As a type of phase transition in natural rubbers, strain-induced crystallization is a phenomenon where amorphous polymer molecules transform to perfect order structures (crystallites) under the course of extension. Strain-induced crystallites are supposed to play an important role in elastomer reinforcement and crack growth resistance in natural rubbers. To thoroughly understand the strain-induced crystallization in natural rubbers, conventional mechanical measurements are inadequate because they only provide a macroscopic relation between stress and strain. Strain induced crystallization is usually studied using synchrotron radiation facilities, which are hardly accessible to most of research laboratories. On the other hand, as strain-induced crystallization is strongly exothermic, the synchrotron X-ray diffraction technique is also insufficient to study the thermodynamics of strain-induced crystallites. In this project, a computational thermodynamic framework coupled with the infrared thermography based quantitative surface calorimetry is proposed and applied to detect strain-induced crystallinity in multiaxial deformations of filled natural rubbers. While microstructural information (e.g. crystal orientation and distribution) as well as thermodynamics of strain-induced crystallization are still accessible via this coupling approach, it is superior to synchrotron X-ray diffraction as (1) no expensive synchrotron radiation facility is required and (2) it is applicable for a classical mechanical laboratory. Thus, the proposed approach will shed new light on strain induced crystallization under realistic multiaxial strain states and enable practical application of this phenomenon in rubber products especially for strength enhancement.
DFG Programme
Research Grants
International Connection
France, Poland
