Solvent applied consolidant

Twisting involves twisting a piece of paper tape with a composition in the core. This is applied, e.g., to a kind of Japanese sparkler Senko-Hanabi or some fuses. Loading involves filling a container with a composition lightly, e.g., in the case of reports in which the composition is filled with an apparent specific gravity of about 0.6 to allow it to explode perfectly, or in the case of lances, where the composition is consolidated rather better to avoid explosion. No water or solvent is added to the composition, and there is no need for drying, but they are... 

The TH-600, in the form of a finely precipitated powder, was held in a vacuum oven at 100°C for several days to remove solvent and absorbed moisture. Preweighed quantities were then introduced into a preheated (235°C) mold and 100 psi pressure was immediately applied using a hydraulic press. After dwelling for 1/2 hour at these conditions, a consolidated and partially cured bar 0.1" x 0.5" x 3" was removed from the mold. Bars made in this manner were later postcured to the conditions shown in Table 1. 

Application of wax and various wax resin mixtures was predominantly employed in England until the middle of the last century as a result of misunderstanding of the ancient Roman techniques. The application caused detrimental results. After it was agreed that wax as a consolidant was not appropriate, subsequently techniques of de-waxing had to be devised, which may, however, only reduce the amount of wax in the painting, not remove it completely. Moreover all those removal techniques applied until now involve use of organic solvents, with enormous risks both to paintings and conservators. 

Films dried for 30 days at 50°C showed normal values of Tg for Acryloid B72 and only a trace of retained solvent. For Butvar B98 the solvent removal was not as complete. The data also show that the solvents with higher boiling points (i.e., ethyl acetate and the ethanol-toluene mixture) are more diflScult to remove than acetone or methanol. When the same process of drying at 50°C was applied to wood specimens treated with consolidants, the Butvar B98 specimens dried at the elevated temperature had greater improvement factors than those dried at room temperature, whereas for Acryloid B72 the opposite was true (i6). The data of Table II would have indicated improvements connected to drying at elevated temperature for both resins. 

Kuk et al. [55] applied a PA membrane with molar weight cutoff of 1000 Da in a mixture containing ethanol and crude cotton seed oil. The recovery of solvent was 99% with an operational pressure of 2-4 bar, temperature of 25°C, and permeate flow ranging between 1 and 4 L m h. The authors conclude that small pore diameters result in low permeate flows. Typically, low permeate flux can be correlated with fouling consolidation (Figures 23.14 and 23.15), which limits an industrial application of NF processes by polymeric membranes to solvent recovery from micelle (usually ranging between 20% and 40% w/w or v/v of oil in hexane or another organic solvent) in coupled UF/ NF processes. 

There is as yet no consolidated opinion as to the optimum electrolyte for lithium-sulfiir batteries. Experiments with solid polymer electrolyte are described, but aprotic electrolyte in a Celgard-type separator commonly used in lithium ion batteries is applied more frequently. A large number of electrolytes has been studied that differ both in solvents and the lithium salt. The greatest acceptance was gained by lithium imide solutions in dioxolane (or in a mixture of dioxolane and dimethoxyethane) and also lithium perchlorate solutions in sulfone. Dissolution of polysulfides in electrolyfe is accompanied by a noticeable increase in viscosity and specific resistance of electrolyte. It is the great complexity of the composition of the electrochemical system and that of the processes occurring therein that prevent as yet commercialization of lithium-sulfiir electrolytes. 

Problems associated with the use of prepreg for composite fabrication included a high bulk factor and difficulties in obtaining an optimum resin pre-cure to ensure correct consolidation. One approach was to use pressure assisted resin injection, where a fiber preform contained in a mold was evacuated and a fairly mobile resin pumped in under pressure [64]. To help maintain the accurate alignment of the fiber in the perform, it was held in place by a resin binder made of about 4% polysulfone applied as a solution in methylene chloride, drying to remove solvent and then followed by a short treatment at 320° C to fuse the polysulfone onto the fiber. Next, a laminate of primed sheets was prepared, which was about 2.5 times the bulk volume of the finished composite (i.e., when compressed at 0.65 f/). Two techniques were used to consolidate a preform. 

