in Fig. 7.9a, b, c; multi functionalities were created by GO reduction with NaBH 4 .
The growth of SMB crystals in the GO layers leads to the formation of a
“nacre-like” structure, which exhibits multiple modes of fire protection. Industrial
GO/SMB composite wood coatings exhibited a strong intumescent character,
non-flammable nature, and self-extinguishability. Therefore, it has been reported
that the combination of rGO and SMB shows IFR activity, similar to nitrogen and
phosphorus-based salts. In the presence of hydrated SMB which is present in
between rGO layers, swelling is possible. At the same time, rGO leads to the
formation of char. rGO/SMB starts releasing water at high temperatures, which
increases the volume of char. During combustion the evaporated water molecules
inside char come out through impermeable graphene layers, which lead to the
formation of intumescent char formation. This characteristic prevents the evolution
of combustible and toxic gases as shown in Fig. 7.9d; further, it prevents oxygen
attack on the material [104]. Tang et al. [105] prepared FR systems of DDPPU in
combination with traditional FRs. They observed that in the case of DDPPU
combined with H 3 BO 3 , there was a significant improvement in the LOI values
(46%) due to a synergetic effect and char formation. An intumescent flame retardant, PPSPB, was covalently grafted on the surface of GO and used to prepare EVA
nanocomposites. The results showed increased FR activity for the resulting
nanocomposites and increase in T g and modulus due to surface modification with
PPSPB, which help in the uniform dispersion of graphene in polymer matrix. In
addition, the THR, PHRR, and AMLR decreased [106]. Generally, phosphonamidates decrease dripping and increase the melt viscosity at high temperatures.
Guo et al. [107] synthesized hybrids of phosphonamidates/rGO and incorporated
them into EP resins; the resulting nanocomposite resins displayed simultaneous
improvement in mechanical and FR properties. Nanocomposite with 4 wt% filler
loading showed remarkable FR activity, achieved a V-0 rating in the UL-94 test
without dripping, and significantly reduced THR and PHRR values compared to
neat EP resins. Jin et al. [108] modified GO with P,N-containing dendrimers
(PND-GO) and used them to prepare PU nanocomposites. The formed exfoliated
structures exhibited strong FR activity with a reduction in PHRR and increased
ignition time compared to neat PU. GO surfaces were also modified with DOPO via
covalent bond formation and the modified GO particles were used to prepare EP
resins with excellent mechanical properties and FR activity. DOPO modification
improved the dispersion quality and at high temperatures, uniform sheet-like char
layers were formed, which hindered flame propagation [89, 109].
GOTP foams were prepared by mixing GO solution and hexachlorocyclotriphosphazenes (HCTP); the foams showed excellent FR activity compared to traditional polymers and their nanocomposite [110]. In the presence of flame,
HCTP-functionalized GO spontaneously converted into a 3D graphene network
structure, which improved the melt viscosity of the polymer. It is well known that
metal oxides improve char formation owing to a catalytic effect. Studies revealed that
DOPO in combination with rGO showed excellent FR activity due to a synergetic
effect between DOPO and rGO; further, a combined gas-phase and solid-phase FR
activity was observed [111]. Ethylene-vinyl acetate thermoset rubbers (EVM) are
7.3 Graphene-Based FR PNCs
101
The growth of SMB crystals in the GO layers leads to the formation of a
“nacre-like” structure, which exhibits multiple modes of fire protection. Industrial
GO/SMB composite wood coatings exhibited a strong intumescent character,
non-flammable nature, and self-extinguishability. Therefore, it has been reported
that the combination of rGO and SMB shows IFR activity, similar to nitrogen and
phosphorus-based salts. In the presence of hydrated SMB which is present in
between rGO layers, swelling is possible. At the same time, rGO leads to the
formation of char. rGO/SMB starts releasing water at high temperatures, which
increases the volume of char. During combustion the evaporated water molecules
inside char come out through impermeable graphene layers, which lead to the
formation of intumescent char formation. This characteristic prevents the evolution
of combustible and toxic gases as shown in Fig. 7.9d; further, it prevents oxygen
attack on the material [104]. Tang et al. [105] prepared FR systems of DDPPU in
combination with traditional FRs. They observed that in the case of DDPPU
combined with H 3 BO 3 , there was a significant improvement in the LOI values
(46%) due to a synergetic effect and char formation. An intumescent flame retardant, PPSPB, was covalently grafted on the surface of GO and used to prepare EVA
nanocomposites. The results showed increased FR activity for the resulting
nanocomposites and increase in T g and modulus due to surface modification with
PPSPB, which help in the uniform dispersion of graphene in polymer matrix. In
addition, the THR, PHRR, and AMLR decreased [106]. Generally, phosphonamidates decrease dripping and increase the melt viscosity at high temperatures.
Guo et al. [107] synthesized hybrids of phosphonamidates/rGO and incorporated
them into EP resins; the resulting nanocomposite resins displayed simultaneous
improvement in mechanical and FR properties. Nanocomposite with 4 wt% filler
loading showed remarkable FR activity, achieved a V-0 rating in the UL-94 test
without dripping, and significantly reduced THR and PHRR values compared to
neat EP resins. Jin et al. [108] modified GO with P,N-containing dendrimers
(PND-GO) and used them to prepare PU nanocomposites. The formed exfoliated
structures exhibited strong FR activity with a reduction in PHRR and increased
ignition time compared to neat PU. GO surfaces were also modified with DOPO via
covalent bond formation and the modified GO particles were used to prepare EP
resins with excellent mechanical properties and FR activity. DOPO modification
improved the dispersion quality and at high temperatures, uniform sheet-like char
layers were formed, which hindered flame propagation [89, 109].
GOTP foams were prepared by mixing GO solution and hexachlorocyclotriphosphazenes (HCTP); the foams showed excellent FR activity compared to traditional polymers and their nanocomposite [110]. In the presence of flame,
HCTP-functionalized GO spontaneously converted into a 3D graphene network
structure, which improved the melt viscosity of the polymer. It is well known that
metal oxides improve char formation owing to a catalytic effect. Studies revealed that
DOPO in combination with rGO showed excellent FR activity due to a synergetic
effect between DOPO and rGO; further, a combined gas-phase and solid-phase FR
activity was observed [111]. Ethylene-vinyl acetate thermoset rubbers (EVM) are
7.3 Graphene-Based FR PNCs
101