Wyniki wyszukiwania - BazTech

1

Multiblock segmented polyurethanes and polyurethane-ureas based on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) macrodiols. Synthesis and characterization

Filip D., Macocinschi D., Ioanid E., Vlad S.

Polimery

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2010

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T. 55, nr 5

358-365

EN

The amphiphilic behavior of poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) block copolymers has been broadened by introducing new urethane-urea as well as poly(ethylene glycol) co-segments in polyurethane (PUR) and polyurethane-ureas (PURU) materials. Supermolecular organization and self-assembly was confirmed by electron microscopy transmission observations. The driving force for self-assembling is represented by the amphiphilic nature of these materials, the interactional segment length and stabilization through hydrogen bonding. FT-IR spectroscopy was used to investigate the hydrogen bonding related to phase segregation. Phase transitions and phase segregation was evidenced by DSC analyses. The relationship between structure and thermal stability was investigated by thermogravimetric analysis.

PL

Opisano sposób syntezy amfifilowych multiblokowych poliuretanów (PUR) i poliuretano-moczników (PURU) w wyniku wprowadzenia odpowiednich segmentów do łańcucha wymienionych w tytule makrodioli. Scharakteryzowano skład, strukturę oraz wartości Mw i Mw/Mn (tabela 1) uzyskanych PUR (2 typy) oraz PURU (również 2 typy). Przedyskutowano i porównano wyniki ich badania metodami FT-IR (rys. 5), derywatograficzną (rys. 1 i 2), różnicowej analizy termicznej (DSC, rys. 3, tabela 1), rentgenograficzną (rys. 4) i elektronowej mikroskopii transmisyjnej (rys. 6). Zinterpretowano zdolność do samorzutnego tworzenia agregatów przez opisywane produkty, wiążąc ją przede wszystkim z ich amfifilowym charakterem oraz stabilizacją poprzez wiązanie wodorowe. Wyniki uzyskane metodami DSC i FT-IR posłużyły do wyjaśnienia przebiegu zjawisk segregacji fazowej a także przemian fazowych.

2

Tunable topographical cellulose for electro-optical liquid crystal cells

Costa I., Almeida P. L., Filip D., Figueirinhas J. L., Godinho M. H.

Opto-Electronics Review

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2006

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Vol. 14, No. 4

299-303

EN

In this work we have used acetoxypropylcellulose (APC) to produce free standing solid films (~60 µm) that were used for assembling electro-optical devices. Thin films were obtained from concentrated lyotropic solutions of cellulose derivatives. Induced by the cast and shearing preparation conditions wrinkles and band textures can be observed in their free-surface plane. In order to eliminate and control these textures we used a process similar to that introduced in literature [1] which consists of storing the films in the same solvent-vapour atmosphere as the solution system. Lyotropic APC liquid crystalline solutions in dymethylacetamide (DMA) with crosslinker were prepared, thin films were obtained by using a shear/casting technique and stored in the solvent-vapour atmosphere until a planar structure was achieved. The dried crosslinked films were analyzed by optical polarised microscopy (POM) and scanning electron microscopy (SEM). The films with different topographies were used to produce optical cells composed by the cellulose derivative film covered on both free surfaces by a layer of the nematic liquid crystal E7 and placed between two transparent conducting substrates. The electro-optical properties of these cells were obtained.

3

Mixed radiation-convection boundary layer flow of an opically dense fluid along a vertical flat plate in a non-Darcy porous medium

Takhar H. S., Beg O. A., Chamkha A. J., Filip D., Pop I.

International Journal of Applied Mechanics and Engineering

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2003

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Vol. 8, no 3

483-496

EN

The combined effects of thermal radiation flux, thermal conductivity, Reynolds number and non-Darcian (Forcheimmer drag and Brinkman boundary resistance) body forces on steady laminar boundary layer flow along a vertical surface in an idealized geological porous medium are investigated. The classical Rosseland one-dimensional diffusion approximation is implemented in the energy equation to avoid solving the general integro-differential equation for radiative transfer. Pseudo-similarity transformations are invoked and the resulting highly coupled and non-linear set of ordinary differential equations for momentum and energy equations are solved numerically using a well-tested and highly accurate shooting Runge-Kutta quadrature with a Merson-Gill algorithm. It is shown that the dimensionless velocity functions generally increase with rising radiation parameter and the Prandtl number, and the dimensionless temperature functions decrease as the non-Darcian body forces decrease. It is also shown that the dimensionless temperature functions rise in magnitude with rising radiation parameter and the Prandtl number but are depressed by lowered non-Darcian resistance parameter and rising Reynolds number. Generally radiation is seen to substantially boost the overall heat transfer.

4

The dynamics of an ideal fluid flow into an inclined cavity of a paraboloid form

Filip D., Trimbitas R., Pop I.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 4

947-968

EN

The present paper is a theoretical study of the motion of an inclined cavity of a paraboloid form filled with an ideal and incompressible fluid. The cavity is placed in the gravity field and its roto-translation motion is unknown. We look for determining the translation and rotation velocities of the cavity, the velocity potential of the fluid particles as well as the form of the fluid free surface. To this end, we shall use both the analytical and numerical methods. Numerical examples are presented in tables and graphs to elucidate the accuracy and efficiency of the proposed method.