Investigation of strain-induced crystallization of carbon black and silica filled natural rubber composites based on mechanical and temperature measurements

- Strain induced crystallization is detectable using temperature and mechanical data.
- The developed method is simple and efficient, thus allowing broad-scale measurements.
- Carbon black filled samples show increased SIC compared to silica filled ones.

Strain-induced crystallization (SIC) in unfilled and carbon black or silica filled Natural Rubber (NR) with and without silane is investigated. The method introduced in this paper is based on measurements of the surface temperature during tensile test, whereby SIC is quantified by dividing the produced heat into different contributions, namely the dissipative heat, entropy-related reversible heat and crystallization enthalpy. It turns out that there is pronounced SIC in unfilled and carbon black filled NR, while silica/silane systems show less SIC. The degree of crystallinity correlates with the tensile strength of the samples. For silica/silane systems at the same strain level self-reinforcement by SIC is less pronounced possibly due to a lower crosslink density or strain amplification factor. Because of its simplicity, the method developed here is a promising option to investigate SIC on a broad experimental scale and provides an alternative access next to well-established methods like WAXS.

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