Influence of expandable graphite on flame retardancy and mechanical properties of organic–inorganic hybrid material based on sodium silicate and polyisocyanate

Influence of expandable graphite on flame retardancy and mechanical properties of organic–inorganic hybrid material based on sodium silicate and polyisocyanate has been investigated. The results of mechanical measurement show that adding expandable graphite decreases the maximum of the compressive strength from 5.98 to 1.49 MPa. The thermal property is evaluated by thermal conductivity test, thermogravimetric analysis. The results indicate that adding the expandable graphite increases thermal conductivity of composite and lowers maximum heat release rate. The material with expandable graphite has better flame retardancy than original material with an obvious decrease in heat release rate, fire spread and thermal decomposition rate. What is more, intumescent graphite has the obvious effect to suppress flame and prevent the composite from fire. Scanning electron microscope shows that many large particles and gaps appear after compression deformation.