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In this work, based on the results of dynamic mechanical studies, the damping efficiency of two-layer polyurethane (PU) composites designed by gluing two films of synthesized PU with different glass transition temperatures (Tg) was estimated. The damping efficiency was estimated by the parameters of the mechanical losses (tanδ) peak. To vary Tg, three types of PU with different chemical nature and structure were synthesized. The effect of an increase in the difference between the Tg of the initial PU (ΔTg) on the damping efficiency of the two-layer PU composites formed from them is analyzed. The effective damping temperature range (ΔT) was estimated as the temperature range under conditions tanδ ≥ 0,3 and tanδ ≥ 0,6. It was shown that at ΔТg = 7 °С a two-layer PU composite has one relaxation maximum, and its temperature range of damping efficiency expands in comparison with ΔТ for individual PU. Under the conditions ΔТg = 23 °С and ΔТg = 30 °С, two-layer PU composites exhibit damping efficiency in two temperature regions at tanδ ≥ 0,3, which provides an additional temperature range of effective damping. The essential role of the PU structure of each of the layers in the formation of a two-layer composite by gluing has been determined. Easier penetration of residues of the adhesive organic solvent into the surface of the PU film with a linear structure leads to plasticization of the corresponding layer in the composite and reduces Tg. It is shown that a two-layer structure can be used to solve specific problems related to the adjustment or broadening the effective damping temperature range. [ABSTRACT FROM AUTHOR]

The swelling of the polymers into solutions represents by itself the complicated process depending on their different properties. That is why the swelling degree can not be determined via any one physical-chemical property of the solvent. The adequate relationship between the swelling degree and the properties of solvents can be obtained only under condition of taking into account the all acting factors by means of the linear multi-parametric equations. [ABSTRACT FROM AUTHOR]

The chemical composition of stalks of kenaf and sugar sorghum was studied. Established that the kenaf and sugar sorghumstalks contain more cellulose, pentosans, minerals and less lignin than wood. The influence of main technological parameters on the quality indexes of organosolvent pulp obtained from kenaf and sugar sorghum stems was investigated. The possibility of bleaching organosolvent pulp obtained from stems of kenaf using hydrogen peroxide without chlorinecompounds to 80% whiteness was experimentally proved. The parameters of selectivity of lignin's dissolution byalkali-sulphite-alcohol delignification of kenaf and sugar sorghum stems were calculated. It was found that withincreasing temperature and duration of cooking, such selectivity indexes as degree of removal of carbohydrates and degree of delignification are increasing and selectivity index is decreasing. Efficiency of various representatives' delignification plant materials by means of diagrams depending on the content of pulp out there residual lignin was compared. Recommended use organosolvent pulp from kenaf and sorghum sugar stems for different types of cardboard and paper products. [ABSTRACT FROM AUTHOR]