**4. Conclusion**

The generally accepted estimate of binders by the contact angle of wetting of the filler surface reflects only the initial stage of the adhesive interaction of the components of the composites. Wetting of fillers with binders is a necessary but not sufficient condition.

The activity of the fillers with respect to the particular binder is characterized by the adhesive strength of the material obtained after the carbonization of the "binder-filler" system. The activity of the fillers determines the sintering ability and sintering capacity of the pitch binders.

The external curve describes the dependence of the strength of composites on the content of fillers in them. Both step V and anthracite in the place of the extreme ratio of the filler-binder are 9:1, and the strength of the composite is 3,10 MPa. At this stage, the pitch matrix is in the interfacial layer on the surface of the filler particles. This optimal ratio is valid only for the given experimental conditions: temperature and grain size of the filler.

We show that anthracite is the most active filler for the resins under study. Some methods use anthracite as a reference filler to determine the sintering of coal and tar. Therefore, it can serve as a standard of activity in evaluating the activity of other fillers.
