A Novel Self-Assembled Graphene-Based Flame Retardant: Synthesis and Flame Retardant Performance in PLA

Abstract

In this study, a novel flame retardant (PMrG) was developed by self-assembling melamine and phytic acid (PA) onto rGO, and then applying it to the improvement of the flame resistance of PLA. PMrG simultaneously decreases the peak heat release rate (pHRR) and the total heat release (THR) of the composite during combustion, and enhances the LOI value and the time to ignition (TTI), thus significantly improving the flame retardancy of the composite. The flame retardant mechanism of the PMrG is also investigated. On one hand, the dehydration of PA and the decomposition of melamine in PMrG generate non-flammable volatiles, such as H2O and NH3, which dilute the oxygen concentration around the combustion front of the composite. On the other hand, the rGO, melamine, and PA components in PMrG create a synergistic effect in promoting the formation of a compact char layer during the combustion, which plays a barrier role and effectively suppresses the release of heat and smoke. In addition, the PMrGs in PLA exert a positive effect on the crystallization of the PLA matrix, thus playing the role of nucleation agent.

An overview of the recent advances in flame retarded poly(lactic acid)

“…[110][111][112] 2D nanoscale FRs are layered materials with strong in-plane chemical bonds and weak interlayer force. They have high modification flexibility, mainly including graphene, [113][114][115][116][117][118][119] clay, 120,121 and layered double hydroxide (LDH). 122,123 Nanofillers alone cannot meet the flame-retardant requirements of polymers, and their agglomeration tendency and poor interfacial compatibility with the matrix will damage the mechanical properties.…”

“…Melamine and phytic acid (PA) were self-assembled onto graphene oxide (rGO) to obtain flame retardant (PMrG), as shown in Figure 4D. 113 the tensile strength increased by 49.1%, further improving the performance of PLA.…”

“…112 (D) Preparation of PMrG. 113 (E) The synthesis of GPZ. 115 As a whole, phosphating bio-based compounds are more popular due to their high flame-retardant efficiency.…”

“…In recent years, the preparation of nanocomposites using nanoparticles and polymers has attracted great attention due to its excellent performance 104–106 . Polymers loaded with nanofillers as low as 1–5 wt% can improve flammability and thermal stability 107–129 . Nanofillers have large specific surface area, high thermal stability, excellent physical, and mechanical properties, which can act as a carbon layer during combustion, improve the density of the carbon layer and delay heat transfer.…”

Synthesis of High-Efficiency, Eco-Friendly, and Synergistic Flame Retardant for Epoxy Resin

“…Graphene oxide (GO) is one of the most promising materials as the flame retardant for EP because it presents high thermal stability and an excellent barrier effect during combustion [20][21][22][23][24]. In addition, taking advantage of the abundant functional groups, GO is easily doped by metal ions or chemically reduced with other molecules, leading to the formation of a variety of flame-retardant systems with further improved fire-resistant performances, in which the reduced graphene oxide (rGO) component functions as the multi-layered skeleton [25][26][27][28][29][30]. In Wang's work, a flame retardant for EP was prepared by functionalizing the rGO with a sheet-like metal-organic zinc N, N'-piperazine (bismethylene phosphonate) [31].…”