Strain-induced crystallisation (SIC) significantly enhances the mechanical performance of natural rubber. However, the presence of reinforcing fillers such as carbon black or silica complicates the identification of the crystallisation onset with hysteresis measurements due to overlapping of chain orientation and viscoelastic effects. This study proposes a novel, indirect approach to identification of the SIC onset by analysing overstress evolution during multi-step relaxation tests (MSRT) in both filled and unfilled natural rubber compounds. A custom clamp system was designed to enable large, consistent deformations without specimen slippage. Unfilled specimens exhibited minimal overstress until stretches above at room temperature, where a sharp increase in relative overstress indicated crystallite formation. This result was validated by hysteresis measurements at slow deformation rates, which showed a plateau in the stress response consistent with crystallisation. For filled materials, viscoelastic contributions were, as expected, observed from the very beginning of the test, and SIC onset was observed at lower stretches of . The crystallite growth appeared more gradual due to filler interference with the material matrix. Finally, it was confirmed that the SIC onsets determined directly by X-ray diffraction exactly coincide with those determined by the mechanical analysis. These findings suggest that overstress analysis is a valuable tool for identifying SIC onset in filled elastomer compounds, offering an effective alternative to less accessible measurement methods.     «

Strain-induced crystallisation (SIC) significantly enhances the mechanical performance of natural rubber. However, the presence of reinforcing fillers such as carbon black or silica complicates the identification of the crystallisation onset with hysteresis measurements due to overlapping of chain orientation and viscoelastic effects. This study proposes a novel, indirect approach to identification of the SIC onset by analysing overstress evolution during multi-step relaxation tests (MSRT) in bo...     »