Studies on the effect of the foams’ polymeric matrix’ properties on the tension and compression properties of pour rigid polyurethane (PUR) foams, apparent core density 65—70 kg/m3, at 296 and 77 K were carried out. PUR foams were produced by the hand mixing method from polyol systems that comprised polyether, polyester polyols, and chain extenders. To produce PUR foams, crude MDI was used, and Solkane 365 mfc/227 ea was used as a blowing agent. The molecular weight per branching unit (Mc) of the polymeric matrix of PUR foams was varied in the range 300—1150. Cohesion energy densities of the blocks forming the polymeric matrix were calculated. The effect of Mc on the formation of hydrogen bonds between the urethane groups was estimated from FTIR spectroscopy data and ratio NHbonded /NHfree. It has been found that, with increasing polymeric matrix’ Mc, the tensile strength and elongation at break of PUR foams at 296 and 77 K increases, while Young’s modulus decreases. The increase in the parameter Mc promotes the decrease in the compressive strength and modulus of elasticity of PUR foams at 296 K, while compressive strength indices at 77 K are higher for the foams, whose polymeric matrix has the highest Mc. With increasing polymeric matrix’ M c, the concentration of the urethane groups bonded with hydrogen bonds increases. Structural and mechanical properties of layered spray polyurethane foams, apparent core density approx. 48 kg/m3, having two layers and polymeric matrix’ Mc = 740 were investigated.

Amide and ester type polyols were synthesized from different kinds of tall oil and two types of ethanolamine (diethanolamine and triethanolamine). Poly(urethane amides) and polyester urethanes based on the synthesized polyols were prepared. The influence of the chemical structure of the obtained polyurethanes on density, glass transition temperature, thermal stability, mechanical properties and adhesive strength was investigated. The effect of the content of rosin acids in original tall oil on the specified characteristics was estimated. It has been found that poly(urethane amides) have higher mechanical characteristics, but their thermal stability is lower than that of polyester urethanes. The chemical structure of the synthesized polyols and polyurethanes is qualitatively confirmed by IR-spectroscopy data.

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The dependence of physical and mechanical properties of oligoether-based foam polyurethanes on the molecular mass (Me) of polymer chains between the nodes of the polymer network and on the content of rigid segments in theRigid foam polyurethanes (FPUs) and their different modifications are efficient insulants in a wide interval of operating temperatures. They are widely used either at elevated temperatures as a heat insulation or at low temperatures as a cryogenic insulation of tanks for condensed gases [1][2][3][4][5][6][7].In order to find the upper bound of operating temperatures for foam plastics, the heat resistance, shape stability, and other characteristics are used. At the same time, unfortunately, no similar conventional characteristics for obtaining the lower bound of operating temperatures for foam plastics are known to date. The possibility of using a certain material as a cryogenic insulation is generally judged by the mechanical properties of the material in tension and the coefficient of linear thermal expansion at a respective temperature. The necessity of determining just these properties is dictated by the results of analyzing the distribution of temperattires, stresses, and strains in the layer of external insulation during freezing and thawing tanks. A similar analysis is, in particular, performed in [ 1 ], where it is shown that, upon freezing, in the foam plastic layer contacting with the wall of the tank, large tensile stresses arise due to a difference in the coefficients oftbermal expansion, which are responsible for cracking of the insulation while in service. The value of these stresses depends not only on the final temperature, but also on the rate of cooling. Meanwhile, the compressive stresses arising in the external layer of foam plastics are not as dangerous.The majority of studies reporting on the successful application of FPUs of different types at low temperatures generally present the mechanical characteristics and the coefficients of thermal conductivity and linear thermal expansion at the indicated temperatures, as well as the variation of these indices during aging and after cyclic temperature loads [1][2][3][4][5][6]. However, for known reasons, the complete composition and structure of FPU, as a rule, are not given in these studies. Only in [7] it was reported that, in developing materials resistant to cryogenic temperatures, the key factor is the type of rigid and soft segments in the structure of FPU and their mutual ratio. Therefore, the purpose of the present study is to estimate the effect of the chemical structure of a polymer matrix on the properties of FPU at low temperatures.As is known [8,9], the properties of rigid FPUs, which are cross-linked polymers, are determined by the concentration of urethane groups in the polymer chains, their flexibility, and the frequency of their cross-linking. Urethane groups and the residues Latvian State Institute of Wood Chemistry, Riga, LV-IO06, Latvia.

The efficiency of using intumescent flame retardants in polyurethane coatings based on tall oil fatty acids esters was assessed. The influence of the content of each of the flame retardants (ammonium polyphosphate, melamine and pentaerythriol) separately on the flammability parameters of wood samples with polyurethane coatings in a cone calorimeter test, as well as on the thermal and mechanical properties of the polyurethane itself, was investigated. The effect of the ratios of double and triple combinations of the mentioned flame retardants on the specified properties was studied. It has been found that, for the given type of polyester urethane, ammonium polyphosphate decreases the flammability of polyurethane most. Melamine, and melamine in combination with ammonium polyphosphate decrease the smoke release upon polyurethane combustion.

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