Insights into Phosphorus-Containing Flame Retardants …
251
Textile materials provide an excellent source of fuel during the burning process,
are found to be a rich source of inflammable or ideal fire carriers like hydrocarbons.
The potential hazards and risks associated with textiles are described in depth by various researchers [1, 2, 7, 11]. In this prospect, textiles with lower flammability are still
experiencing some changes like the improvement in effectiveness and the replacement of toxic chemical products with counterparts that have a low environmental
impact and, more sustainable [4, 5]. Health and environmental concerns associated
with halogenated as well as formaldehyde-based FRs driven R&D for identifying
and utilizing safer alternatives. Because of the social concerns onto eco-preservation
using eco-friendly FRs, the new FRs needs to be halogen-free and formaldehyde-free.
Phosphorus, nitrogen, and silicon-containing compounds are generally considered
as environment-friendly FRs, due to their safer-nature for human-ecosystem and
synergistic effects [6, 14]. The effectiveness of P-based FRs towards fire mainly
because of its characteristics, for example, low water solubility, low volatility, less
dose requirement, less degradation to possibly hazardous substances, and no toxic
emissions [2, 6, 31]. P-based FRs, play a key role possibly in combination with
silicon- or nitrogen-containing structures, to the design of new and efficient FRs for
textile substrates. Mechanistically, phosphorous based FRs, during a fire form poly
and meta-phosphoric acids which form an oxygen-barrier layer [15].
Phosphorus based FRs have been found very reactive to inhibit fire and are used
as thermosets for many substrates such as unsaturated epoxy resins, polyesters or
polyurethanes. These type of substrates contain activated functional groups (i.e.
halogens, alcohols, epoxy, amines etc.), which allow incorporation into the polymer matrix during the process [42, 43]. In case of cotton fibre, organic assembled
phosphorus compounds (i.e. Pyrovatex CP and Pyrovatex CP New) can either with
the cotton fabric to form cross-linked adducts/linked structures with the fibers [48].
In a study, a formaldehyde-free, inorganic-organic hybrid FR was developed and
markedly found inferior FR performance compared with conventional formaldehydecontaining organic phosphorus FR. Lessan et al. [49] investigated the flame retardant behavior of sodium hypophosphite (SHP)—nano-TiO 2 hybrid on woven cotton
fabric through pad-dry-cure process. As a result, decreasing the flammability with
increasing the char formation of the treated fabrics was observed [49].
Despite the use of toxic and not environmentally-friendly chemicals, highmolecular-weight proteins even DNA derived from animal or microbial sources
have been investigated as “green” FRs for cotton fabrics [42, 49]. Current trends
are made towards high-molecular-weight FRs based on P-moiety combined with
polymeric/complex textile substrates impart multifunctional structures will aid in
reducing flammability without a loss of their valuable properties. A novel organic
phosphorus-based flame retardant has reported the enhancement of flame retardancy of cotton fabrics through the high-molecular-weight grafting of cellulosephosphonic acid by Gao et al. [50] as an alternative to halogen-formaldehyde-based
FRs [50]. In this study, an ammonium salt of hexamethylenediamine-N,N,N’,N’tetra(methylphosphonic acid) (AHDTMPA), was fabricated using the reaction of urea
with hexamethylenediamine-N,N,N’,N’-tetra(methylphosphonic acid) (HDTMPA).
Further, new P–O–C covalent bonds were formed by this ammoniated salt reacted
251
Textile materials provide an excellent source of fuel during the burning process,
are found to be a rich source of inflammable or ideal fire carriers like hydrocarbons.
The potential hazards and risks associated with textiles are described in depth by various researchers [1, 2, 7, 11]. In this prospect, textiles with lower flammability are still
experiencing some changes like the improvement in effectiveness and the replacement of toxic chemical products with counterparts that have a low environmental
impact and, more sustainable [4, 5]. Health and environmental concerns associated
with halogenated as well as formaldehyde-based FRs driven R&D for identifying
and utilizing safer alternatives. Because of the social concerns onto eco-preservation
using eco-friendly FRs, the new FRs needs to be halogen-free and formaldehyde-free.
Phosphorus, nitrogen, and silicon-containing compounds are generally considered
as environment-friendly FRs, due to their safer-nature for human-ecosystem and
synergistic effects [6, 14]. The effectiveness of P-based FRs towards fire mainly
because of its characteristics, for example, low water solubility, low volatility, less
dose requirement, less degradation to possibly hazardous substances, and no toxic
emissions [2, 6, 31]. P-based FRs, play a key role possibly in combination with
silicon- or nitrogen-containing structures, to the design of new and efficient FRs for
textile substrates. Mechanistically, phosphorous based FRs, during a fire form poly
and meta-phosphoric acids which form an oxygen-barrier layer [15].
Phosphorus based FRs have been found very reactive to inhibit fire and are used
as thermosets for many substrates such as unsaturated epoxy resins, polyesters or
polyurethanes. These type of substrates contain activated functional groups (i.e.
halogens, alcohols, epoxy, amines etc.), which allow incorporation into the polymer matrix during the process [42, 43]. In case of cotton fibre, organic assembled
phosphorus compounds (i.e. Pyrovatex CP and Pyrovatex CP New) can either with
the cotton fabric to form cross-linked adducts/linked structures with the fibers [48].
In a study, a formaldehyde-free, inorganic-organic hybrid FR was developed and
markedly found inferior FR performance compared with conventional formaldehydecontaining organic phosphorus FR. Lessan et al. [49] investigated the flame retardant behavior of sodium hypophosphite (SHP)—nano-TiO 2 hybrid on woven cotton
fabric through pad-dry-cure process. As a result, decreasing the flammability with
increasing the char formation of the treated fabrics was observed [49].
Despite the use of toxic and not environmentally-friendly chemicals, highmolecular-weight proteins even DNA derived from animal or microbial sources
have been investigated as “green” FRs for cotton fabrics [42, 49]. Current trends
are made towards high-molecular-weight FRs based on P-moiety combined with
polymeric/complex textile substrates impart multifunctional structures will aid in
reducing flammability without a loss of their valuable properties. A novel organic
phosphorus-based flame retardant has reported the enhancement of flame retardancy of cotton fabrics through the high-molecular-weight grafting of cellulosephosphonic acid by Gao et al. [50] as an alternative to halogen-formaldehyde-based
FRs [50]. In this study, an ammonium salt of hexamethylenediamine-N,N,N’,N’tetra(methylphosphonic acid) (AHDTMPA), was fabricated using the reaction of urea
with hexamethylenediamine-N,N,N’,N’-tetra(methylphosphonic acid) (HDTMPA).
Further, new P–O–C covalent bonds were formed by this ammoniated salt reacted