Swelling behaviour

In the homogenous mixture of Starch and Polyvinyl alcohol (PVA), 30 % of plasticizer was mixed to make Pure blend. Then 10 % cellulose was mixed into above mixture followed by removal of extra water gave Cellulose-Reinforced starch-PVA blends. The different proportions of Fly ash were mixed into mixture of Cellulose-Reinforced starch-PVA blends to get various fly ash inserted Cellulose-Reinforced starch-PVA blends. Solubility, swelling behaviour and water absorption studies of Fly ash blends were measured at different time intervals at relative humidity of 50-55%. The insertion of Cellulose into starch-PVA blend decreases the solubility of blends due to the hydrophobicity of cellulose, but the solubility further increases by insertion of Fly ash into starch-PVA matrix that indicating the mechanical stability enhancement of blends. The water absorption behaviour of fly ash blends increases rapidly upto 150 min and then no change. The optimum concentration of Fly ash into Cellulose-Reinforced starch-PVA blend was 4%. 

Figure 2.11 The change in volumetric swelling behaviour due to (a) loss of cell wall material but not cell wall bulking agent, and (b) loss of cell wall cross-linking agent.

For moderate reduction the changes are completely reversible but they are progressively less so with more thorough reduction (Stucki et al 1984 Komadel et al 1995 Gates et al 1996). There are concomitant changes in the clay s physical and chemical properties, including its surface area, swelling behaviour, and capacity to sorb cations. 

Drug delivery induced by swelling may be achieved with swellable polymer layers based on cellulose ethers or acrylates, where with the latter pH-dependent swelling behaviour is feasible [92]. Examples are the oral Chronotopic delivery system [93], the Tune-controlled Explosion ystem (TES) [94,95] and the TIME-CLOCK -System [96-98] (Figure 6.4). 

Shomer, I. (1995). Swelling behaviour of cell-wall and starch in potato (Solanum-Tuberosum L) tuber cells. 1. Starch leakage and structure of single cells. Carbohydr. Polym., 26,47-54. 

The viscous systems that are of most concern are those which may give rise to laminar flow in the relief system. The level swell in the vessel may also be affected. These two topics are covered below. It should be noted that only moderately high viscosities, of 100 cP or more, may be sufficient to cause laminar flow or to change the level swell behaviour. Failure to take account of the effects of laminar flow could lead to the serious undersizing of the relief system. 

Thus, this consideration shows that the thermoelasticity of the majority of the new models is considerably more complex than that of the phantom networks. However, the new models contain temperature-dependent parameters which are difficult to relate to molecular characteristics of a real rubber-elastic body. It is necessary to note that recent analysis by Gottlieb and Gaylord 63> has demonstrated that only the Gaylord tube model and the Flory constrained junction fluctuation model agree well with the experimental data on the uniaxial stress-strain response. On the other hand, their analysis has shown that all of the existing molecular theories cannot satisfactorily describe swelling behaviour with a physically reasonable set of parameters. The thermoelastic behaviour of the new models has not yet been analysed. 

Synthetic rubber ebonites do not fundamentally differ from natural rubber ebonites in swelling behaviour. Synthetic rubbers combine more nearly completely with the added sulphur. Nitrile ebonites are outstanding in that they are almost unaffected even by solvents such as benzene carbon-disulphide which strongly swell natural, butadiene and styrene butadiene ebonites [4,5]. 

Table 7.1 Swelling behaviour, loss tangents (tan 8) and boiling points for solvents used in microwave-assisted solid-phase synthesis...

Similar to the solvent-free approaches discussed in Section 3.2, a combinatorial approach also has been employed to scale-up the synthesis of desired compounds100. The microwave-assisted reactions are performed on solvent-swollen polymeric beads and are classified herein as being carried out in the presence of a solvent. Examination of these supports after 20 min of microwave irradiation (700 W) revealed that neither the appearance nor swelling behaviour of the beads had altered65. 

J.A. Menjivar, E.N. Chang and L. Maciel, Extrudate Swell Behaviour of Wheat Flour Doughs, in "Theoretical and Applied Rheology", P.Moldenaers and R. Kennings (eds.), Elsevier Science B.V., 1992, pp. 714-716. 

Stimuli-responsive homo- and copolymeric hydrogels with pH, temperature, ionic strength, solvation, electrical field, or magnetic field-sensitive pendent groups have been produced for drug, peptide and protein delivery devices, for biosensors and for tissue engineering. Their swelling behaviour, net-... 

Mucoadhesive polymers can be divided into non-covalent binding and covalent binding polymers. On the one hand the mechanism of mucoadhesion is based on hydrogen bonds, ionic interactions and van der Waal forces for non-covalent binding polymers, and on the other hand, on covalent bonds between the mucus and certain residues of the polymer. Moreover, physical interactions such as interpenetration of the polymer into the mucus gel layer entangle the polymer chains, which is strongly influenced by the swelling behaviour of the... 

Fig. 8.1 Correlation between pH of anionic polymer polycarbophil and its swelling behaviour pH 3 (A), pH 5(B), pH 7 ( ). Adapted from Bernkop-Schniirch and Steininger (2000)...

The swelling behaviour of rye starch is very similar to that of wheat starch and occurs at two temperatures. At temperatures of 50-55°C, the swelling of large granules is in one plane and radial in nature, whereas the small granules swell to... 

Figure 3. Influence of the concentration of various phenols on the equilibrium swelling behaviour of PNIPA gel at 20°C. Symbols are the same as in Figure 1.

Furthermore, crystalline polymers do obey the rules even at room temperature in so far as swelling behaviour is concerned. This again is a demonstration that crystalline regions serve as physical cross-links. Some crystalline polymers with strong hydrogen bonding groups can be made to dissolve at room temperature. But in these cases a very specific interaction between polymer and solvent must occur. For example, cellulose is soluble in 70% sulphuric acid and in aqueous ammonium thiocyanate nylon 6.6 is soluble in phenol and in a 15% calcium chloride solution in methanol. 

Hellweg T, Dewhurst CD, Eimer W, Kratz K (2004) PNIPAM-co-polystyrene core-shell microgels structure, swelling behaviour and crystallisation. Langmuir 20 4330-4335... 

No matrix resins have also been prepared by the polymerization of methacrylamide (MAAm) or acrylamide (AAm) and TAA using y-irradiation. The solvent used for polymerization has a profound influence on the capacity, but a smaller effect on the swelling behaviour. Ethanol, methanol, and DMF are to be preferred to just water, and ethanol is found to be the best solvent for this system giving a resin having a capacity of 1.07 meq/g when the ratio of MAAm to TAA in the polymerization mixture is 1.7. 

H. Rave, R. Staudt, J.U. Keller Measurement of sorption and swelling behaviour of polymer/C02 systems by a combined oscillometric-gravimetric method. Proeedings. of P3AC2, Brisbane, May 14-18, 2000, World Scientific, Singapore 2000. 

Yan J and Pal R. Isotonic swelling behaviour of w/o/w emulsion bquid membranes under agitation. J Membr Sci 2003 213 1-12. 

Xue, W. Champ, S. Huglin, M.B. Thermoreversible swelling behaviour of hydrogels based on A-isopropylacry-lamide with a zwitterionic comonomer. Eur. Polym. J. 2001, 37, 869-875. 

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