Peptization


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Related to Peptization: Co-precipitation

peptization

[‚pep·tə‚zā·shən]
(chemistry)
Aggregation in which a hydrophobic colloidal sol is stabilized by the addition of electrolytes (peptizing agents) which are adsorbed on the particle surfaces.
Liquefaction of a substance by trace amounts of another substance.

Peptization

 

the spontaneous breakup of aggregates— lumps, flocs, or clots that have formed by the accumulation of cohered colloidal particles—into smaller aggregates or individual primary particles. A particularly graphic example is the peptization of gelatinous precipitates (coagels), which are formed by the coagulation of sols and highly dispersed suspensions. Peptization involves the “colloidal dissolution” of the precipitate; that is, the coagulate becomes a sol once again. The term “peptization” is derived from the apparent similarity between this phenomenon and the breakdown of proteins by the enzyme pepsin.

Peptization may be observed upon elevation of temperature or upon removal of the coagulating reagents by rinsing the precipitate. The most typical form of peptization occurs upon introducing peptizing agents—substances that promote disaggregation, that is, the separation of cohered particles—into a dispersion medium. The peptizing agents may be electrolytes or surfactants, which cause particle surfaces of the disperse phase to become lyophilic. For example, the peptization of ferric hydroxide gel in an aqueous medium is made possible by the addition of small quantities of ferric chloride, whereas kaolin is peptized by humic acids.

Agitation usually accelerates peptization. Recrystallization and coalescence, which often occur in colloidal precipitates upon aging, hinder peptization, since they promote the consolidation of particles. The coagulation of sols by polyvalent ions and polyelectrolytes yields precipitates that also resist peptization.

Peptization is used to obtain liquid disperse systems from powders or pastes in chemical and food-processing technology. It plays an important role in the group of processes determining the cleansing action, formation, and destruction of various disperse structures. Sometimes peptization may be harmful, for example, if it occurs during the process for the purification of water or the clarification of wine.

L. A. SHITS

References in periodicals archive ?
The peptization of units and the increase of aggregate stability of suspensions can be observed.
When a low surface area adsorbent (the red or yellow dispersant) is present, an excess of the triblock in the aqueous phase builds, and the interaction of the oxyethylene units with the talc surfaces begins a peptization of large platelet aggregates that results in an increasingly competitive adsorbent surface area to the colorant's surface area.
The 300% modulus, being a measure of strain-induced crystallization, responds to higher degree of peptization.
Table 1--basic chemical structures of processing additives Group Examples Hydrocarbons Mineral oils Petrolatum Paraffin waxes Petroleum resins Fatty acid derivatives Fatty acids Fatty acid esters Fatty alcohols Metal soaps Fatty acid amides Synthetic resins Phenolic resins Low molecular weight polymers Polyethylenes Polybutenes Organo thio compounds Peptizers Table Table 2--the effect of processing additives Effects Examples Peptization 2.
26) and since with only the rubber present the mixer is relatively underloaded for peptization within the batch, relatively larger amounts of chemical peptizer (0.
1 units, (which is low for a polychloroprene compound, and achievable in this case through the peptization of the polymer) and that compound had levels of -2A, -2B and +2C.