The exothermic reaction and overheating during radical polymerization of an Elium® resin and glass fiber reinforced Elium® composites are critically evaluated in this work. The polymerization kinetics of the Elium® resin is obtained by performing differential scanning calorimetry (DSC) scans. The measured data is fit to a temperature and degree of polymerization (DoP) dependent kinetics model. A coupled thermo-chemical process model is developed to predict the temperature evolution and DoP. First, the model is validated with the water bath experiments in which the pure Elium® resin is polymerized at different temperatures (30, 50 and 70 °C). The validated process model is then applied to a vacuum infusion process of glass reinforced Elium® composite laminates with different thicknesses (3.8, 7.5 and 11.3 mm) at room temperature. The produced laminates have the void content lower than 1%. The peak temperature is found to be approximately in the range of 155-160 °C during the water bath experiments. On the other hand, the peak exothermic temperature is approximately 49 °C and 70 °C for 3.8 mm and 11.3 mm thick laminate, respectively. The developed polymerization kinetics model is found to be effective as the predicted temperature evolutions match well with the measured temperatures for different laminates. The effect of laminate thickness and processing teperature on the peak temperature is studied by the developed numerical model. The thermo-chemical process model developed in this work is therefore capable of predicting the polymerization overheating for Elium® composites and can enable the optimization of the manufacturing process to control the thermal and DoP histories.

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A cementitious system embedded in microcapsules can achieve self-healing, and the fracture and triggering behavior of microcapsules is with great importance. In this study, the crack behavior of the concrete-microcapsule system was simulated by a three-dimensional lattice model. Based on the results of the fracture energy test on concrete beams and the nanoindentation test on microcapsules, the local mechanical properties of the lattice elements were determined. The aim of this paper is to set up a three-dimensional lattice model to study the trigger mechanism of the microcapsule-interface-concrete zone.@en

Microcapsules containing rejuvenator are particles used to increase the self-healing capability of asphalt. To date, no reports focus on studying their behaviors in asphalt binders between the aggregates. The purpose of this work was to directly observe the states of self-healing microcapsules in asphalt binders. Asphalt samples were prepared by mixing bitumen and various weight contents of microcapsules. Experimental tests were carried out to observe the morphology, integrity, distribution, thermal stability, interface bonding and triggered rupture of microcapsules in asphalt binders. Fluorescence microscope morphologies and X-ray computed tomography images showed that microcapsules survived in asphalt resisting high temperature and strong agitation without premature damage. At the same time, microcapsules were homogenously dispersed in asphalt binders avoiding particles aggregation and adhesion. A circular heating-cooling process was used to simulate temperature changes in the natural environment. It was found that microcapsules still kept a stable state after an extreme temperature change. In addition, interface debonding phenomenon did not appear. Microscopic observation results reflected that microcapsules could be pierced by microcracks in the asphalt binder and the encapsulated rejuvenator flowed out under the force of capillary action. All the above conclusions indicate that microcapsules containing rejuvenator meet the application conditions and play the role of self-healing material in asphalt binders.

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The aging problem of bitumen leads to pavement failure after years of usage. Microcapsules containing rejuvenator is a promising chemical product applied to improve the self-healing ability of bitumen. The aim of this work was to fabricate and characterize the self-healing microcapsules containing bituminous rejuvenator with nano-inorganic/organic hybrid shells. The shell had a two-layer structure: the inside layer material was the cross-linked methanol modified melamine-formaldehyde (MMF) resin and the outside materials was composed of methanol modified MMF resin and nano-particles of calcium carbonate (nano-CaCO₃). The forming mechanism of the two-layer structure was described based on a twice-condensation process. Fourier transform infrared spectroscopy (FT-IR) and Energy Dispersive Spectroscopy (EDS) results confirmed the nano-inorganic/organic hybrid structure of shells. The ideal content of nano-CaCO₃ particles was optimized through the morphologies observation. The addition of nano-CaCO₃ particles did not greatly influence the mean size of microcapsules. On the contrary, the nano-CaCO₃ particles increased the shell thickness of microcapsules owing to the loosely composite structure of shells. Thermal stability tests showed that the microcapsules could survive in the bitumen with a temperature of 200 °C. Moreover, the microcapsules could resist a violent temperature change process without destruction attributing to the protection of nano-CaCO₃ particles. The nano-particles on microcapsules decreased the deformation possibility of shells tested by nanoindentation.

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