Adhesion strength of polymer-containing protective coatings

Abstract

The use of composite coatings based on a polymer matrix and inorganic fillers is a real way of protecting the working parts of technological equipment against corrosion and wear in chemical, petroleum processing, and food industries. The important factors which define wear and corrosion resistance of coatings are the chemical stability of every component and the bond strength on the "polymer-filler" interface [ 1,2]. As a polymer matrix in the creation of coatings, it is promising to use epoxy low-molecular resins and compositions based on them, which are characterized by fluidity at the stage of formation of the coating, small stresses at the boundary with the metal base, high adhesion to any materials, and sufficient heat resistance and chemical resistance. They are easily mixed with various fillers, and their wear resistance in the solid state is close to that of aluminum alloys [3,4].To ensure high wear and corrosion resistances of protective composite coatings, it is expedient to use dispersion powders of compounds of transition metals of groups IV-VI of the periodic system (carbides, borides, and oxides), which have high hardness, mechanical strength, and chemical resistance [5,6].In this work, in the formation of a polymer matrix, we use resin ED-16 which, due to its great molecular mass and the considerable number of polar groups, has higher adhesion strength, wear resistance, and chemical resistance against the action of corrosive media as compared with those of resins ED-20 and ED-22 [7]. To ensure the optimum technological properties and plasticization of the matrix, the epoxy oligomer was modified by aliphatic resin DEG-1 in the proportion of 20 mass parts to 100 mass parts of resin ED-16. The compositions are polymerized by using a low-temperature polyethylenepolyamine hardener according to the following scheme: formation of a glue union of cylindrical specimens of 20.0 mm in diameter made of steel 45 and their holding for 2 h at 20~ heating with a rate of 2.5 deg/min to a temperature of 170~ and holding for 2 h, and slow cooling down to 20~ For the stabilization of the structure, we held specimens for 48 h in air at a temperature of 20~ then tested them for adhesion strength under uniform rupture (Or) and shear (~s), and determined the internal stresses (Oin)" Experimental results (Fig. 1) show that, for a content of polyethylenepolyamine equal to 10 + 0.5 mass parts, the adhesion strength of the composition is maximum (35-37 MPa), and internal stresses increase from 1.5 to 3.3 MPa. This correlation of values of adhesion strength and stresses is explained by the optimum relation between the components of the composition and by the complete formation of its three-dimensional grid.To a great extent, the physicomechanical characteristics of composite coatings depend on the supermolecular structure of the polymer matrix, which can be controlled by initiating artificial centers of structure-forming processes by introducing dia-, para-, and ferromagnetic fillers different in their magnetic nature. Upon th...

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