Rubber-solvent systems

Although Fickian diffusion has been used to describe the diffusion mechanism of liquid through the rubbery material because of its simplicity and mathematical tractability, most of the rubber-solvent systems do not fit such a simplified explanation. Then, non-Fickian diffusion was developed. The case of non-Fickian diffusion was investigated using the following equation ... 

A more quantitative estimation of compatibility can be obtained with the solvent cloud point test. The solvent cloud point is based on the idea that resins will be compatible with elastomers of similar chemical nature. Thus aliphatic resins will be effective tackifiers for aliphatic elastomers, such as natural rubber, while aromatic solvents are needed for aromatic elastomers, such as SBR. Solvent cloud point tests are carried out in three solvent systems which represent aliphatic, aromatic, or polar systems [16j ... 

Phenolic-neoprene contact cements are used for structural metal-metal bonding. especially where fatigue resistance and low temperature performance are important [209]. They are also used for bonding textiles, wood, rubbers, plastics, ceramics, and glass to metal and to one another. Solvent toxicity and flammability has greatly reduced the use of contact cements in the wood products industry. Water-based contact cements persist, but generally do not perform as well as the solvent systems, thus allowing market erosion by alternative binders. 

Dobry and Boyer-Kawenoki have investigated a number of solvent-polymer-polymer systems, with results which confirm all of the qualitative predictions of the theory. Fig. 125 shows their experimental results for the benzene-rubber-polystyrene system with coordinates expressed in weight percent. The symmetry resulting from the stipulations X2 = Xs and xi2 = Xi3 in the case treated theoretically... 

LC-MS is now a nature technology and operation of an LC-MS system is no longer the realm of an MS specialist. The proper choice of the LC-MS mode to be used in a specific situation depends on analyte class, sample type and problem (detection, confirmation, identification). On-line LC-MS is used more for specialised applications than for general polymer or rubber compound analysis. This derives from the fact that LC-MS method development (column, solvent system, solvent programme, ionisation mode) is rather time consuming. LC-MS (in particular with API interface) enables analysis of a wide range of polar and nonvolatile compounds which cannot be analysed by GC (icf. Scheme 7.7). 

Solvent-resistant elastomers, 9 560-562 Solvent-resistant membranes, 27 656 Solvent-resistant rubber, 22 583-584 Solvent selection, in liquid-liquid extraction, 70 746-749 Solvent-solute interactions, 26 855,23 91-96 acid/base interactions in, 23 96 dispersion in, 23 92-93 electrostatic forces in, 23 91-92 hydrogen bonding in, 23 94-95 hydrophobic interactions in, 23 95 polarization in, 23 92 repulsion in, 23 93-94 Solvent strength, of pure fluids, 24 3-4 Solvent systems, for acid gas removal, 72 376-377... 

In the same manner, with decreasing of diffusion coefficient and interaction parameter, the spinodal is reached during the evolution of the system in the pregel stage. The very low values of interfacial tension in rubber modified epoxies (interfacial tension of polymer-polymer-solvent system were reported in range of 10-4-10-1 mN/m) therefore lead to an NG mechanism for phase separation. 

Such techniques have been tried with solid propellants, but reproducible results depend on attaining complete binder-filler release and adequately measuring the binder sol fraction. Preliminary swelling studies to determine a solvent system and conditions which do not degrade the propellant are required. Common extraction techniques are used to determine the sol fraction. This determination is then applied as a correction when computing crosslink density. The force-deformation relationship for swollen rubbers is... 

In order to understand the relationship between the difference in the interaction parameter of rubber-solvent (Xab) and clay-solvent (xcd) systems and the properties of HNBR/SP nanocomposites, the plots of modulus at 100% elongation and tensile strength versus Xab-Xcd are represented in Fig. 45a, b. An exponential decay in both modulus and tensile strength is observed with the increase in difference of interaction parameter. 7) and 7max follow the same trend as above. 

In homogeneous networks such as that of crosslinked rubber, the equilibrium degree of swelling qm depends on the molecular weight of the network chain Mc, satisfying the following relation for a given rubber network-solvent system [56],... 

Michaels et al.50 53) reported the chemical and physical properties of the polyelectrolyte complex of NaSS-PVBMA. This complex is used as a membrane in various fields. Polyelectrolyte complexes prepared by casting homogeneous solutions of ternary-solvent systems mentioned above are transparent and amorphous. Dried polyelectrolyte complexes are hard materials whereas wetted ones are rubber-like or skin-like. The polyelectrolyte complex with an equimolar composition is neutral whereas that with a non-equimolar composition can display ion-exchange properties. The range of the water content depends on the excess of polycation or polyanion in the complex. 

Several in vivo and in vitro studies conclusively demonstrate that benzene can be absorbed through human skin (Blank and McAuliffe 1985 Franz 1984 Susten et al. 1985 Tsuruta 1989). In general, skin absorption is considered a minor source of concern in the occupational environment as it occurs at a much lower rate and extent compared with benzene absorption through the respiratory system (OSHA 1989). However, benzene absorption through the skin as a result of benzene contamination in rubber solvents is a major route of exposure in tire building operations (Susten et al. 1985). Benzene is an irritant to the skin and, by defatting the keratin layer, may cause erythema, vesiculation, and dry and scaly dermatitis... 

