Study On Photothermal Healing Process In Gold Nanoparticles/Thermoplastic Composites

The thermoplastic composite materials have many advantages,such as good toughness and recyclability. Thermoplastic composites have important applications in many fields, due to the rapid development of high performance thermoplastic polymer. So the basic research of thermoplastic is particularly important. The crack is a major problem for material safety, which is due to the external load and ambient temperature changes, etc.The tiny crack will grow into macroscopic crack and finally make the material failure. To solve this problem, the photothermal effect of gold nanoparticles(Au NPs) was applied to heal the cracks of thermoplastic composites, due to the local heating ability of Au NPs.In this paper, light controlled healable materails was prepared and the healing mechanism was also investigated. In addition, the healing factors were also investigated to get the best healing effect.First of all, the spherical Au NPs are synthesized through chemical reduction method,which have well mono-dispersion, regular shape. The size of Au NPs can be diversified and calculated precisely. The photothermal effect was verified by testing the prepared Au NPs. The results show that Au NPs can effectively convert light energy into heat, and heat the surrounding medium. But the photothermal effect requires a specific frequency of the incident light source, which should be similar to the vibration frequency of Au NPs. The particle size of Au NPs has great impact on photothermal effect, but the the too larger size may not enhance photothermal effect. The test results show that the photothermal effect of Au NPs will achieve the optimal conversion efficiency, when the size of Au NPs is 28 nm.In this paper, a novel method is demonstrated for light trigger self-healing of thermal plastic coatings. Normal thermal polymer coatings can be healed efficiently via local heating generated by photothermal effect of Au NPs. Small amounts of Au NPs were successfully dispersed into the coatings. Once the scratch occurred in the coating surface,a laser could be used to illuminate Au NPs to generate a large amount of heat and dramatically increase the local temperature through the photothermal effect. This would melt the polymer and form inward expansion to reconnect the fracture surface and efficiently merge the scratch. It has been confirmed that the coatings containing Au NPs has the healing ability. The mechanism of the healing was also investigated and it is found that the Au NPs weight ratio and irradiation intensity play the key roles in the healing process. This method confirmed that photothermal effect of Au NPs can heal the large-scale surface scratches.The photothermal effect of Au NPs could heal the cracks not only large-scale on the surface, but also small-scale inside the material. In this context, a novel method is demonstrated for interfacial healing of fiber reinforced composites using photothermal effect of gold nanoparticles(Au NPs). Au NPs were successfully dispersed into the interfacial region of fiber reinforced composite by electrophoretic deposition or chemical sorption.Once the interfacial damage occurred, a laser could be used to illuminate Au NPs to generate a large amount of heat through the photothermal effect. This would melt the resin and form mechanical interlock between the fiber and resin to create a new interface. It has been confirmed by micro bond test that the composite containing Au NPs has the healing ability with a maximum healing efficiency of 93.9 % under optimized conditions for carbon fiber reinforced composites. In addition, the test results show that the photothermal effect can also heal the interface of glass fiber reinforced composites and have perfect healing efficiency.The graphene oxide(GO) can greatly enhance the photothermal effect Au NPs, when they get together. The temperature test results show that GO can make an increase of 1.6times for temperature rises from photothermal effect Au NPs. And this enhancement still has a high stability after repeated heating. In this article, the Au NPs was adsorbed on the surface of GO by chemical adsorption. The GO-Au NPs was mixed into the thermoplastic resin to provide the composites with healing ability. The test results showe that after healing, both surface morphology and mechanical properties of material all perfectly recovered. The optimal healing efficiency can reach 90.1%, when the GO-Au NPs content was 1% and the healing intensity was 400 W/cm2. It is also found that the content of Au NPs and irradiation intensity play the key roles in the healing process.