Fire Retardants

The Tuesday, September 23rd, 2003 edition of USA TODAY contained an article on flame retardant in breast milk. The front page article entitled "Flame retardant found in breast milk; U.S. levels highest in the world, study says" is available at the following link: http://www.usatoday.com/usatonline/20030923/5523798s.htm

Toxic Flame Retardants are of Increasing Concern. LCP Tech’s Flame Retardants are Non-Toxic.
LCP Tech Inc. Is Looking for Partnerships to Commercialize This Technology in the Flame Retardant Industries Plastics-Textiles-Wood Composites-Others. Please contact us if you have an interest.
 

DEVELOPMENT OF NOVEL FIRE RETARDANTS

 Dr. Rakesh Govind

LCP Tech, LLC

 Commercial polymers and their products are inherently combustible due to their high carbon content.  In most cases, they pose little flammability problems, except when they are used in enclosed areas or in close proximity to ignition sources.  Flame retardants can be added to these polymers which are used in a wide variety of industries – building, transportation, mining, etc.  It is estimated that 1.1 million metric tons of fire retardants were used in 1998 valued at $2.3 billion. With proposed California Regulations, that figure could increase substantially. The three most popular types of flame-retardant systems used are based on halogen/antimony, organophosphorus and metal hydrates.

 There are many mechanisms involved in the action of fire retardants when used with polymers.  When polymeric products are heated, temperature rises until the polymer reaches its decomposition point.  At the decomposition temperature, hydrocarbons pyrolyze into hydrogen (H+) and carbon monoxide.  These pyrolysis gases mix with oxygen in the surrounding air and undergo further reaction.  The initial degradation reaction is endothermic, while the final oxidation, especially with excess air,  is highly exothermic, which causes the initial fire to propagate.  A flame-retardant additive can inhibit or suppress the combustion process in many ways such as by interfering, either during the heating stage by absorbing the heat, during the combustion stage or flame spread  phase by coating the pyrolyzed polymer or forming a char around it.  It can also form inert gases which prevent oxygen from reaching the fire zone or scavenge the degradation radicals.   An ideal flame-retardant should participate in all stages of combustion, effectively stopping the flame in its tracks. 

Metal hydrates act by cooling the fuel source and diluting the gases with water vapor.  Metal hydrates release water vapor when heated, which reduces the temperature of the polymer and thereby prevents degradation of the polymer.  The water vapor released also dilutes the gases produced during the combustion process, thereby reducing the heat of combustion and reducing the rise of temperature.  Normally large quantities of metal hydrates are required to be effective, thereby resulting in degradation of polymer properties. 

Phosphorus based flame-retardants work in different ways – they coat the condensed combustible layer with a solid or gaseous protective layer and exclude them from gaseous oxygen.  These retardants form a carbon char on the surface (intumescent layer) which protects the remaining condensed combustible layer from escaping into the flame and combining with oxygen to propagate the flame. 

Halogenated flame-retardants work in the gas phase by interfering with the free radical chain oxidation mechanism.  During the initial combustion process, hydrogen radicals are produced due to degradation of the polymer.  The flame-retardants produce halogen radicals, when decomposed, which combine with the hydrogen radicals to prevent oxidation. 

Table 1 summarizes the various mechanisms of fire retardants, when compared with the novel fire retardant that has been produced by LCP Tech.  This fire retardant can be manufactured in solid powder form or as a liquid.  It can be incorporated in porous materials by spraying, dipping, or high pressure incorporation, as in the case of lumber.  As a powder, it can be mixed with the polymer.  This fire retardant contains less than 0.5% moisture, less than 100 ppm chlorides and can be granulated with particle size in the range of 20 – 60 microns.  The pure fire-retardant powder loses weight less than 0.5% by weight at 300oC and less than 6% by weight at 350oC.  Hence, it can be mixed with polymer in the melt stage, without any degradation of the material.  Typically usage in the polymer is expected to be in the 5% - 30% by weight of the polymer product, to impart flame-retardant properties, which usually would not result in changing the properties of the polymer significantly. 

 Table 1:  Flame-retardant mechanisms of various types of flame retardants.

Further, LCP fire retardants produce significantly reduced emissions of all types in fire situations, as shown below.  All current fire retardants produce significant quantities of Carbon monoxide, smoke, Hydrogen bromide and hydrogen cyanide.  LCP Tech’s flame retardant produces low amounts of carbon monoxide and smoke, which is significant factor in most fires.