Tetrahydrofuran. physical properties

The physical properties of finish removers vary considerably due to the diverse uses and requirements of the removers. Finish removers can be grouped by the principal ingredient of the formula, method of appHcation, method of removal, chemical base, viscosity, or hazardous classification. Except for method of apphcation, a paint remover formulation usually has one aspect of each group, by which it can be used for one or more appHcations. A Hst of the most common organic solvents used in finish removers has been compiled (3). Many are mentioned throughout this article others include ethyl lactate [97-64-3] propylene carbonate [108-32-7] furfural alcohol [98-01-1/, dimethyl formamide [68-12-2] tetrahydrofuran [109-99-9] methyl amyl ketone [110-43-0] dipropylene glycol methyl ether [34590-94-8] and Exxate 600, a trade name of Exxon Chemicals. 

Noell et al. reported the preparation of silica-poly(ether ether ketone) hybrid materials with improved physical properties.155 An amine-end-capped poly(ether ether ketone) was used to react with isocyanatopropyltriethoxysilane in tetrahydrofuran (THF). The triethylsilane-end-capped poly (ether ether ketone) was mixed with tetraethoxysilane (TEOS) in THF. Quantitative amounts of water were introduced into die system, and the mixture was reduxed at 80°C. The entire reaction mixture was allowed to further react in Tedon molds. Tough transparent materials were obtained by diis approach. 

In addition to the desired polymerization reaction, the dialcohol reactants can participate in deleterious side reactions. Ethylene glycol, used in the manufacture of polyethylene terephthalate, can react with itself to form a dialcohol ether and water as shown in Fig. 24.4a). This dialcohol ether can incorporate into the growing polymer chain because it contains terminal alcohol units. Unfortunately, this incorporation lowers the crystallinity of the polyester on cooling which alters the polymer s physical properties. 1,4 butanediol, the dialcohol used to manufacture polybutylene terephthalate, can form tetrahydrofuran and water as shown in Fig. 24.4b). Both the tetrahydrofuran and water can be easily removed from the melt but this reaction reduces the efficiency of the process since reactants are lost. 

The physical properties of the anhydrate form and two polymorphic monohydrates of niclosamide have been reported [61], The anhydrate form exhibited the highest solubility in water and the fastest intrinsic dissolution rate, while the two monohydrates exhibited significantly lower aqueous solubilities. In a subsequent study, the 1 1 solvates of niclosamide with methanol, diethyl ether, dimethyl sulfoxide, N,/V -dimethyl formamide, and tetrahydrofuran, and the 2 1 solvate with tetraethylene glycol, were studied [62], The relative stability of the different solvatomorphs was established using desolvation activation energies, solution calorimetry, and aqueous solubilities. It was found that although the nonaqueous solvates exhibited higher solubilities and dissolution rates, they were unstable in aqueous media and rapidly transformed to one of the monohydrates. 

Since BAMO polymer is a solid at room temperature, BAMO monomer is copolymerized with tetrahydrofuran (THF) in order to formulate a liquid BAMO copolymer that is used as a binder in propellants and explosives, as shown in Fig. 4.9. The terminal OH groups of the BAMO-THF copolymer are cured by reaction with the NCO groups of hexamethylene diisocyanate (HMDl) and then cross-linking is carried out with trimethylolpropane (TMP). The physical properties of such a copolymer with a BAMO/THF composition of 60/40 mol% are shown in Table 4.7.1151... 

New copolymer diols derived from ethylene oxide and tetrahydrofuran yield linear polyurethanes of superior physical properties [16]. 

Summaries of the work in tetrahydrofuran polymerizations (7, 2, 3) have appeared as late as 1963. However, in the last four to five years the number of publications has been so numerous and the advances in the understanding of tetrahydrofuran polymerizations have been so rapid that it is worth reviewing again at this time. New catalysts have been reported, significant studies with old catalysts have been made, and a number of papers on the physical properties of polytetrahydrofuran have appeared. We will emphasize this new work and attempt to point out some areas where new investigations or a reinvestigation of earlier studies would be helpful. 

