Yu. S. Lipatov

Application of cluster model for the description of epoxy polymer structure and properties

Abstract A study was made of the structure and physico-mechanical properties of epoxy polymers obtained using different curing agent–oligomer ratios. The results were analysed within the framework of the cluster model of structure of the polymer amorphous state. It was shown that the model under consideration can be used for determining the quantitative structure–property relationships for cross-linked polymers.

Effect of a filler on the rheological and mechanical properties of the liquid‐crystalline polyester–poly(methyl methacrylate) blends

The rheological and mechanical properties of the blends of liquid-crystalline polyester (LCP) and poly(methyl methacrylate) (PMMA) filled with aluminum borate whiskers have been studied. It was established the combined action of reinforcing LCP and filler onto the property of PMMA matrix leads to marked reinforcing of PMMA. At 10% of filler and 30% of LCP, the tensile strength of PMMA increases by 30% and elasticity modulus by 110%, the processability being no worse. The viscosity of the blend PMMA + 30% LCP + 10% filler practically is the same as the PMMA melt viscosity at 220°C. With increasing concentration of LCP up to 30%, the filler effect in binary matrix becomes more essential. The possible reason is the preferential adsorption of LCP at the filler interface (surface segregation) and additional ordering of LCP near the surface, possible, due to additional stretching of nematic phase in the convergent flow zone.

Microheterogeneous structure of liquid crystalline polymers

Abstract Liquid crystalline polymers with phenyl benzoate side groups with various lengths of flexible chain-end were synthesized. Small-angle X-ray scattering studies were carried out. Layer structures in the liquid crystalline polymers were characterized and the microheterogeneous structure was investigated. It was concluded that the microstructure is dependent on the length of the flexible mesogenic chain-end.

Effect of spatial constraints on phase separation during polymerization in sequential semi-interpenetrating polymer networks

The viscoelastic properties of sequential semi-interpenetrating polymer networks prepared via the swelling of network polyurethane in different monomers (butyl methacrylate, styrene) followed by their polymerization in the polyurethane matrix have been studied by means of dynamic mechanical analysis. It is found that the relaxation behavior of the test systems and the degree of segregation of the components depends on Mc of the polyurethane matrix because of a change in the molecular mass of the polymer block. The compatibility of the components in sequential semi-interpenetrating polymer networks substantially increases when the network inner space in the polyurethane matrix decreases.

What is the Reason for Adhesion and Adhesive Joint Strength

Abstract Recently some papers were published, where criticism of current theories of adhesion had been given.1,2,3 As a most general theory the rheological theory of adhesion has been proposed, or the theory of mechanical deformation of adhesive joints. This conception should be very useful if only it could give any reasonable clue to understanding of the cause of interfacial adhesion.

Complexation of Fe3+, Cu2+, and Cr3+ β-diketonates with poly(urethane) and poly(methyl methacrylate) in semi-interpenetrating networks: Effect on phase separation

Complexation of iron, copper, and chromium β-diketonates with poly(urethane) and poly(methyl methacrylate) in semi-interpenetrating polymer networks was studied by IR spectroscopy and ESR using various paramagnetic probes. It was shown that types of complexes arising in semi-interpenetrating polymer networks depend on the central metal ion in a chelate. In the networks containing iron and copper β-diketonates, formation of complexes between chelates of these metals and donor groups of PUR and PMMA promotes mutual penetration of poly(urethane) and poly(methyl methacrylate) phases. As a consequence, the degree of their separation decreases and the interphase region widens.

Some Thoughts About Unsolved Physico-Chemical Problems of Composite Polymeric Materials

INTRODUCTION Substantial progress in understanding of the phenomena taking place at the interphase in composite polymeric materials has been made lately.1,2 The production industry of polymeric composite materials, i.e. polymers with dispersed mineral fillers and reinforced plastics with organic and inorganic fibers is nowadays very highly developed. Advent of the new types of reinforcing fibers—carbon, boron, high-modulus and heat-stable synthetic fibers—along with successes of chemistry in the development of new resins has made possible the solution of a number of important technical problems. However, as a rule, these solutions are not based on clearly established mechanisms of the processes taking place at the interphase between the two components, although these phenomena determine the most important physical and mechanical properties of the compositions, and although the interphase is the region whose properties in large measure control the properties of the material. Despite a great number of works...

Filler Debonding in Particulate-Filled Composites

The decrease in Youngs modulus after mechanically loading particulate-filled composites serves as a measure of the fraction of debonded filler particles. For composites based on plasticized rubber and fine ammonium perchlorate these effects have been studied for various stresses and for both varying amounts and particle sizes of the filler. It was found that debonding filler particles during loading is strongly dependent both on the filler concentration and the particle size. Composites with small particles are characterized by higher stresses at which debonding takes place. The effects observed are supposed to be connected with different conditions of the stress distribution depending on the filler particle size and amount. Another reason is the varying fraction of the interphase zone formed at the filler-matrix boundary.

An Investigation of the Relation Between the Adhesion of Polyurethanes to Solid Surfaces and Network Structure

Abstract It is known that polymer interaction with solid surface limits the mobility of the polymer chain and this consequently affects the physico-chemical properties of the polymer.1 In the course of polymer lattice formation, the presence of a solid surface leads to the formation of more defective spatial network.2

Formation of a linear-polyurethane-linear-polystyrene blend in situ

Blends of linear poly(urethane) and linear polystyrene formed simultaneously in situ by different mechanisms (radical polymerization and polyaddition) at various initial mixture compositions and initiator and catalyst concentrations have been studied by DSC and light scattering. It has been shown that formation of the poly(urethane)-polystyrene blend is characterized by the same kinetic and thermodynamic features as the previously studied poly(urethane)-poly(methyl methacrylate) system. However, the poly(urethane)-polystyrene blend forms much slower than the poly(urethane)-poly(methyl methacrylate) blend owing to different reactivities of the starting components, which are determined by their chemical nature. Phase separation in the poly(urethane)-polystyrene system, which at initial stages proceeds via the spinodal mechanism, occurs much faster than that in the poly(urethane)-poly(methyl methacrylate) system because of a poor mutual solubility of the poly(urethane) and polystyrene being formed and probably because of a higher mobility of their macromolecules at the onset of phase separation.