Expandable Graphite in Polyurethane Foams

Expandable Graphite in Polyurethane Foams

Expandable Graphite an intercalation compound used in Polyurethane Foams

Polyurethane Foams are widely used in our daily lives from sleeping matters to insulation for industrial sector as well as to aerospace. A lot of work is going on to make PU foams more durable , less flammable, with less wetting property and so on. Many additives have been tried in PU foams to improve the property and expandable graphite is one of them. The inclusion of Expandable Graphite seems to have improved many properties specially the transfer of heat as well as reduced flammability. The brief write up tries to explore the various facets of this novel effort.

Expandable Graphite

Expandable graphite is a kind of graphite intercalation compound, which is prepared by the method of chemical oxidation. It belongs to a group of products called «intumescents»; the main property of which is the ability to expand when heated. Expandable graphite, also called flexible graphite, is made from high quality natural flake graphite by chemical treatment. The material has the characteristics of high temperature resistance, thermal conductivity, lubricity, stable chemistry, heat shock resistance etc.

An important feature of graphite polyurethane foam is that it does not melt and drip when exposed to a high heat source which helps in preventing flame spread. Creation of a char layer dramatically reduces the heat release rate, mass loss, smoke generation and toxic gas emission. Due to its very good fire retardant property graphite foams can be modified to meet a number of high hazard applications.

Benefits of graphite inclusion

The introduction of EG particles into a RPUF matrix will modify the cellular structure of foam, and there will be an increase in density of the foam too. The open cell content shall slightly increase with EG addition, and cell size will also increase along with the size of EG particles.Thus, the EG filler could be considered as an effective material for the improvement of the fire reaction in flexible polyurethane foams. The combination of EG and cellulose can reduce the flammability. At the same time it improves the thermal conductivity which takes heat away from the body of the person sleeping on the EG based PU foam mattress creating a kind of “Cool Mattress”.

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