Paraformaldehyde is a white, solid polymer of formaldehyde with the pungent, characteristic formaldehyde odor. Paraformaldehyde is made up of connected formaldehyde molecules. Paraformaldehyde is slightly soluble in alcohols and insoluble in ethers, hydrocarbons, and carbon tetrachloride. It is relative insoluble in cold water, but soluble in hot water with depolymerization. The solubility and rate of solution of paraformaldehyde in water are greatly influenced by pH and temperature. Both acidic and alkaline pHs and higher temperatures accelerate the rate of solution. Once dissolved, the paraformaldehyde solution behaves like the methanol-free formaldehyde solution of the same concentration. Paraformaldehyde is composed of varying molecular weight polymers of polyoxymethylene glycols. It is generally prepared as 91 or 95% formaldehyde by weight with the remainder being free and combined water. The combined water is the terminating agent for the paraformaldehyde chains. Paraformaldehyde reacts chemically as formaldehyde at a rate determined by its rate of depolymerization under the conditions of use. The rate of depolymerization and thus perceived reactivity decreases with increasing molecular weight of the polymer chains.

Paraformaldehyde is widely used by resin manufacturers seeking low water content, or more favorable control of reaction rates when compared to aqueous formaldehyde solutions. With less dehydration required, paraformaldehyde resins are made in less time. Better yields result from the complete or partial elimination of dehydration because fewer reactants are lost in the distillate. Utility costs are reduced because paraformaldehyde requires less steam, cooling water and power for water removal. The capability of charging more reactants to the process equipment (in the volume otherwise occupied by water and extra azeotroping agent) increases reactor capacity, and reduces capital required for equipment versus the equipment costs and capacity when using aqueous formaldehyde. Finally, and of increasing importance, less wastewater is produced. Paraformaldehyde provides a source of formaldehyde for the synthesis of phenol-, urea-, furfural alcohol-, resorcinol- and melamine- formaldehyde resins. These products find extensive usage in industrial coatings, wood products, textiles, and foundry resins. Oil well drilling chemicals, lubricating oil additives, adhesive resins, and electrical component molding materials also use Paraformaldehyde. Miscellaneous end uses include photographic and graphic arts chemicals, pigments, rubber antioxidants, fluorescent tube and ink chemicals, pharmaceuticals, slow release fertilizers and others.

Information provided by Celanese Corporation.