TO IMPROVE THE DURABILITY OF FLAME RETARDANT FINISH ON POLYESTER COTTON

BLENDED FABRIC.

By

MUHAMMAD KASHIF HAYAT

A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of

Bachelor of Science in Textile Engineering

Department of Textile Processing

National Textile University, Faisalabad

March 2011

“This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that the copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the prior written consent of the author”

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Abstract

This project was an effort towards improving the durability of flame retardant finish

on polyester cotton blended fabric by using a compatible cross linker with the finish. The

purpose was to check whether the addition of cross linker to the recipe of flame retardant

improves the washing durability of the flame retardant finish on polyester cotton blended

fabric.

The fabric selected was Polyester Cotton (50/50) blend. In the practical work the

samples were treated with different concentrations of both the cross linker and the Flame

Retardant. From each recipe the samples were cured at three different temperatures. The

purpose of cross linker was to improve the durability and the purpose of varying curing

temperatures was to improve the fixation and washing durability. Although the Flame

Retardant finish didn’t prove to be durable to washing but some interesting results and

conclusions were obtained.

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Dedication

Dedicated to

iv

The Mother Institute of Textiles

National Textile UniversityFaisalabad.

ANDThose who love me for what I am.

The Mother Institute of Textiles

National Textile UniversityFaisalabad.

ANDThose who love me for what I am.

Acknowledgements

Selecting this project was not less than a challenge for me, as in the initial stages I got

some discouraging comments from the people around. But after discussing it with the

HEAD OF THE DEPARTMENT Dr. Rashid Masood, I was quite keen to do this

project. Mr. Rashid really motivated me by explaining what research is and how brave

you have to be without thinking about the results much. I would like to thank Dr. Rashid

Masood as he was always very helpful when ever I went to ask for the right direction.

As this project was carried out under the supervision of Mr. Qummer Zia, I really

want to thank him as he explained me the steps and the guidelines to achieve the project.

And last but not the least I would like to thank the Staff of Textile Processing

Laboratory, as they were very helpful and polite.

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Table of Contents1. Introduction:................................................................................................................1

1.1. Background:.........................................................................................................11.1.1. Area of research:.........................................................................................11.1.2. Research problem:.......................................................................................2

1.2. Significance of the project:..................................................................................31.3. Theory:.................................................................................................................3

1.3.1. The fire triangle:..........................................................................................41.3.2. Hazards of textile burning:..........................................................................51.3.3. Burning behavior of textiles materials:.......................................................61.3.4. Mechanism of combustion:..........................................................................8

1.4. Textile flame-retardants:....................................................................................101.4.1. History:......................................................................................................101.4.2. Functioning of flame retardants:...............................................................10

1.5. Polyester cotton blend:......................................................................................141.5.1. Polyester:...................................................................................................141.5.2. Cotton:.......................................................................................................151.5.3. Blend benefits:...........................................................................................151.5.4. Blend cons:................................................................................................151.5.5. Uses:..........................................................................................................15

1.6. Literature review:...............................................................................................161.6.1. Significant researchers and their findings:...............................................161.6.2. Flame-retardants under study:..................................................................181.6.3. Further identified areas of studies:...........................................................19

1.7. Objective and scope of the project:...................................................................191.7.1. Objectives:.................................................................................................191.7.2. Scope of the project:..................................................................................19

2. Experimental..............................................................................................................212.1. Materials:...........................................................................................................21

2.1.1. Fabric specifications:................................................................................212.1.2. List of chemicals and auxiliaries used:.....................................................21

2.2. Machinery & equipment:...................................................................................282.2.1. Application equipment:..............................................................................282.2.2. Testing equipment:.....................................................................................29

2.3. Methods:............................................................................................................292.3.1. Application methods:.................................................................................292.3.2. Testing methods:........................................................................................30

2.4. Project work plan:..............................................................................................313. Results and discussions:............................................................................................34

3.1. Results................................................................................................................343.1.1. Results for Flame Retardancy:..................................................................343.1.2. Results for tear strength:...........................................................................373.1.3. Results for Tensile Strength:......................................................................41

3.2. Overall discussion:.............................................................................................454. Summary:...................................................................................................................46

4.1. Key findings of the project:...............................................................................46

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4.2. Implications of the findings:..............................................................................474.3. Suggestions for the future work:........................................................................47

5. References:................................................................................................................48

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List of Tables

Table No. Label Page No1.1 The LOI values of some common textile fibers 61.2 The ignition temperatures of some common

textile fibers7

2.1 Compatibility Check 222.2 Design of Experiment 323.1 Results for Flame Retardancy 343.2 Results for Tear Strength 373.3 Results for Tensile Strength 41

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List of figures

Figure No. Label Page No1.1 Fire Triangle 41.2 How Fire initiates 51.3 Combustion cycle for fibers 92.1 Recipes keeping Flame Retardant Concentration 400 g/l 332.2 Recipes keeping Flame Retardant Concentration 350 g/l 332.3 Recipes keeping Flame Retardant Concentration 450 g/l 333.1 Effect of Flame Retardant on Char Length 353.2 Effect of Cross Linker on Char Length 353.3 Effect of Temperature on Char Length 363.4 Effect of Flame Retardant on Warp wise Tear Strength 383.5 Effect of Flame Retardant on Weft wise Tear Strength 383.6 Effect of Cross Linker on Warp wise Tear Strength 393.7 Effect of Cross Linker on Weft wise Tear Strength 393.8 Effect of Temperature on Warp wise Tear Strength 403.9 Effect of Temperature on Weft wise Tear Strength 403.10 Effect of Flame Retardant on Warp wise Tensile Strength 423.11 Effect of Flame Retardant on Weft wise Tensile Strength 423.12 Effect of Cross Linker on Warp wise Tensile Strength 433.13 Effect of Cross Linker on Weft wise Tensile Strength 433.14 Effect of Temperature on Warp wise Tensile Strength 443.15 Effect of Temperature on Weft wise Tensile Strength 44

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Chapter 1

1. Introduction:1.1. Background:1.1.1. Area of research:

Textile finishing:

In order to impart the required functional properties to the fiber or fabric, it is

customary to subject the material to different type of physical and chemical treatments

[14].

