Cyanoacrylates

Cyanoacrylates are a family of fast-setting adhesives derived from cyanoacrylic esters. They polymerize rapidly in the presence of moisture and are used in consumer, medical, dental, and industrial applications. Commonly known as super glues, they form strong bonds to many substrates, including metal, glass, ceramic, wood, and many plastics, though bonding to polyolefins often requires surface treatment or primers.

Chemically, cyanoacrylates are esters of cyanoacrylic acid. The general structure is CH2=C(CN)COOR, where R is an alkyl group of varying length. They cure by an anionic polymerization mechanism initiated by trace moisture or weak nucleophiles on surfaces. The polymerization proceeds quickly at room temperature, releasing a small amount of heat and forming a solid polycyanoacrylate adhesive network.

Formulations vary by alkyl group. Methyl cyanoacrylate cures very quickly but tends to be brittle and more irritating to skin; ethyl cyanoacrylate is common in household products. Medical-use cyanoacrylates employ longer-chain alkyl groups, such as 2-octyl cyanoacrylate, which offer greater flexibility and improved biocompatibility. Medical and dental adhesives are formulated to reduce tissue toxicity and control cure rate, while industrial grades emphasize bond strength and viscosity options.

Uses include quick repairs in households and offices, wound closure and tissue adhesion in medicine, bonding in dental procedures, and various industrial applications where rapid curing is advantageous. Safety considerations include potential skin and eye irritation, strong and sometimes difficult removal, and exothermic heat during cure. Some formulations release vapors that can irritate mucous membranes; medical-grade products are designed to minimize tissue reaction and special handling is advised for all cyanoacrylates.

The first cyanoacrylates were developed in the mid-20th century and were later commercialized for broad use, becoming a versatile adhesive family.