Fire Retardant Research Paper

III Types of fire retardants
Numerous chemicals having different structure and physical properties could impart fire resistant characteristics when used alone or in combinations. Combinations of different fire retardants with varying proportions can produce an additive, synergistic or antagonistic effect. The synergy of combining fire retardant chemicals has gained considerable practical importance as they are usually less expensive [13, 20].

Fire retardant chemicals can be either chemically bonded reactive type or the additive type where the retardant is applied as coating to the base material and the retention of retardant is by weak secondary bonding and not covalent bonding unlike the former [13,20].

The various classes of fire retardant

The inorganic fire retardant acts simultaneously on the surface of the solid phase by cooling the substrate via endothermic breakdown process and reducing the formation of pyrolysis products [13].

A Mixture of borax and boric acid, primarily used as a preservative in wood was found to have efficacy in retarding flame spread on wood surface. Because of their benefits including, preservative effectiveness, neutral pH, and less impact on mechanical properties compared to other flame retardant chemicals like phosphorous, boron compounds are often considered a good flame retardant [25].

In addition to the char forming catalytic effect, they have low melting point and form glassy films when exposed to high temperatures in fire. The formation of this glassy film barrier inhibits the flow of combustible volatiles to the fire exposed surface. Borax tends to reduce flame spread but can promote smouldering or glowing whereas boric acid suppresses smouldering and has little effect on flame spread, which makes these compounds, used together [25].

Mechanism of Fire

Cooling process: By cooling down the material through some chemical reactions in which energy absorbing (endothermic) processes triggered by additives and/or the chemical release of water cool the substrate to a temperature below that required for sustaining the combustion process, e.g. magnesium hydroxide [26,13,20].

Coating process: By forming a protective layer or coating that prevents or shields the underlying combustible layer of material with a solid or gaseous protective layer from heat and oxygen necessary for the combustion process, e.g. phosphorous and boron compounds [26,13,20].

Dilution process: By incorporating inert substances (e.g. fillers) and additives that release inert gases, water or Carbon dioxide during decomposition, and dilute the fuel in the solid and gaseous phases so that the lower ignition limit of the gas mixture is not exceeded, e.g. aluminium hydroxide leaving water [26,13,20].

Fire retardation by Chemical action

The most significant chemical reactions that interfere with the combustion process take place either in the solid and gaseous phases:

Reaction in the gaseous