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81.
The telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol initiated by 2,2′-azobisisobutyronitrile was first investigated at 70 °C and the influence of the type of solvent was studied. The results showed that well-defined telomers of DMAEMA could not be synthetized via telomerization of DMAEMA in water or water/acetonitrile mixture since the telomerization reaction is in competition with the nucleophilic addition of thiol onto the monomer. Transfer constants for mercaptoethanol in benzene and acetonitrile were determined by Mayo's and O'Brien's methods. The transfer constant obtained in acetonitrile (0,6) was higher than that obtained in benzene. This difference can be explained by the fact that the thiol was consumed by two reactions: nucleophilic addition and telomerization. The influence of solvents on the polymerization kinetics was enlightened. These results were applied to the synthesis of macromonomers of DMAEMA with isocyanatoethyl methacrylate (IEM). These macromonomers were copolymerized with styrene. 相似文献
82.
Emulsions of silicone oil-in water were formed using a Brinkmann Polytron homogenizer with Igepal CO-530 as an emulsifier. Silicone viscosities ranged from 10 to 33,000 mPa.s at 25°C. Rheological characteristics and particle size analyses of silicone oil-in-water emulsions were studied. At high volume fraction of the dispersed phase (70%-75%), silicone oil-in-water emulsions were stable. At lower volume fractions (50%-60%), emulsions formed were less stable and the two phases easily separated in a few days. The emulsions formed with high volume fraction silicone oil show highly non-Newtonian behavior (shear thinning). Emulsions made with low viscosity oils had lower viscosities than those made from high viscosity oils. Relative viscosity-concentration data could be correlated by the Frankel and Acrivos Equation. Increasing the emulsifier concentration of 70% oil-in-water emulsions resulted in a decrease in mean droplet size and an increase in emulsion viscosity. Increasing the intensity of agitation also resulted in higher viscosity and smaller droplet size until a critical energy input above which droplet size increased. Emulsification with low shear mixing provides more control in decreasing mean droplet size with time. 相似文献
83.
Jacques Teghem Daniel Tuyttens 《International Transactions in Operational Research》2014,21(6):871-898
We consider a one machine scheduling model, minimizing a classical objective function—either the total completion time or the maximum tardiness—and with two sets of jobs: one with initial jobs already scheduled and one with new jobs that must be inserted in the schedule. As such rescheduling can create a modification of the schedule of the initial jobs, a disruption objective is considered in addition to the original objective. This additional objective can be formulated in four different ways. Such model has been introduced by Hall and Potts, minimizing either a linear aggregation of the two objectives or the initial objective under a constraint giving an upper limit of the disruption objective. In this paper, the aim is to obtain the set of efficient schedules in regard to the two objectives. Algorithms are provided for the eight possible bi‐objective problems and illustrated by some didactic examples. 相似文献
84.
85.
Simple thermodynamic relationships as well as semiempirical solubility parameter plotting techniques were examined as methods for predicting critical crazing strains of polycarbonate exposed to linear and branched alkanes. In general, measured critical strains correlated with predicted solubilities based on the Flory–Huggins equation. Solubility parameters could also be used to predict critical strains if molecular size differences between specific alkanes were taken into account. These techniques were then extended to polar and hydrogen bonding liquids using two-dimensional solubility parameter plotting representations. A comprehensive listing of critical strains for polycarbonate exposed to over 80 liquids and liquid mixtures is included. 相似文献
86.
Racemic -methyl--n-propyl--propiolactone is readily polymerized with zinc and cadmium chiral glycolates leading to optically active polyesters. The stereoelectivities observed are lower than for oxiranes and thiiranes with the same initiator system. A value of rotatory power for pure enantiomer o, is deduced from NMR measurements in the presence of chiral solvent. The structure of polymers is discussed on the basis of NMR results. 相似文献
87.
Résumé La réaction entre l'homopipérazine, HN<(CH2)5>NH, et le dibromo-1,5-pentane, Br(CH2)5Br, conduit à la formation du dibromure de diazonia-6,9-dispiro[5.2.5.3]heptadécane de formule C15H30N
2
2+
·2Br–. Par permutation en milieu aqueux ou organique on obtient le sel iodé. Ce diiodure est associé à l'iodure d'argent dans des proportions variant entre 75 et 95% en équivalent de AgI. L'étude de la conductivité électrique totale de ce système en fonction de la température montre que le sel double renfermant 82,5% en équivalent de AgI présente, à 25°C, une conductivité électrique totale de 0,0083 ( cm)–1.
The reaction between homopiperazine, HN<(CH2)5>NH, and dibromo-1,5-pentane, Br(CH2)5Br, gives a diazonia-6,9-dispiro[5.2.5.3]heptadecane dibromide, C15H30N 2 2+ ·2Br–. This salt is iodized by permutation in aqueous or organic solution. This diiodide is associated with silver iodide in proportions varying between 75 and 95% equivalent silver iodide. The study of the total electric conductivity shows that the double salt, containing 82.5% equivalent silver iodide, gives a conductivity of 0.0083 ( cm)–1 at 25°C.相似文献
88.
Michael St. Jacques 《Polymer Engineering and Science》1982,22(4):241-247
To illustrate the potential effect of unbalanced cooling on warpage of flat parts, a simplified two-part analysis is presented. First a computational model for amorphous polymers cooling in an injection molding cavity is presented. The simulation is a finite difference solution of the one-dimensional, transient heat conduction equation with constant material properties. Plastic and mold temperature profiles are calculated through the cooling cycle and the transients from cycle to cycle are included. Temperatures are predicted for both sides of the mold allowing asymmetrical cooling to be analyzed. The model is verified analytically and is in agreement with published data. Secondly, a simplified method of predicting the thermal warpage of a fiat part from calculated temperature profiles is discussed and illustrated. The relative effects on calculated part warpage of asymmetric mold geometry and cooling fluid temperature are predicted with this analysis method. The sensitivity of warpage to these design factors is illustrated for an example part. 相似文献
89.
Effect of Water on the Partial Oxidation of Propane to Acrylic and Acetic Acids on Mo-V-Sb-Nb Mixed Oxides 总被引:1,自引:0,他引:1
It is shown that the major effect of water in the oxidation of propane to acrylic and acetic acids on Mo1V0.3Sb0.25Nb0.08O
n
catalysts is to stabilise the active sites and increase the rates of formation of both acids. The usual effect of favoring desorption of the products is considered to be secondary. 相似文献
90.
For oil sand extractions with microemulsions it is important to disperse large quantities of light hydrocarbons in an aqueous medium. Fundamental studies on the properties of 2-butoxyethanol (BE) and diethylmethylamine (Et2McN) in water suggest that these two liquids could be more effective cosurfactants than the usual alcohols used for this purpose. The phase diagrams of microemulsions using BE and Et2MeN as cosurfactants, combined with typical ionic and non-ionic surfactants and typical aliphatic and aromatic hydrocarbons, were therefore investigated and compared with microemulsions based on n-butanol. Although the phase diagrams depend significantly on the nature of the surfactant and of the oil, the monophasic region generally increases with the cosurfactant in the order n-butanol < Et2McN < BE. With the active mixture BE-cetyltrimethylammonium bromide, temperature has little effect on the phase diagram and NaCl generally destabilizes the microemulsion. 相似文献