Synthesis and characterization of chiral liquid crystal polymers containing donor–acceptor group

A series of new chiral side-chain liquid crystalline polymers with electron donor–acceptor action were prepared containing chiral monomer with donor group and nematic LC monomer with acceptor group. All polymers were synthesized by graft polymerization using polymethylhydrosiloxane as backbone. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), thermogravimetric analyses (TGA), and X-ray diffraction measurements (XRD). The chemical structures of monomers and polymers were confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (¹H NMR and ¹³CNMR). M ₁ did not show liquid crystalline phase and M ₂ turned out nematic phase on heating and cooling cycle. Polymers P ₂ –P ₇ were cholesteric phase. Cholesteric phase and low glass temperature liquid crystalline polymers have been obtained, which offered the possibility of application. Experimental results demonstrated that the glass-transition temperatures rose and isotropization temperatures decreased and the ranges of the mesophase temperature reduced with increasing the content of chiral agent. All of the obtained polymers showed high thermal stability.     

EFFECTS OF LIQUID VISCOSITY ON RHEOLOGY OF CONCENTRATED SUSPENSIONS

ABSTRACT

This paper presents the experimental results on the effects of liquid viscosity on the rheology of concentrated suspensions of solid particles in Newtonian liquids. Specifically, the relative viscosity of a pseudoplastic suspension decreases as the viscosity of the suspending liquid increases, indicating excess energy dissipation in a less viscous liquid. In contrast, the relative viscosity of a Newtonian suspension is only slightly affected by the liquid viscosity. It is in excellent agreement with the value predicted from the rigid sphere model which neglects nonhydrodynamic interactions, and assumes zero particle-to-liquid relative velocity. The flow behavior indices of both concentrated suspensions are independent of the liquid viscosity.     

Experiments on interaction of liquid tin with solid copper

Abstract

The reaction of liquid tin with solid copper has been studied by heating small volumes ofpure tin on copper coupons at various temperatures and times, and evaluating the resulting reaction metallographically. Three reaction temperatures were used:260,400,and450 ° C. Specimen geometry was chosento simulate a typical solder joint. The reaction was observed to occur in two stages: an initial fast stage with copper/liquid tin interface movement rates from 0.2 μm s^-1 at260 ° C to 0.8 μm s^-1 at 450 ° C, followed by a much slower stage. It was concluded that the first stage corresponds to direct dissolution of copper in liquid tin up to or beyond the liquidus concentration for the reaction temperature used.This is followed by the formation of an intermetallic compound layer atthe copper/liquid interface. Subsequent copper dissolution then occurs by solid state diffusion through the compound layer, a much slower process than direct dissolution.     

A structural supercapacitor based on activated carbon fabric and a solid electrolyte

ABSTRACT

This paper presents investigations to create a structural supercapacitor with activated carbon fabric electrodes and a solid composite electrolyte, consisting of organic liquid electrolyte 1?M TEABF₄ in propylene carbonate and an epoxy matrix where different compositions were considered of 1:2, 1:1 and 2:1 w/w epoxy:liquid electrolyte. Vacuum-assisted resin transfer moulding was used for the impregnation of the electrolyte mixture into the electrochemical double layer capacitor (EDLC) assembly. The best electrochemical performance was exhibited by the 1:2 w/w epoxy: liquid electrolyte ratio, with a cell equivalent-in-series resistance of 160?Ω?cm² and a maximum electrode-specific capacitance of 101.6?mF?g^?1 while the flexural modulus and strength were 0.3?GPa and 29.1?MPa, respectively, indicating a solid EDLC device.     

Instant Mixing Agglomeration

ABSTRACT

This paper presents one particular method of Agglomeration, which incorporates two specific characteristics unique to the method, by their combination. Any time powders are mixed with liquids, agglomeration to some degree is the result. By proper selection of the mixing parameters and careful control of the total powder:liquid ratio, reliable particle size distribution is possible. Instant mixing of powder(s) with liquid(s) is capable of producing dust free, flowable granules, which retain many of the beneficial properties of the parent powder(s). These properties, which may be enhanced by proper selection of liquid or solid additives, include: dispersibility, solubility, compressibility, porosity, effective surface area, and wettability.     

A VUV prism spectrometer for RICH radiator refractometry

Abstract

A prism spectrometer has been developed to operate in the VUV wavelength range from 120 to 200 nm. It can be used as a pre-disperser in conjunction with a Fabry-Perot based gas refractometer. This instrument has also been used to measure the refractive index of the liquid radiator C₆F₁₄ in various spectral lines. This radiator is used in the RICH detectors of the DELPHI experiment and has been proposed for ALICE, and LHCb experiments. The spectral resolution of the system is improved as the wavelength decreases and the data are consistent with a wavelength accuracy about 0.4 nm at 140nm. The results for the dispersion curve of the above liquid are presented.     

