Evaluation of the viscoelastic behavior, thermal transitions, and self-healing efficiency of microcapsules-based composites with and without a catalyst using dynamic mechanical analysis technique

This comprehensive study investigates the viscoelastic behavior, thermal transitions, and self-healing efficiency of microcapsule-based composites with and without a catalyst. The composites consist of urea-formaldehyde/dicyclopentadiene microcapsules embedded in an epoxy matrix, with the addition of Grubbs' catalyst. Our research examines the impact of repetitive dynamic mechanical analysis (DMA) testing and the presence of Grubbs' catalyst on the composites' self-healing efficiency and dynamic mechanical properties. Using laser microscopy, optical microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis, we employ various characterization techniques to enhance our understanding of the composite behavior. The findings emphasize the importance of evaluating self-healing efficiency through DMA, which is a reliable, expeditious, and non-destructive method. The results show that incorporating Grubbs' catalyst significantly enhances the self-healing performance of the composites, effectively mitigating the degradation of mechanical properties due to aging. Furthermore, the inclusion of catalyst particles improves stiffness, rigidity, and energy dissipation characteristics, facilitating the self-healing process. However, careful consideration is necessary to balance mechanical properties and the glass transition temperature when designing self-healing composites. This study demonstrates a promising self-healing efficiency of approximately 73% and 44% in the second and third DMA tests, respectively, for composites containing microcapsules and Grubbs' catalyst.