**4. Discussions**

of AFM and SEM, the composite C 308 surface morphology shows that the nanosized schungit fillers are homogeneously dispersed in the polymer matrix and are well adhered to the polymer matrix. This finding is very important for understanding the reasons of reinforcing the physical-mechanical properties of initial CKTH-A rubber with used nano-

**Figure 8.** SEM pictures of the structure of the cross sections of the surface of sample C 311. Unite scales: (a) 1 micron and

AFM surface images of C 311 composite CKTN-A rubber with silica SIPERNAT 360 fillers are shown in **Figure 5**, and of composite C313 in **Figure 6**. The internal microstructure and agglomerates sizes of this filler in composites are of the same dimensions as in the case of

SEM images of the top surface topography of the plate of the same C 311 composite are shown

in **Figure 7** and of the plate perpendicular cross section in **Figure 8**.

structured schungit filler.

(b) 200 nm, respectively.

22 Characterizations of Some Composite Materials

nanosized schungit filler.

The application of SEM and AFM methods to visualize topography of surfaces and cross sections of investigated silicone rubber composites with schungit and silica SIPERNAT 360 fillers allowed direct observation of changes in the structure of composite elastomers on the micro- and nanometer range by increasing their concentrations. It is known that in silicone compositions, along with the interactions between the filler and the polymer matrix, there is also a process of agglomeration and structuring of the filler particles [1, 2]. As established by the data of AFM and SEM (**Figures 3**–**8**), a rather homogeneous distribution of the filler in the elastomeric matrix takes place in the investigated composites. Correlation of these results with the physical-mechanical properties of these materials, studied in [8], makes it possible to understand the cause of the enhancing ability of nanostructured schungit in organosilicon elastomers, due to the formation of a spatial filler network in the polymer matrix. These data make it possible to understand the reasons for the schungit filler manifestation of the reinforcing properties in the CKTH-A rubber, as conditioned not only by the chemical affinity of the amorphous carbon and the silica with the polydimethylsiloxane matrix, but also by a fairly uniform spatial distribution of the filler in the composite. The role of polar hydroxyl groups (OH) bounded to silica part of the schungit (silanol groups) interacting with siloxane segments (Si–O–Si) of matrix is also important, because the formed complex prevents the macroscopic agglomeration of initial schungit particles during the introduction of the polymer. The resulting increase in the interaction surface of the nanostructured filler with the polymer macromolecules leads to an effective reinforcement of the initial polydimethylsiloxane matrix. As reported in [8], the tests of these composites on a machine UTS-10 showed an increase in the tensile strength from about 0.5 MPa in original CKTH-A rubber to 3.6 MPa in C 308 composite, and tear resistance from 1.3 to 7.0 kN/m, respectively. It was also showed that these rubber composites with nanostructured schungit fillers have values of the specific work deformation for destruction belonging to the same regions of magnitude as silica filled composites with the same matrix. These results, when compared with traditional silicon dioxide filler [1, 2], show good effectiveness of the present nanostructured schungit as reinforcement filler in polydimethylsiloxane.

The obtained images of the topography and material contrast of the surface of the composites with silica SIPERNAT 360 fillers also made it possible to visualize a fairly uniform distribution of silica particles in a matrix of silicone rubber. Tests of vulcanizates of these mixtures on a tensile machine UTS-10 showed an increase in the tensile strength from about 0.5 MPa in C300 to 3.0 MPa in C 311 composites, and tear resistance from 1.3 to 3.4 kN/m, respectively, and in C313 composite to 4.1 MPa and 7.1 kN/m accordingly [8]. Studies on the NanoTest 600 measuring system by the method of nanoindentation are in accord with these results. The obtained data make it possible also to understand the reasons for the manifestation of the SIPERNAT 360 filler, with the reinforcing properties in the CKTH-A rubber as conditioned not only by the chemical affinity of the silicon dioxide and the matrix, but also by the fairly uniform spatial distribution of the filler in the composite. The role of polar hydroxyl groups (OH) associated with the filler SIPERNAT 360 (silanol groups) interacting with silicone segments (Si–O–Si) of the SKTN-A silicone analogous to nano schungit is important, with the formation of a hydrogen bond. This also makes it possible to prevent macroscopic agglomeration of the silica when introduced into the polymer, ensuring homogeneity of the filler distribution in the composite. The resulting increase in the interaction surface of the filler with the polymer leads to an effective hardening of the initial silicone matrix.

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