Preparation Of Novel Graphite Intercalation Compounds And Study On The Expansion And Flame Retardant Mechanism

Graphite intercalation compounds (GIC) intercalated with sulphuric acid (SA-GIC) were widely used as intumescent flame retardants, but such GIC showed limited applications in flame retardant polymers because of the lower flame retardant properties and the lower initial expansion temperature. By now, few literatures have been delivered on the flame retardant properties and flame retardant mechanism of GIC intercalated with other compounds.The paper aims at the preparation of GIC intercalated with different compounds and the investigation of their flame retardant properties and flame retardant mechanism. For that, direct and two-step intercalation methods were used to prepare GIC. According to the results of orthogonal experiments, the optimal reaction conditions were obtained to prepare nitrate-sulphuric acid-GIC and phosphorous compounds-sulphuric acid-GIC. The structure and expansion volume of GIC were analyzed by means of XRD, SEM, XPS and EDS, based on the results of which, the intercalation theory and expansion process were proposed. GICs as prepared were applied in flame retardant polyethylene (PE) whose flame retardant properties and mechanism were studied. As a result, the key factors on expansion properties and flame retardant properties were determined.The following results can be concluded. Initial expansion temperature, thermal stability and expansion volume of GIC can be controlled by stage structure of GIC and intercalating agents. Compared with direct method, two-step one was in favor of the preparation of muli-components GIC with lower stage structure and better expansion properties. GIC with different intercalating agents possessed different flame retardant properties, among which ammonium polyphosphate-sulphuric acid-GIC had the best flame retardant properties because of its self-synergistic effect. GIC underwent redox process during its expansion. The flame retardant mechanism of GIC can be attributed to two main factors, that is expanded graphite layers formed during expansion of GIC and enhanced charring process by GIC.