As mentioned above, formaldehyde shows a complicated nature as it adopts many different forms either by cyclization, polymerization or dissolution ; however, it continues to show the same chemical characteristics as formaldehyde. Given all the benefits though, formaldehyde is known to be a human carcinogen and, in fact, is toxic to all animals as exposure to formaldehyde can cause serious health issues. These act as stabilizers and prevent the oxidation and polymerization of formaldehyde within the formalin solution preserving its activity.
If stabilizers are not added, formaldehyde aqueous solutions are highly unstable and would polymerize into large molecules that are insoluble and would precipitate out of solution. During the production of formaldehyde from methanol, water is also produced as a by-product; hence the process can produce formalin directly when correct concentrations are reached.
Formalin also has an irritating smell similar to formaldehyde. Furthermore, it possess similar toxic properties of formaldehyde as formalin readily releases formaldehyde gas and is also highly flammable. However, formaldehyde is easily subject to photodegradation and biodegradation, which produces carbon dioxide and water.
Formalin is a saturated solution of formaldehyde gas in water. Without stabilizer, formaldehyde solution is very unstable, and it tends to polymerize, forming macromolecules that are insoluble. Complete hydration of formaldehyde gas mostly yields methylene glycol.
Subsequently, it leads to the production of paraformaldehyde by polymerization. The Figure 3. Illustrates the structure of paraformaldehyde. In order to prevent polymerization, methanol is added to formalin. Formalin is a colorless liquid. It has a sharp irritating smell due to off-gassing of formaldehyde. This solution has a neutral P H value, but it can act as a reducing agent to reduce other substance while producing formic acid.
Strong formalin solutions are flammable. This solution can be used as disinfectants and germicides, as they can destroy harmful microorganisms. It is a thermosetting plastic material consisting of melamine and formaldehyde. This resin material was introduced by William F.
Talbot in This resin material can easily be cured through heating. Here, dehydration and crosslinking occur. We can cure either the melamine-formaldehyde resin or the monomer of this resin material through the treatment with any type of polyol. The major application of melamine-formaldehyde resin is the production of high-pressure laminates.
The laminate types that we can produce using this resin include Formica and Arborite. Furthermore, we can use the tile wall panels of this resin as whiteboards.
In addition, there are some other applications of melamine-formaldehyde resin, including the use of the resin in kitchen utensils and plates. It is also important for saturating decorative paper that is laminated under heat and pressure where it becomes easy to be pasted on particle boards. Urea-formaldehyde and melamine formaldehyde are thermosetting polymers.
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