Chapter 4
Types of Flame Retardants Used
for the Synthesis of Flame-Retardant
Polymers
Currently, a variety of chemical compounds are being used as Flame-retardants
(FRs) and they can be classified according to the type of element present, such as
phosphorus, nitrogen, silicon, boron, or halogens. Halogenated FRs are not environmentally friendly as they tend to release toxic corrosive gases and dense smoke
while burning. Therefore, halogenated FRs have been banned in the USA, Europe,
and several other countries. As mentioned earlier, fire retardants containing phosphorus or nitrogen are being focused upon nowadays and numerous efforts are
concentrated towards developing P-, N-, and P & N-containing FRs for the synthesis of effective FR polymers. A brief summary and applications of these
halogen-free FR polymers is included in the following sections.
4.1 Nitrogen-Based FRs
Nitrogen-containing FRs are one of the most important groups of halogen-free FRs
and are widely used for the synthesis of FR polymers. Organic nitrogen-based
compounds, such as melamine, guanidine, and their derivatives are widely used for
various applications. For example, melamine is used in flexible PU cellular plastics,
melamine cyanurate is applied in unreinforced nylons, guanidine sulfamate is used
as a FR in PVC wall coverings, and guanidine phosphate is used as a FR for textile
fibers [1, 2]. Melamine is a type of hetero cyclic nitrogen-rich compound; it is
crystalline and thermally stable with a high melting temperature of 345 °C. At high
temperatures, melamine decomposes endothermally, which means that it acts as a
heat sink during combustion and releases non-combustible ammonia gas. Further, it
also forms thermally stable condensed compounds, including melam, melem, and
melon, which produce a strong char structure [3]. Therefore, most nitrogen
derivative-containing polymers exhibit FR activity as they act like heat sinks and
evolve non-flammable gases, such as N 2 , NH 3 , CO 2 , and H 2 O into the flame zone
area, which cool it down and dilute oxygen concentration. Su et al. [4] synthesized
© Springer Nature Switzerland AG 2020
S. Sinha Ray and M. Kuruma, Halogen-Free Flame-Retardant
Polymers, Springer Series in Materials Science 294,
https://doi.org/10.1007/978-3-030-35491-6_4
15
Types of Flame Retardants Used
for the Synthesis of Flame-Retardant
Polymers
Currently, a variety of chemical compounds are being used as Flame-retardants
(FRs) and they can be classified according to the type of element present, such as
phosphorus, nitrogen, silicon, boron, or halogens. Halogenated FRs are not environmentally friendly as they tend to release toxic corrosive gases and dense smoke
while burning. Therefore, halogenated FRs have been banned in the USA, Europe,
and several other countries. As mentioned earlier, fire retardants containing phosphorus or nitrogen are being focused upon nowadays and numerous efforts are
concentrated towards developing P-, N-, and P & N-containing FRs for the synthesis of effective FR polymers. A brief summary and applications of these
halogen-free FR polymers is included in the following sections.
4.1 Nitrogen-Based FRs
Nitrogen-containing FRs are one of the most important groups of halogen-free FRs
and are widely used for the synthesis of FR polymers. Organic nitrogen-based
compounds, such as melamine, guanidine, and their derivatives are widely used for
various applications. For example, melamine is used in flexible PU cellular plastics,
melamine cyanurate is applied in unreinforced nylons, guanidine sulfamate is used
as a FR in PVC wall coverings, and guanidine phosphate is used as a FR for textile
fibers [1, 2]. Melamine is a type of hetero cyclic nitrogen-rich compound; it is
crystalline and thermally stable with a high melting temperature of 345 °C. At high
temperatures, melamine decomposes endothermally, which means that it acts as a
heat sink during combustion and releases non-combustible ammonia gas. Further, it
also forms thermally stable condensed compounds, including melam, melem, and
melon, which produce a strong char structure [3]. Therefore, most nitrogen
derivative-containing polymers exhibit FR activity as they act like heat sinks and
evolve non-flammable gases, such as N 2 , NH 3 , CO 2 , and H 2 O into the flame zone
area, which cool it down and dilute oxygen concentration. Su et al. [4] synthesized
© Springer Nature Switzerland AG 2020
S. Sinha Ray and M. Kuruma, Halogen-Free Flame-Retardant
Polymers, Springer Series in Materials Science 294,
https://doi.org/10.1007/978-3-030-35491-6_4
15