Исследовали влияние размера частиц на механические характеристики двуосно-ориентированного композита ПП/SiO2. Материал ориентировали в плоскости, сдавливая две пластины сплава свинец-олово с помещенной между ними пленкой композита.

The introduction of hydrophilic fillers in the matrix of hydrophobic thermoplastic polymers is a complicated issue, due to thermodynamic incompatibility of the components and poor adhesion properties. These complications are the most pronounced in the case of a hydrophilic polymer which cannot melt without decomposition (as polysaccharides) used as the filler. In this study, we have taken advantage of the solvent-free extrusion method both to modify the chitosan chemical structure in order to impart amphiphilic properties and to mix the obtained derivatives with polyethylene. The influence of the processes parameters, the presence of plasticizer, and the filler content on the thermal and mechanical properties of the composite film materials as well as their morphology has been investigated. It has been found that the introduction of hydrophobic fragments in the structure of chitosan insignificantly improved the mechanical properties of the materials in comparison with the pristine polysaccharide. A more significant effect has been caused by simultaneous introduction of the plasticizer, affording the materials with uniform morphology and improved plasticity.

The influence of different types of deformation of the metal matrix on mechanical behavior of the amorphous PET film upon its transverse compression in the ductile metal matrix has been investigated. Three deformation modes have been probed. In the first case, a disc-shaped polymer specimen has been put between two 5 mm thick discs of the lead–tin alloy and squeezed in the press. In the second and the third cases, planar elongation has been performed in the so called “dead channel”, i.e., the channel with fixed side walls, the film being elongated due to decrease in the width or thickness, respectively. The plots of true yield stress at different draw ratios have formed a common master curve. At high total draw ratio Λ, the true yield stresses have been close for the considered three types of drawing in the metal. At the draw ratio Λ > 2.6, the neck has not appeared, and the specimen has been deformed uniformly. When the film in the channel is elongated due to the decrease in thickness at constant width, the specimen width has been mainly decreased during subsequent elongation in the testing machine. When the film in the channel is elongated due to the decrease in width at constant thickness, further elongation has mainly led to the decrease in the specimen thickness. The true stress Σ has been expressed as Σ = Σ 0 + K Λ 3 , with K being a constant. Deformation of the polymer in the channel occurred with the formation of shear bands . At the preliminary draw ratio Λ = 1.82, the bands have been oriented at the angle 21.5° with respect to the stretching axis. The planar elongation has led to abnormally strong deformation softening of the polymer. The drawing has been accompanied by an increase in the elasticity modulus of the polymer. The obtained results have suggested that the macromolecules orientation is the main reason for strain hardening of the polymer.

The effect of plane cold drawing on the mechanical characteristics of polypropylene during subsequent tension was studied. After the drawing, the yield stress was observed to decrease by about 30%. The true yield stress is described by a single curve as a function of the total axial elongation during the preliminary plane deformation and the subsequent tension.

The effect of particle size on the mechanical characteristics of biaxially oriented composite polypropylene/SiO2 is studied. The material is oriented in plane by squeezing two lead-tin alloy plates with the composite film being placed between them. Deformation is defined by the composition of the plates. This makes it possible to obtain the material with low degrees of orientation. The oriented composite preserves plasticity typical of the polypropylene matrix. After biaxial orientation of the unfilled PP, the yield point decreases by approximately 40% upon subsequent stretching. A reduction in the size of particles changes their adhesion behavior during stretching. Coarse particles with a size of about 20 µm separate from PP during stretching. On the contrary, nanoparticles with sizes of 200 and 500 nm do not separate even under plastic deformation of the composite. As a result, nanoparticles reinforce the thermoplastic the same way as carbon black nanoparticles reinforce rubber. The energy detachment criterion explaining an increase in the detachment stress with decreasing particle size is derived.

Исследовали пластическое деформирование плёнок аморфного полибутилен сукцината (ПБС) при растяжении. Обнаружено автоколебательное распространение шейки при очень низких скоростях растяжения, когда по существующим представлениям колебаний быть не может. Сделан вывод, что автоколебания являются следствием неизвестного ранее механизма неустойчивости пластического течения.

The effect of planar orientation on the mechanical characteristics of biodegradable poly(butylene succinate) filled with ZnO, FeO, Al2O3, SiO2, and TiO2 micro- and nanoparticles was studied. A film sample of composite was placed between two lead disks and was compressed in a press. Under stretching, nonoriented poly(butylene succinate) was deformed in an unstable manner through alternate jumps and stops of the neck front and was fractured during the neck propagation. The deformation was of the self-oscillation type throughout the entire range of the test machine rates. The instability of the neck deformation was suppressed by a twofold prestrain of the polymer in the press and load jumps were not observed. The addition of as low as 10 vol % of particles resulted in a twofold increase in the elastic modulus of the composite, further increase in the degree of filling did not enhance the material rigidity. A 2.5-fold prestrain of the composite made it possible to suppress the brittle fracture for particles of all five types.

Plastic strain of amorphous poly(butylene succinate) films in stretching was studied. Self-oscillating necking was detected at very low stretching rates, at which, according to the existing concepts, oscillations are impossible. It was concluded that the self-oscillations are a consequence of a previously unknown mechanism of instability of plastic flow.