Swell agent

In the depolymeri2ed scrap mbber (DSR) experimental process, ground scrap mbber tines produce a carbon black dispersion in ok (35). Initially, aromatic oks are blended with the tine cmmb, and the mixture is heated at 250—275°C in an autoclave for 12—24 h. The ok acts as a heat-transfer medium and swelling agent, and the heat and ok cause the mbber to depolymeri2e. As more DSR is produced and mbber is added, less aromatic ok is needed, and eventually virtually 100% of the ok is replaced by DSR. The DSR reduces thermal oxidation of polymers and increases the tack of uncured mbber (36,37). Depolymeri2ed scrap mbber has a heat value of 40 MJ/kg (17,200 Btu/lb) and is blended with No. 2 fuel ok as fuel extender (38). 

Uses. The largest use for sodium thiocyanate is as the 50—60 wt % aqueous solution, as a component of the spinning solvent for acryUc fibers (see Fibers, acrylic Acrylonitrile polymers). Other textile appHcations are as a fiber swelling agent and as a dyeing and printing assist. A newer commercial use for sodium thiocyanate is as an additive to cement in order to impart early strength to concrete (376). 

Dissolved fouling material may pass into the membrane pores. Reprecipitation upon rinsing must be avoided. Membrane-swelling agents, such as hypochlorites, flushout material which may be lodged in the pores. 

Ethylenediamine (70,71), benzyl alcohol and acetone (72), ethylene glycol (73) and C2—C g carboxyUc acids (74) are claimed to increase the reactivity of cellulose toward acetylation. Sodium hydroxide and Hquid ammonia (71) are excellent swelling agents and have been used to activate cellulose before esterification. Ultrasonic treatment of cellulose slurries (75) reportedly swells the fibers and improves reactivity. 

J. O. Warwicker, R. Jeffries, R. L. Colbran, and R. N. Robinson, M Eeview of the Eiterature on the Effect of Caustic Soda and Other Swelling Agents on the Fine Structure of Cotton, Shirley Institute Pamphlet No. 93, Didsbury, Manchester, UK, 1966. 

Acid dyes can be ptinted on acetate, produciag prints with very good wetfastness and exceptional brightness. The print paste contains a solvent, urea, and ammonium thiocyanate, as a fiber swelling agent to aid ia diffusion of the dye. Again, fixation and scouting foUow the procedures for polyamide. 

In the 1960s materials became available which are said to have been obtained by chlorination at lower temperatures. In one process the reaction is carried out photochemically in aqueous dispersion in the presence of a swelling agent such as chloroform. At low temperatures and in the presence of excess chlorine the halogen adds to the carbon atom that does not already have an attached chlorine. The product is therefore effectively identical with a hypothetical copolymer of vinyl chloride and symmetrical dichloroethylene. An increase in the amount of post-chlorination increases the melt viscosity and the transition temperature. Typical commercial materials have a chlorine content of about 66-67% (c.f. 56.8% for PVC) with a Tg of about 110% (c.f. approx. 80°C for PVC). 

Figure 2.21 shows the on-line extraction gas chromatogram of 2.25 ml of water spiked at 5 ppb levels with 14 different organic pollutants (40). In this case, the authors concluded that wall-coated open tubular traps (thick-film polysiloxane phases) can be used for the on-line extraction of organic compounds from water. However, when using swelling agents such as pentane, non-polar analytes can be trapped quantitatively, while for more polar compounds chloroform is the most suitable solvent. 

Auftriebt m, buoyancy upward thrust lift plankton, -mittel, n. buoying agent swelling agent. 

The role of a swelling agent in the activated swelling method may be explained by considering the theoretical basis of the process. The swelling of pure polymer particles with the monomer can be described by the Morton equation ... 

If the swelling process is carried out in the presence of a swelling agent, the Morton equation may be written as follows ... 

In another method, the liquid resin is sprayed onto wood chips. The condition for rapid and complete impregnation of the wood chips or sawdust in resins is to dilute the resins either in monomer [40] or in swelling agents [41]. Dilution of the resin with monomers of roughly 10% permits complete impregnation within a very short period. The mixed or impregnated product was subjected to press under pressure and temperature to produce a board with a natural appearance. Percent-... 

When a bead of a gel-type CFP material is in the dry state, for practical purposes it can be considered as a solid material (thus possessing a mass, a volume and a shape). When in the swollen state, a CFP material can be still considered as a solid from the practical point of view, but this circumstance is now an authentic approximation. In fact, physico-chemical analysis reveals that under some circumstances this alleged solid material is rather a very viscous liquid. More precisely, it is a suspension of interconnected polymer chains in the swelling agent. Each swollen CFP bead can be considered as a drop, which can retain a definite shape owing to the existence of the polymer framework. 

PGSE-NMR provides direct information on the translational mobility of a liquid medium capable of swelling a given CFP. The self-diffusion coefficient of the swelling agent is found to be related to the nanoporosity of the matrix as determined from ISEC and to the rotational correlation time of a suitable paramagnetic probe (ESR) [22]. 

Figure 4. Schematic description of the swelling process. The molecules of the swelling liquid start to penetrate inside the polymer framework from its surface (a) and to solvate the polymer chains. The polymer chain start to stretch out and to move away from one another the apparent volume of the polymer increases and the first nanopores are formed (b). Swelling stops when increasing elastic forces set up by the unfolding of the polymer chains counterbalance the forces which drive the molecules of the swelling agent into the polymer framework (c).

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