Polymeric Composites Based on Thermoplasts Reinforced With Long Fibers of Different Nature: Production, Properties, Application (Review)

Long-fiber polymer composites (LFPC) occupy the most important place among structural materials.LFPC are characterized by higher mechanical properties compared to classical plastics, and their specific characteristics are superior to traditional steels, aluminum and magnesium alloys, which makes it possible to use LFPC as metal substitutes in various fields of technology.The purpose of the work is to summarize scientific information on the results of theoretical and experimental studies in the field of LFPC, carried out over the past few decades, and to analyze the general situation and development prospects in this area.In this review, special attention is paid to LFPC based on thermoplastic matrices, since the widespread use of LFPC based on thermosetting binders is limited by poor processability, low productivity due to the length of molding technological cycles, and limited shelf life of semi-finished products.The paper shows that, compared with short fiber polymer composites (SFPC), LFPC are characterized by higher values of mechanical strength, stiffness, impact resistance, and heat resistance.The main advantages of LFPC over CFPC are due to higher values of the aspect number (the ratio of fiber length to its diameter), which is higher than the critical values for LFPC.The issues of the influence of prescription factors related to the fiber concentration and its length, and technological parameters such as the configuration of the screw, the frequency of its rotation, the order of fiber insertion, temperature conditions, on the mechanical and thermophysical properties of LFPC are discussed.Methods for improving the adhesion between fiber and matrix in LFPC based on the processes of matrix modifi-cation, fiber modification and the use of special compatibilizers are analyzed.Generalized information on the most efficient technological process for the production and processing of LFPC based on D-LFT technology is given, which combines several technological stages in one production line and is a single production process, from the preparation of raw materials to the manufacture of the final product.It is shown that, due to a valuable set of properties, LFPC are widely used in the automotive industry, the aerospace industry, in the manufacture of sports equipment, as well as in everyday life and public services.