peak at 2935 cm −1 is attributed to the vibration of aliphatic C–H groups, the bands at 1763 and 1706 cm −1 are ascribed to the C=O vibration of aldehydes and ketones, respectively, and the bands at 1625, 1505 and 1452 cm −1 are attributed to the C=C stretching vibration of the aromatic ring. In addition, the band at 1141 cm −1 is assigned to C–O–C vibration, while the peaks at 963 and 927 cm −1 are ascribed to NH 3 , which is a specific pyrolysis gas of FR-PA [ 29 ]. Compared with FR-PA, the peaks at 1625 and 1452 cm −1 decreased and the peak at 1763 cm −1 increased for the FR-PA/Ca-Alg composite paper, indicating that Ca-Alg changed the degradation process of FR-PA, reduced the formation of NH 3 and aromatic products, and increased the formation of aldehyde products.…”

“…Compared with FR-PA, the peaks at 1625 and 1452 cm −1 decreased and the peak at 1763 cm −1 increased for the FR-PA/Ca-Alg composite paper, indicating that Ca-Alg changed the degradation process of FR-PA, reduced the formation of NH 3 and aromatic products, and increased the formation of aldehyde products. It is possible that the Ca 2+ ions from the Ca-Alg fibers catalyze the char formation of FR-PA [ 18 , 19 , 29 , 49 ], reduce the generation of volatile combustibles, and the resulting char deposited on the surface of the Ca-Alg fibers inhibits the smoldering of Ca-Alg. Moreover, the absorption intensity of hydrocarbons, ether components and NH 3 for FR-PA/Ca-Alg are lower and the absorption intensities of CO 2 are higher than those of FR-PA.…”

“…Moreover, the absorption intensity of hydrocarbons, ether components and NH 3 for FR-PA/Ca-Alg are lower and the absorption intensities of CO 2 are higher than those of FR-PA. According to the Lambert–Beer law [ 29 ], this means that the degradation of the composite paper produces more non-combustible gases and less combustible gases, which inhibits the spread of flame after ignition.…”

“…Blending is a low-cost and high-efficiency method of mixing two or more kinds of materials to maximize their respective advantages [ 29 ]. Studies have confirmed that the flame retardancy of materials can be improved by blending different components in a certain proportion, such as flame-retardant viscose/alginate fibers, flame-retardant cotton/alginate fibers, and flame-retardant vinylon/poly(m-phenylene isophthalamide) fibers, among others [ 21 , 29 , 30 , 31 , 32 , 33 ]. However, not all fibers can improve their flame retardancy by blending, but it depends on whether there is a condensed or gas phase interaction between the blended fiber components during combustion [ 32 , 34 ].…”