Mercerizing, singeing, flame retardant, water repellent, water proof, antistatic finish,

peach finish etc are some of the important finishes applied to textile fabric [3].

The properties of synthetic fibers like polyester, polyamide etc are essentially

different from natural fibers like cotton and wool. Hence the finishing sequence is

different for both natural and synthetic fiber.

While cellulosic's require a resin finishing treatment to impart easy-care properties,

synthetic fibers already have these easy-care criteria and require only a heat setting

operation [3].

Special finishes for natural fibers:

Bio-polishing Mercerisation Raising Peach Finish Fulling Calendering Sanforizing Crease Resist Finishing Anti-Microbial Finishing Flame Retardant Finishing

Special Finishes for Synthetic Fibers:

Heat Setting Filling Process

1

Hydrophilic Finishes Anti-Pilling Finish Anti-Static Finish Non-Slip Finishes Flame Retardant Finishing Anti-Microbial Finishing

Flame retardant finishing:

A flame retardant fabric can be defined as a fabric, which does not

propagate the flame, or fire or simply it does not burn, although it may burn or

char when such a fabric is subject to any form of heat [1].

The primary objective of giving a durable flame retardant finish on different

fabrics i.e. cellulosic fabrics, polyester fabrics, p/c blend fabrics etc is to attract

various fields. The field of applications include defense, industrial area, in space

research, for fire fighters, kids wear etc.

In order to induce flame retardancy in a fiber or fabric the burning cycle must be

interrupted in one or more of the three steps of burning cycle [12].

Different flame retardant finishes work in a number of different ways to disrupt

the combustion cycle. Basically this depends on the type of substrate on which the

flame retardant is to be applied and then selecting an appropriate flame retardant for a

specific substrate so that best flame retardancy is achieved [12].

There are a few stages in flame retardancy or modes of action of flame-retardants.

These stages are to be discussed in the next (Theory) section.

1.1.2. Research problem:

The gains in textile performance obtained from blending polyester and cotton are

not carried over into the flame retardant performance of the textile. This is due to the

thermosetting properties of polyester. Also cotton is hydrophilic so when a flame

retardant finish is applied, it is absorbed only by cotton not by polyester.

2

Due to this better or durable flame retardant results are not achieved on pc blend

fabric. Also by the application of flame retardant finish on pc blend certain properties of

the fabric are affected i.e. loss of strength, change in color etc

1.2. Significance of the project:

The main focus in this research is to achieve the same degree of flame retardancy

properties in pc blend fabrics as achieved in 100% cotton or 100% polyester alone.

As mentioned in the RESEARCH problem section due to different natures of

cotton and polyester it is quite difficult to induce brilliant flame retardant properties in pc

blend fabrics.

By achieving better flame retardancy properties in pc blend, the comfort of cotton,

strength of polyester and flame retardancy can be there in a single fabric. And this is the

order of the market.

Also the effect of flame-retardants on different properties of pc-blended fabric can

be identified in this RESEARCH.

1.3. Theory:

For many years such finishes for textiles there, which would not burn when

exposed to flame or heat. Such finishes are called flame retardant finishes.

After the Second World War the flame retardant finishes have become

established, this due to the recognition of different hazards of burning of textiles. Also the

need to produce effective durable finishes for textiles, which not affect the handle,

comfort, and aesthetics of the fabric rather impart good flame retardancy in the fabrics.

Fire:

Fire is our oldest technology and has been crucial to each step in our

development. Now fire, through controlled burning, provides most of our energy,

which in turn causes nearly all the world's air pollution [1].

Unwanted fires, ranging from the burning of textiles to a major fire disaster

resulting in hundreds of deaths, are a growing problem. The desire for textiles having

3

a reduced tendency to ignite and burn has been recognized for considerable time

during man’s recorded history. The use of asbestos as flame-resistant material has

been recorded in Roman times [3].

1.3.1. The fire triangle:

For combustion to take place three components are necessary, suitable fuel,

oxygen and heat. These components form the ‘fire triangle’ and removing any one of

these components will prevent or extinguish a fire [2].

Fuel:

There must be a source of fuel for any fire to take place. In most cases the fuel

does not itself burn (except if it is a gas) but breaks down under the influence of the

applied or generated heat to produce combustible volatiles that are then burnt. This is

important in terms of how some materials may initially ignite but then form a ‘char

layer’ that prevents the formation of further gases and further combustion.

Oxygen:

This is a basic component of combustion.

Ignition source:

The ignition source is needed to heat up the fuel sufficiently to generate volatiles

and then to ignite them. In the case of a gas the ignition source can act directly on the

gas.

Ignition

source(Heat)

Fuel

Air

(O2)

Figure 1.2 Fire Triangle

4

How does fire initiates?

At first the fuel molecules react slowly with oxygen, generating heat, which

warms the rest of the material [3]. As they react, they form unstable radicals, capable

of reacting billions of times faster than ordinary molecules. Radicals are fragments of

molecules that are capable of reacting with other stable molecules, forming even

more radicals. This starts a chain reaction and the radical concentration increases.

