Effects of Moisture and Stresses on the Structure and Properties of Polyester Resin

The results of a complex study of structural changes in a cured Norpol 440 polyester resin under the action of damp environment and mechanical loading are presented. A considerable effect of absorbed moisture on the structure and some characteristics of the material is revealed by using thermophysical methods and X-ray diffractometry. The joint effect of moisture and mechanical stress is estimated by investigating the creep in stationary and nonstationary moisture conditions. The anisotropy of the material structure formed during creep is evaluated from the results of dilatometric measurements. It is found that the degree of anisotropy of the material after creep accompanied by moisture sorption is higher than that after creep in the conditions of moisture equilibrium with atmosphere. It is established that the aftercure and relaxation of the residual creep deformation come to an end at heating to 80-85°C. At a further rise in temperature and repeated heating, changes in the material structure are not observed.     

Synthesis and investigation of the biological activity of shortened analogues of luliberin

Five new luliberin analogues with shortened amino acid sequences have been synthesized. The different variants for obtaining the compounds under consideration are discussed. In an investigation of the biological activities of the analogues it was shown that they possess a pronounced action of the course of the ovulation processes in experimental animals.     

Effect of force fields on a thermotropic liquid-crystalline copolymer of hydroxybenzoic acid and ethylene terephthalate. 1. Creation of oriented copolymer structure in a uniform magnetic field

A melt of a copolymer of 60% hydroxybenzoic acid and 40% ethylene terephthalate was subjected to a uniform magnetic field with B = 0.65 T at 300 °C. The structure and thermal expansion of the material was studied by x-ray diffraction and dilatometry. The magnetic field produced a highly oriented structure. Dilatometry revealed previously unreported relaxation transitions in this material.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 2, pp. 269–281, March–April, 1995.     

Influence of Moisture on the Structure and Properties of the Interphase Layer of a Composite Based on an Epoxy Binder with a Disperse Filler

Properties of a model composite based on an ED-22 epoxy binder, cured with polyprophylene polyamine, and disperse LiF crystals as a filler were investigated by the methods of dilatometry and X-ray diffractometry. It was established that the density of cross-links of the epoxy binder in the interphase layer was lower than in a block specimen. Therefore, the thermal expansion of the composite on heating to 120°C, in terms of that of the binder, grew significantly with the degree of filling ϕ, and the water uptake also increased at the initial stage. The presence of absorbed water led to considerable changes in the structure and properties of the composite interphase: the binder became more cross-linked, its structural ordering decreased, the thermal expansion at heating diminished by a factor of 3. 7 (at ϕ = 50%), and the glass-transition temperature increased. As a result of long-term action of moisture, changes in the internal stresses had an extreme character.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 535–544, July–August, 2005.     

Synthesis of a new cyclic analogue of luliberin

A new cyclic analogue of luliberin possessing the capacity for stimulating ovulation in sexually mature and infantile rats and also exhibiting a pronounced prolongation of its influence on a number of behavioral reactions of animals has been synthesized.     

Synthesis and investigation of the biological activity of shortened analogues of luliberin

Five new luliberin analogues with shortened amino acid sequences have been synthesized. The different variants for obtaining the compounds under consideration are discussed. In an investigation of the biological activities of the analogues it was shown that they possess a pronounced action of the course of the ovulation processes in experimental animals.Scientific-Research Institute of Midwifery and Gynecology, USSR Academy of Medical Sciences, Leningrad. A. A. Zhdanov Leningrad State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 590–595, July–August, 1987.