Synthetic And Characterization Of Microcapsules For Self-Healing Polymer Composite

It was inescapable that microcracks and partial damage often happened within the structure when polymer composite were used, which resulted in the mechanical performance of material descend. So it was very important to repair the microcracks in time. One new material called self-healing material was developed. The self-healing material could increase the reliability and service life of polymers. Especially in such applications as aircrafts and bridges where the damaged material was very hard to heal, the self-healing material had a great potential.One method for composites repair was to apply the technology of microcapsulates. The self-healing polymer material with microcapsulated healing agent was a structural polymeric material with the ability to heal cracks autonomically. The healing was accomplished by incorporating a microcapsulated healing agent and a catalytic chemical trigger within an epoxy. An approaching crack ruptured the embedded microcapsules, releasing the healing agent into the crack plane through capillary action. Polymerization of the healing agent was triggered by contact with the embedded catalyst, bonding the crack faces.The microcapsule with urea and formaldehyde as the raw shell material, and dieyclopentadiene (DCPD) as the core material was synthesized by in-situ polymerization in an oil-in-water emulsion. The optimum conditions of surfactant and mass ratio of the shell material to the core material in microencapsulation was studied in detail to ensure the microcapsules possess excellent maneuverability. The diameter of microcapsules were measured and the distribution of diameter was calculated by using optic microscope (OM). The surface morphological was examined and the wall thickness was measured by scanning electron microscopy (SEM). It was proved the wall materials have been formed by Fourier-transform infrared spectrometer (FTIR). The thermal properties were studied by thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) experiments. And the osmosis of microcapsules was investigated. The results showed that the poly(urea-formaldehyde) microcapsules containing DCPD had been successfully synthesized. The optimum conditions are as follows: mass ratio of the shell material to the core material, 0.5:1; final pH value, 2.5~3.0; surfactant, sodium dodecylbenzene sulfonate (DBS), 0.5g/L; agitation rate, 500r/min, reaction temperature, 60℃, reaction time, 2~3h. The processing parameters, such as mass ratio of the shell material to the core material, final pH value, agitation rate, and surfactant, greatly influence the properties of microcapsules during in-situ polymerization. And the state of microencapsulation is dramatically dependent on mass ratio of the shell material to the core material, final pH value and surfactant.