retarders

Retarders are substances or devices that decrease the rate of a chemical reaction, a physical process, or a motion. They are used to achieve better process control, improve workability, ensure safety, or tailor release characteristics across many industries.

Chemical retarders fall into several families. In civil engineering, concrete retarders slow cement hydration to extend work time and reduce premature stiffening, especially in hot weather or long transport. Common examples include lignosulfonates, cellulose ethers, and some sugars or inorganic salts. In polymer chemistry and coatings, radical or ionic inhibitors slow polymerization, enabling storage stability of monomers, resins, and fresh formulations; typical inhibitors include hydroquinone, tert-butylcatechol, and related phenolic compounds. In pharmaceutical science, retarded-release (extended-release) formulations use matrix or coating materials to slow drug diffusion or erosion, producing a longer action profile; carriers include ethylcellulose, methylcellulose derivatives, and other polymers.

Mechanisms vary. Many retarders work by adsorbing onto reactive surfaces, scavenging reactive species, or forming diffusion barriers that delay reaction or cure. Temperature, pH, and concentration influence effectiveness.

Mechanical retarders describe devices that slow motion or energy flow, such as braking systems or dampers used in machinery, vehicles, or structural components to control movement and absorb energy.

See also: inhibitors, retardation, extended-release formulations, admixtures.