Swelling linear

Bark Extracts Density O.D. (gm/cc) Modulus of Rupture (psi) Internal Bond (psi) 24-hr Water Absorption (%) Immersion Thickness Swelling (%> 2-hr Boil Test Thickness Swelling (%> Linear Expansion (%)... 

Binder Press Time Min. Water Absorption % Thickness Swell % Linear Expansion %... 

Poly(dimethyl siloxane)s are optically clear, inert, nontoxic, and nonflammable, and possess excellent thermal, oxidative, chemical, and biological stability. Silox-anes do not swell in water, but most organic solvents are able to penetrate into the material and cause it to swell. Linear polysiloxanes, which are routinely used... 

Many solids show marked swelling as a result of the uptake of a gas or a liquid. In certain cases involving the adsorption of a vapor by a porous solid, a linear relationship exists between the percentage of linear expansion of Ae solid and the film pressure of the adsorbed material [134, 135]. 

The swelling of the adsorbent can be directly demonstrated as in the experiments of Fig. 4.27 where the solid was a compact made from coal powder and the adsorbate was n-butane. (Closely similar results were obtained with ethyl chloride.) Simultaneous measurements of linear expansion, amount adsorbed and electrical conductivity were made, and as is seen the three resultant isotherms are very similar the hysteresis in adsorption in Fig. 4.27(a), is associated with a corresponding hysteresis in swelling in (h) and in electrical conductivity in (c). The decrease in conductivity in (c) clearly points to an irreversible opening-up of interparticulate junctions this would produce narrow gaps which would function as constrictions in micropores and would thus lead to adsorption hysteresis (cf. Section 4.S). 

Similarly, polymers dissolve when a solvent penetrates the mass and replaces the interchain secondary bonds with chain-solvent secondary bonds, separating the individual chains. This cannot happen when the chains are held together by primary covalent cross-links. Thus, linear and branched polymers dissolve in appropriate solvents, whereas cross-linked polymers are insoluble, although they may be swelled considerably by absorbed solvent. 

Swelling Behavior. One way to visualize the interaction of solvents with PVP is to examine the effect the former have on lightly cross-linked PVP, as a model for the linear polymer (78). 

Only particles of linear or very slightly cross-linked <0.6%) polymers may be produced by dispersion polymerization. Obviously, dispersion polymerization may be used for the production of monosized seed particles, which, after transfer to aqueous conditions, are used for the production of different cross-linked and macroporous particles by the activated swelling and polymerization method. 

Sephadex type Grade Dry bead diameter (/urn) Fractionation range peptides and proteins (g/mol) Fractionation range dextrans (g/mol) Swelling factor (ml/g dry Sephadex) Maximum operating pressure" (cm H,0) Permeability Ko Maximum linear velocity" (cm/hr) Swelling time (h) ... 

As we have seen previously not all polymers are capable of being dissolved. In principle the capacity to dissolve is restricted to linear polymers only crosslinked polymers, while they may swell in appropriate solvents, are not soluble in the fullest sense of the word. While individual segments of such polymers may become solvated the crosslinks prevent solvent molecules from establishing adequate interactions with the whole polymer, thus preventing the molecules being carried off into solution. 

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