Preparation And Performance Study Of Dynamic Covalent Bonding Self-healing Epoxy Asphalt

Epoxy Asphalt(EA)is composed of epoxy resin,curing agent,and asphalt in specific proportions.It fundamentally alters the thermoplastic nature of asphalt,imparting excellent high-temperature performance,fatigue resistance,and corrosion resistance to it.Once chemically cross-linked,epoxy asphalt forms an insoluble and non-melting threedimensional network structure.Consequently,repairing cracks in epoxy asphalt road surfaces becomes challenging,and post-removal during maintenance generates a substantial amount of waste epoxy asphalt mixture that is difficult to recycle.Traditional disposal methods(abandonment,stacking,burial)pose direct environmental pollution,leading to massive resource wastage and damage.Hence,there’s an urgent need for optimizing and improving epoxy asphalt to address its inherent recyclability issue,ensuring sustainability and efficiency in its application.To address these crucial issues,the proposed approach involves incorporating dynamic disulfide bonds into the epoxy asphalt system.This not only retains the excellent mechanical properties of thermosetting epoxy asphalt but also utilizes the exchange characteristics of dynamic disulfide bonds to achieve self-healing and recyclability of epoxy asphalt.The primary research objectives and conclusions of this study are outlined as follows:(1)Integrating polyethylene glycol diglycidyl ether as a flexible chain segment with bisphenol A-type epoxy,utilizing 2,2’-diaminodiphenyl disulfide containing disulfide bonds as a curing agent to produce self-healing epoxy resin.The overall mobility of the crosslinked network is adjusted to obtain self-healing materials with different properties by varying the content of flexible chain segments.Various macro and micro-level characterization techniques are employed to explore the impact of different flexible chain segment contents on the structural properties,thermodynamics,and self-healing performance of the epoxy resin.Rheological studies investigate the dynamic response temperature of disulfide bonds,exchange rate,and the degree of network formation.Results indicate that the introduction of flexible resin reduces the crosslink density,enhances polymer segment mobility,and improves the repair efficiency of self-healing epoxy resin.A linear correlation model between crosslink density and dynamic exchange is established based on stress relaxation results,enabling control of stress relaxation behavior by adjusting crosslink density at specific temperatures.(2)Molecular dynamics simulations(MD)are employed to construct models of selfhealing epoxy resin with disulfide bonds from a molecular-level perspective,focusing on the structural characteristics.Perl scripting facilitates dynamic crosslinking in the model.Analysis is conducted on system energy,free volume,radial distribution functions,mean square displacement,and glass transition temperature to assess the impact of crosslinking density and resin ratio on the performance of self-healing epoxy resin.Furthermore,simulation and analysis of the interfacial dynamic diffusion and healing process of disulfide bond exchange are conducted at the molecular scale.The results indicated that the glass transition temperature,chain mobility,and mechanical properties of self-healing epoxy resin increase with increasing crosslink density but decrease with higher flexible resin content.During the repair process,self-healing epoxy resin maintains the integrity of the crosslinked structure.Resins with higher flexible content exhibit shorter relaxation times,consistent with experimental results.In addition,the Kohlrausch Williams Watts function can be used to fit the stress relaxation of self-healing epoxy resin and obtain the characteristic relaxation time.(3)The self-healing epoxy resin is combined with asphalt to create epoxy asphalt materials with self-healing and regenerative properties.Incorporation of polycyclic aromatic hydrocarbon compatibilizers enhances the compatibility between self-healing epoxy resin and base asphalt.The addition of self-healing epoxy asphalt,along with external compatibilizers,ensures the system’s stability.Viscosity tests evaluate its construction adaptability,and tensile tests explore its mechanical properties.The solidification process of self-healing epoxy asphalt was analyzed using non isothermal differential scanning calorimetry,offering a theoretical foundation for its manufacturing procedure.Experimental results demonstrate that the viscosity increase rate of selfhealing epoxy asphalt increases with temperature and epoxy content.Self-healing epoxy asphalt exhibits mechanical properties comparable to conventional epoxy asphalt,with increasing epoxy content leading to gradual increases in tensile strength and decreases in elongation at break.The curing exothermic characteristic temperature of self-healing epoxy asphalt increases with the increase of heating rate.As the curing temperature increases,the time required for self-healing epoxy asphalt curing gradually shortens.The curing degree and temperature exhibit typical self-catalytic curing reaction characteristics.By solving the three kinetic factors,an n-order curing kinetic equation can be established,which can be used to reasonably predict its curing time in different construction environments.(4)High-temperature shear rheology evaluates the rheological properties of selfhealing epoxy asphalt,comparing them with base asphalt and traditional thermosetting epoxy asphalt.The impact of incorporating self-healing epoxy on asphalt viscoelasticity is extensively studied.Real-time fluorescence microscopy monitors the repair process of self-healing epoxy asphalt,while fracture-heal-fracture and heat-resistance tests evaluate its repair and reprocessing properties under different conditions.Results indicate that selfhealing epoxy asphalt exhibits high-temperature performance similar to traditional epoxy asphalt.With the rearrangement of the crosslinked network topology,self-healing epoxy asphalt transitions from a viscoelastic state to a high-elastic state to a viscous flow state as temperature increases.The transition from viscoelastic to viscous flow shifts toward higher frequencies as the content of self-healing epoxy increases,indicating that higher self-healing epoxy content can enhance material dynamic response speed.The selfhealing efficiency of self-healing epoxy asphalt increases with the increase of self-healing epoxy resin content after healing at 120 ℃ for 3 h.However,thermal cycling may induce fatigue aging,consequently reducing repair efficiency.Self-healing epoxy asphalt achieves crosslink degradation through thiol exchange,demonstrating superior degradability and environmental friendliness compared to traditional epoxy asphalt.