Flame Retardants

by Dhruv Sapra

Introduction

As plastics replace wood, glass, and metal materials in the home, domestic fires have been found to burn much faster and hotter than they did a few decades ago with the average 'escape time' from a burning home dropping significantly from 17 minutes in 1975 to just 3 minutes today according to UL (Underwriters Laboratories) studies. The higher fire load of home construction, furnishings and consumer products has made flame retardants for plastic materials more important than ever before. Increasingly strict fire protection standards and flammability requirements, particularly in building materials and consumer products, are pushing demand for flame retardants steadily higher. Meanwhile, government regulations and directives, as well as consumer demand for more environmentally friendly materials have directed the plastics and flame retardant industries to seek alternatives to the halogenated additives generally used for flame retardancy, especially in electrical and electronic applications.

Flame-retardant additives are incorporated into plastics to help prevent a fire or it's propagation by interrupting or hindering the combustion process and thus protect lives, property and the environment.

The decisive factors for flame retarded materials are a low combustibility, a late ignition point, the slowest possible propagation of flames and a low release of heat and smoke. This gives people more time to escape and flashover can be avoided. Flame retarded plastics can prevent a small cause, such as an electrical short circuit, from becoming a major fire catastrophe which can result in major material damages and even loss of life.

TYPES OF FLAME RETARDANTS

A distinction is made between reactive and additive flame retardants.

● Reactive flame retardants are reactive components chemically built into a polymer molecule.

● Additive flame retardants are incorporated into the polymer either prior to, during or (most frequently) following polymerization.

There are three main families of flame-retardant chemicals :

1. The main inorganic flame retardants are aluminium trihydroxide, magnesium hydroxide, ammonium polyphosphate and red phosphorus.This group represents about 50% by volume of the worldwide flame retardant production. Some of these chemicals are also used as flame retardant synergists, of which antimony trioxide is the most important (OECD, 1994).

2. Halogenated products are based primarily on chlorine and bromine. This group represents about 25% by volume of the worldwide production (OECD, 1994), but due to their adverse effect, their use is discouraged nowadays.

3. Organophosphorus products are primarily phosphate esters and represent about 20% by volume of the worldwide production. Products containing phosphorus, chlorine and/or bromine are also important.

In addition, nitrogen-based flame retardants are used for a limited number of polymers.

In this assignment we will discuss about the various flame retardants used in the industries, their composition to be added and its effect on the properties of the polymer mix.

Let us now see different flame retardant polymer products and how they alter the polymer properties:

Company Name
Product Name	Saytex BT-93 and 93 W is a Bromine-based flame retardants
Appearance	White or yellow powder
Chemical Name/ Composition	Ethylene bis-tetrabromo-phthalimide
Used with Polymer(s)	Phenolic thermosets, PVC, PE, Elastomers, ABS, HIPS, PP, PC
Percentage Composition and properties Affected 1.FR additive results with Polyesters-PBT and PET 2. PP formulations 3. thermoplastic elastomer system (TPE)
Application	These Bromine-based flame retardants for electronic enclosures, electronic and electrical components, insulation foams and textiles

Company Name
Product Name	Martinal OL-107c An Aluminum hydroxide-based flame retardant
Appearance	Coated white powder
Chemical Name/ Composition	Aluminium hydroxide
Used with Polymer(s)	Polyolefins(foams), Elastomers, PE, Phenolic, epoxy thermosets
%age Composition/ Specialty/ Properties Affected	Specialty: surface modified Al(OH)3 content[%]:98.5-99 Moisture(150oc):<=0.4 Loss on ignition(1200 oc) [%]: 35-36 Particle Size (Laser diffraction, Cilas) d10 [μm] 0.4 – 0.8 d50 [μm] 1.1 – 1.7 d90 [μm] 1.5 – 3.5 Particle shape platelet, pseudo-hexagonal Reaction in water -no wetting of particles Refractive index [%] 1.58 Whiteness (Elrepho 457 nm) [%] ≥ 95.0 Specific Surface Area (BET) [m2/g] 6 – 8 Oil absorption [cm3/100g] 30 – 40 DOP-absorption [cm3/100g] 30 – 40 Density [g/cm3] 2.4 Bulk Density [kg/m3] ≈ 250
Application	These Aluminum hydroxide flame retardants (white powder) for processing temperatures up to about 210° C, for wire and cable, electronic and electrical components based on thermoset resins, building materials, mass transportation, paints and varnishes, paper and plaster with organic binder.

