Preparation of expandable graphite with silicate assistant intercalation and its effect on flame retardancy of ethylene vinyl acetate composite

Abstract

A halogen‐free intumescent flame retardant expandable graphite composite (EG), with an initial expansion temperature of 202°C and expansion volume of 517 mL g−1, was successfully prepared via a facile two‐step intercalation method, i.e. using KMnO4 as oxidant and H2SO4, Na2SiO3·9H2O as intercalators. The prepared EG flame retardant was characterized by field emission scanning electron microscope, X‐ray diffraction spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, flame retardancy and thermal property of various ethylene vinyl acetate copolymer (EVA) composites, including EVA/EG and EVA/EG/APP (ammonium polyphosphate) specimens, were studied through limiting oxygen index instrument (LOI), vertical combustion UL‐94 rating, thermal gravimetric and differential thermal analysis. The results indicate that the EVA/EG and EVA/EG/APP composites exhibit a better flame retardancy. Addition of EG at a mass fraction of 30% leads LOI of 70EVA/30EG composite improved to 28.7%. Even more, the synergistic effect between EG and APP improves the LOI of 70EVA/10APP /20EG composite to 30.7%. This synergistic efficiency is attributed to the formation of compact and stable layer‐structure, and the prepared EG can make EVA composite reach the UL‐94 level of V‐0. POLYM. COMPOS., 36:1407–1416, 2015. © 2014 Society of Plastics Engineers

Improvement in thermal conductivity and mechanical properties of ethylene‐propylene–diene monomer rubber by expanded graphite

“…The characteristic absorption peaks between 3,300 and 3,600 cm −1 correspond to the stretching vibration of –OH groups , which are much stronger in EG than in graphite. Compared to graphite, an additional strong peak appears at 1,616 cm −1 in EG, representing the stretching vibration of CO . The appearance of CO groups in EG may be associated with the oxidation of graphite during EG preparation.…”

Preparation of Boric Acid Modified Expandable Graphite and Its Influence on Polyethylene Combustion Characteristics

“…16,17 However, there are still some shortcomings when EG is used as a FR. Firstly, due to its limited efficiency, a normal 30 wt% dose is needed to achieve satisfying effect, 18 which often leads to obvious deterioration of the mechanical properties.…”

“…Whereas, the improvement by combined addition or EG modification is usually very limited, especially the simple mix of EG with other retardants. 17 The main reason should be the insufficient mix caused by the inconsistence of particle size, density, polarity and addition dosage between these FRs and matrix.…”

“…It was reported the H 2 SO 4 /APP (APP, ammonium polyphosphate, a assistant intercalating agent) GIC, prepared through two-step method, exhibited a higher expansion volume (EV, 240 mL g -1 ) than that of the H 2 SO 4 intercalated EG (210 mL g -1 ). 19 An EG, intercalated by H 2 SO 4 and Na 2 SiO 3 through two-step intercalation reaction, 17 presented an EV of 517 mL g -1 and combustion limiting oxygen index (LOI) of 28.7% for EVA. However, the EV of referenced EG, which is intercalated by only H 2 SO 4, was merely 433 mL g -1 , and the LOI was just 24.4%.…”

Improving the flame resistance and thermal conductivity of ethylene‐vinyl acetate composites by incorporating hexachlorocyclotriphosphazene‐modified graphite and carbon nanotubes

“…EVA is an ideal insulating material used in the cable industry due to its desirable physicochemical properties and easy acceptance for additives . However, the low flame resistance of EVA copolymers due to their organic polymer chain restricts the applications in many areas . The poor thermal conductivity (TC) of EVA may be against the emission of heat, especially in electrical fields.…”