Preparation And Properties Of Organosilicon Anti-sticking Coatings

The production and consumption of rubbers,plastics and synthetic fibers are huge in China.In the new century,the Chinese demand of these synthetic materials is growing rapidly,and the corresponding outputs are the largest in the world.In the production process of polymer products,some problems usually arise,such as sticking to the mold.There are two routine solutions:spraying mold release agent in the mold cavity and carrying out anti-sticking treatment on the surface of the mold,including vapor deposition,hard chromium plating and anti-sticking coating.However,the former increases the production cost and brings environmental pollution,and the traces of mold release agent on the surface occurring in this method reduces the product quality.Moreover,the hard chromium plating in the latter brings environmental pollution,limiting the application scope of this method.Therefore,with the rapid development of polymer industry,the application of coating is more and more extensive,and the research of anti-sticking coating has become a hot topic.To date,the best way to solve the adhesion between molds and products is to use silicone based anti-sticking coating,but there are still some shortcomings for practical applications,such as poor wear resistance and short service life.Hence,the research regarding the preparation and performance of silicone based anti-sticking coating is very urgent.In this paper,vinyl silicone oil,hydrogenated silicone oil,methyl vinyl MQ silicone resin and platinum catalyst were used as raw materials to fabricate siloxane high polymers with three-dimensional network structure through addition reaction.Using the strong physical adsorption,physical entanglement and chemical adsorption produced in the mixing of the fabricated polymers and nano-SiO₂ powder,the crosslinking degree of the release agent is increased,and then the mechanical properties is improved.In addition,due to the agglomeration of nano-SiO₂ powder,the surface roughness of the release agent is changed,and then the surface free energy reduces and the anti-sticking effect is improved.According to the test of physical properties?shore hardness,tensile strength,and so on?and the calculation of surface free energy,it is found that the surface free energy is the lowest with the value of19.46 mJ/m² when the content of nano-Si O₂ powder is 2 wt.%.Meanwhile,the tensile strength and shore hardness reaches the values of 413.32 kPa and 53.03 HA,respectively,increased by 82.62%and 12.52%in comparison with those without addition.To further improve the performance of the anti-sticking coating,vinyl fluorosilicone oil was further added.Addition reaction occurs between the vinyl group of vinyl fluorosilicone oil and the hydrogenated silicone oil,forming denser and more crosslinked fluorine-containing silicone anti-sticking coating.The mechanical properties are further improved.Since CF₃ existing in the vinyl fluorosilicone oil is a non-polar group and it can migrate to the coating surface during the curing process,the surface free energy further decreases and the demoulding effect is improved.By controlling the content of vinyl fluorosilicone oil,the effect of vinyl fluorosilicone oil content on the properties of fluorosilicone coating was studied.It is found that the surface free energy of vinyl fluorosilicone oil is 18.84 mJ/m2 when the content of vinyl fluorosilicone oil is 7 wt.%.Meanwhile,the tensile strength reaches 842.63 kPa,and the shore hardness is 54.06 HA,which are increased by 104.87%and 5.32%in comparison with those without addition,respectively.