	Company Name
	Product Name	Green Armor A new Brominated ecofriendly FR.
	Appearance	Pellets
	Chemical Name/ Composition	Proprietary polymeric Flame Retardant
	Used with Polymer(s)	PE, PA, PP, ABS, PVC and elastomers.
	Percentage Composition and properties Affected The performance of GreenArmorTM is summarized in the table below properties for 1.PP formulations Compare these values with standard PP values mentioned later. Cone Calorimetry data shows that GreenArmorTM has the lowest heat release rate compared to other FRs tested in all three polyolefin systems. 2.Thermoplastic elastomer system(TPE) Overall, GreenArmorTM is an excellent FR in Polyolefins and provides good physical properties, comparable FR properties at lower Br content, lower Peak HRR vs. other FR’s, equivalent or better electrical properties, improved process ability translating to higher throughput. 3. Polyamide 6,6: Table 3 summarizes the comparison of GreenArmorTM when added to polyamides as a flame retardants and how the properties vary. With the highest bromine content, GreenArmorTM has the best FR efficiency and overall physical and mechanical properties. With its lowest melt-viscosity, it offers the best MFI and high gloss. Polyesters: A similar study is conducted and tables are given below: GreenArmorTM is an excellent FR in Polyamides and polyesters and provides comparable or better mechanical properties, low melt viscosity i.e. higher MFI, comparable FR properties at lower loadings than other BrPS products, better Impact properties, better Gloss, equivalent or better electrical properties and improved process ability resulting in higher throughput left table-PBT right table-PET GreenArmorTM is a high performing polymeric fire safety solution that is versatile and can be used in almost every polymeric system. It is melt blendable, easy to process, has excellent FR efficiency, is thermally stable (no degredation products), color stable (Aesthetics!), and recyclable. The polymeric nature of GreenArmorTM makes it an environmentally friendly and sustainable fire safety solution for a wide range of polymeric systems B E N E F I T S : •High melt flow •Excellent thermal and color stability •High gloss •Great impact strength •Compliant with ROHS •Supports VECAP principles
	Application	A family of products that follow strict environmental-friendly standards, along with practicing green chemistry principles. It can be used in hot melts, fibres, foams and for wire and cable, electronic purposes. Being a green additive, it has great potential future in other areas of polymer application
Company Name
Product Name	Exolit AP 422 (non-Halogenated)
Appearance	White Powder
Chemical Name/composition	Ammonium Polyphosphate
Used with Polymer(s)	· UPR- Unsaturated polyester resin · EPR-Epoxy resin · PUR-Polyurethane · PF-Phenol Formaldehyde · Rubber · Acrylics
%age Composition	Imparts good flame- retardant effect to adhesives and sealants when incorporated into base formulation at 10-20% rate
Properties Affected and Applications	Used extensively for flame retardant properties as: Char forming component in intumescent coatings and adhesives / fillers • Polyurethane rigid foames • Materials containing cellulose (paper, wood, wood chip based products) • Intumescent systems for unsaturated polyester resins or epoxy resins • Systems for polyolefins

Company Name
Product Name	POLYDIS 3710-Halogen free, reactive,phosphorous organic substance
Appearance	White Flakes
Chemical Name/composition	Hydrogen functional,organo phosphorous compound. [-DOPO-9,10-Dihydro-9-oxa-10-phosphaphenanthrene- 10-oxide]
Used with Polymer(s)	· EPR-Epoxy resin · PUR-Polyurethane
%age Composition	Phosphorous content:14.3%
Properties Affected and Applications	Raw material for the prereaction with epoxides, phenolics, urethanes to build flame retardant resins. Synergies with other FRs existing. Phosphite structure can act as UV-stablizer Specially designed for the use in thermoset resins. As reactive phosphorous substance it cross-links during curing. Therefore mechanical behaviour like tenacity and modulus as well as chemical resistance are not influenced negatively. This makes STRUKTOL POLYDIS 3710 superior to metal hydroxides or non reactive phosphorous substances.

Mineral Based Flame Retardancy with Metal Hydrates:

APYRAL, a product of Nabaltec company has been discussed here.

The Endothermic Phase Transition for APYRAL begins at 200 ⁰C.The decomposition of APYRAL releases water, characteristic for metal hydrates.

Some Information pertaining Flame Tests conducted on products:

UNDERWRITERS LABORATORY test: UL94V-0

Test is run with bars one half inch wide and five inches long. These are held vertically and exposed to burner flame ¾ in high.Each sample is ignited for 10 seconds.The time taken for flame to go out is measured.

To pass UL94V-0 flame must be out in 10 seconds or less, no glow beyond 30 seconds and no burning material can fall.

LOI[%O2] Without APYRAL

21

19

17.8

17.5

17.5

FIG:Minimum APYRAL fillings to reach required LOI values.

APYRAL® and APYMAG® actively reduce the smoke density and in parallel reduces the corrosivity by neutralizing the acidic gases in PVC-compounds. The black smoke evolving by the decomposition of PVCcompounds contains harmful toxic gases and corrosive hydrohalogen acids which will be adsorbed by the highly porous ash of Al2O3.

Furthermore, in case of an open flame situation, APYRAL® filled PVC shows a significantly reduced smoke density compared to an Antimony Trioxide (Sb2O3) filled system.

With APYRAL® filled compounds, the processability and the flammability is comparable to each other while the smoke density is drastically reduced in comparison to non filled PVC compounds.

For the above described investigations, compounds of plasticized PVC have been prepared, filled with either.5 phr Sb2O3 or 50 phr APYRAL® 40CD .In the above diagram, the optical smoke density according to ASTM E662 procedure is shown for all three compoundsin flaming and non-flaming mode.

