The paper presents the results of studies of adhesive strength under shearing, thermal stability, and the content of the gel fraction of adhesive materials and enamels based on modified phenol-formaldehyde resins. Epoxy resin and polyvinylpyrrolidone were used to modify the phenol-formaldehyde resin. The influence of the content of components in the phenol-formaldehyde composition and the curing conditions on the properties of the obtained adhesive materials and coatings is analyzed. The effect of polyvinylpyrrolidone on internal stresses in adhesive joints has been established. By mathematical planning, the isolines of the characteristics of composite materials based on modified phenol-formaldehyde resin depending on their component’s compositions are plotted, and the regression coefficients are found, enabling one to get materials with predicted properties. From a technical and economic point of view, the following content of additives in modified phenol-formaldehyde resin is most optimal: epoxy resin from 25 to 50 wt%, polyvinylpyrrolidone from 0.5 to 1.0 wt%, curing catalyst from 1 to 2.5 wt%.