Surface Free Energy And Contact Angle Measurement Of Solid Polymer

The surface free energy of the polymer is the important parameters for calculating the interaction free energy between the polymers’surface and other substances. It is closely related to the properties of polymers, such as adhesive, adsorption, friction, biological compatibility, therefore, detecting the surface free energy has very important significance in determining the surface properties of polymers. The contact angle measurement method is the important means on obtainning the solid surface free energy, and the contact angle measuring is closely related to contact time, surface roughness, liquid volume and so on. In this paper, In this thesis, the polymer plates’contact angles measuring be the sessile drop method, the effects of contact time, liquid volume and surface roughness on contact angles were investigated, and hope to obtain rational explanations on the effects on contact angles through combining experimental data with theoretical analysis.Based on the researchers of the change on the contact angles of distilled water, glycerol, formamide, diiodomethane and ethylene glycol on polymers surface, the results showed, for the polymers of different kinds, the contact angles’equilibrium time is different, and the difference between the original contact angle and equilibrium contact angle is different, this is the result of the joint action of Lifshitz-van der Waals attraction interaction and Lewis acid-base attraction interaction between polymers and liquids, and the Lewis acid-base interaction plays a main role. Through the researchers of the change on the contact angles of distilled water on a series of polymers’surface of different kinds, the results showed that the solid surface roughness is the important reason on resulting in the hysteresis of contact angle, with the increasing of solid surface roughness, the advancing angles of the polymers increased, while the receding angles decreased, and the hysteresis of roughness surface can be well explained by importing the static friction force in the there phase interface contact line. Based on the studies of the change of contact angles of distilled water of different liquid volumes on polymers’surface, the results showed that the liquid volume dependence of contact angles is not only the result of line tension in the solid-liquid-gas interface contact line, but also the effect of static friction.Based on the above researches, the contact angles of the smooth polymers’were measured, using the Owens and Wendt method and the LW-AB method calculated the surface free energy of the polymers, the results showed that the Owens and Wendt method is only suitable for determining the surface free energy surface of nonpolar polymers, however, the LW-AB method is fit to calculate the nonpolar polymers and polar polymers’surface free energy. Therefore, the surface free energy parameters of PP, PS, ABS and PMMA were obtained by the LW-AB method. In addition, the dependence of contact angle on contact time is better explained through the calculation of interface interaction surface free energy between solid and liquid.