Almost all impermeable graphite that be applied in chemical industry are manufactured via impregnation . Impregnant is not only applied to filling hole but also to improving mechanical strength of impregnated graphite. But while different impregnat is used, different mechanical strength appear, such as chemical stability, thermal ability, hardness, etc. So when you are choosing impregnant, it should conform to following characteristics:
Good chemical stability
Good mechanical ability
Steady Volume which can suffer impregnation
Low water content
Low viscosity
Peopley usually choose phenolic resin, modified phenolic resin, furfural acetone resin, furfuryl alcohol resin and coal pitch. However, sometimes, people choose organic silicon resin, sodium silicate, molten sulfur, paraffin as impregnant.
Impregnated impermeable graphite is simmilar with other graphite material, which have better chemical ability than other non-metallic corrosion resistant materials.
There are several tips should be noticed：
① Graphite pieces should not contain dust, oil, moisture.
② In order to Impregnate thoroughly, and in case of graphite expending, Vacuum degree should be as high as possible.
③ The quality of impregnant needs special care. If shrinkage process of resin is incomplete or dehydration is incomplete, the quality of impregnant will change.
④ Residual resin on the surface of graphite should be wiped.
⑤ Vacuum degree, pressure, time and temperature can decide whether the qualit of first impregnation is good enough.
