Abstract

AbstractThe crystallinity of stretched crystallizable rubbers is classically investigated using X‐ray diffraction. In this study, we propose a new method based on temperature measurement and quantitative calorimetry to determine rubber crystallinity during mechanical tests. For that purpose, heat power density are first determined from temperature variation measurements and the heat diffusion equation. The increase in temperature due to strain‐induced crystallization is then deduced from the heat power density by subtracting the part due to elastic couplings. The heat capacity, the density, and the enthalpy of fusion are finally used to calculate the crystallinity from the temperature variations due to strain‐induced crystallization. The characterization of the stress–strain relationship and the non‐entropic contributions to rubber elasticity is not required. This alternative crystallinity measurement method is therefore a user‐friendly measurement technique, which is well adapted in most of the mechanical tests carried out with conventional testing machines. It opens numerous perspectives in terms of high speed and full crystallinity field measurements.

Highlights

  • The strain-induced crystallization (SIC) of rubber is classically investigated using X-ray diffraction (XRD)

  • We propose to determine crystallinity from heat power density instead of temperature, by using infrared thermography during the mechanical tests

  • This study proposes a new measurement technique to determine the crystallinity in stretched crystallizing rubber using IR thermography

Read more

Summary

INTRODUCTION

The strain-induced crystallization (SIC) of rubber is classically investigated using X-ray diffraction (XRD). In the 1970s, Göritz and co-workers showed that crystallinity can be quantified accurately during stretching through calorimetric measurements and carried out numerous studies on the calorimetric response of stretched natural rubber (see for instance Göritz and Müller[12]).1 This remarkable work on unfilled natural rubber provided the crystallinity in relation with the stretch during a mechanical loading and during stress relaxation tests carried out at different stretch levels. A systematic deviation from the thermomechanical model was obtained in all the crystallinity measurements and led to a negative crystallinity at low stretches for which the material is not crystallizing This was attributed by the authors themselves to the effect of nonentropic contributions (mainly rotation of carbon bonds, network bonds effects, and interactions between chains).

METHODOLOGY FOR CRYSTALLINITY MEASUREMENT
Calorimetry under stretching
Determination of the crystallinity
APPLICATION TO AN UNFILLED NATURAL RUBBER
Mechanical and calorimetric responses
Determining crystallinity
CONCLUSION

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.