This makes the reaction go faster still, increasing the radical concentration

exponentially. When it reaches a certain value, ignition occurs. Flames contain high

radical concentrations.

Fires tend to grow in stages [3]. The graph shows that fires start with a slow

induction period, but once ignition is reached they grow very quickly, until they are

limited by the access of oxygen, reaching a steady state. Once the fuel is consumed,

the fire decays.

Figure 1.2 How Fire initiates

1.3.2. Hazards of textile burning:

In 1997 a famous incident occurred in Saudi Arabia when fire erupted in a tent

during HAJ and many pilgrims were burned due the fire as it was uncontrollable due the

5

burning of tents. After that in 1998 fire retardant tents were used this worked very well

[4].

Cotton and cellulosic materials are the mostly flammable but at the same time

cotton is used almost in every other textile. So to avoid any hazards there is a requirement

of flame retardancy on textiles made up of cotton or any other natural or synthetic

material.

1.3.3. Burning behavior of textiles materials:

Limiting oxygen index (LOI):

The limiting oxygen index is a measure of the percentage of oxygen that has to be

present to support combustion of the material [2]. As the percentage of oxygen in the

air is around 21%, it is clear that all fibers with an LOI lower than this level will burn

easily, while those with a higher LOI will tend not to burn [6].

Table 1.1 The LOI values of some common textile fibers

L.O.I. of the main textile fibersTextile fiber L.O.I. %

Wool 25Cotton 18Viscose 20Acetate 18

Triacetate 18Chlorofibers 48

Acrylic 18 – 20Modacrylic 22 – 28Polyester 20

Polyamide 20

Oxygen index methods, which describe the tendency of a material to sustain a

flame, are widely used as a tool to investigate the flammability of different materials.

They provide a convenient, reproducible, means of determining a numerical measure

of flammability. These methods have been used to systematical investigate the

relative flammabilities of flame-retarded materials, frequently comparing the

effectiveness of flame-retardants and flame-retardancy mechanisms. The

effectiveness of fire retardants is measured by the change in the critical oxygen

6

concentration that they induce as a function of their concentration. The limiting

oxygen index (LOI), also called the critical oxygen index (COI) or oxygen index

(OI).

The LOI values of some main textile fibers are given in the table. Wool has LOI

value higher than the oxygen contents of normal air, which suggests that wool fibers

are inherently less flammable than most other textile fibers [4].

Nature of textile material:

Each type of textile fiber will require its own particular form of flame-retardant

treatment since various fibers differ in respect of their behavior when exposed to a

flame. For example, cotton and most cellulose fibers ignite at a temperature about

350 OC while wool has a much higher ignition temperature. From this difference

arises the greater need to treat cellulose fiber materials with flame-retardants, while in

fact wool materials are seldom treated [7].

Table 1.2 the ignition temperatures of some common textile fibers

Construction of fabric:

The flaming properties of fabric also depend upon its structure and nature of its

surface as well. For the rapid burning of a fabric its fibers must have ready excess to

oxygen (air) to allow burning to continue after initial ignition. Fabrics with compact

weave, high twist yarn and close structures are relatively less flammable. Knitted

fabrics having air trapped in their loops catch fire more readily than woven fabrics.

Generally, we may say that an open mesh fabric will burn very readily [7].

Textile fiber Ignition temperature (oC)Wool 570 – 600Cotton 350Viscose 420Nylon 6 450

Nylon 6.6 530Acrylic > 250

Modacrylic 690Polyester 480

7

Also, if the fabric surface has been brushed or otherwise given a pile character

with a large amount of air trapped between the protruding fiber ends then this will

much assist the fabric to burn rapidly. Cotton flannelette is of this type and it will

allow the flame to spread exceptionally rapidly over its surface. The protruding fiber

ends will burn before the real burning of fabric itself starts [7].

1.3.4. Mechanism of combustion:

In order to understand the mechanisms of flame-retardants, the mechanism of

combustion should be clarified first. Cellulose combustion is a process that occurs in

stages:

Pyrolysis:

When heat is applied, the temperature of the fiber increases until pyrolysis

temperature, TP, is reached. Due to the action of heat, the fiber undergoes

irreversible chemical changes and produces non-flammable gases (carbon dioxide,

water vapours and higher oxides of nitrogen and sulfur), carbonaceous char, tars

(liquid condensates) and flammable gases (carbon monoxide, hydrogen and many

oxidisable organic molecules). For cotton, the temperature at which rapid pyrolysis

is triggered is 300oC [3].

Combustion:

The temperature continues to rise and the tar also pyrolyse, producing more non-

flammable gases, char and flammable gases. Eventually, the combustion

temperature, TC, is achieved. In combustion process, the flammable gases combine

with oxygen and a series of gas phase free radical reactions take place. These are

highly exothermic reactions and produce large amount of heat and light. The heat

produced during combustion is used for further pyrolysis of the fiber [3].

Post- combustion:

After the repeated cycles of pyrolysis ad combustion, a carbonaceous residue

(char) remains [6]. It undergoes slow oxidation (also exothermic) and continues to

glow until it has been completely burned up [3].

8

Classification of burning fabric into different zones:

A fabric undergoing combustion will present the following zones [13]:

A zone in which there are no longer any flames and only combustion residue (ash) is present.

A carbonaceous zone, glowing but flame-free. A burning zone where violent oxidation of flammable gases (a series of

reactions) taking place. A zone in which initial carbonization is possible to observe and cellulose

is undergoing reactions of pyrolysis. An intact zone.

