Combination effects of graphene and layered double hydroxides on intumescent flame-retardant poly(methyl methacrylate) nanocomposites

A novel intumescent flame-retardant poly(methyl methacrylate) (PMMA) nanocomposite has been prepared via in situ polymerization by incorporating intumescent flame retardants (IFRs), graphene and layered double hydroxides (LDHs). Results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that a fine dispersion of IFR particles, intercalated LDHs and exfoliated graphene is achieved in the PMMA matrix. Thermal and flammability properties of PMMA nanocomposite were investigated using thermogravimetry, cone calorimetry, limiting oxygen index (LOI) and vertical burning (UL-94). The use of IFRs in combination with graphene and LDHs in the PMMA matrix improves greatly the thermal stability and flame retardant properties of the nanocomposites. The PMMA/IFR/RGO/LDH nanocomposites, filled with 10. wt.% IFRs, 1. wt.% graphene and 5. wt.% LDHs, achieve the LOI value of 28.2% and UL-94 V1 grade. Compared with neat PMMA, the PHRR of PMMA/IFRs/RGO/LDHs is reduced by about 45%, while the mechanical properties of PMMA/IFR/RGO/LDH nanocomposites exhibit almost no deterioration. The results from scanning electronic microscopy (SEM) confirm that the compact and dense intumescent char enhanced with LDHs and graphene nanosheets is formed for the PMMA/IFR/RGO/LDH nanocomposites during combustion, which inhibits the transmission of heat and mass when exposed to flame or heat source, and thus improves the flame retardant properties of the nanocomposites

Poly(acrylic acid)/Clay Thin Films Assembled by Layer-by-Layer Deposition for Improving the Flame Retardancy Properties of Cotton

A flame-retardant poly­(acrylic acid) (FR-PAA) was prepared by copolymerization of <i>N</i>-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)-ethylacetamide-2-propenyl acid (DPEPA) and acrylic acid and used to fabricate various FR-PAA/montmorillonite (MMT) thin films via layer-by-layer (LbL) deposition as a flame-retardant coating system for cotton fabric. Thermogravimetric analysis (TGA) indicated that treatment of FR-PAA/MMT thin films improved the thermal stability of cotton fabric. Cone calorimeter testing showed that the cotton fabrics coated with the FR-PAA/MMT thin films had less flammability with lower peak heat release rate (PHRR), lower total heat release (THR), and lower average mass loss rate (AMLR). In addition, scanning electronic microscopy (SEM) demonstrated that the surface of the fabrics coated with FR-PAA/MMT films after combustion was covered by a layer of continuous and compact char

Ultrafast growth of single-crystal graphene assisted by a continuous oxygen supply

Graphene has a range of unique physical properties(1,2) and could be of use in the development of a variety of electronic, photonic and photovoltaic devices(3-5). For most applications, large-area high-quality graphene films are required and chemical vapour deposition (CVD) synthesis of graphene on copper surfaces has been of particular interest due to its simplicity and cost effectiveness(6-15). However, the rates of growth for graphene by CVD on copper are less than 0.4 mu m s(-1), and therefore the synthesis of large, single-crystal graphene domains takes at least a few hours. Here, we show that single-crystal graphene can be grown on copper foils with a growth rate of 60 mu m s(-1). Our high growth rate is achieved by placing the copper foil above an oxide substrate with a gap of similar to 15 mu m between them. The oxide substrate provides a continuous supply of oxygen to the surface of the copper catalyst during the CVD growth, which significantly lowers the energy barrier to the decomposition of the carbon feedstock and increases the growth rate. With this approach, we are able to grow single-crystal graphene domains with a lateral size of 0.3 mm in just 5 s.ope