Results 1 - 10 of 472
Results 1 - 10 of 472. Search took: 0.022 seconds
|Sort by: date | relevance|
[en] The properties and producing methods of polyolefin fibrillating fiber were introduced in this paper. The research progress of polyolefin fibrillating fiber and the fibrillating device were reviewed. At the same time, the disparity of fibrillating device at home and abroad was discussed. The problems existing in the domestic polyolefin fibrillating fiber were pointed out, and the development trend of f polyolefin fibrillating fiber was discussed. (paper)
[en] This invention relates to compositions of olefinic polymers suitable for high energy radiation treatment. In particular, the invention relates to olefinic polymer compositions that are stable to sterilizing dosages of high energy radiation such as a gamma radiation. Stabilizers are described that include benzhydrol and benzhydrol derivatives; these stabilizers may be used alone or in combination with secondary antioxidants or synergists
[en] Full text: Luminescence compositions on the basis polyethylene (PE) and polyethylene (PP) with different contents of binary compounds based on cadmium sulfide and of zine sulfide (CdS and ZnS). Compositions as films have been obtained with thickness of about 100 mkm by mixing of powders of polymer and sulfides with the subsequent pressing at temperature of melting of a polymeric matrix. Molecular mobility of a polymeric matrix of luminescence compositions is investigated by a method of radio thermo luminescence (RTL). RTL spectra have been obtained in visible oblast on thermo luminograph of TLG-69M (on base of PhM51) at heating rate ∼ 10 degree/minute. Excitation was carried out at 77K from a source 60Co at a doze 104Gy. Comparison of RTL spectrums of unfilled polymer and compositions with various contents of filler is lead. It is established, that RTL spectrums of composites on basis of PE have four maxima at temperature ranges of 146†155K; 172†178K; 238†250K; 293†308K, two peaks of which concern to a polymeric matrix (146†155K; 172†178K). RTL spectrums of composites on the basis of PP have a maximum at temperature ranges of 160?170K; 242?250K; 301?305K, one of which concerns to a polymeric matrix (160†170K). The maxima relating to polymeric matrix characterizes molecular mobility in area of β relaxation of small kinetic segments (on Boer) and second maximum of β relaxation of larger segments of macromolecules of polymer. Presence of luminophore on the basis of double sulfides with an impurity of atoms of silver results on the one hands in more clear split of β relaxation (β' and β) and on the other hand filler has own luminescence. At studying of RTL spectrums the shift of temperature displacing in to high temperatures with increase of filler content was observed. The amplitude of a luminescence has extreme character and at 10% vol. content of filler in a polymeric matrix gets maximal values.It is shown, that introduction of luminescence filler strongly influences on molecular mobility of polymeric matrix and as a result the density of energy levels in interphone boundary of polymer-luminescent particle changes and this in turn influences on luminescence properties of compositions on their basis. A polyolefin's with binary compounds allows identify complex character of molecular mobility in these systems.
[en] A method was developed for calculating the molecular weight distribution of a polymer melt from its rheology, specifically dynamic or relaxation moduli data. The molecular weight range covered by the solution is specified by the source data or the entanglement molecular weight, and the blending rule consistent with double reptation was used. The solutions for both the discrete relaxation spectrum and final molecular weight distribution were obtained by Tikhonov regularization with the molecular weight distribution solution being particularly sensitive to the value of the regularization parameter λR used in the calculations. Here, λR was varied and patterns developed between the most appropriate values for an acceptable solution and the polydispersity of the corresponding samples. For relatively low λR values, the algorithm was precise enough to resolve individual components in nearly monodisperse, binary blend, and multimodal systems with as many as 13 components. Results for commercial materials of varying polydispersity generally agreed with the molecular weight distributions from chromatography with slightly higher λR values, particularly the location of peak molecular weights. Commercial polyolefins, which required still higher λR values, gave consistently poorer results due to restricted molecular weight ranges allowed by the source data
[en] Transforming renewable biomass into cost competitive high-performance biofuels and bioproducts is key to US energy security. Butanol production by microbial fermentation and chemical conversion to polyolefins, elastomers, drop-in jet or diesel fuel, and other chemicals is a promising solution. A high temperature fermentation process can facilitate butanol recovery up to 40%, by using gas stripping. Other benefits of fermentation at high temperatures are optimal hydrolysis rates in the saccharification of biomass which leads to maximized butanol production, decrease in energy costs associated with reactor cooling and capital cost associated with reactor design, and a decrease in contamination and cost for maintaining a sterile environment. Butanol stripping at elevated temperatures gives higher butanol production through constant removal and continuous fermentation. We describe methods used in an attempt to genetically prepare Geobacillus caldoxylosiliticus for insertion of a butanol pathway. Methods used were electroporation of electrocompetent cells, ternary conjugation with E. coli, and protoplast fusion.
[en] Degradation rates are normally increased by increasing the responsible environmental stresses. The authors describe results for a semi-crystalline, crosslinked polyolefin material that contradicts this assumption. Under combined radiation plus thermal environments, this material mechanically degrades much faster at room temperature than at elevated temperatures. The probable explanation relates to the importance on mechanical properties of the tie molecules connecting crystalline and amorphous regions. Partial melting and reforming/reorganization of crystallites occurs throughout the crystalline melting region (at least room temperature up to 126 degrees C), with the rate of such processes increasing with temperature. At low temperature, where this process is slow, a large percentage of the radiation-damaged tie molecules will still connect the amorphous and crystalline regions at the end of aging, leading to rapid reductions in tensile properties. At higher temperatures, the enhanced annealing rate will lead, during the aging, to the establishment of new, undamaged tie molecules. This healing process will reduce the degradation rate. Evidence in support of this model is presented
[en] Fibre-reinforced concrete (FRC) allows reduction in, or substitution of, steel-bars to reinforce concrete and led to the commonly named structural FRC, with steel fibres being the most widespread. Macro-polymer fibres are an alternative to steel fibres, being the main benefits: chemical stability and lower weight for analogous residual strengths of polyolefin-fibre-reinforced concrete (PFRC). Furthermore, polyolefin fibres offer additional advantages such as safe-handling, low pump-wear, light weight in transport and storage, and an absence of corrosion. Other studies have also revealed environmental benefits. After 30 years of research and practice, there remains a need to review the opportunities that such a type of fibre may provide for structural FRC. This study seeks to show the advances and future challenges of use of these polyolefin fibres and summarise the main properties obtained in both fresh and hardened states of PFRC, focussing on the residual strengths obtained from flexural tensile tests.
[es]El hormigón reforzado con fibras (HRF) permite la reducción parcial o total de barras de acero en el hormigón armado, acuñándose término HRF estructural, siendo las fibras de acero las más usadas. Las macro-fibras poliméricas son una alternativa a las de acero, aportando estabilidad química y menor peso para resistencias residuales iguales. Además, las fibras de poliolefina ofrecen beneficios adicionales tales como mayor seguridad de trabajo, menor desgaste de equipos de bombeo, menor peso en el transporte y almacenamiento, y ausencia de corrosión. Otros estudios también han revelado beneficios medio-ambientales. Después de 30 años de investigación y práctica, sigue siendo necesario analizar las oportunidades que estas fibras de poliolefina pueden proporcionar al HRF estructural. Este estudio muestra los avances y posibilidades del uso de estas fibras y resume las principales propiedades obtenidas tanto en estado fresco como endurecido, centrándose en la resistencia residual obtenida en los ensayos de tracción por flexión.