**4. Discussion of the results**

*Renewable and Sustainable Composites*

**Figure 9.**

*TEM images of grounded Neosyl-120.*

**46**

proper organosilanes.

**Figure 10.**

The graphs of conventional strain-strength properties of these elastomer composites with shungite [9]—are shown in **Figure 5**. These curves are typical ones for each type, corresponding to mean values from five repetitions for tests. Designations SHIKNI and SHIKNM in **Figure 5** mean rubber is filled by original and milled nanoshungit, respectively, and others by nanoshungit, modified by

*The graphs of conventional strain-strength properties of studied composites with taurit, diatomite, and Neosyl-120. Engineering strain (%) are plotted in abscissa and engineering stress (MPa) in ordinates.*

SPM images of the surface structure of the synthesized composites with taurit

Scanning electron microscopy images of the original Neosyl-120 powder are presented in **Figure 8**. From the data obtained, it is clear that the particle size varies from submicrosized to large, with a size of the order of several hundred micrometers, with the second prevailing. Particles Neosyl-120 have a rough, sometimes porous, and layered structure, which implies a large value of its specific

and diatomit are shown in **Figures 6(a, b)** and **7(a, b)**.

Surface topography SPM images and the phase contrast of the composite material allowed to directly visualize the distribution of the fillers in the matrix rubber SBR-30ARK (**Figures 1**–**4**).

Analysis of **Figure 1** revealed the uneven distribution of original micro shungite filler in the rubber matrix. Predominant size of the shungite aggregates remains in the micron region. The distribution of aggregates and agglomerates of milled nanoshungit in the rubber (**Figure 2**) is considerably more homogeneous with a primary particle size of the filler already in the nanometer range. **Figure 3** shows that the use of organosilane Glymo as nanoshungit chemical modifier significantly improves the uniform distribution of the agglomerates and the aggregates in the matrix rubber. The aggregates and agglomerates of nanoshungit modified by organosilane Thiol (**Figure 4**) are distributed more uniformly at the rubber matrix even in comparison with modification by Glymo.

Analyses of the experimental data allow deducing certain conclusions. Modification of nanoshungit filler by organosilanes significantly improves the quality of rubber compounds. Using the Thiol organosilane, we obtained the highest tensile strength at 5 MPa more than rubber filled with nanoshungit without modification, with the extension not reaching 300%, which shows good mechanical properties of the vulcanizate. Organosilane Glymo sulfur-free showed an increase in rubber tensile strength, but its elongation was over 300%. The use of Si 264 as nanoshungit modifier also showed an increase in elastomer strength about 3 MPa relative to composites filled by nanoshungit without modification. This shows that the modification has been successfully completed. The sample with TESPT showed increased elastic-strength properties up to 30%.

Due to using force modulation or phase-contrast modes, separate aggregates and agglomerates of taurit or diatomit in sizes from 100 nm to 1 μm in the elastomeric matrix are visualized by SPM. The form of these aggregates and agglomerates in **Figures 6** and **7** is characterized by a sharp anisotropy of shape and an isolated heterogeneity of the filler particle structure. The images obtained show that in samples with microdispersed taurit or diatomit, the filler forms large inclusions with a size of several micrometers. When grinding the filler, a much more uniform distribution of nanostructured aggregates in the elastomeric matrix is observed. The results of experiments demonstrate also that the dispersity of the filler has a significant effect on tensile behavior of composites. Materials with microdispersed fillers have much lower tensile strength than samples with nanodispersed fillers. When grinding taurit to the nanodispersed phase, the strength of the vulcanizates increased from 3 to 12 MPa, and diatomit from 5 to 13 MPa, respectively. Grinding of particles of the Neosyl-120 products allows increasing the level of interaction of the filler with the elastomeric matrix, which leads to a noticeable improvement in the elastic-strength

properties: the conventional strength increases from 3 to 10 MPa. Grinding of these fillers did not lead to significant changes in the modulus of elasticity.

Theoretical analysis of obtained results for these different fillers in such elastomer matrix allows to conclude that the reason for strength reinforcement of these composites is due to the redistribution of valence π electrons of butadiene-styrene rubber between acceptor fillers and the donor matrix of the elastomer. The resulting interatomic interactions lead to more uniform distribution of fillers in the rubber matrix and the corresponding effects of enhancing the physico-mechanical characteristics of the composites.
