Mathematical Simulation of the Behavior of a Cumulative Jet with Inert and Reactive Components

The purpose of the research was to investigate the processes associated with the free flight of a cumulative jet formed from a composite liner of a cumulative charge. We mathematically simulated the process from the perspective of continuum mechanics using numerical methods for solving the corresponding equations. The cumulative jet was simulated in the quasi-two-dimensional nonstationary approximation as a high-gradient cylindrical compressible elastoplastic or liquid rod. The material of the jet was considered as a one-speed three-phase medium. The compressibility of each phase was described by its inherent barotropic dependence of pressure on density. The resulting pressure in a multiphase mixture of particles of the cumulative jet, considered as a composite material, was determined on the basis of the additivity condition of the volumes. When assessing the composition of the jet, we determined the initial concentrations of the components using a software package for thermo-dynamic simulation of chemically reacting systems. To find the numerical solution of the multi-phase, i.e., composite, jet extension problem, we used a finite-difference method based on Neumann --- Richtmyer scheme. The numerical analysis of the process under study was carried out on the example of a laboratory cumulative charge. Within the research, we found the characteristic features and possible variations in the behavior of the jet depending on the presence of the components of the composite liner, i.e., matrix, inert and reactive additives, and their properties. Finally, we estimated the change in the penetrating power of the jet compared to the reference variant of the cumulative liner of a homogeneous single-phase monolithic material.

Rheological and Mechanical Gradient Properties of Polyurethane Elastomers for 3D-Printing with Reactive Additives

Polyurethane (PU) elastomers with their broad range of strength and elasticity are ideal materials for additive manufacturing of shapes with gradients of mechanical properties. By adjusting the mixing ratio of different polyurethane reactants during 3D-printing it is possible to change the mechanical properties. However, to guarantee intra- and inter-layer adhesion, it is essential to know the reaction kinetics of the polyurethane reaction, and to be able to influence the reaction speed in a wide range. In this study, the effect of adding three different catalysts and two inhibitors to the reaction of polyurethane elastomers were studied by comparing the time of crossover points between storage and loss modulus G′ and G′′ from time sweep tests of small amplitude oscillatory shear at 30°C. The time of crossover points is reduced with the increasing amount of catalysts, but only the reaction time with one inhibitor is significantly delayed. The reaction time of 90% NCO group conversion calculated from the FTIR-spectrum also demonstrates the kinetics of samples with different catalysts. In addition, the relation between the conversion as determined from FTIR spectroscopy and the mechanical properties of the materials was established. Based on these results, it is possible to select optimized catalysts and inhibitors for polyurethane 3D-printing of materials with gradients of mechanical properties.

Toughness Enhancement of PHBV/TPU/Cellulose Compounds with Reactive Additives for Compostable Injected Parts in Industrial Applications

Poly(3-hydroxybutyrate-co-3-valerate), PHBV, is a bacterial thermoplastic biopolyester that possesses interesting thermal and mechanical properties. As it is fully biodegradable, it could be an alternative to the use of commodities in single-use applications or in those intended for composting at their end of life. Two big drawbacks of PHBV are its low impact toughness and its high cost, which limit its potential applications. In this work, we proposed the use of a PHBV-based compound with purified α-cellulose fibres and a thermoplastic polyurethane (TPU), with the purpose of improving the performance of PHBV in terms of balanced heat resistance, stiffness, and toughness. Three reactive agents with different functionalities have been tested in these compounds: hexametylene diisocianate (HMDI), a commercial multi-epoxy-functionalized styrene-co-glycidyl methacrylate oligomer (Joncryl® ADR-4368), and triglycidyl isocyanurate (TGIC). The results indicate that the reactive agents play a main role of compatibilizers among the phases of the PHBV/TPU/cellulose compounds. HMDI showed the highest ability to compatibilize the cellulose and the PHBV in the compounds, with the topmost values of deformation at break, static toughness, and impact strength. Joncryl® and TGIC, on the other hand, seemed to enhance the compatibility between the fibres and the polymer matrix as well as the TPU within the PHBV.

The properties of new epoxy networks swollen with ionic liquids

In this work, ionic liquids based on trihexyl(tetradecyl)phosphonium associated with bis(2,4,4-trimethylpentyl)phosphinate [TMP] and dicyanamide [DCA] counter anions were used as reactive additives within epoxy/amine networks.

Control Model of the Synthesis of Binary Systems under Loading Reactive Additives into the Mixture

It has been calculated that the introduction of nickel-aluminum additives leads to an increase in the heat effect and allows for the development of materials with the desired phase composition. A comparative analysis of the results of design and instrumentation experiments has shown a satisfactory agreement which allows us to speak about the correctness of the developed numerical model as well as the possibility of selecting optimal initial values ​​of the heat energy source as a factor which allows for controlling the reaction of self-propagating high-temperature synthesis and eventually the phase composition of the final product.