Pentacarbonyl(methoxymethylcarbene)chroniiuin(0) is a dull-yellow, crystalline solid mp 34°. It slowly decomposes in the solid state at room temperature in air, but may be stored at 5° for a few days before appreciable decomposition is observed. It is soluble in aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and other common laboratory solvents such as benzene, 1,4-dioxane, tetrahydrofuran, chloroform, dichloromethane, and methanol, and is slightly soluble in ethanol. The infrared spectrum (cyclohexane solution) has v(CO) bands at 2065, 1985, 1965, and 1950 cm-1. The H nmr spectrum in chloroform-d shows the methoxy proton resonance at t6.15 and the methyl proton resonance at t7.70. Other physical properties are reported in the literature.6,7... 

Ligands 179 and 180 were synthesized by the nucleophilic substitution of the sodium glycolate of TV-methyldiethanol amine on either 2,6-dichloropyridine or 2,6-6 (chloromethyl)pyridine. However, 183 and 184 were synthesized by the qua-temization of 181 or 182 with l,2-6is(P-ethoxy)ethane in acetonitrile. In both instances the resulting diquatemary ammonium salts were demethylated by L-Selec-tride in refluxing tetrahydrofuran to afford the desired pyridino coronand. Com-piexation studies have not been performed on any of these coronands and the physical properties of these compounds do not indicate any unusual characteristics m). 

As can be seen in the following examples, both Cu and Cu" salts such as CuCl. CuBr, Cul, CuCN, Cu(acac)2, and Li2CuCl4 (known as Kochi s catalyst [22]), introduced at 0.2 10% to a Grignard or a substrate are most typical for these reactions. The choice of copper salts is dependent on their intrinsic reactivities, as well as on physical properties, such as solubility and ease of handling. For example, Li2CuCl4 is soluble in tetrahydrofuran (THF) and is frequently quite useful to obtain clean cross-coupled products. An added Cu species is considered to be reduced to Cu in situ by the Grignard reagent to participate in the catalytic cycle [see Eq. (36)]. 

Organolead-alkali compounds are the least stable of the group-IVB-alkali compounds. They are thermolabile and air and moisture sensitive but are stabilized in such donor solvents as Et O, tetrahydrofuran (THF) or NHj. Information on their isolation is sparse and no physical properties of pure R PbM (M = alkali metal) or R2PbM2 are available. Nevertheless, RjPbM in situ is a powerful tool for synthesizing unsymmetrical RjPbR tetraorganoleads ... 

The recovery of the waste streams was complex, since a series of azeotropes had to be separated. Different alternatives were simulated and initial cost estimates were made by computer simulation alone. The first simulations were based only on the physical properties incorporated in the software data bank. In a second step additional physical properties mostly liquid liquid equilibrium (LLE) data were measured in order to increase the accuracy of the simulation of the most critical steps. First screening experiments of pervaporation to eliminate water and polar impurities such as methanol and ethanol from the tetrahydrofuran (THF) mixtures were stopped early, as it appeared that the alternatives based on counter current extraction (CCE) and rectification alone were less expensive and probably more robust. The most promising processes were piloted. The pilot experiments allowed confirmation of the results of the simulations and allowed the simulations to be updated to reflect the pilot results. A large part of the work during the pilot experiments was to verify the behaviour of further impurities contaminating the solvents, which had not been taken into account in the first screening. All impurity substances had to be purged efficiently, so that they would not accumulate after repeated recoveries of the solvents. 

With this background information, it was decided to see how these blends would behave as films. In Table II are tabulated some physical properties of extruded films of PVC/acrylic copolymer blends (9/1, 1/1, and 1/9). In Table III are tabulated physical properties of solution-cast blend films, cast from tetrahydrofuran solution. The cast films contained no lubricants or stabilizers (which were present in the extruded films) nevertheless, their optical property deficiencies were similar to those of the extruded films. The additives used were PVC stabilizer (e.g., organotin compounds), lubricant (e.g., metallic stearates), and plasticizer (phthalate type). 

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