Regularities of Changes in the Physical and Mechanical Properties of Composites Based on Liquid Phenol–Formaldehyde Resins and a Dispersed Fiber Filler

Abstract— Rational compositions of a polymer composite material are proposed and technological prerequisites for manufacturing technical products for chemical engineering, based on liquid resol phenol–formaldehyde resins and dispersed fibrous filler manufactured by mechanical processing of the organic waste from fiber production in the pulp and paper industry are evaluated. Methods and parameters of technological stages, including the preparation of raw materials and their mixtures, production of a polymer dispersed filled press material, and hot molding (pressing) products, were determined and tested. Recommendations are given on the hardware and process design of the technological stages of the production of a quality polymer composite material and improvement of its properties. The regularities of changes in the physical and mechanical properties (response on compression, tension, and bending, as well as impact strength and moisture and oil absorption) of the composites with the concentration of dispersed fibrous filler at the recommended thermal pressing parameters (temperature 170 °C, specific pressure 20 MPa, exposure time 1 min/ 1 mm product thickness). Clear evidence is provided showing that the upper limit of the percentage of dispersed fibrous filler in the studied phenolic samples is 40-60%, and at higher percentages the mechanical parameters are strongly deteriorated and the moisture and oil absorptions become much higher than the limits permitted by standards for technical phenolic plastics. The results of the study make it possible to recommend the compositions based on liquid resol phenol–formaldehyde resins and modified fibrous waste from the pulp and paper industry and the hardware and process design for the production of phenolic products of chemical engineering. The developed composites allow homogeneous coloring in various colors (except for white) and imparting to their surface a smooth shiny texture.