Figure 1.3 Combustion cycle for fibers

RadiationHeat

Combustion (TC)

Fibre

Pyrolysis (TP)

Flammable gases

Heat

Oxygen

Liquid condensates, Tars

Char

Non-flammable gases

Non-flammable gases (CO2, H2O, NOX,, SOX)

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1.4. Textile flame-retardants:

Flame retardants are materials that inhibit or resist the spread of fire. These can be

separated into several categories: *Minerals such as asbestos, compounds such as

aluminium hydroxide, magnesium hydroxide, hydromagnesite, antimony trioxide,

various hydrates, red phosphorus, and boron [15].

1.4.1. History:

Chemical flame retardants have been used since Roman times when they

prevented siege towers from catching fire. However, the first patent on a flame retardant

was the British Patent 551, patented by Obadiah Wilde in 1735 to flame retard canvas for

use in theatres and public buildings. In the plastics industry, brominated flame

retardants were first used in cellulose nitrate which is extremely inflammable [15].

In the early 1970’s, the increasing use of flammable materials such as plastics in

electrical equipment or synthetic fibers in sofas and curtains led to the wider use of flame

retardants. At this time, manufacturers of appliances and furniture began such as plastics

for appliances and polyurethane foam and fiber-based fillings for furniture, moving away

from traditional materials such as wood and metals. While these new materials provided

many benefits, they had one problem - they were far more combustible than the materials

they replaced. Flame Retardants are able to contribute greatly to reducing the risk of fires

providing safety in the home and in public places [15].

1.4.2. Functioning of flame retardants:

Combustion is an exothermic process and requires three components, heat,

oxygen and suitable fuel. Combustion is self-catalyzing and if left unchecked, it will

continue until any of the three components is depleted.

The effective fire retardants work in a number of ways to disrupt this cycle. We

broadly classify the working mechanisms of flame-retardants into following two classes

[8].

10

1) Condensed phase mechanism2) Gas / vapour phase mechanism

1.4.2.1. Condensed phase mechanism:

The condensed phase strategy includes the removal of heat and the enhancement

of decomposition temperatures as in heat resistant fibers [13]. Flame-retardants

perform actions on fiber like char formation and promotion, glassy coating on fibers

etc. It’s suitable for cotton and wool and decreases the formation of burnable

volatiles by dehydration and carbonization [8].

Providing heat sink on fiber:

In this method we use such materials that thermally decompose through strongly

endothermic reactions. These endothermic reactions absorb enough amount of heat

and as a result pyrolysis temperature of the fiber is not reached. So, no combustion

takes place. Examples of such compounds are aluminium hydroxide or ‘alumina

trihydrate’ and calcium carbonate [8].

Al2O3.3H2O Al2O3 + 3H2O

CaCO3 CaO + CO2

Endothermic decomposition reactions

1) Condensed phase

a) Providing heat sink on fiber.

b) Coating insulating material.

c) Decreasing the formation of Flammable volatiles.

2) Gas / Vapour Phase

a) Decreasing access to oxygen / flame dilution.

b) Interfering with flame Chemistry.

Working mechanisms of flame-retardants

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Coating insulating material:

In this approach, a material is applied that forms an insulating layer around the

fiber at temperatures below the fiber pyrolysis temperature. Generally, boric acid and

its hydrated salts are used in this capacity. These are low melting point compounds

and when heat is applied, they release water vapour and produce a foamed glassy

surface on the fiber. In this way fiber is insulated from the applied heat and oxygen

[8].

2H3BO3 2HBO2 B2O3

Formation of foamed glass

Decreasing the formation of flammable volatiles:

The pyrolysis reaction is influenced in such a way that it produces less flammable

volatiles and more residual char [4]. In case of cotton and wool, most phosphorous

and nitrogen containing flame-retardants work on these bases. The phosphorous

containing flame-retardants thermally decompose and produce phosphoric acid. This

phosphoric acid either by cross linking or by single esterification with cellulose will

alter the pyrolysis to yield less flammable volatiles.

Cross linking with phosphoric acid

Actually, these phosphorous esters catalyse the dehydration and prevent the

formation of undesired levoglucosan, which is the precursor of flammable volatile.

12

Levoglucosan

Thermal degradation of cellulose

1.4.2.2. Gas phase mechanism:

In the gas phase mechanism, materials act with free radicals that generate heat for

process continuation. Flame-retardants dilute the flame density either by preventing

oxygen access or by enhancing the ignition temperature of gaseous fuels. The

materials that act in this mechanism include halogen-containing compounds often in

combination with antimony oxides [8].

Decreasing access to oxygen / flame dilution:

The flame-retardants decrease the access to oxygen and dilute the flame density.

Halogen containing flame-retardants release halogen halide [4]. These halogen

halides form relatively long-lived, less reactive free radicals. These radicals reduce

the heat available for perpetuating the combustion cycle, and which decrease the

oxygen content by flame gas dilution [8].

MX HX + M*

{MX is halogen-containing compound}

H* + HX H2 + X*

HO* + HX H2O + X*

RH + X* R* + HX

R* + X* RX (not flammable)

Free radical reactions during combustion of halogen (X) containing material

350 oC

13

Interfering with flame chemistry:

Flame-retardants interfere with flame chemistry and/or enhance the temperature at

which gaseous fuel ignite. Halogen containing flame-retardants often in combination

with antimony oxides are present in this category.

Sb2PO3 + 6HX 2SbX3 + 3H2O

SbX3 + 3H* Sb + 3HX

Sb + HO* SbOH

SbOH + H* SbO + H2

SbO + H* SbOH

SbX3 SbX2 + X*

RH + X* R* + HX

R* + X* RX (not flammable)

Gas phase free radical reactions with antimony

1.5. Polyester cotton blend:

Fabrics made of a polyester cotton blend are exactly what they sound like, made

from fibers of both the natural cotton and the synthetic polyester. While both fibers have

pros and cons, a blend is often used in garments to give the consumer the benefits of

both.

