SELF-HEALING MECHANISM AND APPLICATION OF ACRYLIC MATERIALS

Abstract

Self-healing materials have attracted significant attention from researchers during last decades. However, self-healing materials cannot find practical applications yet due to a weak mechanical strength. Recently, it was identified that an acrylic elastomer, VHB 4910, has an excellent self-healing ability accompanied with a good mechanical strength. This material has been used to fabricate artificial muscles because it has unique dielectric properties. Our study demonstrated that VHB 4910 has a self-healing ability. The self-recovery and self-healing ability of this material after separation by cutting was tested by unidirectional and cyclic tensile tests. It was demonstrated that the strength can be completely recovered or even improved when an elevated temperature is used to accelerate the healing process. The self-healing mechanism was also analyzed by recording the Raman spectra at different distances from the cut and at various times. Analysis of Raman spectra and X-ray diffraction experiments were used to generate a support for the proposed model of self- healing. According to this model the self-healing mechanism of the acrylic elastomer can be attributed to the synergistic effect of the re-association of hydrogen bonding and the diffusion of molecular chains. Furthermore, another application of self-healing materials was proposed in this research. The coating that has not only the self-healing ability but also highly improved corrosion resistance was developed. In this research, a self-healing anticorrosion coating via layer-by-layer (LbL) assembly of the poly(acrylic acid) and poly(ethylene imine) was prepared on the magnesium alloys and electrogalvanized steel (EGS). This coating exhibits a rapid self-healing ability in the presence of water. The self-healing ability can be attributed to the swelling behavior of the damaged area of the coating. In the healing process, water played a role of plasticizer and allowed to increase the mobility of the molecular chains in the polyelectrolyte coating. When graphene oxide (GO) was added into the multilayer coating the corrosion resistance improved by two orders compared to the bare magnesium alloy. The GO layer acts as a strong barrier against the penetration of the corrosive electrolytes and provides an extended corrosion protection to the substrate. Therefore, the proposed multilayer coating with the addition of GO has a rapid self-healing ability and an excellent corrosion resistance.