PSI - Issue 32

Kseniia A. Mokhireva et al. / Procedia Structural Integrity 32 (2021) 137–143 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

140

4

strain values were estimated according to the movement of the marks applied to the specimens using a video extensometer. Figure 2 shows the averaged loading curves of rubbers filled with a small amount of granular particles and graphene flakes. The mechanical properties of these vulcanizates do not depend on the choice of the load axis. It can be seen from the graphs that a small filling of the matrix with graphene and carbon black does not lead to an increase in the material rigidity even at threefold elongation. Very interesting results were obtained in the case when the matrix is filled with nanodiamonds, which increase the rigidity and strength properties of the matrix, though their volume fraction in the material is very small.

Fig. 2. Curves of uniaxial loading of elastomers: 1 – unfilled and with fillers (7 phr): 2 – carbon black, 3 – graphene, 4 – detonation nanodiamonds. Loading rate is 100%/min.

Elastomers filled with a small amount of multi-walled nanotubes are isotropic. Moreover, the preliminary purification of the filler leads to their better dispersion and interaction with the matrix, and, consequently, improves material hardening. Rubbers filled with purified single-walled nanotubes have an initial anisotropy obtained during manufacturing – calendaring (see Fig. 3). Note that the anisotropy appears even at a low level of filling. In our opinion, this is due to the difference in flexibility (the structural feature) of particles of single-walled and multi walled carbon nanotubes.

Fig. 3. Curves of uniaxial cyclic loading of elastomers filled with purified single-walled carbon nanotubes (7 phr): dashed line - specimens cut along the calendaring direction, solid line – specimens cut across the calendaring direction.

Similar tests were carried out for highly filled vulcanizates with 43 phr of carbon black and 7 phr of particles of one of the nanocarbons examined in this study. Based on the previously obtained results, we suggested that