Development of Novel Polyamide 11 Multifilaments and Fabric Structures Based on Industrial Lignin and Zinc Phosphinate as Flame Retardants

Abstract

Biobased lignin represents one of the possible materials for next-generation flame retardant additives due to its sustainability, environmental benefits and comparable efficiency to other flame retardant (FR) additives. In this context, this study presents the development of FR polyamide 11 (PA11) multifilament yarns and fabric structures containing different industrial lignins (i.e., lignosulfonate lignin (LL), and Kraft lignin (KL)) and zinc phosphinate (ZnP). The combination of ZnP and lignin (KL or LL) at different weight ratios were used to prepare flame retarded PA11 blends by melt mixing using a twin-screw extruder. These blends were transformed into continuous multifilament yarns by the melt-spinning process even at a high concentration of additives as 20 wt%. The mechanical test results showed that the combination of KL and ZnP achieved higher strength and filaments showed regularity in structure as compared to the LL and ZnP filaments. Thermogravimetric (TG) analysis showed the incorporation of lignin induces the initial decomposition (T5%) at a lower temperature; at the same time, maximum decomposition (Tmax) shifts to a higher temperature region and a higher amount of char residue is reported at the end of the test. Further, the TGA-FTIR study revealed that the ternary blends (i.e., the combination of LL or KL, ZnP, and PA11) released mainly the phosphinate compound, hydrocarbon species, and a small amount of phosphinic acid during the initial decomposition stage (T5%), while hydrocarbons, carbonyls, and phenolic compounds along with CO2 are released during main decomposition stage (Tmax). The analysis of decomposition products suggests the stronger bonds formation in the condensed phase and the obtainment of a stable char layer. Cone calorimetry exploited to study the fire behavior on sheet samples (polymer bulk) showed an improvement in flame retardant properties with increasing lignin content in blends and most enhanced results were found when 10 wt% of LL and ZnP were combined such as a reduction in heat release rate (HRR) up to 64% and total heat release (THR) up to 22%. Besides, tests carried out on knitted fabric structure showed less influence on HRR and THR but the noticeable effect on postponing the time to ignition (TTI) and reduction in the maximum average rate of heat emission (MARHE) value during combustion.

Flammability Tests and Investigations of Properties of Lignin-Containing Polymer Composites Based on Acrylates

“…Combination of the phosphorus-based additives with the nitrogen-containing products, like melamine cyanurate, melamine phosphate, or melamine polyphosphate, exhibit high performance because of synergistic effects [ 30 ]. In turn, the bio-based flame retardants composed of lignin represent one of the most promising trends for new-generation flame retardants due to their sustainability and environmental benefits [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Moreover, the exploitation of other biomacromolecules as effective flame retardants for textiles was also studied [ 38 ].…”

Insights into the Sustainable Development of Lignin‐Based Textiles for Functional Applications

“…Mandlekar et al. [ 87 ] developed multifilament yarns and fabric designs of polyamide 11 (PA11) carrying various types of industrial lignins such as lignosulfonate lignin (LL), Kraft lignin (KL), and LL/zinc phosphinate (ZnP). PA11 blends were prepared by melt mixing employing a twin‐screw extruder.…”

Experimental Investigation of the Tensile Behavior of Selected Tire Cords Using Novel Testing Equipment

“…The newest application of polyamide and aramid fibers is 3D printing. They are used for example as PCL scaffold reinforcement [16] and filaments [17] or multifilaments [18].…”