Gelation


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gelation

[jə′lā·shən]
(chemistry)
The act or process of freezing.
Formation of a gel from a sol.

Gelation

 

the transformation of a readily mobile or viscous fluid into a solid (a body without fluidity) that is elastic, plastic, and brittle. Gelation is characteristic of solutions of macromolecular compounds and of disperse colloidal systems. It is caused by the formation of a three-dimensional structural network (skeleton), which fills the entire volume of the liquid and destroys its mobility. In solutions of polymers such a network is formed from macromolecules linked by intermolecular forces or chemical bonds; in colloidal systems, it is formed from coupled particles of the dispersed phase.

Gelation may be caused by an increase or decrease in temperature, an increase in the concentration of the dissolved or dispersed material, a change in chemical composition of the system as a result of a chemical reaction between its components, or the introduction of specific reagents. Gelation is sometimes reversible— that is, when conditions change, a system may pass repeatedly from the liquid state to the solid state and vice versa. However, in the case of pro-found chemical or physical changes in a system, the process is irreversible.

Gelation is often observed and plays an important role in many natural and manufacturing processes. The liquid layer of a paint, lacquer, glue, or photographic emulsion gelates before finally drying. Gelation occurs upon the introduction of electrolytes into rubber latex, during the hardening of synthetic resins in the manufacture of plastics, during the cooling of gelatin and starch paste solutions, and during the coagulation of blood.

References in periodicals archive ?
The effect of epoxy on the gelation behaviors of these systems will also be investigated using this rheometry technique.
The epoxy resin gave a mild condition of the curing reaction without turbidness or gelation.
The stability of the beverages was evaluated by assessing their turbidity, gelation, solubility and protein stability as they were stored at room temperature and at 35 C for three weeks.
The apparent activation energy for gelation can be calculated from the gel time ([t.
Casein aggregation (caused by rennet activity), gelation, syneresis and particle-curd fusion are the critical steps involved in the structural development of cheese.
In molded flexible PU foams, Stanclere TL reportedly promotes faster gassing while delaying gelation of the foam to allow complete filling of the mold before the foam begins to set.
2-trifluoroethanol as well as slightly to moderately toxic solvent such as acetic acid for easy dissolution and the prevention of gelation at room temperature (3), (5), (22).
During gelation, proteins unfold and re-aggregate in such a way that large quantities of water are bound by the denatured proteins.
For example, fast-gelling foam systems can be obtained, eliminating need for a gelation catalyst.
When compared with melt processing methods of common polymers, the process of gelation of PVC plastisol appears to be more complicated.
During heating, the emulsions formed encapsulated gels, which were caused by the gelation of whey protein isolate and the gelatinization of starch in ginseng.
Delayed activity allows better flow, and the additive is useful as a co-catalyst with stronger gelation catalysts.