The spectra of internal friction and temperature dependencies of the frequency of a free-damped oscillation process excited in the specimens of an amorphous–crystalline copolymer of polyoxymethylene with the co-monomer trioxane (POM-C) with a degree of crystallinity ~60% in the temperature range from −150 °C to +170 °C has been studied. It has been established that the spectra of internal friction show five local dissipative processes of varying intensity, manifested in different temperature ranges of the spectrum. An anomalous decrease in the frequency of the oscillatory process was detected in the temperature ranges where the most intense dissipative losses appear on the spectrum of internal friction. Based on phenomenological model representations of a standard linear solid, the physical–mechanical (shear modulus defect, temperature position of local regions of inelasticity) and physical–chemical (activation energy, discrete relaxation time, intensities of detected dissipative processes) characteristics of each local dissipative process were calculated. It was found that the intensities of dissipative processes remain virtually unchanged for both annealed and non-annealed samples. The maximum variation in the shear modulus defect is 0.06%. Additionally, according to computational data, small changes are also characteristic of the following parameters: the activation energy varies from 0.5 to 1.4 kJ/mol and the relaxation time changes from 0.002 to 0.007 s, depending on the presence or absence of annealing. As a result of annealing, there is a significant increase in the relaxation microinheterogenity of the polymer system across the entire temperature range (250% for the low-temperature region and 115% for the high-temperature region).

The distribution of filler particles in composite materials based on molded polyurethane has been studied. Introduction of various particles into molded polyurethane improves its mechanical and performance properties. Based on the research results, it was concluded that the most uniform distribution of particles is observed in talc-based composites (coefficient of variation of 7.3%, and the greatest spread of particles in composites with basalt fiber of 28.3%).

Conditions of agricultural machinery operation necessitate improving the operational characteristics and service life of parts. Polymer composite materials, unlike metals, are not subject to corrosion and have a long service life. Research was conducted to determine the influence of the type and concentration of a diluent on the rheological and technological properties of epoxy composites intended for manufacturing the exterior parts of agricultural machinery. Special attention was paid to studying the effect of the diluent on the viscosity and microstructure formation of the composite. Epoxy resin ED20 was used as the polymer matrix, and the filler was an emulsion glass mat EMC450-1250-E. Two types of diluents were investigated: inactive (white spirit and solvent 646) and active (DEG-1). The viscosity of the mixtures was measured according to GOST 25276-82 using a rotational viscometer. The porosity of the composite was determined by a multi-parameter microscopy method. The authors studied the relationship between the viscosity of ED-20 epoxy resin and the addition of active and inactive diluents at 5, 10, and 15 wt.%. As a result of the research, the active diluent DEG-1 was selected. An analysis was conducted of the porosity in the composite material based on epoxy resin and glass mat with 5, 10, and 15 wt.% of the DEG-1 diluent. Experimental results showed that the introduction of DEG-1 significantly reduces the resin viscosity, facilitating better penetration into the fibers of the filler. The optimal concentration of the DEG-1 diluent was determined to be 10 wt.%, which provides a 60% reduction in resin viscosity, uniform distribution in the glass fiber matrix, and minimal porosity in the composite material (30 pores/cm²). For manufacturing polymer composites for exterior parts of agricultural machinery, it isrecommended to use the DEG-1 diluent at a concentration of 10 wt.%.

—Studies on the dynamic viscosity of composites based on a two-component polyurethane compound with fillers in the form of shungite, talc, and basalt fibers (3 vol %) with addition of dichloromethane as an organic solvent (10 vol %) are presented. Based on the results of the studies, it is revealed that the most rational composites for casting into elastic molds are the composites containing shungite and talc as fillers.

The technological properties of three marks of casting polyurethane compounds Advaform 80, Silagerm 6080, Polyflex 80A were considered in the article. Those products were intended for manufacturing piston pump diaphragm. The effect of preparation of the mixture, expressed in the presence of vacuum processing, on the quality of the product was investigated. The viscosity of these marks of polyurethane compounds were determined with a rotary viscometer. It is shown that the time of vacuum processing is an important parameter of quality of castings, which in turn depends on the pot time of the polyurethane. It was also noted that the low viscosity of the compound does not always guarantee the best casting quality in processes of manually pouring, and the pot time of the compound has a much greater effect on the quality. As the optimal material for producing diaphragm was chosen Advaform 80 due to its long pot time, which made it possible to carry out high-quality vacuum processing with the formation of a minimum amount of bubbles.

Релаксационные и физико-механические характеристики полиэтиленов с различной молекулярной массой