Effect of stirring on cellulose graft copolymerization

Dissolving pulp was grafted with several monomers ranging from hydrophilic (dimethylaminoethyl methacrylate) to hydrophobic (styrene). The conversion of these monomers to polymer and copolymer was investigated in dependence on the number of revolutions of the agitator. The formation of grafted copolymer was found to be strongly influenced by stirring. For all the monomers employed, almost no copolymer was formed above 400 rpm. The formation of homopolymer was also severely reduced at higher stirring speeds. For some monomers, a maximum was obtained at about 200–300 rpm with both copolymer and homopolymer yields dropping off sharply at both lower and higher stirring speeds. The position of this maximum was affected by the size of the reactor. The behavior displayed by the xanthate? Fe²⁺–H₂O₂, Fe²⁺–H₂O₂, and ceric ion initiation systems was very similar. Also, monomer solubility in water seemed to have little importance in determining the general behavior.     

An approach to a simplified universal calibration for gel permeation chromatography

Criteria for establishing a universal GPC calibration for poly-1,2-butadiene on the basis of polystyrene standards are considered. The number-average molecular weights of the two polymers are related by a linear expression on the assumption that their respective Mark-Houwink exponents are equal. The coefficient C_n of this expression, determined from GPC and viscosity measurements, remained constant for a considerable range of molecular weights and polydispersities. The applicability of C_n beyond the interval of present measurements is considered on the basis of results in the literature. The results are comparable to those obtained from a universal calibration based on the unperturbed dimension of polymer chains, but do not agree with those obtained from a model based on extended length.     

Influence du dodecyl sulfate de sodium sur la tension interfaciale du système biphasé butanol-eau

Interfacial tension between the two phases formed by the partially miscible system composed of butanol-1 and water has been investigated. Using the method of drop volume tensiometry, the effect of a surface-active agent, sodium dodecyl sulfate, on interfacial tension was investigated. Addition of surfactant to the butanol-rich phase, which forms the droplet, has been found to bring about a decrease in interfacial tension the magnitude of which was influenced by the time of contact. When the surfactant was added to the aqueous (bulk) phase, the decrease in interfacial tension was greater and it was equal to that observed when the surfactant was added to both phases. It is concluded that the orientation of phases in the instrument has an important effect on the apparent interfacial tension observed.     

DYNAMIC TENSIONS IN FINITE OIL DROPLETS

In reacting systems, dynamic interfacial tension (IFT) values above 10-20 mN/m are often encountered. For such high tension values, infinitely long oil droplets will not be realised in spinning drop tensiometry. Hence, Vonnegut's solution will not be strictly valid. The experimentalist is then compelled to use one of the several alternative solution schemes proposed in the literature. We have obtained dynamic IFT data for 0.3125 mM oleic acid in hexadecane contacted with various NaOH solutions by the use of a novel experimental scheme called photo-micropendography. These tension values were then compared with spinning drop tensiometer data calculated by using three alternative solution schemes, namely, Vonnegut's method, the formula of Slattery and Chen and the analysis of Princen el al. The comparison showed that when the droplet's length/width ratio was below 2.5, Vonnegut's formula was severely in error. The solution scheme proposed by Slattery and Chen gave tension values close to those found by photo-micropendography over the entire range of IFT values exhibited by the oleic acid/caustic systems. However, the most consistent and reasonably accurate tension values resulted from the use of Table I in the paper by Princen, Zia and Mason. A simplified computer algorithm has been proposed for calculating dynamic interfacial tensions using the formulas and tables proposed by the latter authors. However, at length/width ratios above 2.5, the agreement between interfacial tensions determined by micropendography and spinning drop data calculated by the use of Vonnegut's solution was quite good.     

The xanthate method of grafting. V. Graftability of mechanical pulp

Softwood mechanical pulp was copolymerized with acrylonitrile using the xanthate redox grafting process. Experiments carried out under different reaction conditions (temperature, H₂O₂, concentration, pH, reaction time) showed that mechanical pulp is less apt to form graft copolymers than chemical pulps. In most cases, long inhibition periods were observed, and the product formed thereafter contained large quantities of homopolymer. It was not possible to raise grafting efficiency by increasing the concentration of hydrogen peroxide. A series of experiments with pulps having different particle size showed a moderate increase in total conversation to polymer with decreasing mean fiber length. The latter, however, produced little influence on the copolymer/homopolymer ratio.     

