Surface Micro-Nano Structure Preparation And Wetting Properties Of Polypropylene/Graphene Composites

Porous anodized aluminum has the advantages of controllable nanoporous structure,good chemical stability,thermal stability,high hardness and extremely large specific surface area,etc.It has gradually become an important template for the preparation of polymer superhydrophobic surfaces.It breaks the limitations of the traditional polymer superhydrophobic surface,such as complicated construction,expensive cost,unstable wetting resistance,etc.,making the superhydrophobic polymer surface gradually become practical.In this paper,porous anodized aluminum with different pore sizes and morphologies were obtained by changing the electrochemical parameters.Polypropylene(PP)with good hydrophobicity and good formability and graphene(GP)with low surface energy were selected as the materials,and a multi-layer micro/submicro/nanopore structure was prepared on the surface of pure aluminum by anodizing technology;Using porous anodized aluminum oxide(AAO)as a template,a multi-layer micro/submicro/nano structure was prepared on the surface of PP/GP by hot stamping to obtain a super-hydrophobic polymer surface with good wetting properties.The research results are as follows:(1)Precise preparation of micro / nano structures on the surface of PP/GP: Using AAO as a template,the micro/nano structure was prepared on the surface of PP/GP using hot stamping technology.In terms of matching with the AAO template structure,it was found that PP/GP surface micro/submicro/nanostructure> PP/GP surface micro-nano structure> PP / GP surface nanostructure> pure PP surface nanostructure,indicating that the increase in the scale of the surface structure of the porous anodizing aluminum template and the addition of GP materials can improve the accuracy of replication.(2)Wetting properties: When contacted with 4,6,8 ?L droplets,PP/GP surface micro/sub-micro/nano structure,PP/GP surface micro/nano structure and PP/GP surface nano structure all show low adhesion.For 4 ?L droplets,the PP surface nanostructures has a CA of 135 °and RA> 90 °,and PP/GP surface nanostructures has a CA of 152 °and RA <5 °,while for 6 ?L droplets,PP/GP surface nanostructures cannot maintain superhydrophobic properties again;for 4 ?L droplets,PP/GP surface micro-nano structure has a CA of 164.5 °and RA <5 °,for 8 ?L droplets,the CA of PP/GP micro-nano structure surface still maintains at 153.7 °,but for 10 ?L droplets,the CA of micro/nano structure on PP/GP surface drops to 147.8 °,which cannot maintain the super-hydrophobic properties;for 10 ?L droplets,PP/GP surface micro/submicro/nanostructure has a CA of 155 ° and a RA closer to 0.5 °.This indicates that in terms of hydrophobicity,PP/GP surface micro/submicro/nano Structure> PP/GP surface micro-nano structure> PP/GP surface nanostructure> pure PP surface nanostructure.(3)Static wetting stability: PP/GP surface micro/submicro/nanostructure,PP/GP surface micro/nano structure and PP/GP surface nanostructure samples were immersed in a measuring cylinder with an underwater pressure difference of 3626 Pa for 60 min.After being taken out,the PP/GP micro/submicro/nanostructure surface and the PP/GP micro/nanostructure surface still maintain Cassie-Baxter state,while the wetting state of some areas of the PP/GP nanostructure surface changes from Cassie-Baxter state into Wenzel state;this shows that the underwater wetting stability of PP/GP surface micro/submicro/nanostructures and PP/GP surface micro/nanostructures are better than PP/GP surface nanostructures.(4)Dynamic wetting stability: when impacted by droplets of different speeds,PP/GP surface micro/submicro/nanostructure,PP/GP surface micro-nano structure and PP/GP surface nanostructure can stably maintain Cassie-Baxter state.However,local pinning occurs on the surface of PP/GP nanostructure when the droplet impact velocity is 1 m/s,and only when the droplet impact velocity reaches 1.73 m/s,the PP/GP micro/submicro/nano structure surface and PP/GP micro-nano structure surface can observe the local pinning phenomenon;It indicates that PP/GP surface micro/submicro/nano structure and PP/GP surface micro/nano structure are superior to PP/GP surface nano structure in terms of dynamic wetting stability.(5)Frost resistance: During the formation of frost crystals,PP/GP surface micro/submicro/nanostructure,PP/GP surface micro-nano structure and PP/GP surface nanostructure surface can make the droplets suspend on the surface,but the size of the condensed droplets on the surface of PP/GP micro-nano structure is small and the distribution density is high,indicating that the mobility of the condensed droplets on the surface of micro-nano structure is relatively low;Compared with PP/GP smooth surface,the frosting completion times of PP/GP surface nanostructures,PP/GP surface micro/nano structures,PP/GP surface micro/submicro/nanostructure are extended by 40 s,99 s and 162 s,respectively.It indicates that in terms of frost resistance,PP/GP surface micro/submicro/nano structure > PP/GP surface micro/nano structure > PP/GP surface nano structure > PP/GP smooth surface.