Mini-Encyclopedia of Papermaking Wet-End Chemistry
Part Two: Definitions and Concepts

Colloid

A colloidal substance has the following attributes: (a) at least two phases, (b) at least one dimension of a liquid or solid phase than is less than one micro-meter, and (c) properties that are dominated by interactions within and between surfaces. Examples of colloids are suspensions, emulsions, foams, and aerosols. Most colloids are thermodynamically unstable. Given enough time, most foam bubbles pop, and most suspensions coagulate or settle. Many colloids can be stabilized by additives that decrease the interfacial tension, i.e. the free energy per unit area of surface. Such substances are known as surface-active agents or surfactants. Aqueous suspensions and emulsions can be further stabilized by addition of suitable water-loving polyelectrolytes to the aqueous phase (see steric stabilization).

Request from the webmaster: Our goals include brevity and accuracy. Hopefully we have succeeded with the first goal without sacrificing the second. Please let us know right away if you find an error or omition. Also, please indicate points that need a clearer description.


RETURN TO INDEX PAGE OF ENCYCLOPEDIA

Home page Research opportunities Business opportunities Background information Links to wet-end chemistry E-Mail
This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, m_hubbe@ncsu.edu .