Study On The Wetting Transition Behavior Of Carbon-based Nanomaterials/polymer Composite Coatings Under Tensile Conditions

Superhydrophobic surfaces show great application prospects in daily life and industrial production due to their unique wetting properties,such as waterproofing of textiles,self-cleaning of exterior walls,anti-freezing of cables and drag reduction of pipes.Water droplets typically have two wetting states on the superhydrophobic surface,namely the Wenzel state and the Cassie state.In the Wenzel state,the water droplets are adsorbed on the superhydrophobic surface and are not easy to roll;In the Cassie state,the water droplets are extremely easy to roll.If the two wetting states can be converted back and forth on a single surface,the surface can be used to transfer liquid.Namely,the Wenzel-surface adheres droplets well,once it turns to the Cassie-surface under certain stimuli(such as light,electric field and temperature),the droplets can be released.Integrating chemical compositions with responsive properties into the surfaces is a highly effective method to control surface wettability.But,the surface with chemical response often suffers several drawbacks such as complicated chemical treatment steps,slow response,and limited lifetime.Alternatively,topography patterns with mechanical response are employed to achieve a more rapid and durable wettability switch.Their geometric parameters(e.g.,space distance and size)can be significantly changed through mechanical stimuli(e.g.,bend and stretch).However,fabrication of the ordered patterns often needs expensive and complicated micro/nano-fabrication technique(e.g.etching).The disordered patterns with micro-nano structures,which can be easily fabricated at large scale by conventional methods,are rarely used for wettability switch due to their fractal structures that are insensitive to mechanical deformation.In this paper,we propose a new mechanism to control the wetting transition of the coating with disordered pattern structure:the Wenzel-Cassie transition is achieved by stretching the carbon-based nanomaterials/polymer composite coating induces cracks to form a multi-layer structure.Here are the main contents:In the first chapter,several species of plants and animals with superhydrophobic surface in nature are introduced firstly,and their structures are simply analyzed.The concept of superhydrophobic wettability is introduced,while the superhydrophobic surface energy and surface tension are briefly introduced;secondly,the classical superhydrophobic model theory and equations,namely Young's equation,Wenzel wetting theory model and Cassie-Baxter wetting theory model are introduced.Then,the research status of reversible superhydrophobic surface wettability are described while the realization method of wetting-reversible coating and related applications are emphatically introduced;finally,the background meaning and research content of the topic are highlighted.In the second chapter,the raw materials,instruments and main characterization methods required for the experiment are briefly introduced;the experimental conditions and experimental schemes are highlighted.In the third chapter,a carbon black(CB)/polybutadiene(PB)coating is prepared on a flexible natural latex substrate using a simple solution spray method.First the relationship between CB content and coating wetting properties is investigated,and a superhydrophobic surface with Wenzel state is obtained.Secondly,the effect of stretch strain on the wetting property of the coating is studied.It is found that the Wenzel state changed to the Cassie state under stretch strain.Next,a corresponding model is constructed to explain and predict the transition of coating wettability,correlating the development of microcracks with macroscopic wettability changes.Finally,the reversibility of coating wetting is studied,and the application of coating in the field of no-loss transfer of microdroplets was introduced.In the fourth chapter,a carbon nanotube(CNT)/PB coating is prepared in the same manner.The effect of CNT content on the wettability of the coating is investigated;The superhydrophobic surface with Wenzel wetting state is screened;The change of wettability of the coating under stretch strain is studied,scanning electron microscopy(SEM)and atomic force microscopy(AFM)are used to obtain the morphology and roughness of the coating during the stretching process,then we explain the Wenzel-Cassie transition of CNT/PB coating by means of the models in Chapter 3;The effect on the conductivity of CNT/PB coatings is compared and the similarities and differences between CB/PB and CNT/PB coatings are compared.In the fifth chapter,the full text is summarized.