1.5.1. Polyester:

Polyester is a manmade polymer material. It is made from coal, air, water and

petroleum products. Polyester is a strong fiber that keeps its shape and therefore resists

wrinkling. The fiber does not withstand medium to high temperatures and melts and

burns at the same time, therefore ironing polyester must be done at a cool temperature, if

at all. Threads of polyester last for a long time and wear well, so are used for many

14

garments and sewing projects. Polyester does not shrink like its natural counterpart and

holds dye extremely well, a good thing for textile artists, but bad for stain-removal from

polyester items. Polyester was extremely popular in the 1950s but since then is used more

as a blend than the main fiber used for garments or fabric [1].

1.5.2. Cotton:

Cotton is an all-natural fiber made from the pod of a cotton plant. It is the

principal fiber used in making the world's clothing. Cotton is known for being light, cool,

comfortable and absorbent. Many people describe cotton as a fabric that "breathes." It is

also easy to dye and to clean, though dyes do not hold as fast to natural fibers as to the

synthetic fibers of polyester. Cotton can withstand high temperatures, but does wrinkle

easily and shrinks with washing [1].

1.5.3. Blend benefits:

A polyester cotton blend can be versatile, as it most likely retains the coolness and

lightness of the cotton fiber, but also adds the strength, durability and wrinkle-resistance

of polyester. A polyester cotton blend should only shrink slightly in comparison to a

garment or fabric that is 100 percent cotton. This blend is often preferred by at-home

sewers and quilters as it is extremely easy to sew [1].

1.5.4. Blend cons:

Adding polyester to cotton can cause unattractive pilling of the fabric and make

the fabric not withstand high temperatures as well. Many people prefer pure cotton to a

polyester blend cotton in clothing that they need to breathe, as the blend does not breathe

or stay as cool as pure cotton [1].

1.5.5. Uses:

Polyester cotton blend is mostly used in the garment industry to make clothing

that people want to be able to wash and wear without having to iron and that will be

tougher than a 100 percent cotton blend and withstand more washing. Many home sewers

15

prefer polyester cotton blends as it is more forgiving and easy to sew than pure cotton, as

it wrinkles and shrinks less [1].

1.6. Literature review:

1.6.1. Significant researchers and their findings:

Peter J. Wragg CCol. ASDC. CText.ati. OF Schill & Seilacher explains the criteria to

be considered in the flame retardant treatment of textiles. There is much to be achieved

by using topical treatments to FR treat textiles and Schill & Seilacher believe that they

have a proper place in the textile industry. The requirement to control the hazard involved

in using textiles must be reconciled with our natural desire to enhance our living and

working environments. Topical flame retardant treatments will have an increasing role to

play in the future [5].

Judi Barton, profiles the market for flame retardant chemicals. J. Barton discusses the

market share of different flame retardants. The market share of Bromine flame retardants

is 39%, phosphore flame retardants 24%, inorganic flame retardants 27%, chlorine 6%

and melamine 4% [9].

Thomas Paulini. Found that FLAMMEX DS is a new, durable flame retardant that is

specially designed for the flame proof finishing of polyester. If properly applied the

product is durable up to 50 launderings or 10 chemical dry cleanings [6].

Thomas Futterer, Chemist Fabrik Budenheim Germany, presented recent flame

retardancy solutions for PP (polypropylene) based on ammonium phosphates (specially

treated to improve thermal stability, facilitating processing of plastics containing the

product) and for PBT, PET (polyamides and thermoplastic polyesters) used particularly

in automotive parts, based on melamine polyphosphate. These flame retardants act by

accentuating charring of the plastic surface in contact with a flame, enabling the material

to be self-extinguishing (ignition resistant) and also reducing smoke emissions [10].

Rudi Borms, Dead Sea Bromine Group, presented developments in “reactive”

brominated flame retardants for fire safety treatment of soft and rigid foams (PUR =

polyurethane) for furniture, building and other applications. These molecules react with

the foam polymer molecules themselves, thus being fixed into the foam matrix. Tests

show zero leaching of the flame retardant out of the treated foam, even with strong

16

chemical solvents. The most recent developments in such reactive molecules enable fire

safety to be achieved whilst offering good material quality (foam flexibility, durability),

without “scorching” in application [10].

Reiner Saurwein, Nabeltec GmbH, presented recent developments in mineral flame

retardants, showing both the importance of quality/characteristics of aluminum hydroxide

(ATH) and the potential of flame retardancy synergies with other minerals such as

boehmite (aluminum oxide hydrate) and zinc borate. New ATH products without organic

post-treatment but with good powder properties enable good product handling and

improved treated polymer viscosity, rheology and extrudability to be achieved. Boehmite

has proven an effective synergist for ATH in certain polymer (e.g. vinyl acetate free

polyolefin’s), enabling mineral loadings to be reduced and polymer properties to be

improved [11].

François Minec & P. Lambert of Atofina presented developments in TV fire safety

specifications. The authors presented a new halogen-free V1 flame resistant polystyrene

system for TV casings, capable of achieving fire resistance comparable to V0, and

useable in manufacturers’ existing polystyrene (HIPS) processing equipment [11].

Sebastian Haröld, Clariant GmbH, presented a new generation of flame retardants for

polyamide polymers (PA66) based on phosphinates. These compounds enabled UL94-V0

classification to be achieved in glass fibre reinforced polyamides at relatively low flame

retardant addition levels (15-18% by weight) with good mechanical properties, including

electrical non conductivity, being maintained, compatible with injection moulding for

demanding applications in the electrical and electronics industries[11].

