Solvent release

Acrylics. There are two principal classes of acryHc sealants latex acryHcs and solvent-release acryHcs. 

Table 7. One-Part Solvent-Releasing Butyl Sealant Formulation ...

Regenerable absorption processes have also been developed. In these processes, the solvent releases the sulfur dioxide in a regenerator and then is reused in the absorber. The WelLman-Lord process is typical of a regenerable process. Figure 11 illustrates the process flow scheme. Sulfur dioxide removal efficiency is from 95—98%. The gas is prescmbbed with water, then contacts a sodium sulfite solution in an absorber. The sulfur dioxide is absorbed into solution by the following reaction ... 

Many components of ships and marine stmctures are now coated in the shop under controlled conditions to reduce the amount of solvents released into the atmosphere, improve the quaUty of work, and reduce cost. Regulations designed to limit the release of volatile organic compounds into the air confine methods of shop apphcation to those having transfer efficiencies of 65%. Transfer efficiency is defined as the percent of the mass or volume of sohd coating that is actually deposited on the item being coated, and is calculated as... 

Environmental conditions under which solvent release from the adhesive on the substrate is produced must be carefully controlled. Humidity is critical because loss of heat due to solvent evaporation may allow attainment of the dew point (the evaporation of the solvent is an endothermic process), and then condensation of water on the adhesive can result. This phenomenon is often called moisture blooming. The presence of water on the adhesive film causes a detrimental effect because the autoadhesion of rubber chains is greatly inhibited. Therefore, humidity must be controlled and avoided by increasing the temperature during solvent evaporation. 

The high heat resistance produced by adding phenolic resins to solvent-borne CR adhesives is due to the formation of the infusible resinate, which reduces the thermoplasticity of the adhesive and provides good bond strength up to 80°C (Table 11). The resinate also increases the adhesive bond strength development by accelerating solvent release. 4 phr of magnesium oxide for 40 phr of phenolic resin are sufficient to produce a room temperature reaction. A small amount of water (1-2 phr) is necessary as a catalyst for the reaction. Furthermore, the solvent... 

Figure 4-6. The Edman reaction. Phenylisothiocyanate derivatizes the amino-terminal residue of a peptide as a phenylthiohydantoic acid. Treatment with acid in a nonhydroxylic solvent releases a phenyithiohydantoin, which is subsequently identified by its chromatographic mobility, and a peptide one residue shorter. The process is then repeated.

The carbonyl insertion step takes place by migration of the organic group from the metal to the coordinated carbon monoxide, generating an acylpalladium species. This intermediate can react with nucleophilic solvent, releasing catalytically active Pd(0). 

The main advantage is that the entrapment conditions are dictated by the entrapped enzymes, but not the process. This includes such important denaturing factors as the solution pH, the temperature and the organic solvent released in the course of precursor hydrolysis. The immobilization by THEOS is performed at a pH and temperature that are optimal for encapsulated biomaterial [55,56]. The jellification processes are accomplished by the separation of ethylene glycol that possesses improved biocompatibility in comparison with alcohols. 

The energy is transferred to the glass inner surface of the condenser. We maintain a cool temperature inside the condenser by running a constant flow of water through the condenser s jacketed sleeve. The solvent releases a large amount of heat energy as it converts back to liquid, which passes to the water circulating within the jacket, and is then swept away. 

One-part solvent-releasing butyl sealant formulation, 22 43t One-part urethane sealants, 22 36-37 One-pass clarifier, 22 61 One-photon absorption, 77 455 One-pot oxidation polymerization, 23 713 One-stage separation plants, 75 840 One-step cameras/processors, 79 276-278 One-step Ziegler process, 77 715-718 One-way memory, of shape-memory alloys, 22 341, 345-346... 

Solvent-releasing acrylic sealants, 22 43 Solvent-releasing butyl sealants, 22 43-44 Solvent resistance, of polycarbonates, 79 799-801... 

