Paraformaldehyde

Formaldehyde is the simplest aldehyde with the formula hch=o. It is a gas at room temperature with a pungent smell. It cannot be readily isolated or handled in the pure state because it is extremely reactive. Formaldehyde reversibly polymerizes to its cyclic trimer 1,3,5-trioxane or the linear polymer polyoxymethylene. It is readily oxidized to form formic acid in the air. It is commercially available as an aqueous solution usually 37-50% w/w. Formalin is the solution of formaldehyde in water. Paraformaldehyde is a white crystalline solid formed by polymerization of formaldehyde. Formaldehyde kills most bacteria, and used as a disinfectant and as a preservative and fixative for pathologic specimens. Formaldehyde cross links amino groups. In industry formaldehyde is used in the production of thermoset resins, functional polyols, explosive, hexamine and other chemicals.

Paraformaldehyde is a white crystalline solid formed by polymerization of methanal gas (formaldehyde, hcho) by heating. Lower molecule paraformaldehyde is soluble alkali but insoluble in alcohol, ether, and water. It is used as fumigant, disinfectant, and fungicide. Higher molecule homopolymer is a hard engineering plastic which is strong, rigid, and have good moisture, heat, and solvent resistance. Commercially acetal copolymers are also widely used for industrial and automotive applications with excellent balance of properties and processing characteristics. Paraformaldehyde is used to make various resins with mainly phenol (melamine resin; phenol resin; vinylon; polyacetal resin; terephthalic acid; diphenyl methane diisocyanate, acrylic acid esters)