Binder (paint)

A binder or binding agent is any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, by adhesion or cohesion.

In a more narrow sense, binders are liquid or dough-like substances that harden by a chemical or physical process and bind fibres, filler powder and other particles added into it. Examples include glue, adhesive and thickening.

Examples of mechanical binders are bond stones in masonry and tie beams in timber framing.

Binders are loosely classified as organic (bitums, animal and plant glues, polymers) and inorganic (lime, cement, gypsum, liquid glass, etc.). These can be either metallic or ceramic as well as polymeric depending on the nature of the main material. For example, in the compound WC-Co (Tungsten Carbide used in cutting tools) Co constitutes the binding agent for the WC particles.

Based on their chemical resistance, binders are classified by the field of use: non-hydraulic (gypsum, air-cements, magnesia, hydrated lime), hydraulic (Roman cement, portland cement, hydraulic lime), acid-resistant (silicon fluoride cement, quartz cement), and (harden at 170 to 300°С i.e. 8-16 atm pressure and, e.g., comprise CaSiO3 materials) .

Some materials labeled as binders such as cement have a high compressive strength but low tensile strength and need to be reinforced with fibrous material or rebar if tension and shear forces will be applied.

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