flame retardent polyester

8/7/2019 flame retardent polyester

1/49

Seminar

on

Flame Retardent Synthetic Fibres

By : Raghav Mehra

Mtech 1st year


2/49

Contents

Introduction

Why use of flame retardants?

Burning of fibres

Requirements for flame retardantsFlame Retardant Mechanism

Types of flame retardants

Application Techniques

Thermoplastic fibers

Flame Retardant (FR) Pet Fibers through P-N SynergismFlame Retardancy Testings

Toxicology


3/49

INRODUCTION

Fire is the result of three ingredients:

Heat

Fuel

Oxygen.

Heat produces flammable gases from the pyrolysis of polymer. Then, an

adequate ratio between these gases and oxygen leads to ignition of the

polymer.


4/49

COMBUSTION CYCLE

The combustion leads to a production of heat that is spread out (delta H1) and feed

back (delta H2). This heat feed back pyrolysis the polymer and keeps the combustion

going.


5/49

Air (oxygen)

Ignition source

Fuel

FIRE

Air (oxygen)

Fuel

Ignition source

Fire: when all sides

are connected

No Fire: when any one side

is missing

The FireTriangle


6/49

Why use of Flame Retardants ?

In most cases polymers initiate or propagate fires because,

being organic compounds, they decompose to volatile

combustible products when they are exposed to heat.

In many fields such as electrical, electronic, transport,

building, etc the use of organic polymers is restricted because

of their flammability


7/49

Use of synthetic polymers has greatly increased. In order to

lower the "fire risk" and the "fire hazard of these synthetic

polymers. flame retardants need to be added into the

polymer.

The role of these additives is to :Slow down polymer combustion and degradation (fire

extinction),

Reduce smoke emission,

Avoid dripping


8/49

Fire Dynamics

The goals for fire retardant can be simply stated in the followingitems

1. Prevent the fire or retard its growth and spread i.e. the flash

over :

Control fire properties of combustible items,

Provide for suppression of the fire.

Flash over time vs fire retardant use


9/49

2. Protect occupant from the fire effects :

Provide timely notification of the emergency,

Protect escape routes,

Provide areas of refuge where necessary and possible.

Smoke release vs fire spread


10/49

3. Minimize the impact of fire:

Provide separation by tenant, occupancy, or maximum area.Maintain the structural integrity of property,

Provide for continued operation of shared properties.

4. Support fire service operations:Provide for identification of fire location,

Provide reliable communication with areas of refuge,

Provide for fire department access, control, communication, and

selection.


11/49

5. To increase the escape time of persons.


12/49

Burningoffibers

The burning behavior of the fibers depends on / determined by a

number of thermal transition temperatures and thermodynamic

parameters

Tg - glass transition temperatureTm - transition temperature

(Tp) pyrolysis temperature and

(Tc) the onset of flaming combustion

Lower the Tc (and usually Tp) and hotter the flame, more flammable

is the fiber


13/49

LOI (limiting oxygen index) measures the inherent burning character

of the material.

Fibers that have a LOI values of21 or below ignite easily and burn

rapidly in air (20.8% O2).

LOI values above 21 ignite and burn more slowly.

When LOI values rise above 26-28, fibres and textiles may be

considered to be flame retardant and will pass most of the flame

fabric ignition tests in horizontal and vertical direction.

Limiting OxygenIndex (LO

I)


14/49

Fiber Tg (soften)

oC

Tm (melt)

oC

Tp (pyrolysis)

oC

Tc (ignition)

oC

LOI (%)

Wool - - 245 570-600 25

Cotton - - 350 350 18.4

Viscose - - 350 420 18.9

Nylon 6 50 215 431 450 20-21.5

Nylon 6,6 50 265 403 530 20-21.5

Polyester 80-90 255 420-447 480 20-21

Acrylic 100 >220 290 (with

decomposition)

>250 18.2

Polypropylene -20 165

470 550 1

8.6

Modacrylic 180 >180 450 37-39

PVC 180 >180 450 37-39

meta-Aramid 275 375 410 >500 29-30

para-Aramid 340 560 >590 >550 29

LOI values of different fibers


15/49

Points to be kept in mind while selecting and designing

flam

e pr

otec

tiv

ec

lothi

ng:

The thermal or burning behavior of textile fibers

The influence of fabric structure and garment shape on the burning

behaviour

Selection of non-toxic, smoke free flame retardants additives or

finishes

Design of protective garment depending or its usage with comfortproperties

The intensity of ignition source

The oxygen supply


16/49

Requirements for flame retardants

Fire retardant properties Commence thermal activity before and during the thermal decompositionof the

Polymer

Not generate any toxic gases beyond those produced by the degrading

polymer itself

Not increase the smoke density of the burning polymer

Mechanical properties

Not significantly alter the mechanical properties of the polymer

Be easy to incorporate into the host polymer

Be compatible with the host polymer

Be easy to extract/remove for recyclability of the polymer


17/49

Physical properties Be colourless or at least non-discolouring

Have good light stability

Be resistant towards ageing and hydrolysis

Not cause corrosion

Health and Eenvrionmental properties

Not have harmful health effects

Not have harmful environmental properties

Commercial viability

Be commercially available and cost effective


18/49

Burning and Flame Retardant

Mechanism:

Flame retardants function by their interaction or interference with one of

the three required components of fire:

A combustible substance or fuel.

Heat, supplied either externally or from the combustion process itself.

An oxidizing gas, primarily oxygen.


19/49

1. Dilution:

Reducing the total quantity of combustible material improves overall

flame retardation.

For example; madding fillers, such as clays, to polymer systems

reduces flammability.

In some cases, such as glass fiber reinforced composites, the glass

fiber stiffens the polymer. On exposure to heat or a flame, the glass may

prevent the polymer from melting away from the flame.

In addition, the glass act as a heat sink so that less energy input is

required to ignite the polymer on a second exposure to heat3.


20/49

Example- calcium carbonate decomposes at 825oC to generate the

solid(calcium oxide), and the gas(carbon dioxide); these products do not

support combustion.

Some materials decompose to produce water vapour as the

noncombustible gas.

Example- Aluminumoxide trihydrate (Al2O

3.3H

2O) begins to decompose

at 230oC with the release of34.5 wt% of its original mass as water vapour.

Typically, 50-100 parts by weight of these compounds are required per

100 parts of polymer to achieve flame retardation.

2. Generationof Noncombustible

gas:


21/49

3. Gas-Phase , Free-Radical inhibition:

On Combustion: hydrocarbons fragments vaporize, react with oxygen andform free radicals.

Free radical formation is highly exothermic,

The process continues unless free-radical formation is interrupted and stable

species are produced.

HO. + CO -> CO2+ H. Highly Exothermic

H.+ O2

-> HO. + O. Chain Branching

O. + HBr -> HO. + Br. Chain Transfer

HO. + HBr -> H2O + Br. Chain Termination

The HBr from the decomposing brominated compound deactivates the free

radicals in the vapor phase.

Chlorinated compounds function in the same manner.

In practice, often twice as much chlorine-containing compound is required as


22/49

Antimony tribromide forms a dense white smoke that snuffs the flame by

excluding oxygen from the front of the flame.

Chlorinated compounds function in the same manner.

Generally, twice as much chlorine-containing compound is required as bromine-containing compound.

Compounds containing fluorine generally exist as functional polymers

Very stable and decompose only at high temperature.

Hydrofluoric acid when liberated is an effective deactivator.

Antimony oxide acts as a synergist with halogens, particularly chlorine and

bromine.

Almost ineffective if used without halogen.

Sb2O3 + 6HBr 2SbBr3 + 3H2O


23/49

4. Solid-PhaseChar Formation

Formation of layer of char from from insulating or minimally

combustible material

reduces volatilization of active fragments and absorbs and dissipatesheat.

The effectiveness of the flame retardant is specific for each polymer

For example, phosphorous based flame retardants are effective in

producing minimally combustible char in phenylene oxide-ether polymers,but are essentially ineffective in styrenic polymers


24/49

5.The formation of a glassy

interface on pyrolysis:

Used mainly for borate-derived finishes

Deprive the flame of the oxidizable substrate and hinder further

flame propogation.

Borax/Boric acid is effective on cotton


25/49

Categories of flame retardants

Reactive type:

Added during the polymerisation process

Become an integral part of the polymer.

The result is a modified polymer with flame retardant

properties and different molecular structure compared to theoriginal polymer molecule.

Are used mainly in thermosets

Additive type:

Incorporated into the polymer prior during or after

polymerisation.Not chemically bonded to the polymer.

