The Role of Graphene in Flame Retardancy of Polymeric Materials: Recent Advances

Abstract

Background: From its discovery, graphene has become a very fascinating nanomaterial, thanks to its structure that determines peculiar (and unique) mechanical, electrical and thermal properties. Thus, graphene has stimulated and is still motivating several researchers to widen its potentialities that are currently being exploited in different application sectors, comprising catalysis and energy, nanoelectronics, quantum physics and the design and manufacturing of advanced nanocomposite materials and biomaterials. Being a carbon source, already organized in a well-ordered morphology, graphene is nowadays starting to experience a different application, i.e. in the fire retardancy of polymers, foams and textiles, often in combination with other flame retardant additives or nanofillers, with which graphene can often act in a synergistic way. In fact, it is well reported in the scientific literature that graphene and its derivatives can play a key role either in slowing down the flame propagation or even in providing self-extinction to the thermoplastic or thermosetting matrices, where the nanofiller is incorporated in; furthermore, by exploiting surface engineered approaches, it is possible to design very effective flame retardant coatings on textile substrates. Objective: This paper aims at reviewing the current state-of-the-art about the use of graphene and its derivatives as efficient flame retardant additives for different polymeric materials, highlighting the current limitations/achievements and discussing some possible future developments.

Hybrid Structures Made of Polyurethane/Graphene Nanocomposite Foams Embedded within Aluminum Open-Cell Foam

“…Their positive effect in the thermal stability of PUF nanocomposites may be attributed to the high specific area and layered structure of the nanofillers, which tend to form a dense and continuous char layer acting like a physical barrier at the PUF surface. This barrier becomes an obstacle to the release of the volatile degradation products, preventing or causing the delay of the degradation of the whole composite [39]. It is remarkable that, although the GO nanosheets are not as good dispersed as the GNPs in the polymer foam (photographs in the left side of Figure 2b,c), their effect on the flame retardancy was as efficient or even more efficient than the GNPs.…”

“…GO's benefits in the fire retardancy efficacy over graphene have been referred to and are attributed to the GO oxygen functionalities that decompose and dehydrate at quite low temperatures. This causes a cool down of the polymer substrate during the combustion process and simultaneously release gaseous species that dilute the oxygen atmosphere near the ignition zone [30,39,40]. Graphene and GO are described mainly as co-flame retardants, at loadings from 1.0 to 10 wt% [41].…”

A Review of the Synthesis, Properties, and Applications of 2D Materials

“…The large surface area of graphene could help reduce the flammability of gases by delaying the diffusion process during combustion. [125,126] This enables the use of graphene as an effective reinforcement material for polymeric composites and other materials to increase their flammability resistance. For example, Chen et al [127] developed epoxy/glass fiber hybrid com posites with varying percentages of flame retardant graphene oxide (2%, 4%, 8%) and phosphaphenanthrene (4%, 8%) and investigated their fire retardant properties.…”

“…The large surface area of graphene could help reduce the flammability of gases by delaying the diffusion process during combustion. [ 125,126 ] This enables the use of graphene as an effective reinforcement material for polymeric composites and other materials to increase their flammability resistance. For example, Chen et al.…”