The other method, which was successfully used for the production of nose cones, was to add a measured amount of methylene chloride solvent onto the laminate in the die, applying minimal pressure and when consolidated, warming the die to evaporate the solvent, which boiled at 40° C, again producing a similar preform. The individual laminates could then be peeled apart and relocated to build a de-bulked cone-shaped preform. 

Consolidating with thermoplastic polymers applied in solution is more problematic. Domaslowski and Lehmann (1972) showed, in the majority of trials, that the polymer was deposited in the outer 3-5 mm of a limestone block. The best consolidation of 5 cm x 5 cm x 5 cm blocks of limestone was achieved using a poor solvent for the polymer, then reducing the rate of evaporation by wrapping the object or drying in an atmosphere of the solvent, hi later experiments, this was shown to be the result of reverse migration of the polymer as the solvent... 

FIGURE 5.5 A guide to the application of consolidant to an object If the application is carried out under vacuum, the container should be evacuated before the addition of the liquid consolidating material. A cova- should be placed over the container to prevent premature evaporation or reaction with atmospheric moisture. The object is lifted off the bottom of the container to reduce the pos-sibiUty of air pockets (a). A small amount of polymer in Uquid form is added to start the penetration process. This Uquid is drawn up into the porous material by capillary absorption (b). The object is soaked in consoUdant aUowing time for trapped air to dissolve and the diffusion of the various components in the Uquid to approach equdibrium. Any vacuum that has been applied is broken slowly and carefully to prevent sudden stresses being appUed to the object (c). Excess consolidant is allowed to drain out before the drying ot setting takes place. This reduces excess consoUdant and reduces the fomation of a surface skin with solvent-appUed polymers. 

The solid, subliming materials - camphene, tricyclene, menthol and cyclododecane - have been used as temporary, volatile consolidants and release agents (lagers lagers, 1999 Cleere, 2005). These have been chosen to be suitable because of their ease of use and resistance to polar solvents. Of these, cyclododecane is the preferred material because it is the most stable to degradation, has fewer impurities, and has fewer health and safety risks. It is important that the material applied contains as little as possible non-volatile material, which will remain after treatment as a contaminant. 

These materials are applied to fragile surfaces either in solution or molten. Films applied from different solvents tend to deposit as crystals so are less coherent and resistant to penetration by liquids, such as water. Films applied from molten materials are stronger, more coherent and solvent resistant. Mixtures of compounds may form strong films with smaller crystals, by analogy with similar findings from industrial practice (Araki and Halloran, 2004). The rate of sublimation of the consolidant depends on the vapour pressure of the material, the temperature, the rate of air movement and the depth of penetration into a porous surface. For the high-melting-point, low-volatility materials such as cyclododecane and menthol, it can take many weeks for the consolidant to leave. The more volatile materials will leave faster. 

The osmotic pressure becomes equivalent to a mechanical pressure in a two phase fluid model where the solvent is treated as a pure phase. Under these circumstances, a mechanical pressure increases the solvent chemical potential and it flows to a lower pressure (or lower osmotic pressure), hi a polymer solution, the pressures of the polymer and the water must sum to the applied (often atmospheric) pressure. As the polymer concentration is increased, the chemical potential of the water is reduced. In the two phase fluid models, this is equivalent to reducing the pressure of the solvent (indeed it can go negative). When exposed to suspensions where the solvent is at atmospheric pressure (higher chemical potential) the solvent flows from the suspension to the polymer solution until the pressures (chemical potentials) equilibrate. As a result, osmotic consolidation can be used to densify aggregated suspensions while keeping them saturated and with the application of no external pressure. These same ideas can be applied to drying and... 

N. S. Baer, Risk Assessment as Applied to the Setting of Solvent Toxicity Limits , in Adhesives and Consolidants (London, 1984), pp. 26-31. 

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