The flexible graphite sheet is widely used as an engineering material because of its excellent sealing effect.the main advantage and disadvantage described below:
The advantage:
1)high thermal conductivity
The high thermal conductivity of flexible graphite sheet is much higher than PTFE and asbestos,
During the motive seal,the excellent thermal conductivity could sweep away the heat caused by friction.and avoid the temperature too high.
2)self-lubrication
The flexible graphite sheet is made of flake graphite,as the layered structure,it has a good property of self-lubrication.during the work time, the lamellar orientation parallel to the direction of friction,and combining power between layers is very low,and the crystal is easy to move,so the friction coefficient is very low. During the operation of the equipment,it could form a film on the surface of the metal after about 20min,and after that,the friction will only happen between the crystals instead of the metal and crystal.
The disadvantage:
1) the low tensile strength and flexural strength
Compared with other sealing materials,the tensile strength and flexural strength is lower than them,and it’s really an obvious disadvantage of the flexible graphite sheet.and it’s also lack of toughness,so the flexible graphite sheet is not suitable for sealing parts as lip,and forming packing.
2)the heat loss of the flexible graphite sheet.
The flexible graphite sheet is same as the ordinary graphite products at those property of high temperature oxidation,at about 550℃,the graphite start to oxidate,if this situation lasts long time,the accumulative total of the heat loss is very obvious.
to sum up,although the flexible graphite sheet is widely used as sealing ,but it still has some problem to improve,and the flexible graphite composite material is a good way to solve it,such as spiral wound gasket and adding the ceramics,Al2O3,Si3N4 and Si.so the temperature will be increase to 1260℃.
