The dissertation is devoted to the study of phthalonitrile monomers modified with the introduction of flexible binding fragments.
The first section of this work provides a comprehensive analysis of research on phthalonitrile polymers and presents polymerization conditions, shows the relationship between the curing mode and the polymer structure.
The second section shows methods for studying the main characteristics of phthalonitrile binders, reviews existing phthalonitrile polymers and their use in various fields, presents existing methods for synthesizing phthalonitrile monomers, and presents possible curing initiators.
The third section begins the practical part of the dissertation. Synthesized phthalonitrile monomers with cycloimide cores based on 4,4’-oxy-bis-tetracarboxylic anhydride and 4,4’-carbonyl-bis-tetracarboxylic anhydride with a yield of 71% and 81% on the starting anhydride, with a technological window for processing into polymers of 220-290 ◦C and a maximum achievable conversion of nitrile groups during polymerization of 91 and 94%, respectively;
In the fourth section the process of modifying phthalonitrile monomers with nanodispersed boron particles with introducing a boron compound with a mass fraction of 12% with subsequent treatment of the mixture at pressures in the range of 0.5-1.6 GPa was investigated, and it was found that the minimum size of nanoparticles formed during subsequent polymerization is 5.2-5.5 nm for both types of monomer at a treatment pressure of 1.25 GPa, and remains stable with further increase in pressure;
The ratio of phthalocyanine and triazine cycles in the composition of phthalonitrile polymers doped with boron nanoparticles was determined, and it was shown that the highest content of phthalocyanine cycles, which provide a high level of strength and heat resistance of the polymer, namely 1.2:1, is achieved at a pretreatment pressure of the monomer mixture of 1.25 GPa, which is consistent with the conditions for the formation of the smallest boron nanoparticles, and significantly exceeds the maximum known level of 0.7:1 from available publications.
In the fifth section for the first time, the surface of carbon materials (carbon fibers) was modified by generating paramagnetic centers, i.e. unpaired electrons bound to surface carbon atoms, in contrast to the traditional grafting of molecular fragments of various nature. It is shown that the new modification method provides an increase in the elastic modulus of composites on phthalonitrile binders by 1.3 times compared to the use of unmodified filler, and an increase in coke residue by 1.15-1.25 times compared to the use of carbon fiber modified with aminosilane;
The mechanical properties of composite materials on synthesized phthalonitrile binders filled with carbon fibers were studied in order to manufacture abrasive tool bodies that combine low specific gravity (1.75-1.85 g/cm3), high elastic modulus (up to 6.5 GPa) and high chemical resistance in liquid technological media used on modern CNC grinding machining centers;
The micromechanical behavior of composite materials on phthalonitrile binders, which were previously exposed to pressures of 0.5 and 1.25 GPa, modified with boron nanoparticles, was investigated in comparison with sodium borosilicate glass, which is widely used as a ceramic binder, as well as with traditional binders of polymer-abrasive composites, namely, phenol-formaldehyde polymer and polyamideimide. Practical identity of the elastic-plastic and dissipative behavior of the polymer from phthalonitrile binder, previously exposed to a pressure of 1.25 GPa and glass in contrast to traditional polymer bonds was revealed;
In the sixth section technological parameters for the manufacture of grinding tools of shapes 1A1 and 12A2-45 from cubic boron nitride on phthalonitrile binders with a curing temperature of up to 300-350◦C in steel molds at a clamping force of 50 MPa with a holding time of 1 hour have been worked out, which allowed, for the first time in the practice of abrasive materials science, to obtain polymer composites suitable for precision profile shaping using a diamond dressing tool, using low-temperature technology inherent in polymer-abrasive composites, as opposed to sintering at 1100-1250 ◦C, necessary for ceramic bonds, which had no alternative in grinding processes requiring continuous or cyclic dressing until now; Grinding tools made of cubic boron nitride on phthalonitrile binders were produced, which allowed, for the first time in the practice of abrasive materials science, to obtain polymer composites suitable for precision profile shaping using a diamond-sharpening tool; The monomers and binders obtained as a result of the work can be used to create structures from PCM that retain strength at high temperatures.
