No abstract

This short communication a i m s a t elucidating the effect of high-temperature (HT) annealing on the phonon-phonon relaxation in transmutationally-doped (TD) n-Si crystals. The relaxation is known to govern not only the value but also the anisotropy of the heat e. m. f. caused by the drag of electrons by phonons of longitudinal (1) and transverse (t) polarization.In our study we used TD c r y s t a l s of n-Si which, apart from the common technological annealing (T = 800 OC, t = 2 h), were exposed to HT annealing (T = 1200 OC, t = 2 h) followed by cooling a t a r a t e of about 1 K/min. Below the crystals investigated before and after HT annealing will be denoted by the symbols 'orig.' and 'HT I , respectively.-/6/ P. I. 3ARANSKX1, V. V. SAVYAK, and L. A. SHCHERBINA, Fiz. Tekh. poluprov. -14, 302 (1980).

The preparation of acrylonitrile, methylacrylate, and 2-acrylamido-2-methylpropanesulfonic acid terpolymer fiber and its dyeing by anionic dyes were examined. The stability of the dye in modified polyacrylonitrile fiber was studied. It was shown that the modified fiber had bactericidal properties. The fiber physicomechanical properties changed insignificantly as a result of the modification and coloring.Acrylonitrile terpolymer fibers (trademark nitron) account for a quarter of the volume of chemical fibers manufactured in the Republic of Belarus. They make up about 65% of the staple fibers used by the textile industry. The operational characteristics (high physicomechanical properties, light-and water-resistance, etc.) of these fibers are highly promising for further rapid development of this type of fibrous raw material.Moreover, polyacrylonitrile (PAN) fibers used in wool blends for producing textiles have several advantages and a drawback associated with the poor dyeing by anionic dyes (chrome, acid, direct) that are usually used to color wool items. Therefore, PAN fibers are dyed before being blended with wool during production of blended items in order to ensure even coloring of the finished product. This complicates significantly the industrial process.Another problem that is just as important and must be solved during production of wool blends designed for general use (in hotels, trains, medical establishments, military barracks, etc.) where the danger of infection by pathogenic microorganisms arises is how to give them bactericidal properties. On one hand, this enables the risk of spreading the infection to be reduced; on the other, it protects the natural fibers from biodegradation.Thus, the development of the production technology for PAN fibers with both bactericidal properties and the ability to be dyed by dyes traditionally used to color wool is important and critical. Successful resolution of several industrial and health problems related to the development and production of such fibrous materials would allow the variety of items based on PAN fibers to be expanded.An analysis of the primary structure of PAN fibers produced on an industrial scale from the terpolymer of acrylonitrile (AN) (a = 90.4 mass%), methylacrylate (MA) (b = 8.2 mass%), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) (c = 1.4 mass%) showed that the functional groups capable of producing PAN fiber colored stably by anionic dyes were missing:Bactericidal properties can be imparted to fiber by treating it with quaternary ammonium salts. Modifiers can be absorbed by PAN gel-fiber in several ways: -penetration into the polymer through a system of connected pores; -occurrence of sorption-desorption processes on the internal gel-fiber surfaces; -formation of ionic bonds between polymer acidic groups and cationic modifiers.

Полилактид относят к биоразлагаемым полимерам. Однако активная деструкция полилактида, как в отсутствии, так и в присутствии различных биогенных факторов, начинается фактически лишь при наличии в окружающей среде воды и при повышении температуры. Цель работыисследование гидролитической деструкции полилактида в сравнении с другими гетероцепными полимерами.На основе результатов экспериментальных исследований рассмотрена роль специфической гидролитической неустойчивости сложноэфирной связи полимеров L-молочной кислоты в деструкции материалов на их основе в водных средах. Показано, что процесс деструкции полимерных материалов на основе L-молочной кислоты существенным образом активизируется с повышением температуры и начинается при повышенных температурах с момента проникновения воды в структуру полимера. Вместе с тем, продемонстрирована возможность длительного контакта таких полимерных материалов с водными средами при комнатных температурах без потери массы и изменения внешнего вида полимерными изделиями. Таким образом, разложение полимеров молочной кислоты в условиях компостирования начинается как химический процесс гидролитической деструкции, что не исключает дальнейшую биодеструкцию молочной кислоты до углекислого газа и воды.Ключевые слова: полилактид, молочная кислота, гидролитическая деструкция, кислотное число, молекулярная масса.

The structure of PAN gel fibres spun by the water-thiocyanate method is investigated. It is shown that in identical spinning conditions, the packing density of the structural elements in gel fibres based on poly(ANco-MA-co-ItA) terpolymer is lower than in gel fibres based on poly(AN-co-MA-co-AMPS). A structural model of PAN gel fibre is proposed and substantiated. It is shown that the lower packing density of the structural elements in PAN gel fibres is responsible for the higher sorption power with respect to different inorganic and organic compounds and higher rate of polymer-analog transformations.The important amount of scientific and technical information accumulated in this area suggests that the structural and mechanical properties of polyacrylonitrile (PAN) fibres used both directly in fabrication of textiles and as precursors for manufacture of carbon and chemisorption fibres are predetermined by the primary structure and molecular-weight characteristics of fibre-forming copolymers and the spinning conditions.The basic industrial methods of fabrication of PAN fibres are different versions of wet spinning based on terpolymers of acrylonitrile (90-93 wt. %) with comonomers containing ester (5-8%) and acid (1-2%) functional groups. The structure of wet spun fibres after washing up to heat treatments (drying, thermofixation, hot drawing) is modeled by oriented gels that include water. The specific surface area (S sp ) of these gel fibres and ordering of their structural elements are determined by the conditions of realization of phase transitions during spinning and plasticization drawing [1].The study of the structural features of gel fibres of the composition poly[acrylonitrile(92.3%)-co-methyl acrylate(6.4%)-co-itaconic acid (1.3%)] spun with the water-dimethylformamide and water-thiocyanate methods in identical conditions of orientation drawing showed that spinning using hydrotropic solvents (for example, 51.5% aqueous solution of NaSCN) produces looser packing of the structural elements of the gel fibres than when aprotic solvents are used [for example, dimethylformamide (DMF)] [2]. The kinetics of fibre formation in manufacture of PAN fibres with the water-thiocyanate (salt) method was investigated previously in [3][4][5]. Diffusion of water into the spinning solution jet takes place at a higher rate than diffusion of NaSCN into the spinning bath. This initially causes slight swelling of the spun gel fibre and then insignificant compaction of its structure (before leaving the spinning bath).The two-phase character of the structure of PAN fibres not treated with heat was hypothesized in [6][7][8]. Heating PAN fibres above the glass transition temperature (T g ) intensifies relaxation processes that lead to transition of amorphous regions in the polymer substrate to a more ordered mesophase.We report the results of a systematic study of the structure of PAN gel fibres based on terpolymers of acrylonitrile (AN), methyl acrylate (MA), and itaconic acid (ItA) or 2-acrylamide-2-methylpropanesulfonic acid (AM...