LC solutions of PPTA behave like liquids with a power law of flow and n = 0. 65-0. 78 Liquid-crystalline (LC) sulfuric acid solutions of poly(p-phenylene terephthalamide) (PPTA) with a concentration of 19-20% heated to 80-95"C are used to fabricate high-strength fibres by spinning through an air space [1]. In optimum conditions, the air space is usually small, 4-20 ram, and the diameter of the spinneret chapels is 0.05-0.08 ram. Orientational drawing of the jet in the space with a ratio of 4-8 is used (calculated as the ratio of the fibre take-up rate to the rate of extrusion of the solution through the channel without consideration of spinneret expansion of the jets). The fibre take-up rate is 70-400 m/min and its range can be wider. Water and aqueous solutions of sulfuric acid in low and moderate concentrations with preferred temperatures of O-10*C are used as the spinning bath (SB). These are "harsh" polymer precipitators, since the liminal concentration of PPTA corresponds to a solvent composition with an approximately 10% concentration of water in the sulfuric acid [2]. The possibility of conducting high-speed spinning indicates formation of the structure of the high-strength fibre directly in the SB.It was interesting to study the rheological properties of the solutions and the behavior of the jets in conditions of real spinning of high-strength fibres.We used 19% LC solutions of PPTA in 99.6% H2SO 4 at 82"C with a viscosity of 120-200 Pa-see, determined on a Hoeppler rheoviscometer with shear stress of 200 Pa. The intrinsic viscosity [77] of the polymer, determined in 96 % H2SO 4 at 25~ was 6.0-6.5 dl/g. Standard cup spinnerets made of a precious metal with a 12.5 mm cup diameter and 0.3 mm wall thickness were used. The spinneret channels had a capillary with diameter D from 0.06 to 0.17 and 1.0 mm, ratio of length to diameter L/D equal to 1.0 (0.3 for D = 1.0 mm), and an entry conical part with an angle at the apex of 22"C (except for the channel with D = 1.0 mm). The number of channels in the spinnerets ranged from 18 to 40 and was 1 for the spinneret with D = 1.0 mm. Mono-and .complex filaments were spun through an air space up to 20 mm in size, heated by hot air feed or unheated, into a water SB with a temperature of 10*C, as described in [3]. The flow curve of a LC solution of PPTA with a viscosity of 120 Pa-sec through channels 0.08 mm in diameter is shown in Fig. 1. The shear stress a was calculated as a = DPI4L, where P is the pressure of the solution in the spinneret, and the real shear rate on the wall of the channel 5',o was calculated with the Weissenberg Rabinovich equation:Terlon Industrial Association, Mytishchi.

Using the system approach, we have developed a simulation model for the long-term forecast of the content of toxic chemical elements in grain crop yield. The study was carried out by the example of wheat cultivated in Altai Krai — one of the main grain-producing regions of Russia. Wheat crops were sampled in 10 municipal districts of Altai Krai, which characterize seven different edaphic-climatic zones. The average long-term values of mean monthly air temperature and monthly precipitation for each sampling area were identified using GIS and data of the Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. A total of 19 chemical elements were considered, i.e. Pb, As, Cd, Hg, Na, Mn, Zn, Cu, Fe, Co, etc. It is shown that content of Pb, Na, Mn and Cu in wheat depend on climatic characteristics of the cultivation area. Regression dependences of element content on the average long-term air temperature and precipitation were established. Based on normalization and spatial generalization of air temperature and precipitation providing the uniform dynamics of their relative monthly values (in percent) throughout the study area, a forecast of their changes was made for 2030. A procedure for grain sampling, GIS technologies for processing meteorological and cartographic data, methods for predicting regional climate changes and establishment of quantitative relationships of chemical elements content in grain with climatic characteristics – all together make up the integral predictive simulation model for toxic substance content in grain crop yield. The model was used for estimation of Pb, Na, Mn, Cu changes in wheat by 2030. The lead (Pb) content in wheat crop delivered to elevators from certain municipal districts will exceed the maximum allowable concentration for breadgrain after 2030. Unlike Pb, Na, Mn, Cu, the content of other metals in wheat grain weakly correlate with long-term changes in air temperature and precipitation; therefore, it can hardly change significantly.

In spinning fibres based on poly-(p-phenylene terephthalamide) (PPTA) through an air gap, steady flow of liquidcrystalline (LC) sulfuric-acid solutions chauges into flow with fluctuation of the jet diameters in the gap if the jet stretch ratio is greater than the critical value [1]. The phenomenon is known in jet stretching theory as resonance in drawing.The study is aimed at more precisely defining the boundaries of file stability of jet formation and an analysis of the possible causes of a change in these boundaries under the effect of different spinning conditions.Monofilaments and complex fibres were spun from 19.5% LC solutions of PPTA and a copolyamide (PPTA and polyamide--benzimidazole ram).LC solutions at 77 and 85~ were delivered by piston from the spinning cylinder to the spinneret. The jets passed through an unheated air gap and entered running water at a temperature of 10~ used as the spinning bath (SB). They were repeatedly drawn in air medium to obtain unidirectional orientation of the macromolecules. The fibre formed in the aqueous SB entered a vertical spinning tube with a length of 450 mm and internal dimneter of 8.2-9.2 mm with the water current. The spinning tube was attached to the bottom of the trough. The upper end was positioned at a depth of 60 mm from the level of the water in the trough. The spinning tube was joined with a connecting tube with a horizontal tube 1500 lnm long. The fibre exited the horizontal tube with the freely falling water stream and was womld on a perforated bobbin. The acid was washed off the fibre on the bobbin and it was dried. The linear density, used in calculating the stretch ratio of the LC solution jet, was determined. For a fibre take-up speed of more than 350 m/rain, the horizontal tube was removed to decrease the tension and eliminate fibre breaks in spreading on the receiving-winding device.14 Teflon Co., Mytishchi.

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