Study On The Self-Healing Polymer Material With Microcapsulated Healing Agent

The self-healing polymer material with microcapsulated healing agent is a structural polymeric material with the ability to heal cracks autonomically. The healing is accomplished by incorporating a microcapsulated healing agent and a catalytic chemical trigger within an epoxy. An approaching crack ruptures the embedded microcapsules, releasing the healing agent into the crack plane through capillary action. Polymerization of the healing agent is triggered by contact with the embedded catalyst, bonding the crack faces. Such material can increase the reliability and service life of thermosetting polymers used in a wide variety of applications ranging from microelectronics to aerospace. Especially in such applications as aircrafts and bridges where the damaged material is very hard to heal, the self-healing material has a great potential. Therefore, a study on the self-healing polymer material is conducted regarding the following contents.First, in order to get the suitable microcapsules for the self-healing material, the technological parameters such as the agitation time before reaction, the reaction time, the type and content of the emulsfier are optimized experimentally in order to control the size distribution of the microcapsules. Technological parameters are experimentally chosen as follows: the agitation time before reaction is 15min, the reaction is expended for 4 hours, the type and content of the emulsfier are 0.12% PMN.Secondly, the influence of the microcapsules on the fracture toughness of the polymer material is discussed using the TDCB fracture specimen. When the microcapsule content keeps constant, the fracture toughness of the material decreases linearly with the increase of the microcapsule size. As the microcapsule content increases, the fracture toughness increases to a maximum at the low levels and then decreases gradually.Thirdly, the microcapsule content and microcapsule size are optimized by the uniform design. The experimental data shows that when the microcapsule size is less than 76μm and microcapsule content is 3%, the fracture toughness can reach the maximum 2.15Pa*m^1/2.Finally, the mechanism of the self-healing method is proved primarily. The electron micrographs of fracture planes containing embedded microcapsules indicate that an approaching crack ruptures embedded microcapsules, releasing healing agent into the crack plane through capillary action. By choosing Grubbs' catalyst as the embedded catalyst, an epoxy resin material embedded by 9wt% microcapsules and 2.5wt% catalyst is made. It is found that the material cannot be self-healed when the sample is tested to failure. A partial healing can be accomplished by manual injection of DCPD monomer that is premixed with catalyst onto the crack plane after the sample is tested to failure.