Fire Retardant Unsaturated Polyester Resin: Insight

The need for Fire Retardant resins.

During fire, the most hazardous ingredient is smoke, rather than heat/temperature. A fire occurs when fuel, heat and oxygen come in contact. If one of them is removed, the fire can be stopped.

Fuel: Resin, Catalyst, Rags, Wood, Paper, Plastic Sheeting, Composites. An unsaturated polyester resin basically acts as fuel.

Heat: Smoking, Hot Work, Electrical Equipment, Pilot Lights, Floor Scrubbers, Sparks from Tool Strikes, Static Electricity, Chemical Reaction, Curing, etc.

Oxygen: Found in air. Good ventilation is mandatory in composite operations so there will be lots of oxygen and it will be hard to stop. Lots of surface area (e.g. rags, sprayed resin) affords more contact for oxygen to get into the mix.

Chain Reaction: The Fire Process (sustained burning).The burning process is quite complex and described by the Fire Triangle.
If one angle is missing, the fire is over!

Flammability Properties of un-cured Resins (Liquid form)
Flammability of resin when in liquid form is usually related to the styrene monomer content
Flash Point Range74 –84°F, Class 1C
Flammable Limits (in air)Lower Explosive Limit (LEL) = 0.9%, Upper Explosive Limit (UEL)
= 6.8%This would be intolerable in the breathing zone (NOTE: 1% = 10,000 ppm) Styrene vapors are heavier than air and can collect in low areas
Vapors may also travel great distances to ignition sources

Atomization of liquids effects ignitability. Atomized combustible liquids can easily ignite when used in spray applications.

Fire Retardants, an Indian Perspective
• IS 6746-1994 / UL 94 V0 Compliance (Flammability)
• Filled System Primarily comprise of Halogen additives and Synergistic Flame Retardants like ATH / Antimony trioxide
• If FR Application is for Outside exposure conditions an UV absorber is added in the resin system.
• Applications to which these systems would be used are HLU/RTM/Pultrusion
• Resin System would be designed to have an Ortho/ ISO / Vinyl ester base polymer

Note: Other standards like ASTM E-84, NFF 16 101, EN 45545, etc. are getting more importance in India Specified by Leading OEM especially in Railways and Building & Construction.

A quick look at FR standards :

A. Test compliance IS 6746-1994
Very Low Flammability resins extinguishes in less than 10 Sec and low Flammability less than 25 sec.

Other Compliances to be Met on specific needs of customer are :
ASTM D 635 – Flame Spread
BS 476 part 7 : Surface Spread of Flame
IS 15061/2002 : Burning Characteristic Vertical/Horizontal
ASTM D 2863 – LOI / ASTM D 149 – Electrical

Ashland India’s Product Range
Resins Orthopthalic Base – Aropol IN 2645F, 7102F Resins Isopthalic Base
Aropol IN 5225F

B. Test compliance ASTM E 84 –
Tunnel Test Mainly for CR applications Derakane Resins 510 Series comply to this requirement

C. Test compliance Flame Smoke Toxicity (Non Halogenated System) UIC 564 / NCD 1409/ IS 13501
• Flame : Class B
• Smoke : Class B
• Toxicity : 1

Ashland India’s product Range
Aropol IN 2645 F/ Enguard SO 90202 A IN V3 ( Ortho UPR) Aropol IN 5225 F / Maxguard FRN 10001 A IN V3 ( ISO UPR)

Applications include: Railway coaches/window frames/Cable trays/ Pultruded Platforms CR/FR- Electrical Fuse gear/ Switching and Insulated Rods and profiles,Halogenated – Non Filled System Automotive Vehicles

D. Test compliance Horizontal/Vertical Burning rate IS 15061-2002 Cl 3.2 Annexe A/ Cl 3.3 Annexe B
• Horizontal : Less Than 100mm/Min
• Vertical : Less than 100mm/min

Ashland India’s product Range
Aropol / Hetron resins HLU/RTM/Infusion System Automotive Vehicles
Flammability requirement
Aropol IN 2016 TF / GelCoat Enguard SO 90201 A IN V3 Ortho UPR)


A quick glance – Ashland Products Vs. FR Test results*



* The results obtained at third party laboratories

UV versions of AROPOL IN 5225F and 5335F meets the requirement of ASTM G 154

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