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The conditions of occurrence, nature, size, and shape of combustion hotspots of energetic condensed systems and the spatial dynamics of the hotspot combustion wave are discussed. A model for the propagation of hotspot combustion waves in condensed systems is briefly described based on the cellular automata method. A possible explanation for the occurrence of unsteady effects in the combustion of solid rocket propellants is proposed.

The synthesis of polyurethane block based on oligoesterdiols 4,4′-methylene-bis(phenylisocyanate), and various chain elongating agents was studied. The properties of these copolymers were compared (using literature data) with selected properties of polyurethanes obtained by the reactions of oligoetherdiols, viz., oligo-3,3′-bis(azidomethyl)oxetanediol and oligo-3-azidomethyl-3′-methyloxetanediol with diisocyanates. The complex of rheological and physicomechanical properties of the initial and plasticized polyurethane block copolymers was studied. Regularities of their deformation behavior were established. The process of mutual solubility was studied by the microinterference method for a wide range of systems block copolymers—plasticizers. On the basis of the data obtained, the phase diagrams were constructed for limitedly compatible systems.

NQR studies demonstrated that structure imperfection of RDX crystals is affected by impurities, the particle size, and the modes of crystallization and pressing of the sample. The initial rate of RDX decomposition depends on the same factors. In pure samples, the rate varies 1.5—2 times and is proportional to imperfection. In spite of crystal destruction, the rate of thermal decomposition in pressed samples decreases due, apparently, to strengthening of the cell effect.

1. Experimental data for all of the SKD rubber-base composites filled with particles with a diameter D< 10−4 cm, which were investigated in the study, are not described over the entire interval of fillings by any of the familiar theories, and the discrepancy increases with increasing degree of filling. 2. Experimental and theoretical data can be drawn together by introducing a parameter of the interaction between the matrix material and filler, which is multiplied by the degree of filling, to the equation describing the E/E0 = f(φ) curve; in this case, however, two regions develop where these equations differ; this makes it possible to assume the presence of a percolation effect. 3. The dependence of composite strength on the logarithm of the characteristic dimension of the cell is described by two straight lines with different slopes; this also suggests the presence of a percolation effect. The value of the filler concentration for which these segments intersect is apparently close to the percolation concentration [11].

The influence of plasticizers of various types affecting the physico-chemical and mechanical properties of polyurethane elastomers has been investigated for compositions comprising the copolymer of tetrahydrofuran and propylene oxide (PO), trimethylolpropane and 2,4-toluylenediisocynate. It was found that the amount of polymeric sol fraction and the number of elastically active network chains, as well as mechanical properties of the polyether urethane elastomers, vary significantly acocrding to the type of medium used and the degrees of dilution. An ambiguous relationship was found between the amount of sol-fraction and intersite chains in the networks. The relations obtained are explained in terms of inefficient macrocyclization taking place during polymerization in various media.

A kinetic study has been made of three dimensional polymerization in systems comprising the copolymer of tetrahydroduran and propylene oxide, 1,1,1-trimethylolpropane and 2,4-toluylenediisocyanate. The influence of the polymeric medium on the process of gelation and on the physico-chemical and mechanical properties of the polyurethanes was investigated. The polymeric medium examined was a urethane copolymer prepared by reacting the copolymer of tetrahydrofuran and propylene oxide with m-chlorophenylisocyanate.

A study is made of differences in the morphology of compositions consisting of butyl rubber and polyacrylates, obtained by mixing the macromolecular components and by polymerizing acrylate monomers in a matrix of butyl rubber, with simultaneous vulcanization of the latter. In the first instance heterogeneous systems are formed, the actual morphological type of which is determined by the magnitude of the interfacial tension. In the second method more homogeneous, metastable mixtures are formed, stabilized by interpenetrating networks of the components, arising as a result of simultaneous polymerization of the acrylates and vulcanization of the butyl rubber. The results are analysed on the basis of the thermodynamics of the relaxation processes.

Two tensile-testing machines are described for physicomechanical tests of polymeric materials with deformation up to 100 and 1,000% in which the conditions of deformation are assigned directly to the measurement base of the specimen by using an automatically regulated electric drive, ensuring parity of the measured quantity (force, elongation, or stress) with the requisite preset functional controller.

Using compositions containing a tetrahydrofuran-propylene oxide copolymer, 1,1,1-trimethylolpropane and 2,4-toluylenedi-isocyaante a study was made of the catalytic activity of a high molecular weight branched polyurethane-tin dibutyl dilaurate system. It was shown that the catalytic activity of tin dibutyl dilaurate is maintained at the same level as with the usual addition of a catalyst to a composition that can undergo polymerization, and the high molecular weight branched polyurethane itself is quantitatively linked within the polyurethane network.