While the benefits of using flame retardants appear self-evident, it is important to ensure that the retardants themselves are safe.
There are two main aspects to consider:
- Are the materials the correct ones for the situation and conditions of use?
- Are the flame-retardant materials themselves safe?
Flame retardants consist primarily of halogens (brominated or chlorinated), phosphorus and inorganic types. While their applications vary depending on the types of plastics, parts, finished products and desired functions, they can be broadly categorised as shown in Figure X, based on their composition and usage.
There are two main approaches to flame retarding. The first is to use flame retardants. These are incorporated into plastics and rubber products during manufacturing, or are applied as a treatment to the surface of fibres and paper. These do not render materials totally non-combustible; rather, they will burn (ignite) for a short time when heated by fire, but the flame will not spread. The material extinguishes when separated from the flame source (self-extinguishing).
The second approach uses flame retardant promoters. This relies on chemical substances that are not flame retardant in their own right, but can enhance the effectiveness of other flame retardants such as halogen compounds.
Ensuring the materials used to manufacture flame retardants are safe
While the importance of flame retardants in improving product safety is clear, it is equally important that the materials themselves are safe and non-toxic.
The term ‘flame retardant’ is a description of the function of a chemical, rather than a substance itself. In reality, there are a wide range of substances used – more than 200 – to provide this function, sometimes alone on their own, but often in combination. However, there are only a small number of substances that dominate use; bromine, phosphorous, nitrogen, and chlorine along with a several mineral-based substances.
Using the correct flame retardants
The decision on which materials are the correct ones for each situation is governed by the fire safety standards. Fire safety standards have seen flame retardation become an integral part of a huge range of products. These standards are constantly under review and subject to continuous improvement, as regulators learn from experience.
The application of these regulations has proved highly effective. For example, the introduction of a European fire safety standard for audio, video and similar electronic apparatus – standard EN 60065 – stipulates that these devices now have to be designed in such a way that avoids the risk of spontaneous ignition and minimises the spread of fire wherever possible. The use of flame retardants has allowed manufacturers to replace older, potentially more flammable materials with lightweight and inexpensive plastics with improved fire resistance. Given the increasing numbers of electronic devices in all settings, this represents a considerable contribution to safety in the home, office and transport. Similar advances have been seen in making foam-filled furniture and textiles.
Many manufacturers pursue standards that are above and beyond those required for compliance with existing fire safety standards and deploy them in areas where their use is not yet prescribed. In addition, innovation to improve the effectiveness – and the safety – of flame retardants continues.