Continuous low-dose feeding of highly active pharmaceutical ingredients in hot-melt extrusion

Context: Manufacturing solid low-dose pharmaceutical products has always the homogeneity challenge. In continuous manufacturing, there is the additional challenge of feeding active pharmaceutical ingredient (API) dry powder at low rates. This paper presents a method for feeding API particles into a continuous extrusion process using a suspension. The challenges for feeding and the product homogeneity are both addressed.

Objective: The objective of this study is to demonstrate the feasibility of manufacturing low-dose extrudates by feeding the API particles in a diluted anti-solvent suspension.

Materials and methods: Extrudates with an Ibuprofen content of 0.021% and 0.043% (w/w) were prepared by feeding a 0.9% w/w suspension of Ibuprofen particles into a Coperion extruder.

Results and discussion: The homogeneity (RSD) of extrudates was tested during a time span of 30?min and had values between 2% and 7%.

Conclusion: Feeding particles in an anti-solvent suspension offers a simple feeding option for API and minor components which yield products of desired homogeneity. The liquid feeding approach offers a simplified process with enhanced process control possibilities.     

Optimal Massing Liquid Volume Determination by Energy Consumption Measurement: Study of the Influence of Some Physical Properties of Solvents and Products Used

Abstract

This study tried to investigate, by the power comsumption technique, the influence of the powder's and solvent's properties on wet granulation.

It could be shown that the required amount of granulation liquid decreases when the particle size of the powder to be granulated increases. This relationship is however only true when the particle size distribution of the powder to be granulated is rather narrow.

Powders having the same solubility in different solvents require the same optimal liquid quantity for granulation, but the properties of resulting granules depend on surface tension and wetting properties of the solvent.

When the powder to be granulated contains crystallisation water, the temperature rising in the mixer can be sufficient to liberate this water, which must be taken into account in the optimal granulation liquid requirement.

The effect of a macromolecular binder (PVP, HPMC) has also been studied: the optimal liquid quantity required changes with the kind of binder used and the manufacturing process (binder used in solution or added as dry powder).

It was also shown that in the case of lactose, the optimal quantity of PVP or HPMC can be determined from the power consumption records and from the granules friability studies     

Properties of reacto-thermitically sintered stainless steel

Abstract

Reacto-thermitic sintering (RTS) is a novel process capable of producing near net shape powder metallurgical stainless steel components with negligible interconnected porosity at sintering temperatures of 1150°C. It utilises chemical reactions between oxides present on the surface of conventional stainless steel powders and small quantities of reactive additives to produce a transient liquid phase. This liquid can be frozen during cooling to consolidate the component without slumping. Previous work by the authors has studied the fundamental mechanisms underpinning the evolution of this liquid phase and its subsequent behaviour in eliminating porosity. The present paper investigates the effect of varying the quantity of reactive additive on the dimensional stability, mechanical properties, and corrosion resistance of stainless steel specimens produced by RTS in the light of this work.     

Letter surface and bulk reorientation in ferroelectric liquid crystals

Abstract

The switching processes in ferroelectric liquid crystals are probed optically using a combination of transmission between crossed polarizers and surface evanescent field reflection techniques. This allows the behaviour of the liquid crystal director reorientation to be studied in the bulk of a device and near the surface simultaneously. Interesting behaviour is observed, and it is found that the processes can be adequately modelled using a simple one-dimensional model to represent the director structure across the thickness of the liquid crystal layer.     

Quantitative Evaluation of the Wettability of Powders

Abstract

The wetting of powders can be evaluated by different manner : direct measurement of the solid - liquid contact angle; indirect measurement of that angle (h and ∈ method); liquid penetration rate into a powder bed; a.s.o.     

Influence of Technological Factors on the Optimal Granulation Liquid Requirement Measured by Power Consumption

Abstract

The optimal liquid requirement for wet granulation can be investigated by recording the power consumption of the mixer during liquid addition. In this work it was tried to use this technique on a small laboratory scale (one kg or less) for lactose wet granulation with water. The validity of the power consumption method could be confirmed by granule size analysis. Different factors were studied: kind of mixer, powder quantity, mixer speed, liquid addition speed, granulator screen size, mixing time.     

Density Determination of Powders by Liquid Displacement Methods.

Abstract

The densities of a number of powders were determined by liquid pycnometry and flotation as well as the more usual method of gas pycnometry. Replicate samples showed more variation when determined by liquid methods. Howeverlarge differences between results obtained from liquid and from gaseous methods were not obtained. The significance of these differences in terms of powder compression and porosity calculations was assessed. The sample size and degree of ultrasonic agitation was shown to affect the value of density obtained by liquid pycnometry.     

