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What is the difference between formaldehyde and paraformaldehyde?

What is the difference between formaldehyde and paraformaldehyde?

Presumably most people attach great importance to formaldehyde, which is a harmful gas. When the content in the air reaches a certain concentration, it will have a very serious impact on the human body. And formaldehyde is very common in life, especially in home-decoration, a lot of building materials containing formaldehyde will be used. What is the difference between paraformaldehyde and formaldehyde? Let's take a look at it briefly below.

This passage is going to talk about the followings of formaldehyde and paraformaldehyde:

(1) Definition of formaldehyde

(2) What is paraformaldehyde?

(3) What is the difference between formaldehyde and paraformaldehyde?

 

(1) Definition of formaldehyde

Formaldehyde is an organic chemical substance, the chemical formula is HCHO or CH₂O, the molecular weight is 30.03, also known as formic aldehyde.

Formaldehyde is a colorless and irritating gas, which is irritating to human eyes and nose. The relative density of gas is 1.067 (air=1), and the density of liquid is 0.815g/cm³ (-20℃). Melting point -92°C, boiling point -19.5°C. Easily soluble in water and ethanol. The concentration of the aqueous solution can reach up to 55%, generally 35%-40%, and usually 37%. It is called formalin, commonly known as formalin.

Formaldehyde has reducibility, especially in alkaline solution, it has stronger reducing power. It can burn, steam and air form an explosive mixture, the explosion limit is 7%-73% (volume), and the ignition point is about 300°C.

Formaldehyde can be produced by dehydrogenation or oxidation of methanol under the catalysis of metals such as silver and copper, and can also be separated from the oxidation products of hydrocarbons. It can be used as raw material for phenolic resin, urea-formaldehyde resin, vinylon, urotropine, pentaerythritol, dyes, pesticides and disinfectants. Industrial formaldehyde solution generally contains 37% formaldehyde and 15% methanol as a polymerization inhibitor with a boiling point of 101°C.

 

(2) What is paraformaldehyde?

Paraformaldehyde is a high molecular polymer with the molecular formula (CH2O)n. It is a white amorphous powder with the smell of formaldehyde. It is a linear polymer of formaldehyde. It has no fixed melting point and decomposes on heating. The melting point is 120~170℃. It is easily soluble in hot water and releases formaldehyde, slowly soluble in cold water, soluble in caustic alkali and alkali metal carbonate solution, insoluble in alcohol and ether, and its high polymer is insoluble in water. Reactions similar to formaldehyde can occur, such as chloromethylation and the formation of acetals with alcohols. Used in synthetic resins, adhesives, medicines, fungicides, insecticides, disinfectants, etc.

 

(3) What is the difference between formaldehyde and paraformaldehyde?

The main difference between paraformaldehyde and formaldehyde lies in the form of expression and the way of use. In terms of manifestation, paraformaldehyde is a solid powder, while formaldehyde is an aqueous solution; in terms of use, paraformaldehyde cannot be used directly, it can only be used after depolymerization, because it is formed by hydrogen bond polymerization of formaldehyde. , And formaldehyde can be used directly.

Paraformaldehyde, also known as solid formaldehyde, is a low molecular weight mixture of formaldehyde.

Since polyformaldehyde is a solid, the content of formaldehyde in the active ingredient is higher than that of industrial formaldehyde, which is convenient for storage and transportation. Mainly used in chemical, pesticide, resin, papermaking, foundry, aquaculture and other industries, especially in the use of anhydrous or low water content formaldehyde as the raw material for synthetic products. The international trend is that the application of industrial formaldehyde as a raw material has been used as a raw material in the process of technological upgrading.

Polyformaldehyde is usually produced by industrial formaldehyde through vacuum concentration, polymerization, dehydration, and drying. The choice of manufacturing process and the control of operating conditions affect the molecular weight and various indicator properties of polyoxymethylene, especially the water solubility. The dissolution process of paraformaldehyde in water is accompanied by depolymerization, which depolymerizes into lower molecular weight formaldehyde hydrate, and has good water solubility. This means that paraformaldehyde with good dissociation performance and good water solubility is easy to release formaldehyde when it is decomposed by heat.

Since the reaction using paraformaldehyde as a raw material usually directly participates in the reaction of formaldehyde, the water-soluble dissociation performance is good. This means high reactivity. Therefore, many manufacturing industries that use paraformaldehyde hope to obtain water-soluble paraformaldehyde products.

 

 


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