Used especially in thermoplastics.

If they are compatible with the plastic they act as

plasticizers, otherwise they are considered as fillers.


26/49

Inorganic flame retardants

Organophosphorus flame retardants

Nitrogen-based flame retardants

Halogenated flame retardants

Barrier technologies i.e intumescent systems

Flame retardents cam also be

classified as:


27/49

1. Inorganic flame retardants

Generally are metal hydroxides

Functionas smoke suppressants.

Widely used as substitutes tobrominated flame retardants.

Added as fillers into the polymer

Considered as immobile

Types of inorganic flame retardents:-

Aluminium hydroxide

Magnesium hydroxideAmmonium polyphosphate

Red phosphorus

Antimony trioxides

Zinc borate

Zinc hydroxystannate (ZHS) and Zinc stannate (ZS)


28/49

1.Aluminium hydroxide (ATH)

Available in a variety of particle sizesheat sink effect

Due to the dilution of combustible gases by the water formed as a result of

dehydroxylation.

Alumina formed as a result of thermal degradation of ATH slightly above

200

C high loading levels

2 Magnesium hydroxide

Acts, in the same way as ATH,Thermally decompose sat slightly higher temperatures around 325 C.

Combinations of ATH and magnesiumhydroxide function as very efficient

smoke suppressants in PVC.


29/49

E

fficient as a flame retardant in oxygen containing polymers such aspolycarbonates, polyethylene terephatalate (PET), polyamide and phenolic

resins.

Flame retardancy takes place due to formation of phosphorus-oxygenbonds

that reduces the ester linkages into cross linking aromatic structures with

lesservolatility.

Drawbacks:-

The red colour that could lead to discoloration of polymers

The formation of toxicphosphine gas during combustion and long termstorage

3. Red phosphorus


30/49

4. Ammonium polyphosphate (APP)

Used as an acid source in intumescent systems

Effective in polyamides

5. Antimony trioxideAlone does not function as a flame retardant

But in combination with halogenated flame retardants it functions as a

synergist.

Advantage:addition ofantimony trioxide is to reduce the amount of halogenated

flame retardants applied to thepolymer.


31/49

6. Zinc borate

Used mainly in PVC

Cannot be used alone acts as synergist together with brominated

compounds.

Used as alternative non-toxic synergists to Antimony trioxide in PVC

and other halogen-containing polymer systems.

Acts as fillers

7. Zinc hydroxystannate (ZHS)and Zinc stannate (ZS)


32/49

2. Organophosphorus Flame Retardants

Are primarily phosphate esters

Manly used for cellulose fibres

Types of Organophosphorus Flame Retardants:-

Triethyl phosphate

Aryl phosphates


33/49

Tri

ethyl phospha

teCan be used alone or together with a bromine synergist, such as antimony

trioxide

Used for unsaturated polyester resins

Arylphosphates

Include triphenyl-, isopropyl-, andt-butyl-substitutedtriaryl and cresylphosphates.

Used for phthalate plasticized PVC


34/49

3.Nitrogen-based flame retardants

Inhibit the formation of flammable gases

Used in polymers containing nitrogen such as polyurethane andpolyamide

Examples:

melamines and melamine derivatives


35/49

4.Halogenated flame retardants

Primarily based on chlorine and bromine

React with flammable gases to slow or prevent the burning process

Polybrominateddiphenylethers (PBDEs) form an important class of

halogenated flame retardents

Halogenated flame retardants can be divided into three classes:

Aromatic, including PBDEs in general and PentaBDE in particular.

Cycloaliphatic, including hexabromocyclododecane (HBCDD).

Aliphatic


36/49

5. Barrier technologies

(Intumescent system)

Involve layers of materials that provide fire resistance.(

Examples-

boric acid-treated cotton material sused in mattresses , blends of

natural and synthetic fibers used in furniture and mattresseshigh performance synthetic materials used in fire fighter uniforms

and space suits.

Almost all intumescent systems comprise, in general, of three basic

components

a dehydrating component, such as APP a charring component, such as pentaerythritol (PER)

a gas source, often a nitrogen component such as melamine

The main function of APP is to catalyse the dehydration reaction of

other components in theI

ntumescent system


37/49

Other intumescent systems :

Expandable graphite and silica-based and metal hydroxide compounds,

incorporated as nanocomposites

Extended nanoparticles of clay as char-forming fillers for good fire

protection.