Alexander Morgan, Dow Chemicals, also discussed the use of nano particles of clay as a

flame retardant additive to plastics, considering both natural and synthetic clays, and also

organically treated clays. These authors again indicated that nano clay addition could

reduce peak heat release, but accelerate the reaching of the peak. The organo-clays

offered somewhat better flame retardancy properties than either natural or synthetic

untreated clays, but in no case were able to alone achieve UL94-V0 fire safety. The

mechanism of fire retardancy of the nano clays is hypothesized as resulting from

synergistic accentuation of base polymer charring [10].

17

Birgit Östman, Trite Sweden, presented ongoing developments in know-how concerning

flame retardancy for wood and timber. Ordinary untreated wood will generally achieve

Euro Class D for reaction to fire performance [10].

1.6.2. Flame-retardants under study:

Following basic flame retardant systems are studied:

Halogen containing flame retardants:

This is the most effective class of flame retardants. However the use of certain

bromide containing flame retardants is prohibited. There principle of action is that

they interfere with the radical chain mechanism that takes place in the gas phase of

the combustion process [7].

Phosphorus containing flame retardants:

This class uses organic and inorganic phosphorus compounds. In a fire

dehydration takes place and these products form a vitreous layer. This way further

oxygen supply is stopped [7].

NITROGEN CONTAINING FLAME RETARDANTS:

These are mainly used together with phosphorus containing flame-retardants.

They stabilize the bonding of phosphorus in the polymer. Further Cross linked

structures are formed supporting carbonization during the combustion process [7].

INTUMESCENT SYSTEMS:

These consist of an acid source, a carbon supplier and an expansion agent. The

effect of the system is based on the formation of a heat insulating, carbon rich foam

layer and on foam expanding or swelling the mixture [7].

MINERAL BASED FLAME RETARDANTS:

Aluminum or magnesium hydroxides are used as mineral based flame-retardants.

Here chemically bonded water is separated resulting in cooling of the polymer and

diluting the combustible gases [7].

There are some other flame-retardants, which are nano composites or

products containing borax.

18

PERMANENCE OF FLAME-RETARDANTS:

Permanence can be achieved by reactant cross linker, self-cross linker, migration

or ion-pair bonding [7].

1.6.3. Further identified areas of studies:

The main areas that can be studied or looked further in are:

To manufacture such flame retardants that give durable flame retardancy on

polyester cotton blended articles and also does not affect their properties.

To manufacture such flame retardants, which have little or no halogen, content

and are environmental friendly.

To introduce an application procedure which has less waste, gives good results

and should be environment friendly.

1.7. Objective and scope of the project:

1.7.1. Objectives:

The main and the basic objectives of this project include:

To get better flame retardant properties on P/C blend fabric. The flame retardant fabric should be durable i.e. should withstand its

cleaning and retain its flame resistant property after multiple washes. The flame retardant PC fabric should have a soft handle after the

application of finish. The flame retardant PC fabric should retain its color i.e. no yellowing of

the fabric The flame retardant fabric should retain its strength. The flame retardant should not shrink.

1.7.2. Scope of the project:

The main advantage attained from this project is there is a wide application of PC

blended fabrics i.e. in home textiles, furnishing, military, fire fighters etc so achieving

flame retardant properties in such articles is of great importance.

The flame retardant properties in pc-blended articles will avoid the hazards of

burning.

19

Also there is a scope to look into the application of flame retardant finishes. As

some of the flame-retardants are not environmental friendly i.e. Halogen containing

flame-retardants. So there is a scope in this project to look into the chemistry and

application of flame-retardants to avoid the environmental hazards.

Also the properties of the substrate that get modified after the application of

Flame retardant finish can be analyzed and compared.

Chapter 2

20

2. Experimental2.1. Materials:

The substrate used for the application of chemicals was 50/50 polyester/cotton

blended fabric.

2.1.1. Fabric specifications:

Type of Fabric: Bleached 50/50 Polyester-Cotton Bleached Fabric.Weave: 1/1 Plain WovenEnds/inch: 80Picks/inch: 56Count of Warp: 30Count of Weft: 31GSM: 100Width: 96”

2.1.2. List of chemicals and auxiliaries used:The major chemicals used during the course of project were

PYROVATEX CP (Flame Retardant) Knittex RCT (Cross Linker) TURPEX CAN, (Softener) INVADINE PBN (wetting agent)

Brief Description of the chemicals and their compatibility table is given on the

next page:

21

Compatibility check:

Table 2.1 Compatibility Check

Chemical Name

Chemical Constitution

PH (100 g/l) Physical Form Compatibility

PYROVATEX CP(FLAME RETARDANT)

Organic phosphorus compound

3.5-6 Viscous, Clear, Colorless to

Yellowish liquid

PYROVATEX® CP NEW can be

used in combination with

Many other finishing agents.

KNITTEX RCT(Cross linking Agent)

Modified dihydroxy

ethylene urea

4.0-6.0 Colorless to light yellow liquid

Can be used with other finishes to give good cross

linkingINVADINE PBN(Wetting Agent)

Surface-active preparation of

ethoxylated fatty alcohol and

araliphatic ether alcohol

7.5-9.5 Clear to opalescent liquid

Compatible with different finishes

( as a wetting agent)

TURPEX CAN(Softner)

Emulsion of polyalkylene

3.5-5.5 White to yellowish emulsion

TURPEX® ACN NEW can be used

in combination with mostProducts

commonly used in finishing.

