Graphite sheets are made from expanded vermicular particles compressed to form graphite based sheets. A typical way to make expanded vermicular particles is to immerse flakes of natural graphite in some acid solution and expose the immersed flakes to high temperature. Such steps will make the graphite flakes expand in a direction perpendicular to the crystal plane of graphite atoms. A form of a substantially flat, flexible, integrated graphite sheet is made by compressing expanded graphite particles at least 80 times that of the original particles under a predetermined load and without a binder. The density and thickness of the sheet may be varied by controlling the degree of compression.

A graphite sheet made by the process described above shows suitable properties to be used for graphite gasket and seal applications. The normal requirement for graphite gasket and seal application include compressibility, recovery, resistance to chemical attack, high yield point and low creep value which will produce high sealability of gasket that gives the gasket ability to inhibit leakage of gas or liquid through a seal. Creep describes the progressive deformation of a material at constant stress. A creep value is measured as a strain after applying compressive stress on a material for a certain passage of time. The yield point or crush point of a material describes the highest compressive stress point where the material will decrease in thickness without extruding in planar dimensions.

Satisfying the requirements of compressibility, recovery, resistance to chemical attack, high yield point and low creep concurrently to the degree required by commercial applications is hard to achieve and the properties of the graphite sheets depend also on the environment where it is applied and density and thickness of the products, although graphite exhibits compatible for all properties as a gasket. It is difficult to combine low creep and high conformability. Elastic materials that conform well to rough surfaces tend to creep under high pressure.

Graphite material has good chemical resistance. Graphite material also has a high affinity to wetting agents, like oils. Such affinity contributes to erosion of graphite based gaskets, such as in internal combustion engines. Besides, the high temperature of the environment makes it easier for oil to penetrate between layers of graphite sheets. Therefore, graphite material exposed to an environment where oil is abundant can exhibit a high creep value and low sealability. Graphite gasket consists of layers of carbon atoms held together by weak Waals forces. This weak force between the atomic layers may be the source of the leakage when the graphite sheet is used as a gasket and seal because alien substance can penetrate between these layers of materials.