Energy Storage In Cold Non-Elastic Deformation of Glassy Polymers

Experimental results on work W(epsilon), heat Q(epsilon) and stored energy U(epsilon) of deformation for glassy polymers such as linear PS, PC, PMMA, Polyimid, amorphous PET, thermotropic aromatic polyesters, Vectra T for example, crosslinked epoxy are presented. All the data was obtained by a deformation calorimetry technique. Loading and unloading of samples were performed at room temperature with strain rate epsilon = 10(-2) - 10(-4) sec(-1) under uniaxial compression up to engineering strains of epsilon(def) = 40-50%. During straining all polymers accumulate an excess of the latent energy U( e). Elastic fraction of the energy is released completely at sample unloading and only residual U-res(epsilon) energy is conserved in samples. The latent energy U-res(epsilon) grows up to epsilon(def) = 20-25% and levels off then. Shapes of the U-res(epsilon) curves are the same (S-shape) for all polymers. However, the saturation level is different for each polymer. The ratio U(epsilon)/ W(epsilon) was also measured. It was found that at strains epsilon(def) \u3c epsilon(y) (epsilon(y) - strain at the yield point) U(epsilon)/ W(epsilon) approximate to 100%. I. e. all W is stored by sample in a form of U. The ratio decreases up to 60-30% for different polymers at higher strains. Release of the residual energy U-res (DSC measurements) and strain epsilon(res) ( thermally stimulated strain recovery technique) was measured for deformed and unloaded samples at heating. It was found that about 85-90% of U-res stored by samples is released in glassy state of polymers (below T-g). The U-res is related to a small fraction of epsilon(res), only to 7-10%. The rest of U-res and epsilon(res) are recovered at the softening (devitrification) interval, around T-g. Computer modeling ( molecular dynamics) of an isothermal shear deformation was performed for 2-dimentional two component atomic glass containing 500 Lennard-Jones particles of two different diameters. It was found that localized deformation events are of anelastic nature. The epsilon(an) appears at early deformation stage in a form of localized shear events ( transformations). Such events are nucleated in a sample and merged and united at later deformation stages, when concentration of the events becomes high enough. Finally, merged transformations form kind of shear band crossing entire sample. On the basis of experimental data and computer modeling the deformation mechanism for glassy polymers is proposed. The first stage of the process is the nucleation of the carriers of non-elastic strain , anelastic shear transformations (ASTs). All these ASTs are energetically excited. The concentration of the ASTs is responsible for the amount of U-res(epsilon) stored by a sample. It is suggested that such nucleation is the rate-controlling step in non-elastic deformation of any non-covalent glass. Saturation of the stored energy is defined by the reaching the steady state regime in carrier\u27s concentration. In this regime the rates of nucleation and termination ( decrease of the stored local energy by AST) of carriers becomes equal. The termination proceeds spontaneously and easy ( fast). The decrease of local energy of ASTs follows by local uncoiling of chains and by an appearance of new, extended chain conformers. However, such uncoiling is not the rate-controlling step forentire deformation process. Suggested mechanism very well describes all existing experimental facts. Deformation mechanisms for glasses seriously differ from that operating in rubbers and crystals

Оцінка біологічної дії комплексу спеціальних речовин мінерально-рослинного походження в умовах дії малих доз інкорпорованого ізотопу цезію-137

The assessment of the biological action of the herb and mineral origin nutritional supplement complex produced by Mineral Resources International (USA) was experimentally conducted on laboratory rats which were under the long term exposure to incorporated low level Caesium-137 isotope (137Cs) radiation at 1200 Bk and immobile stress. The influence of the studied complex on accumulation and elimination of 137Cs, the level of hormone activity in blood, lipid peroxydation processes in endocrine organs, hypothalamus, as well as hepar and lungs was detected. Besides the morphofunctional state of the brain and endocrine organs was studied. It was revealed that the tested complex of nutritional supplements has the aptitude to decline 137Cs accumulation. The normalization of the lipid peroxydation processes and the prevention of rough dystrophic and destructive alterations development in endocrine organs both the blood microcirculatory surfaces and secretory cells in its turn proves radioprotective properties of this nutritional supplement complex (registered in Ukraine, patent № D 000128 applied for).В експерименті на лабораторних щурах була проведена оцінка біологічної дії спеціального комплексу харчових домішок, виготовлених фірмою Mineral Resources International (США), в умовах довготривалого надходження радіонуклідної контамінанти ізотопу цезію-137 (1200 Бк щоденно) і хронічного стресу. Досліджувався вплив комплексу, що вивчався на накопичення та елімінацію цезію-137, рівень гормональної активності, процеси перекисного окислення ліпідів у тканин їх гіпоталамусу, сім'яників, наднирників, підшлункової залози, в печінці і легенях. Крім того, вивчався морфофункціональний стан ендокринних органів. Було встановлено, що спеціальні харчові домішки мінерально-рослинного походження сприяють зменшенню всмоктування або підсилюють елімінацію ізотопу цезію-137, визначена їх регулююча дія на процеси перекисного окислення ліпідів у мембранах клітин сім'яників, печінки, щитовидної та підшлункової залоз і, особливо, в наднирниках. При цьому попередження розвитку грубих дистрофічно-деструктивних змін в мікроциркуляторному судинному руслі і клітинах ендокринних органів, за даними гістологічних та електронномікроскопічних досліджень, підтвердило радіопротективні якості комплексу нутрієнтів. Таким чином, експериментальне дослідження комплексу харчових домішок у складі A Special Ukrainian Adult Herb & Mineral Nutritional Supplement, Stress-X, CellEnergy визначило його радіопротективну дію, а також мембраностабілізуючі властивості (зареєстрований в Україні, сертифікат № Д 000128)