22

2.1.2.1. Pyrovatex CP:

It is a fiber reactive organic phosphorus compound. As this flame retardant is

phosphorus based so it work as a condensed phase flame retardant.

The condensed phase strategy includes:

a) Providing heat sink on fiber.b) Coating insulating material.c) Decreasing the formation of Flammable volatiles.

USES:

Piece goods of native and/or regenerated cellulose fibers and blends with

synthetics. (E.g. for work wear and curtains)

Characteristics & benefits: Effects fast to washing at the boil and dry cleaning due to a chemical bond

of PYROVATEX® CP NEW. Simple Application. Can be combined with other Finishing Additives. Textiles finished with PYROVATEX® CP NEW are flame retardant and

does not cause initial burning. Cost saving by single-bath application with water repellent finishing. After removal of the ignition source these textiles do not or scarcely

afterglow or burn. Under the influence of fire a carbon shield is formed that protects the skin

and other parts from heat.

Ecology/toxicology:

Toxicologically and dermatologic ally tested.

Application:

Dissolving/diluting:

PYROVATEX® CP NEW durable flame retardant is added to cold water

with stirring, a homogeneous distribution in the bath must be guaranteed.

Cellulose cross linking agents, for example KNITTEX® CHN or

KNITTEX® RCT NEW, diluted in water, are added then.

Softeners such as ULTRATEX® FSA NEW or TURPEX® ACN NEW

are added diluted with an equal amount of water.

23

Wetting agents such as INVADINE® PBN can be added in any dilution

with water.

Phosphoric acid (80 or 85 %) serves as catalyst. The catalyst is also pre-

diluted with water before filling with cold water to the required liquor

volume.

Required amount:

The required amount of PYROVATEX® CP NEW durable flame retardant

depends on the standard to be met, the type of fiber, area weight and construction of

the goods as well as on a possible blend with synthetic fibers such as polyester.

Process: Impregnation:

The goods are impregnated on a pad mangle.

Adequate liquor pick-up is essential (70-90 %), depending on weight and

construction of fabric

Drying:

Drying on stenter should be carried out with maximum overfeed.

The recommended drying temperature in the first zone is 110 °C

The temperature in the other zones should not be higher than 130 °C to

minimize migration.

The goods should, if possible, be processed in a partial vacuum (air

extraction).

If the goods are not cured immediately, they must be prevented from

absorbing moisture from the air by being rolled up and wrapped in plastic

film.

Curing:

In the curing oven 5 min at 150 °C must be guaranteed.

In the case of curing on stenter 30 to 60 sec at 170 °C are sufficient.

It is advisable to check the curing effect at regular intervals.

Washing off:

24

The phosphoric acid used as a catalyst for cross linking must be removed

from the substrate, washing off is indispensable.

The goods should be washed off after curing, preferably within 24 h.

Usually, they are washed off in an open width washing machine with not

less than 5 boxes, or in a winch. Smaller lengths of material can be washed

off in a jig.

Alkali is added to the washing bath to neutralize the goods and to make

the goods alkaline and therefore reduce hydrolysis of the finish during

storage of the finished goods. With a continuous process using open width

washing machines, alkali must be added in proportion to the rate of fabric

throughput.

In order to achieve continuous neutralization, the goods must remain in the

alkaline bath for at least 2 min.

They must be thoroughly rinsed with water to avoid fish odor. It is

advisable to add 1-2 ml/l H2O2 to the last rinsing bath.

After neutralizing and rinsing, they should be slightly alkaline and have a

pH of 8–9.

2.1.2.2. Knittex RCT:

Well balanced and highly reactive cross linking agent with low formaldehyde

content for easy care finishes with highest effect level at low curing temperatures.

Characteristics & benefits: Special cross linking properties Very high reactivity Very good wash-and-wear effects and shrink resistance Extremely low content of free and releasable formaldehyde The properties are retained even after several washes respectively dry

cleaning cycles

Application:

25

The product is normally applied by padding.

Dissolving/Diluting:

KNITTEX® RCT cross linking agent can be diluted with cold water.

Application:

Padding with a liquor pick-up of 60–90 %

Bath temperature approx. 20 °C

Curing conditions:

On a baker/hot flue (after previous separate drying)

Curing: 2–3 min at 130 °C (air temperature)

Drying and curing (controlled by fabric temperature) on stenter

Curing: 50–70 sec at 130 °C (fabric temperature) or

20–30 sec at 140 °C (fabric temperature) or

10–15 sec at 150 °C (fabric temperature)

2.1.2.3. Invadine PBN:

Special wetting agent for finishing

Characteristics & benefits: Improves wetting speed and penetration of liquor into core of fibers Higher liquor pick-up in case of synthetic and tight woven cotton fabrics Improved and more uniform effect level Despite of its slightly anionic character INVADINE® PBN special

processing agent is compatible with products commonly used in finishing.

Application:

The product is normally applied by padding.

Dissolving/diluting:

INVADIN® PBN special processing agent is diluted with an equal

amount of cold water.

Pre-diluted product is added first to the bath.

Required amount:

5–15 ml/l INVADINE® PBN

26

2.1.2.4. Turpex CAN new:

Softener and additive in resin finishes

Uses:

Additive and softener for crease-resistant, shrink proof, non-iron, wash and wear

finishes on natural and regenerated cellulose fibers and their blends with synthetic

fibers

Suitable for dry, moist and wet cross linking processes

To improve abrasion resistance, tear strength, bursting strength, sew-ability on all

fabric types

Characteristics & benefits: Increases fiber lubrication Soft, surface smooth handle Excellent durability to washing and dry cleaning Improved tear strength, bursting strength and abrasion resistance of

finished fabrics Suitable for all type of resin finishes Suitable for moist and wet cross linking processes as well FR-finishes

with PYROVATEX® in strong acid medium

Application:

TURPEX® ACN NEW textile softener can be applied by padding, dip spin or

minimum application techniques.

