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Lecture 9
:
Processes moisture sorption hydrophilic biopolymers and
mixtures biopolymeric quality formation
Plan:
1. Processes of moisture sorption and modern technology
2. The two-phase system of water, characteristic
3. Scientific support, the practical importance of processes
organic - inorganic systems
4. The quality characteristics of modern production
5. Composite polymeric hydrogels, characterization, classification
Is considered information on biopolymers and biopolymer blends and their
use in modern conditions.
A comparison of the properties of water in solutions of hydrophilic
polymers with similar properties in solution it their monomeric counterparts. It is
known that the properties of the polar groups grafted to the polymer molecules
remain unchanged, therefore, by comparing with the same conditions in the
properties of water solutions of polymers and their corresponding monomers
obtained information about the influence of water on the polymer properties
linkages in the polymer solution. On this basis, to analyze the influence of
polymer chain crosslinking and bulk water activity and concentration of the
polymer solutions.
The interaction of hydrophilic polymers with water they swell, first, and
then, in most cases, are dissolved to form a solution. But quite often the
dissolution stops at the swelling stage. This usually happens - the presence of
bonds (cross-links) between the polymer molecules. These links limit the
distance between the polymer chains and thereby prevent dissolution. The nature
of relationships may be different. It can be as hydrogen bonds, for example, in
the case of polyvinyl alcohol (PVA) [1] and covalent cross-linked polymers in
which the ion-exchange resins and membranes [2]. With increasing temperature,
the hydrogen bonds are broken and the polymer is dissolved. Covalent bonds can
withstand the effects of temperature. The polymers are cross-linked in this way,
do not dissolve under any circumstances.
When in a steam atmosphere all hydrophilic polymers adsorb water but
complete dissolution does not occur in this case. The amount of adsorbed water
(at constant temperature, pressure) depends on the nature of the polymer and the
relative vapor pressure, and is described by the sorption isotherm. As shown in
[3, 4], the sorption of water crosslinked polyelectrolyte is accompanied by the
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