Flame Retardants for electrical, transportation and building applications from

Exolit AP 760 and 766 features:

v Improved efficiency

v Good electrical and mechanical properties

v Excellent UV stability

v Low smoke density

v Good recyclability

v Non-halogenated

	PP blank	AP 760	AP 766
Melt Flow Rate[g/10min]	12.0	14.7	10.8
Tensile modulus[Mpa]	1550	2270	1870
Tensile yield stress[N/mm2]	35	24	25
Elongation at break[%]	>50	6.9	10.5
Impact str.(Charpy)[KJ/m2]	90	19	26

Exolit AP 76x Product group-compound properties of PP-homopolymers

Exolit AP 760 and AP 766 have been designed for polyolefin resins to pass the V-0 class according to the UL94 flammability test. In PP based compounds loadings of 22% to 30% of flame retardant are needed to meet the test criteria.

Exolit OP 1312

FEATURES:

Ø Low impact on mechanical properties.

Ø Outstanding electrical properties

Ø Colorability

Ø High thermal stability

Ø Non-halogenated

The Comparative Tracking Index or CTI is used to measure the electrical breakdown (tracking) properties of an insulating material. To measure the tracking, 52 drops of 0.1% ammonium chloride solution are dropped on the material, and the voltage measured for a 3mm thickness is considered representative of the material performance

Companies dealing in Flame retardant additives and its products:

International manufacturers:

Company Name	Website	Info.
Avocet Dye and Chemical Co. Ltd.	www.avocet-dyes.co.uk	-This UK based company is a member of Furniture Industry Research Association(FIRA)
Clariant International Ltd.	www.additives.clariant.com	-A Switzerland based company dealing with flame retardants, waxes, etc.
FRX polymers Inc.	http://www.frxpolymers.com	-USA based company, produces FR additives for homopolymer, copolymers, oligomers, blends and alloys.
LATI Industria Termoplastici S.p.A.	http://www.lati.com	-The Italian company deals majorly in self-extinguishing products which covers a large spectrum of thermoplastic resins, from polyolefins to PEEK.
Albemarle Cooperation	http://www.albemarle.com	-Albemarle deals in Fire Safety Solutions, Antioxidants, Curatives, Polyolefin Catalysts, Chemical Catalysts, Stannica, FCC, HPC, Alternative Fuel Technologies

Indian manufacturers:

Company Name	Website	Deals in:
BassTech Exim India Pvt Ltd. (Tamil Nadu)	http://basstech.tradeindia.com/	Various Bromine Compounds, Magnesium Hydroxide, Melamine Pyrophosphate, Ammonium Polyphosphate.
Ayiswarya Polymers (Tamil Nadu)	http://www.ayiswaryapolymers.com	Low smoke fine retardant resin and Industrial low smoke fire retardant resin.
Auropol India Pvt. Ltd. (Kolkata)	http://www.auropolindia.com	Aurocarb C7: Non Staining Fire Retardant Plasticizer in powder form and Compatible with most of the elastomers like NR, SBR, PBR, CR, EPDM, BR & NBR is very good. Aurogaurd: In the case of halogen bearing polymers, AUROGUARD is effective in the wide range of application starting from plasticised and rigid polyvinyl chloride (PVC) to chlorosulfonated polyethylene (CSP) rubber. AUROGUARD also acts efficiently in making Fire Resistant Low Smoke (FRLS) compound from a non-halogenated polymer when used in combination with Antimony Trioxide (Sb2 O3) and trace of halogenated additives. AUROGUARD also reduces the hazard from generation of smoke, toxic and corrosive fumes and does not impair any physical properties.
Niknam Chemicals Pvt. Ltd. (2600/5, Beadonpura, Karol Bagh, New Delhi - 110 005)	http://www.aluminahydrate.com/	Aluminium Trihydrate Aluminium Hydroxide Magnesium Hydroxide Zinc Borate Zinc Hydroxystannate Zinc Stannate Molybdenum Trioxide Antimony Trioxide Flamex Flame Guard
Metachem Manufacturing Company pvt.Ltd.	http://www.indiamart.com/metachem/	leading Manufacturer and Exporter of Expandable Graphite based Flame Retardant additives and ISO 9001:2000 certified company established in year 1964. Expandable Graphite is a single Non-Halogenated, Eco-Friendly and Cost-effective Flame Retardant additive for the Polymer, Foam and Rubber products

References:-

1. http://www.lati.com/pdf/products_en/flame_retardant_news.pdf

2. http://www.tradeindia.com/manufacturers/indianmanufacturers/flame-retardant-additives.html

3. http://www.albemarle.com/Products-and-Markets/Polymer-Solutions/Fire-Safety-Solutions/Phosphorus-Flame-Retardants-185.html

4. hhttp://www.expresspolymlett.com/articles/EPL for epoy resin

5. f0001374_article.pdfttp://144.206.159.178/ft/862/31590/547432.pdf for EVA

6. http://www.kbs.se/MICables6_OxygenInd.htm for PE,PP

7. http://onlinelibrary.wiley.com/doi/10.1002/pat.1851/abstract