Synergistic surfactant mixtures containing lignosulphonates

Enhanced oil recovery (EOR) schemes have been gaining importance over the past several years. Of the various methods being tested, surfactant (or micellar) flooding appears to be one of the most promising ones. It involves injecting into the well the solution of a surfactant which reduces the inter-facial tension between the displacing aqueous solution and the oil trapped in the reservoir. Depending on the concentration of the surfactant, oil displacement proceeds either by a miscible process (surfactant concentration > 10%) or by a immiscible process (surfactant concentration = 2–3%). Miscible flooding converts to the immiscible process as the system is diluted by connate (interstitial) water. Under immiscible conditions, the most significant parameter affecting recovery is the interfacial tension^(1,2). Petroleum sulfonates are perhaps the most important group of surfactants capable of producing very low interfacial tensions between crude oil and the water phase. Their relatively high cost, however, renders many potential applications uneconomical.     

Effect of gravity forces on oil recovery in a Hele‐Shaw cell

The effect of gravity on oil recovery was studied in a Hele‐Shaw cell. An immiscible two fluid system consisting of light paraffin oil as the displaced phase and distilled water as the displacing phase was used. Oil recovery at breakthrough was found to be almost linearly dependent on the Bond number. Maximum recovery was obtained in the case of upward flooding with the cell positioned vertically. The minimum oil recovery occurred when flooding was performed in the downward direction with the cell also placed in the vertical position. The recovery results obtained for the experiments carried out at a 45 degree incline and in the horizontal position were situated between these extremes.     

DYNAMIC INTERFACIAL TENSION IN HEXADECANE/WATER SYSTEMS CONTAINING READY-MADE AND IN-SITU-FORMED SURFACTANTS

Dynamic interfacial tension (IFT) between two immiscible liquids has been investigated by the method of drop volume tensiometry. Hexadecane and water were employed for the measurements. In the case of the pure oil-water system, it was found that with hexadecane as the drop phase the IFT was very close to the published value (53.5 mN/m). When water acted as the drop phase the apparent IFT was about 20% higher, and a correction method was developed to account for the different geometry of droplet formation. A similar effect was observed when a surface active additive was present in either one or both phases. The effects of ready-made surfactants and their in-situ-formed equivalents were examined. It was found that both decreased the IFT between the two phases, but the in-situ-formed surfactant was more effective in that respect, It was also found that the IFT between acidic hexadecane and NaOH solution increased when ready-made surfactant was added to the alkaline solution. Addition of salt (NaCl) produced the expected decrease in IFT while the effect of added NaOH appeared to be more complex.     

Certifying Compilation and Run-Time Code Generation

A certifying compiler takes a source language program and produces object code, as well as a certificate that can be used to verify that the object code satisfies desirable properties, such as type safety and memory safety. Certifying compilation helps to increase both compiler robustness and program safety. Compiler robustness is improved since some compiler errors can be caught by checking the object code against the certificate immediately after compilation. Program safety is improved because the object code and certificate alone are sufficient to establish safety: even if the object code and certificate are produced on an unknown machine by an unknown compiler and sent over an untrusted network, safe execution is guaranteed as long as the code and certificate pass the verifier.Existing work in certifying compilation has addressed statically generated code. In this paper, we extend this to code generated at run time. Our goal is to combine certifying compilation with run-time code generation to produce programs that are both fast and verifiably safe. To achieve this goal, we present two new languages with explicit run-time code generation constructs: Cyclone, a type safe dialect of C, and TAL/T, a type safe assembly language. We have designed and implemented a system that translates a safe C program into Cyclone, which is then compiled to TAL/T, and finally assembled into executable object code. This paper focuses on our overall approach and the front end of our system; details about TAL/T will appear in a subsequent paper.