R.Raghavan of Satyen Polymers Educates us on Fire Retardation (FR) on Polyester Resins. This is Part 1 of a 2-part series.

FR Resins – how important are technology and quality standards?
The major application areas of FR Resins are in Automobile, Transportation, Railways, Buildings and Structures, marine and roofing. The fire retardant composite is formulated to meet the IS, ASTM, DIN, BS & UL standards. The main focus in transportation / building applications are robust systems with low smoke and toxic emissions. This aids longer evacuation time. An FR formulation based composite should be adequately tested and certified by independent Agencies like ARAI, SGS, CIPET laboratories etc. for compliance. In the SPPL laboratory for instance, IS 6746 -1994 testing is done for each batch before dispatch. Fire retardant Fiberglass composite products are graded based on their halogenated /non-halogenated compounds.

Let’s go over the FR (fire retardation) process.

Some of the properties to be examined:
• ease of ignition (ignitability)
• Spread of flame
• Heat evolution (release)
• Smoke
• Toxic gases

Important factors to be considered when discussing fire retardants with the end user.
1. End application of the composite     part and Processing
2. Halogenated or non-halogenated     and Requirements–Plain or filled
3. The Fire standard required and     classification of that standard
4. Laminate construction and design     thickness requirement
5. FR Gelcoat required –Y/N

Some compounds break down endothermically when subjected to high temperatures

The reaction removes heat from the substrate, thereby cooling the material.

A way to stop spreading of the flame over the material is to create a thermal insulation barrier between the burning and unburned parts.
Intumescent additives are often employed; their role is to turn the polymer into a char, which separates the flame from the material and slows the heat transfer to the unburned fuel.

Inert gases (most often carbon dioxide and water) produced by thermal degradation of some materials act as diluents of the combustible gases, lowering their partial pressures and the partial pressure of oxygen, and slowing the reaction rate.

• Chlorinated and brominated materials undergo thermal degradation and release hydrogen chloride and hydrogen bromide or if used in the presence of a synergist like antimony trioxide into antimony halides.
• These react with the highly reactive H· and OH. radicals in the flame, resulting in an inactive molecule and a Cl· or Br· radical.
• The halogen radical has much lower energy than H· or OH·, and therefore has much lower potential to propagate the radical oxidation reactions of combustion.

Aluminium hydroxide also finds use as fire retardant filler for polymer applications at about 180 °C, absorbing a considerable amount of heat in the process and giving off water vapour.

Telefax: 020 – 30724590                            020 – 30727824