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.
Highlights
Textiles play a significant role in our daily life
The ternary blends containing industrial lignin (KL or LL) and zinc phosphinate (ZnP) were transformed into multifilament yarns by melt spinning process and knitted fabric structures were developed
Tensile testing results have shown the mechanical properties of PA-LL-ZnP multifilaments were lowered than PA-KL-ZnP due to poor dispersion of LL particles in the Polyamide 11 (PA11) matrix that has explained the failure of getting fabric structures for these blends
Summary
Textiles play a significant role in our daily life. Most textile fibres and fabrics are made of petroleum-based thermoplastic polymers, which are flammable and present a potential fire risk.Flame retardant (FR) materials have been developed to reduce the risk either by inhibiting the possibility of the textile material ignition or reduction of the rate of heat release during flame spread.Halogen-based FR compounds, which have been in use since the 1930s, are still widely used and very efficient to enhance the fire-retardant behavior of textile materials. Most textile fibres and fabrics are made of petroleum-based thermoplastic polymers, which are flammable and present a potential fire risk. Due to the persistency, bioaccumulation and toxicity of certain halogenated compounds to human health and stringent fire safety regulations, the scientific and industrial communities have been forced to find alternative sustainable solutions [1,2]. To this end there has been a strongly growing interest in sustainable resources, especially in the development of flame retardant systems made of biobased resources as environmentally-friendly non-halogenated alternatives [3,4,5]
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