Paraformaldehyde is the solid form of liquid formaldehyde. Classified as a thermoplastic, this chemical compound exhibits the typical characteristics of similar polymers with long-chain polyoxymethylene glycols, namely the ability to turn to liquid when exposed to heat and solidify upon cooling or being frozen to a hard, glass-like material. In fact, this substance can be melted and cooled repeatedly and still retain these properties.
Since paraformaldehyde is basically a condensed form of formalin, or aqueous formaldehyde, it possesses the same characteristics. In fact, it can be substituted in place of aqueous formaldehyde to produce the resinous binding material needed to make particleboard and plywood when combined with melamine, phenol, or other reactive agents. In addition, there are some advantages to doing so. For one thing, it produces a greater yield of raw product. For another, its use reduces the need to remove water from the reactive agent before processing by up to 20 times.
Paraformaldehyde can be synthesized from formaldehyde solutions. In its naturally occurring state, formaldehyde is a water-soluble gas that forms methylene hydrate when hydrated. Methylene hydrate can then be polymerized, which yields paraformaldehyde as a white precipitate. However, the addition of methanol is necessary to stabilize the polymerization process.
This compound is also classified as an aldehyde, meaning that it contains a carbonyl group. In the case of this particular substance, the carbon atom is bonded to two hydrogen atoms. Aldehydes typically give off a strong odor, as evidenced by the distinct aroma of many familiar botanicals, such as cinnamon and vanilla. Aldehyde-based solutions are also well-known as biological fixatives capable of inhibiting cellular degradation due to the breakdown of enzymes and bacterial replication. That’s why formaldehyde and its derivatives, including paraformaldehyde, are used to preserve tissue samples.
These properties also make this compound useful as a fungicide and pesticide. It is also used in the manufacture of fertilizers, fluorescent lights, and certain chemicals used in photography and printing. It is also found in a wide variety of consumer goods, including vitamins, personal care products, and household cleaning products.
Like formaldehyde, paraformaldehyde is readily absorbed via the respiratory system, but is quickly metabolized to formate and excreted through the lungs or kidneys. However, while this substance degrades rapidly in the environment and does not accumulate in the environment or wildlife, there is evidence to indicate that it is hazardous to human health. Studies have shown that repeated exposure, even in small amounts, may produce nasal squamous cell carcinomas. It is also corrosive to skin and mucous membranes. Therefore, caution should be exercised when handling this substance.
