Influence Of Nano-SiO₂ On Dilational Viscoelasticity Of Liquid/air Interface Of Different Surfactants

"Interface theology" researches on the air-liquid,liquid-liquid interface(film) deformation(strain)and flowing(shear rate)under dynamic interfacial tension variation.The science involves colloid chemistry,polymer,food,cosmetics, biological science and environmental research etc.,domains,which has the fundamental research value and widespread application prospect.Adsorption of surfactants at solid/liquid interface is a process that surfactant molecules or ions move from solution to solid/liquid interface and concentrate at the interface.It comes to a result that the surfactants concentration at solid/liquid interface is higher than it in solution.Nano-particles dispersed in the surfactant solution also may cause the adsorption of surfactants similarly.Many solid powders such as CaCO₃,BaSO₄,clay,carbon,certain metal subcarbonate,starch etc.,are good emulsifiers.The powder emulsifiers can play the emulsifier role as usual surfactants only when they occupy at the interface of the two phases.The emulsion emulsified with powder can stabilize mainly because the powder builds up at the oil - water interface to form a finn layer.It protects the dispersed liquid-drop,enable the emulsion to stabilize.Different solid powders,in particular the nano-particles,have a very tremendous influence on the structures and properties of the air-liquid,liquid-liquid interface.Relaxation processes at the interface or surface are the bases of the dilatational rheological viscoelasticity properties,which will show the resistance ability of interfacial layer to dilatational distortion.The information of relaxation processes can be derived through the research of dilatational viscoelaticity.The information includes the orientation and the configuration changes of molecules at the interface or surface, the diffusion and adsorption of molecules from the bulk to the interface and so on. Many researches have already obtained valuable achievements.So far,most of the results all focus on the research of homogeneous phase systems of single surfactant or mixed surfactants.In practical application,solid particles are often added into the homogeneous systems to satisfy the using such as lavation,printing and crude oil recovery.Such heterogeneous systems involve not only air-liquid interface but also solid-liquid interface.Therefore,there are multi-interactions in these systems,such as interactions between surfactant molecules,surfactants and solid particles,particles and particles and so on.These make the final effect to the interfacial properties more complex.Adsorption is one of the most important behaviors of surfactant.The adsorption to solid particles could reduce the concentration of surfactants consequently and impact the properties of the interface.There are a lot of researches about them.As for nano-particles,they also could influence the properties of surface layers by the adsorption of surfactants.Considering their special size,if there're other processes and what will be the final influence on the surface properties are worth discussing.This article mainly studied the influence of nano-SiO₂ on the air-liquid surface of different system.Through this study a new way was explored for researching the interactions of nanometer solid particles and surfactants as well as the influence on the properties of surface layer.This paper is mainly concerned with the research of dilatational rheological viscoelasticity properties of interface or surface film of mixed system composed with nano-SiO₂ and different kinds of surfactants,including cetyltrimethyl ammonium bromide(CTAB),sodium dodecyl benzene sulphonate(SDBS),TritonX-100, cocoamidopropyl betaine(CAB-30),by the interracial dilatational viscoelasticity meter(JMP2000A),which is designed by our laboratory and produced by Shanghai Powereach Co.Ltd.We get some informations of the dilatational modulus |ε|, dilatational elasticityε,dilatational viscosityη_d,phase angleθand other dilatational rheological viscoelasticity coefficients with sine wave movement methods,interfacial tension relaxation methods and the influence of temperature,surfactant concentration and SiO₂ content to these coefficients.The results of experiments are as follows:(1)The research on the dilational viscoelasticity of liquid/air interface of pure CTAB solution discovered,the change regularity of the viscoelasticity parameters was different from low density scope to high density scope with frequency increasing.It was also different at low concentration along with temperature changing.The viscoelasticity changed complex with the density increasing under the same frequency. This mainly related to the structure of cationic surfactant,hydrophobic part was long and the solubility was low in the water.(2)The adsorption mechanism of four types of surfactants at nano-particles was different.The viscoelasticity parameters of interface changed differently in different mixed system because the adsorption of surfactants at SiO₂ was different.(3)There were multi-interactions in these mixed systems,such as interactions between surfactant molecules,surfactants and solid particles,particles and particles and so on.The competition of several kinds of interactions was not only similar but also different.(4)Dilatational modulus|ε|,dilatational elasticityε_d,dilatational viscosityη_d,phase angleθof cetyltrimethyl ammonium bromide(CTAB),sodium dodecyl benzene sulphonate(SDBS),TritonX-100,cocoamidopropyl betaine(CAB-30)mixed systems were changing regularly with the changing of dilatational frequency.(5)The concentration of surfactant affected on the dilatational process.The viscoelasticity parameters of interface changed differently with the concentration of surfactant increasing.(6)The SiO₂ content affected on the dilatational process.The viscoelasticity parameters of interface changed differently with SiO₂ content increasing.(7)The dilatational rheological viscoelasticity coefficients were influenced greatly by the experiment temperature.With the increasing of temperature,the dilatational modulus,dilatational elasticity and dilatational viscosity of TritonX-100, cocoamidopropyl betaine(CAB-30)increased;but the phase angle decreased.(8)The duplication of the results of the same system was good by sine wave movement methods.