Investigation Of The Preparation And Performance Of Hydrophilic Coating On Silicone Rubber Surface

Silicone rubber has been widely used in defense,military,biomedical and health fields due to its excellent high,low temperature,weather resistance and physiological inertia.However,the strong hydrophobicity of silicone rubber surface limits its application in other fields.Therefore,it is very important to study the hydrophilic modification of silicone rubber interface,and the construction of strong and tough functional coatings on the surface of silicone rubber material is an effective means to improve the wettability of the material interface.This paper intends to carry out the research on the modification strategy of silicone rubber surface coating,namely,optimizing the process flow of hydrophilic coating preparation,characterizing the surface properties of the coating,and deeply studying the influencing factors of coating friction performance.The research results will provide reference for the construction of surface functional coating of flexible materials.Firstly,hydrophilic coating was prepared on the surface of silicone rubber using hydroxyethyl methacrylate(HEMA)as the monomer based on the UV irradiation method.The optimization of coating process was carried out to explore the effect of glycerol/water binary solvent on the surface properties of PHEMA coating.The results show that the crosslinking agent N,N-methylene acrylamide(MBA)can effectively reduce the hardness of the coating and improve the mechanical applicability of the coating and substrate.When the crosslinking agent exists,the hydrophilic polymer polyaspartic acid(PASP)can effectively improve the hydrophilicity of the coating.When the PASP content was 5wt%,the water contact angle of the coating was as low as 9.35°.The glycerol/water binary solvent can reduce the surface roughness and thickness of the coating,and with the increase of glycerol content,the thickness roughness of the coating gradually decreases from 2.12 μm to 0.03 μm.The hydrophilicity of the coating decreased with the decrease of surface roughness.When the solvent contained 40wt% glycerol,the water contact angle of the coating increased to 34.29°.Secondly,PHEMA/AM coating was prepared using HEMA and acrylamide(AM)as reaction monomers by changing the preparation process of the coating using the similar method mentioned above.The effects of glycerol/water binary solvent on its surface properties were studied by SEM,XPS,contact angle measurement and white-light interferometer.The results show that the PHEMA/AM coating has good hydrophilicity,and glycerol has a similar effect on it.The surface roughness and thickness of the PHEMA/AM coating decrease with the increase of glycerol content(the roughness decreased from 5.89 μm to 0.05 μm).However,compared with PHEMA coating,the water contact angle of PHEMA/AM coating showed an opposite trend,that is,with the decrease of surface roughness,the water contact angle first decreased gradually and then increased suddenly.When glycerol was 50wt%,its hydrophilicity was the best(37.98°).Finally,silicone rubber ball/disc friction pair was used to study the influencing factors of friction performance of coating surface by friction testing machine and white light interferometer.The results show that the friction coefficient between silicone rubber ball and substrate is obviously greater than 1,which may be caused by the high adhesion of silicone rubber itself.The friction coefficient of PHEMA coating and PHEMA/AM coating was as low as 0.012 under simulated blood lubrication environment,which was 97.8 % lower than that of substrate.It is found that the friction reduction performance of rough coating is poor,with the increase of surface roughness,the friction coefficient increases gradually.The above research results will provide reference for the development of hydrophilic lubrication coating on the surface of flexible materials.