Preparation method of high-flame-retardancy expandable graphite

Abstract

The invention relates to a preparation method of high-flame-retardancy expandable graphite, which comprises the following steps: oxidizing graphite by using concentrated sulfuric acid/nitric acid mixture, nitric acid/phosphoric acid mixture, fuming nitric acid or concentrated sulfuric acid together with a solid strong oxidizer which accounts for 5-60 wt% of graphite, wherein the reaction temperature is 15-50 DEG C, and the reaction time is 10-100 minutes; after the reaction finishes, filtering, and washing with water until the pH value is 4-7, thereby obtaining the primary expandable graphite; and reacting the primary expandable graphite with guanidine salt solution at 20-80 DEG C for 20-200 minutes, carrying out repeated vacuum filtration, washing with water until the pH value is 6-7, and baking at 40-80 DEG C for 10-72 hours to obtain the high-flame-retardancy expandable graphite. The method provided by the invention intercalates guanidine salts into the interlayer of the expandable graphite, enhances the expansion ratio and flame retardancy, and can be widely used for flame retardancy for plastics, rubber, paint, foam and various other materials.

Description

Technical field [0001] The invention relates to a preparation method of graphite material, in particular to a preparation method of high flame retardant expandable graphite. Background technique [0002] Expandable graphite is a new type of compound with interlayer intercalation formed by natural flake graphite through oxidation intercalation reaction, inserting heterogeneous atoms, molecules or ions between graphite flake layers. When expandable graphite is subjected to high temperature, the interlayer material is rapidly vaporized by high heat, and the formed gas produces huge tension on the graphite sheets, which causes the expandable graphite to expand, and the expansion ratio is as high as tens to hundreds of times. The resulting carbon layer has excellent oxidation resistance and high temperature resistance, which can protect the substances under the carbon layer and achieve the purpose of flame retardancy and fire prevention. Compared with traditional flame retardants, ex...

AI Technical Summary

Problems solved by technology

[0003] However, expandable graphite mainly relies on the expansion insulation layer formed by its own volume expansion to delay or inhibit the combustion of substances, and there is no or little chemical interaction with the flame retardant, which is a typical condensed phase flame retardant mechanism; expandable graphite The carbon layer formed after expansion has weak adhesion to each other. After being burned by the flame retardant matrix, a solid expanded carbon layer cannot be formed. Under the action of flame pressure or heat convection, the expanded graphite layer on the surface may be damaged. When it is destroyed, "fly ash" is formed, which leads to the loss of the thermal insulation expansion layer, and then causes the unburned substance to be ignited, and the flame continues to spread, so the flame retardant efficiency is limited

Moreover, expandable graphite often exhibits a strong "candle wick effect" when it is a flame-retardant polymer, which also weakens its flame-retardant ability to a certain extent.

Therefore, the practical application of expandable graphite in the field of flame retardancy is still relatively limited.