Abstract
A novel hybrid flame retardant combining graphene oxide (GO) with long-chain phosphaphenanthrene was fabricated via surface grafting reaction. Taking advantageous of the double barrier effects, including the physical shield contributed by graphene nanoplates during the initial stage and the chemical char contributed by phosphaphenanthrene during the later stage, greatly decreased the release rate of decomposed volatiles from the resin, as well as minimized the release of oxygen and combustion heat. Hence, such hybrid flame retardant can overcome the shortcomings of early acid catalyzed degradation effects caused by conventional flame retardants containing phosphorus. Satisfactory flame retardance was achieved (UL94 V-0 rating) with only 4% addition of the hybrid flame retardant to the epoxy resin laminate. Due to the long-chain and bulky phosphaphenanthrene groups, the interlayer attractive forces of the modified GO were effectively weakened, thus favoring the exfoliation and dispersion of graphene sheets. As a result, the incorporation of the flame retardant slightly enhanced the mechanical properties of the polymer composites, rather than deteriorating them, as occurs with traditional additive flame retardants. As a potential application for graphene, it is believed that the reported hybrid flame retardant has promising future prospect.
Highlights
Polymers are widely applied in modern society due to their excellent properties and abundant product forms
The effect of graphene nanosheets (GNS) combined with traditional flame retardants was systematically studied by Wang[24], and different synergistic mechanisms were proposed for different flame retardant systems
Making use of the physical carbonaceous shield formed by the Graphene oxide (GO) sheets, this material can prevent the rapid release of combustible gases during the initial combustion stage due to the acid-catalysis degradation effect of phosphorus flame retardants (PFRs), effectively controlling the extension of the early flame
Summary
DPP-GO itself is a carbon-based flame retardant, and its two-dimensional graphene sheets can provide barrier shields in the beginning of flame Such an advantage overcomes the lagging effect of chemical charring to a degree. For DPP-GO/EP, its weight loss behavior occurred at higher temperature, demonstrating that combining DPP and GO enhances the thermal stability of the material This result should be due to the two barrier effects of the materials: the graphene sheets effectively prevent the release of volatiles in the initial stage and, as a result, provide more time for later chemical charring behaviours by the interaction between DPP and the resin. For the DPP-GO/EP composite with the same additive content, the mechanical properties were slightly enhanced compared with those of EP This indicated that the well dispersed graphene sheets reinforced the resin matrix to a degree. High exfoliation and dispersion: the long-chain and bulky group grafted onto the GO sheets, weakened the van der Waals forces and expanded the space between neighboring graphene sheets due to steric hindrance, which is advantageous for obtaining a functional resin with well-dispersed flame retardant
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call