What is Phosphorus?
Phosphorus is commonly found in phosphate rocks and in all living cells where it is essential to all forms of life. The body takes in a level of phosphate every day and stores it, as bones are mainly calcium phosphate; in addition Phosphorus has a major role in DNA and RNA forming part of the structural backbone of these molecules.
Industrially phosphorus is extracted from phosphate rock and phosphorus based products have a variety of uses including detergents and cleaning products, food additives, fertilisers, pesticides, toothpaste, fire safety and many other applications.
What are Phosphate Ester Flame Retardants?
Phosphate esters are produced by reacting phosphorus oxychloride, a chemical derived from white phosphorus, with an alcohol.
In general phosphate ester flame retardants can be divided into four separate product groups:
- Aryl
- Bisphosphate
- Alkyl
- and Chlorinated
Each of these groups is represented by a number of products which offer different levels of compatibility with the end use application and provide different levels of flame retardancy. Certain products such as the alkyl range are used for their main benefit (viscosity modifier) and offer flame retardancy as an additional benefit.
The choice of flame retardant used depends on the type of application, the material to be flame retarded, the fire safety standard to be met and commercial considerations such as production needs, cost etc.
Phosphate Esters as Flame Retardants
The modern world is facing an ever growing demand for consumer goods which are based on flammable materials such as oil-based plastics. In common with all other organic materials these will burn given the application of heat in the presence of oxygen.
The ignitability and burning rate of these products can be reduced by the addition of flame retardants. Different flame retardants work in various ways. Phosphorus based flame retardants form a protective (char) layer which resists high temperatures and protects the underlying product from attack by oxygen and radiant heat. This minimises the development of a full fire and increases escape time.
