Fabrications And Properties Of Graphene/Epoxy Memory Composites

Shape memory polymers(SMP)are the most essential branches of smart materials,which can maintain a temporary shape and subsequently recover their initial shape upon exposure to appropriate external stimuli,such as water,pH,light,heat,electric and magnetic fields.In the past several decades,SMPs have made huge advancement,and have also attracted a large amount of attention from both academia and industries due to their academic and technological significance.Compared with shape memory alloy(SMA)and shape memory ceramic,SMP possess many outstanding aspects,such as easy processibility,ultra-high shape memory recover ratio,low cost,lightweight,good biodegradability,and adjustable shape memory transformation temperature.However,SMP have lower mechanical strengths and thermal conductivities than that of SMA,resulting in lower shape recovery stresses and thermal response speeds,which have greatly restricted their wide applications in human life.Water-borne epoxy(WEP)is a kind of environment-friendly polymer which possess outstanding shape memory performance.However,WEP has a poor mechanical strength and single response mode.Fortunately,the mechanical strength and thermal respond speed of WEP can be improved through adding functional fillers.Moveover,introducing excellent conductive and photo-thermal conversion RGO paper developed electro-and light-responsive RGO/WEP/RGO composite film.Firstly,in order to improve the mechanical strength and thermal respond speed of WEP,graphene oxide(GO)were used to prepare the GO/WEP composites,which have excellent mechanical strength and good water-soluble acting as the reinforcing filler.The research results showed that the mechanical strength and thermal respond speed of the GO/WEP composites increased with the increasing content of GO.For example,compared with WEP,the mechanical strength and thermal respond speed of the 4wt%GO/WEP composites were increased by 54%and 4.3%,respectively.Secondly,the improvement of GO/WEP’s properties were limited due to the damaged phenyl structure of GO after oxidation.Based on GO reinfrocement,the second infrocement carbon nanotube(CNT)was added to the GO/WEP composites.The GO/CNT/WEP composites were prepared via high intensive stirring,freeze-drying and hot-press methods.The weight ratio of CNT to GO was 1:1 in the GO/CNT/WEP composites.The experimental results showed that CNT was uniformly dispered in the composites with the help of GO and obtained high performance GO/CNT/WEP composites.Compared with WEP,the mechanical strength of the4wt%GO/WEP,4wt%CNT/WEP and 4wt%GO/CNT/WEP increased by 54%,33%and 77%,respectively.The thermal respond speeds were increased by 4.3%,3.4%and 6.3%,respectively.The results indicated that GO and CNT showed a remarkable synergetic effect in improving the mechanical strength,thermal respond speed of WEP.In order to enrich actuation method of WEP,the novel reduced graphene oxide RGO/WEP/RGO sandwich structure composite films were fabricated by introducing the RGO paper as a functional layer on the surface of WEP.The outstanding conductive and photo-thermal conversion RGO papers endowed the composite films with thermo-,electro-and light-responsive shape memory behavior simultaneously.When the voltage of 8 V was applied to the composite film,the shape recovery process can be completed within 16 s.When the composite film was irradiated by near-infrared light with an energy density of 3.0 w/cm~2,the shape recovery process can be completed within 7 s.Forthermore,the shape recovery process of the composite film can be intelligently controlled by changing the magnitude of the applied voltage and the energy density of infrared light.