Bristow, G. M., "Phase Separation in Rubber-Poly(methyl methacrylate)-Solvent Systems," J. Appl. Polym. Sci., 2, 120 (1959). 

From the information given in the chapter, suggest up to six solvents (systems) that would allow the electrochemical oxidation of complex organics such as polymerized isoprene (rubber) or even Teflon (polymerized tetrafluoroethylene) at less than 373 K. 

The polymerization sequence can be plotted using a phase diagram (Figure 14.1) [11]. This diagram is representative for nearly all polymer (rubber-polymer (glassy polymer)-common solvent systems. Point a is the composition of the feed. The critical point (phase separation) is reached at point b. Further polymerization generates more glassy polymer (SAN) and phase inversion occurs at point c (rubber continuous —> discontinuous). Point d is reached when all monomer is converted. 

This mechanism of adhesion advanced and originally promoted by the Soviets (1963) is of the greatest importance to applications where a material is being adhered to itself, such as in the self tack of rubber. Another familiar example is the application of the same adhesive to two diflerent surfaces from a solvent system, allowing the solvent to dry partially or totally, and then comhining the treated surfaces, such as in the use of contact cement or self-sealing envelopes. 

Rubber Numerous N/A Silica gel G, thickness of 250-300 pm Numerous solvent systems examined vs. compound class Various UV and visible developing reagents Sample size 3-5 pL [36]... 

For example, in the coating and rubber industries the solubility parameter concept has been used respectively, to select solvents or to study swelling of cured rubber by solvents. Bohn has extended the solubility parameter approach to polymer-solvent systems [Bohn, 1968], Solubil-... 

CHRONIC HEALTH RISKS a rubber solvent induced chromosomal aberrations in human whole-blood cultures repeated exposure can damage the nervous system, including headache, fatigue, poor concentration, emotional instability, impaired memory and other intellectual functions chronic neruotoxic effects include motor polyneuropathy prolonged contact can cause drying and cracking of skin. 

The above thermodynamic expressions for a binary solution of a polymer in a solvent include the dimensionless parameter Its value can be determined by measuring any of the experimentally obtainable quantities, like solvent activity or the osmotic pressure of the solution. The constancy of %, over a wide composition range would be a confirmation of the validity of the Flory-Huggins theory. Figure 12.10 represents such a plot obtained by the measurement of solvent activities for various systems. Only in the case of the nonpolar rubber-benzene system was the predicted constancy of %, observed other systems showed marked deviations from theory. 

Virtually all rubber materials, and plastic materials, can be made into an adhesive or sealant compound. This is because many elastomers begin as monomers dispersed in water or solvent and are polymerized in situ. Latex products can remain so, while solid elastomers that are extracted from either water or solvent systems can be solvated with an appropriate organic solvent system. In addition, most solid elastomers exhibit thermal flow characteristics which can make them suitable for hot-melt formulations. And since there are many different rubber polymer families, it stands to reason that there will be many different rubber-based adhesives to identify and describe. Some, however, have... 

Hydrolyzed rice protein film-former, organic solvent systems Ethyl hydroxyethyl cellulose film-former, overprint varnishes Rubber, chlorinated film-former, paints PVP... 

Adhesives and sealants are manufactured from a variety of polymers. Their selection and their combinations used impact solvent selection. Most solvent systems are designed to optimize the solubility of the primary polymer. Adhesives can be divided into ones which bond by chemical reaction and ones which bond due to physical processes. Chemically reactive adhesives are further divided into three more categories for those that bond through polymerization, polyaddition, or polycondensation. Physically bonding adhesives include pressure sensitive and contact adhesives, melt, or solution adhesives, and plastisols. Polymerization adhesives are composed of cyanoacrylates (no solvents), anaerobic adhesives (do not contain solvents but require primers for plastics and some metals which are solutions of copper naphthenate), UV-curable adhesives (solvent-free compositions of polyurethanes and epoxy), rubber modified adhesives (variety solvents discussed below). 

Melt adhesives and plastisols do not contain solvents. The solution adhesives group includes products made from the following polymer-solvent systems nitrocellulose (typical solvents include solvent combinations usually of a ketone or an ester, an alcohol and a hydrocarbon selected from isopropanol, 2-butylhexanol, amyl acetate, acetone, methyl ethyl ketone), nitrile rubber (main solvent - methyl ethyl ketone), polychloroprene (which is usually dissolved in a mixture of solvents including a ketone or an ester, an aromatic and aliphatic hydrocarbon selected from naphtha, hexane, acetone, methyl ethyl ketone, benzene, toluene), and polyvinyl acetate (water). 

The painting process for VR differs from that used for new cars. While new car bodies can be heated at 120-140°C to cure the OEM paint system, a car for repair, complete with a tank of petrol, electronic equipment, rubber tyres and other heat-sensitive components, must be treated with care. Hence, cure temperatures of 60°C maximum are used for VR coatings. The solvent systems used must be capable of providing the necessary solubility, application, viscosity and flow characteristics. It must also evaporate quickly enough to enable the bodyshop to complete the repair as soon as possible, often under widely varying temperature and humidity conditions. 

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