Abstract. The present work verified the capability of epoxy/mercaptan/tertiary amine system for retarding and/or arresting fatigue cracks in epoxy materials subjected to cyclic loading at room temperature. By using static and dynamic manual infiltration methods, the effects of hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent were revealed. Depending on the applied stress intensity range and the competition between polymerization kinetics of the healing agent and crack growth rate, the above mechanisms exerted different influences on crack retardation under different circumstances. On the whole, the epoxy/mercaptan/tertiary amine system proved to be very effective in obstructing fatigue crack propagation. It formed a promising base for developing self-healing epoxy materials that enable in-situ autonomic rehabilitation of fatigue crack. Vol.4, No.10 (2010) 644-658 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2010.79 dling strength in minutes at room temperature and develop useful bond strengths at ambient temperatures as low as -20°C. Therefore, it should be favorable for repairing fatigue damages under cyclic loading. In our previous work, self-healing epoxy composites containing dual encapsulated healant, i.e. two types of microcapsules that respectively include epoxy prepolymer as the polymerizable component and mercaptan/tertiary amine catalyst as the hardener, were made [18][19][20][21]. Upon fracture the unreacted epoxy can be bled into damage sites together with the hardener fluid and then polymerized to repair cracks. The system proved to work in the case of monotonic fracture as characterized by the attractive healing effect even below room temperature. As a continuation of our project, the present work is focused on examination of the performance of the epoxy/mercaptan/tertiary amine system in suppression and rehabilitation of fatigue crack in epoxy materials via manual infiltration. Effect of adhesive curing process on fatigue crack propagation was systematically studied. The results are expected to provide a knowledge frame for the subsequent in-situ self-healing that has the practical value for engineering application. Keywords: smart polymers, fracture and fatigue, self-healing, epoxy eXPRESS Polymer Letters Experimental 2.1. Materials and specimen preparationTapered double cantilever beam (TDCB) specimens were cast from the mixture of epoxy resin (EPON 828, diglycidyl ether of bisphenol A, Hexion Specialty Chemicals, USA) and 12.5 pph curing agent (diethylenetriamine, DETA, Shanghai Medical Group Reagent Co., China). The mixture was degassed, poured into a closed silicone rubber mold and cured for 24 h at room temperature, followed by 48 h at 40°C. Table 1 shows the material properties.The healing agent consists of epoxy (1:1 mixture by weight of EPON 828 and diglycidyl ether of resorcin (J-80, Wuxi Resin Factory of Bluestar New Chemical Materials Co., China)) and the hardener (pentaerythritol tetrakis (3-merca...

Polymer materials often experience micro-cracks during their service. Self-healing polymeric materials have the built-in capability to substantially recover their load transferring ability after damage. This field of self-healing materials is a relatively new one, beginning in the early 1990s, with the majority of the research occurring in the past decade [1,2]. The ring-opening metathesis polymerization of dicyclopentadiene (DCPD) [3,4], addition and ionic polymerization of epoxy [5], condensation polymerization of polysiloxane [6], organic solvents [7] and isocyanates [8], have been reported for automatically repairing cracks in polymers at room temperature.Several researchers [5,[9][10][11] have successfully measured fatigue-crack propagation in epoxy resins. Brown and coworkers [5,9] investigated the effect of embedded urea-formaldehyde (UF) microcapsules on the monotonic fracture properties of a selfhealing epoxy. In addition to providing an efficient mechanism for self-healing, the presence of liquidfilled microcapsules increased the virgin monotonic-fracture toughness of epoxy by up to 127%. The increased toughening was correlated with a change in the fracture plane morphology from mirror-like to hackle markings with subsurface microcracking. The addition of microcapsules to an epoxy matrix significantly increased the resistance to crack growth under dynamic loading conditions. Abstract. The effect of temperature on the fracture behaviour of a microcapsule-loaded epoxy matrix was investigated. Microencapsulated epoxy and mercaptan-derivative healing agents were incorporated into an epoxy matrix to produce a polymer composite capable of self-healing. Maximum fracture loads were measured using the double-torsion method. Thermal aging at 55 and 110°C for 17 hours [hrs] was applied to heal the pre-cracked samples. The addition of microcapsules appeared to increase significantly the load carrying capacity of the epoxy after healing. Once healed, the composites achieved as much as 93-171% of its virgin maximum fracture load at 18, 55 and 110°C. The fracture behavior of the microcapsule-loaded epoxy matrix was influenced by the healing temperature. The high self-healing efficiency may be attributed to the result of the subsurface micro-crack pinning or deviation, and to a stronger microencapsulated epoxy and mercaptanderivative binder than that of the bulk epoxy. The results show that the healing temperature has a significant effect on recovery of load transferring capability after fracture.