Fig. 16.26 Water dissolution of DNAPL mixture, (a) theoretical dissolution curve for a DNAPL mixture consisting of 10% TCM, 40% TCE, and 50% PCE (v/v) (b) ratios of TCE and TCM, PCE and TCM, and PCE and TCE as a function of source depletion. Reprinted with permission from Broholm K, Eeenstra S, Cherry JA (2005) Solvent release into sandy aquifer. 2. Estimation of DNAPL mass based on multiple-component theory. Environ Sci Technol 39 317-324. Copyright 2005 American Chemical Society...

Pure dry alkali DNM salts are stable at ambient temperature, are heat and shock sensitive, and decompose slowly in polar solvents releasing N2O gas. Small amounts of impurities (e.g. KNO3) considerably decrease the shock and heat sensitivity. Combined IR and MS... 

In addition to enthalpic contributions, the entropy effects accompanying protein-metal ion interactions are substantial. These effects manifest themselves in the desolvation of the metal ion and its binding site. However, as the metal ion binds to a protein, the entropy gain of solvent release may be offset to some degree by the reduction of the conformational entropy of the polypeptide chain as it becomes more firmly bound... 

Apparently future work lies in the investigation of some of the interesting effects mentioned above and other metal ions. In addition, more systematic studies in nonaqueous solvents are required, the paucity of data here being obvious from Table II. What little evidence we have indicates that here too, solvent release from the metal ion may play an important role in forming metal complexes. Already, interesting effects of small amounts of water on labilizing coordinated methanol have been observed (77, 112). 

Acrylics. There are two principal classes of acrylic sealants latex acrylics and solvent-release actylics. High molecular weight latex acrylic polymers are prepared by emulsion polymerization of alkyl esters of acrylic acid, The emulsion polymers are compounded inlo sealants by adding fillers, plasticizers, freeze-thaw stabilizers, thickeners, and adhesion promoters. As is true of the silicone lalex sealants, die acrylic latex sealants are easy to apply and clean with water. 

Another class of acrylic sealants arc the solvent-releasing acrylics. Acrylic monomers are polymerized in a solvent. The natural adhesion of most of the solvent-releasing acrylics produces some of the best unprimed adhesion in the sealant industry. However, slow, continual cure generally produces large compression sets and limits their use to low movement applications. Also, the relatively high amounts of solvent and traces of acrylic monomer in these formulations limits their use to outdoor applications, usually in construction,... 

Bulyk. Butyl-based materials are sold in the form of preformed tapes, thermoplastic hot melts, and one-part solvent-releasing sealants. Butyl polymers are made by the copolymerization of 97-98 mol % isobutylene with 2-3% isoprene. Another butyl-based polymer, polyisobutylene, is produced by the polymerization of isobutylene. Formulations of butyl-based sealants also include plasticizer, filler, and lackifier resins. Poly butenes are common plasticizers for butyl sealants. Solvents, such as mineral spirits, are used for the one-part solvent-releasing formulations. As the solvent leaves the typical one-part butyl, the sealant hardens and loses its elastomeric ability. This limits the use of solvents to low movement applications where durability is not of high concern. 

Solvents are selected such that some will escape relatively quickly from paint films to prevent excessive flow, while others will escape slowly to provide film leveling and adhesion. With typical alkyd coatings, the first 30% of solvent has been observed to evaporate as quickly as the neat solvents, essentially at a constant rate which is dependent on volatility. Later stage evaporation occurred several times more slowly and was rate-controlled by solvent diffusion to the surface of the paint film. The transition point between this behavior was defined as the resin solids content at which the evaporation rate due to volatility equaled that due to diffusion. Transition points have been observed to typically occur at a resin solids content of 40-50% v/v. Thus alkyd paints, normally formulated at 27-40% v/v resin solids, generally exhibit rapid initial solvent-release driven by volatility while high solids coatings (usually 65-75% v/v resin solids) dry solely by a diffusion-controlled process with negligible influence by solvent volatility (Ellis, 1983). 

C 603 C 711 Test Method for Extrusion Rate and Application Life of Elastomeric Sealants Test Method for Low Temperature Flexibility and Tenacity of One Part Elastomeric Solvent Release Type Sealants... 

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