Determining strain-induced crystallization of natural rubber composites by combined thermography and stress-strain measurements

• Published in: Polymer testing 2018-04, Vol.66, p.87-93
• Main Authors: Plagge, J., Klüppel, M.
• Format: Article
• Language: English
• Subjects: Carbon black; Crystal structure; Crystallinity; Crystallization; Filler reinforcement; Natural rubber; Strain; Strain induced crystallization; Stress-strain curves; Stress-strain relationships; Thermography; X ray sources; X-ray scattering
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2017.12.021

Strain induced crystallization is essential to the physicochemical properties of polymer materials, but is difficult to investigate, as it usually requires X-ray sources in combination with stretching machines. We improve and validate a recently developed method which allows the calculation of the crystallinity index using easily available thermography and stress-strain data. For natural rubber, the method is shown to be reproducible and delivers results quantitatively comparable to spectroscopic methods such as wide angle X-ray scattering. The incorporation of different amounts of carbon black is shown to increase the level of crystallization and to change the shape of the strain-crystallization curves. Additionally, crystallinity during partial retraction is investigated and reveals that crystallization characteristics change at sufficiently high strain. •Strain Induced Crystallization (SIC) is quantified using stress strain data and thermography.•Results from scattering for natural rubber are reproduced.•The method is reproducible and checked for consistency with non-crystallizing polymer.•Carbon black filler shifts on and offset to lower strains.•Incomplete stretching cycles exhibit reduced hysteresis, possibly due to less supercooling.