The compounds shown can also be used to synthesize FR PUs, as shown in
Scheme 4.10 [101–103]. Different types of phosphazene-containing PUs were
synthesized, which exhibited high FR activity and thermal stability [104–106].
Mathew et al. [101] synthesized various cyanate derivatives from hydroxyl phenyl
cyclotriphosphezenes and further prepared cross-linked network polymers with
varying percentages of phosphazene and triazine. The resulting polymers displayed
strong FR activity due to the high crosslink density and char residue formation.
PUs have found major applications as fire-proofing additives in textiles, plastics,
foams, synthetic fabrics, and rubbers. Dez et al. [107] synthesized PUs from
derivative compounds of cyclotriphosphazene-containing hydroxyl groups and
diisocyanates as shown in Scheme 4.10, and they observed that the prepared PUs
exhibited high thermal stability and heat resistance. Most of the reported studies
indicate that cyclotriphosphazene derivative-containing polymers exhibit excellent
FR activity without dripping; however, Dez et al. [107] did not study the FR
activity. Chen-Yang et al. [108] synthesized a reactive flame retardant EPPZ
[(4-diethoxyphosphoryloxyphenoxy) (4-hydroxyphenoxy) cyclotriphosphazene]
and used it as a FR to prepare FR PUs. The results indicate that with increasing
EPPZ content in the PUs, the tensile strength, LOI values, and char yield improved.
Further, the EPPZ-containing PUs showed excellent anti-dripping and flameextinguishing ability. Similarly, Yuan et al. [109] prepared diphenylphosphoryloxyphenoxy)(4-hydroxyphenoxy)cyclotriphosphazene (PPPZ)-containing PUs and
studied their thermal, mechanical, and FR properties. The results revealed that the
LOI values significantly increased with increasing PPPZ content in the PUs due to
the aromatic groups in PPPZ containing cyclophosphazenes. Although most
phosphorus-containing FR PUs are thermally less stable than phosphorus-free PUs,
PPPZ-PUs are thermally more stable than the corresponding normal PUs. A novel
Scheme 4.9 Structures of cyclophosphazenes containing –OH, –NH 2 , aryl, and vinyl groups.
Redraw on the basis of information available in [108, 110, 114, 116]
30
4 Types of Flame Retardants Used for the Synthesis of …
Scheme 4.10 [101–103]. Different types of phosphazene-containing PUs were
synthesized, which exhibited high FR activity and thermal stability [104–106].
Mathew et al. [101] synthesized various cyanate derivatives from hydroxyl phenyl
cyclotriphosphezenes and further prepared cross-linked network polymers with
varying percentages of phosphazene and triazine. The resulting polymers displayed
strong FR activity due to the high crosslink density and char residue formation.
PUs have found major applications as fire-proofing additives in textiles, plastics,
foams, synthetic fabrics, and rubbers. Dez et al. [107] synthesized PUs from
derivative compounds of cyclotriphosphazene-containing hydroxyl groups and
diisocyanates as shown in Scheme 4.10, and they observed that the prepared PUs
exhibited high thermal stability and heat resistance. Most of the reported studies
indicate that cyclotriphosphazene derivative-containing polymers exhibit excellent
FR activity without dripping; however, Dez et al. [107] did not study the FR
activity. Chen-Yang et al. [108] synthesized a reactive flame retardant EPPZ
[(4-diethoxyphosphoryloxyphenoxy) (4-hydroxyphenoxy) cyclotriphosphazene]
and used it as a FR to prepare FR PUs. The results indicate that with increasing
EPPZ content in the PUs, the tensile strength, LOI values, and char yield improved.
Further, the EPPZ-containing PUs showed excellent anti-dripping and flameextinguishing ability. Similarly, Yuan et al. [109] prepared diphenylphosphoryloxyphenoxy)(4-hydroxyphenoxy)cyclotriphosphazene (PPPZ)-containing PUs and
studied their thermal, mechanical, and FR properties. The results revealed that the
LOI values significantly increased with increasing PPPZ content in the PUs due to
the aromatic groups in PPPZ containing cyclophosphazenes. Although most
phosphorus-containing FR PUs are thermally less stable than phosphorus-free PUs,
PPPZ-PUs are thermally more stable than the corresponding normal PUs. A novel
Scheme 4.9 Structures of cyclophosphazenes containing –OH, –NH 2 , aryl, and vinyl groups.
Redraw on the basis of information available in [108, 110, 114, 116]
30
4 Types of Flame Retardants Used for the Synthesis of …