38/49

Application Techniques:

Two-bath process

Suspensions and emulsions:

Solvent suspensions Water-in-oil emulsions

Oil-in-waterEmulsions

Cellulose-ester process:


39/49

Flame retardancy of the synthetic fibers is obtained by

Mechanically building the retardant with the polymer before it is

drawn into a fiber, or

Chemically modifying the polymer itself. Incorporation of

Chemicals in the dope before spinning the fiber fiber has not been

very successful.

Binders are also used

Experimental finishes using graft polymerization, in situ

polymerization of phosphorous-containing vinyl monomers or

surface halogenation of the fibers also have been reported.

Thermoplastic fibers


40/49

Flame Retardant (FR) Pet Fibers

thr

oughP

-N S

yner

gism

Acrylamide-grafted-phosphorylated (AM-g-P) PET fibers

containing just 0.189% phosphorus on-weight-of-fiber (owf).

Methacrylamide-grafted-phosphorylated (MAm-g-P) polyester

fibers at the 0.77% phosphorus content level.

Efficiency of phosphorus in presence of nitrogen that was

achieved was at 263% for acrylamide (AM) system

A very small amount of the FR chemical could impart fire

resistance of very high order to polyester.

This is attributed to P-N synergism in case of the FR polyester

system when the nitrogen is in the amido form present in AM and

MAm monomers.


41/49

Two types of groups of vinyl monomers are used -

N-deficient,

Aacrylic acid (AA) and Methacrylic acid (MAA), and the other

N-containing ones like

Acrylonitrile (AN), Acrylamide (AM), and Mthacrylamide (MAm).

The chemical initiation method

Initiator -benzoyl peroxide(0.125%)

On heating,

The benzoyl peroxide decomposes to give a free radical,

abstracts a H atom from another chain. The free radical formed reacts with the monomer molecules to form a chain

on the backbone

This chain propagates till its termination in the bath at a later stage.

Thus the graft is incorporated in the poly (ethylene terephthalate) chain

molecule.


42/49

P

hosphor

yla

ti

on ofGra

fted P

olyester

Fibres

Carried out by treatment of

phosphorus oxychloride in dry benzene along with

2% pyridine as a catalyst in reflux condenser

for1 6 h at 60 110C.

After completion of the reaction,

samples refluxed with benzene for 4 h,

stored in P2O

5desiccators.


43/49

Synergistic Influence of Amido Nitrogen in P-N

Bond in FRPolyester Fibers


44/49

MoistureAbsorptionofGrafted-Phosphorylated

Polyester Fibers


45/49

Dyeability of Grafted-phosphorylated Polyester

Fibers with Cationic and Acid Dyes


46/49

Flame Retardancy Testing

observations made are:

The ease with which the material ignites

The duration of flaming

The duration of afterglowThe extent of burning and length of char

The duration of flaming and smoldering

Assessment of detectable amounts of smoke


47/49

The Federal test

Test 16 CFR1610

16 CFR1615/1616

The National Firefighters Protection Association (NFPA) ASTM D2863-00

The Room CornerItem Test (ISO 9705)

The Cone Calorimeter Test (ISO 5660)

LIFT apparatus test (ISO 5658)

UL 94 of underwriters laboratory Fire resistance

Flammability:

Variousflame RetardantTestings


48/49

Of greatest concern are those with halogens attached to the

carbon backbone, particularly the halogens: chlorine andbromine.

Brominated flame retardants (BFRs), are widely used

cost effective means

durability

performance of the material.Three most commonly used BFs are penta-, octa- and Deca-

brominated diphenyl ethers.

Collectively they are referred to as polybrominateddiphenyl

ethers, or PBDEs

Chlorinated flame retardants (CFRs ) are used in textiles,

paints and coatings, plastics and insulation foams.

chlorine containing flame retardants persist in the

environment and may accumulate in the tissues of humans

and other animals.

Toxicology


49/49

BFRs are very stable-they do not break down easily in the environment

Attach to particles and accumulate in media such as dust and

sediments.

BFRs also are light enough and are transported long distances through

the atmosphere.

Chemicals are readily absorbed by the body where they accumulate in

fatty tissues.

BFRs disrupt thyroid function , causing hyperactivity and problemswith learning and memory.

Documents

flame retardent polyester