Preparation and Antiflame Performance of Expandable Graphite Modified with Sodium Hexametaphosphate

Abstract

A kind of polyphosphate modified expandable graphite (EG p ) was prepared in graphite oxidation and intercalation reaction with KMnO 4 as oxidant, H 2 SO 4 as intercalator, and sodium hexametaphosphate (SHMP) as assistant intercalator. The feasible mass ratio of C : KMnO 4 : H 2 SO 4 (98%) : SHMP was determined as 1.0 : 0.3 : 4.5 : 0.6, H 2 SO 4 was diluted to 77 wt% before intercalation reaction, and the reaction lasted for 40 min at 40 ∘ C. Expanded volume and initial expansion temperature of the prepared EG p reached 600 mL/g (at 800 ∘ C) and 151 ∘ C, respectively. X-ray diffraction spectroscopy testified the intercalation and layer structure of EG p , and Fourier transform infrared spectroscopy illuminated the intercalated functional groups. Flame retardance of the prepared EG p and the referenced EG (with only H 2 SO 4 as intercalator) for linear low density polyethylene (LLDPE) was also investigated. Addition of 30 wt% EG p to the polymer improved the limiting oxygen index (LOI) from 17.5 to 27.3%. On the other hand, the LOI of the same amount of the referenced EG was only 24.6%. Assistant intercalation of SHMP improved the dilatability and flame retardancy.

Investigating The Effect of Various Parameters on The Yield of Graphene Obtained Through Graphite Exfoliation Using CO2 Supercritical Fluid

“…The problem with sodium lignosulfonate is that at the end of the process, due to the very high pressure of the separation process, insoluble cellulose materials and salts that remain from sodium lignosulfonate are separated from the graphite layers and cause the graphene layers to be placed on top of each other again. Thus, sodium hexametaphosphate has a greater intrinsic ability to prevent the re-stacking of graphene layers than sodium lignosulfonate [32].…”

Expandable Graphite as a Fire Retardant for Cellulosic Materials—A Review

“…When EG is used as flame retardant, its dilatability and thermal stability are very important parameters. In terms of thermostability, EG can be divided into three kinds: low (between 80 and 150 • C), middle (between 180 and 240 • C), and high (between 250 and 300 • C) [26]. At temperatures ranging between 280 and 438 • C, high thermostable graphite will expand, creating a porous physical barrier between the material to be protected and the flame [6].…”

“…180 and 240 °C), and high (between 250 and 300 °C) [26]. At temperatures ranging between 280 and 438 °C, high thermostable graphite will expand, creating a porous physical barrier between the material to be protected and the flame [6].…”

“…The characteristics of EG are often influenced by the modifying agent (oxidant, intercalant, and assistant intercalant) used during the intercalation process. The influence of KMnO 4 (oxidant agent) dosage on EG characteristics was studied by Pang et al [34] and Zhao et al [26]. In this research, at the range of 0.2~0.6 g/g, the influence of KMnO 4 dosage was detected at the mass ratio of C: H 2 SO 4 (98%): Na 4 P 2 O 7 = 1.0:5.0:0.6 (g/g), the temperature conditions were 40 • C, with the reaction time of 1 h. In addition, it was observed that H 2 SO 4 should be diluted to the mass concentration of 80% before the reaction.…”