Lyotropic liquid crystal polymers for engineering applications

Abstract

The use of lyotropic liquid crystal polymers such as Kevlar and Twaron in high tech engineering applications has been common for many years. These materials possess excellent temperature resistance and very good mechanical properties. These two materials are polyaramids, but the newer polybenzazoles are also of a liquid crystal nature when present in appropriate solvents. Their rigid rod structures make it possible for these materials to form composite structures with isotropic polymers, where the fibre reinforcement is on a molecular level. This is a unique and very interesting possibility which has yet to be fully developed.

MST/1254     

Evaporation heat and mass transfer in natural convection pipe flow

Abstract

A numerical analysis has been performed to examine film evaporation on natural convection heat and mass transfer in a vertical pipe. Coupled governing equations for liquid film and induced gas flow were simultaneously solved by the implicit finite difference method. Results for interfacial heat and mass transfer coefficients are specifically presented for ethanol film and water film vaporization. The predicted results indicate that the heat transfer from gas‐liquid interface to the gas flow is predominated by the transport of latent heat in association with film evaporation. The results are also contrasted with those of zero film thickness and show that the assumption of extremely thin film thickness made by Chang et al. [5] and Yan and Lin [19] is only valid for a system with a low liquid Reynolds number Re _l1. But as the liquid Reynolds number is high, the assumption becomes inappropriate.     

The mobility of negative charges in liquid hydrogen

There is a great difference in behavior of e^– in liquid hydrogen and helium despite the fact that the adopted theories of the mobility are quite similar. Recently, Levchenko and Mezhov-Deglin (Journal of Low Temperature Physics,89, 457 (1992)) reported large discrepancies of the mobility of the electrons in liquid hydrogen from estimates based on the theory that the electrons are trapped in bubbles forming atomlike structures (bubblonium). They properly suggested that these deviations are related to the existence in liquid hydrogen of another, metastable type of negative charge carrier. The subject of the current paper is the physical explanation of the existence of two types of carriers in liquid hydrogen. We attribute the second type of carriers to the cluster ionH ^– (H ₂ ) _x , which is created by the formation of solid hydrogen around a bound state of a hydride ion. We provide estimates for the radius and the kinetics of degradation of the snowball formed around theH ^– ion on the basis of energy diagrams for a hydride ion submerged in liquid hydrogen.     

The Granulation of a Tablet Formulation in a High-Speed Mixer,Diosna P25. Influence on Intra-Granular Porosity and Liquid Saturation

Abstract

Intragranular porosity and liquid saturation were influenced by the impeller speed, the loss-on-drying of starch, the added amount of water and the drug concentration. A reduction of the impeller speed and the drug concentration decreased the porosity and increased the liquid saturation. Response surface contours were plotted.     

Evolution of complete photonic band gap in anisotropic photonic quasicrystals using liquid crystals

Abstract

In this study, we analyse the evolution of complete photonic band gap in two-dimensional photonic structures by arranging the 12-fold symmetric quasicrystalline unit cells on square and triangular lattices. The unit cells composed of circular air holes in anisotropic tellurium background and the air holes are infiltrated with liquid crystal. Using the supercell method based on plane wave expansion, we study the variation of complete band gap by changing the optical axis orientation of liquid crystals.     

A photographic study of bubble coalescence

Abstract

The coalescence of nitrogen bubbles in liquid was studied by using a high‐speed motion picture camera at speeds up to 3,000 frames per second. Examination of the films frame by frame reveals that the general process of bubble coalescence is growth‐touching‐coalescence‐vibrating‐detachment. A small amount of surface active additive influences the time of coalescence significantly: 0.9ppm of sodium lauryl sulfate (SLS), 1.6 ppm of sodium laury benzene sulfonate (SLBS) or 1.8 ppm of n‐octanol inhibits the bubble coalescence completely. This phenomenon is attributed to the dynamic surface effect or the departure from static surface tension caused by extension of the gas‐liquid interface.     

Effect of carbon and phosphorus addition on sintered density and effect of carbon removal on mechanical properties of high density sintered steel

Abstract

This paper provides data on the effect of carbon and phosphorus levels on the density of liquid phase sintered steel and the impact of subsequent carbon removal on the mechanical properties. After sintering die pressed samples composed of liquid forming additives and coarse water atomised powder at 1250°C or below, followed by postsintering decarburisation, densities of >95% relative density and non-brittle microstructures are achieved. Tensile testing shows the important effect of the microstructure on the mechanical properties. Ductility is improved by the post-sintering decarburisation, corresponding to elongation to fracture of 12% for certain compositions. Apparent diffusion coefficients for carbon were also estimated.