Dissolving/diluting:

TURPEX® ACN NEW textile softener can be diluted with cold water.

Dilute TURPEX® ACN NEW textile softener during constant stirring

with cold water before adding to the bath.

If combined with cellulose cross linking agents, filler, additives, etc., these

products must be pre-diluted; TURPEX® ACN NEW textile softener

should be added last.

Required amount:

27

Padding

5–60 g/l TURPEX® ACN NEW

Application:

Padding with a liquor pick-up of 60–90 %

Bath temperature: about 20 °C

Drying at 110–130 °C

Standby flame retardant:

APYROL DGC (CHT CHEMICALS)

(It is to be applied if a BINDER compatible with it is available in lab)

2.2. Machinery & equipment:

The following equipment and machinery were used:

Beakers Stirrer Pippets Funnel Padder Stenter

2.2.1. Application equipment:

Laboratory padder manufactured by TSUJI DYEING MACHINE MANUFACTURING CO. LTD. OSAKA, JAPAN

Laboratory stenter manufactured by TSUJI DYEING MACHINE MANUFACTURING CO. LTD. OSAKA, JAPAN

2.2.2. Testing equipment:

28

Flame retardant tester Elmendorf tear strength tester Tear strength tester

2.3. Methods:

2.3.1. Application methods:PAD-DRY-CURE

Firstly the recipe was made according to the required concentrations of chemicals.

The pick-up on the padder was set on 75%. The prepared solution was taken in the

trough of the padder and one complete length of fabric was passed through it.

Padding:

Padding was done on the padder installed at NTU lab manufactured by TSUJI

DYEING MACHINE MANUFACTURING CO. LTD. OSAKA, JAPAN. The liquor

pick up at the padder was set from 70-75%. The nip pressure was adjusted by the

pressure gear system. After dipping in the given recipe, the specimen was placed

between the nips of rollers. The extra amount of the liquor was squeezed out of the

fabric and required amount picked up.

Drying:

After padding the sample was taken to stentter for drying. The stentter installed at

NTU LAB is TSUJI DYEING MACHINE MANUFACTURING CO. LTD. OSAKA,

JAPAN. The drying temperature was set at 130ºC and the time given for drying was 2

minutes for each sample. During the drying process water present in the fabric

specimen was evaporated and specimen fully was dried at this stage. So that there

must not be any water or moisture during curing process which effect the cross

linking of the resin.

Curing:

After padding the samples were cured at the stenter. Different samples were cured

at different temperatures i.e. 150ºC, 170ºC and 190ºC. The samples were cured for 90

seconds each. During the curing process the Finish with the help of cross linker, cross

linked with the substrate.

29

Neutralization:

After curing the samples were neutralized with in 24 hrs to remove the phosphoric

acid used as a catalyst. A neutralization solution of liquor ratio with 35 g/l Na2CO3

was made and the fabric sample was immersed in that solution at 60ºC. After that

another solution was made with 12 g/l soda ash and the same sample was immersed

in it for 2 minutes.

Then the fabric sample was washed with simple water and at last the sample was

rinsed with a solution of 1-2 g/l H2O2 to remove the odor.

Washing/laundering:

The fabric samples were washed 5 times before doing the durability testing. The

washing recipe was made with 2 g/l detergent and 5 g/l soda ash. The fabric was

given 30 minutes at 60ºC.

2.3.2. Testing methods:

TEAR STRENGTH TESTING METHOD (ASTM - D 1424 – 96)

TENSILE STRENGTH TESTING METHOD (ASTM - D5035 - 06,

STRIP METHOD)

FLAME RESISTANCE TESTING METHOD (AATCC TEST METHOD

34-1969)

Project Plan:

This idea was taken from some of the seniors in NISHAT Textiles mills. The

discussion started with the application of FLAME RETARDANTS on polyester

Cotton fabrics, because it is quite difficult to achieve the FLAME RETARDANT

result on a PC blended fabric. But at the same time it has demand in the market i.e.

apart from protective clothing in apparel and children wear.

After discussions with my supervisor and HOD I came to the conclusion that i

will try to improve the durability of FLAME RETARDANT on PC blended fabric by

using a suitable i) Cross linker and ii) Binder.

30

At that time I was interested in comparing the durability of flame retardant on PC

fabric by using cross linker and Binder. But after searching for chemicals, only a suitable

cross linker was available with which I carried out my experiments.

2.4. Project work plan:

In my project plan I had three variables i.e. Concentration of Flame Retardant,

Concentration of Cross linker and Curing Temperature. The concentration of Flame

Retardant was varied from 350 g/l to 450 g/l. Concentration of Cross linker was varied

from 60 g/l to 80 g/l and the curing temperatures were 150ºC, 170ºC and 190ºC.

All the other chemical concentrations i.e. Softener, Phosphoric Acid were kept

constant. The drying temperature was also kept constant i.e. 130ºC.

With all these variable concentrations, curing temperatures total number of

samples treated were 27.

Total number of recipes was 9. Three samples were padded with one recipe and

then dried at 130ºC for 2 minutes on the stenter. After drying first sample was cured at

150ºC, second one at 170ºC and the third one at 190ºC. All three samples were given 90

seconds curing time.

After curing the samples were neutralized with in 24 hrs. After neutralization

wash the fabric samples were washed for durability and finally following tests were

performed on the samples:

Flame Retardancy Tear Strength Tensile Strength

Design of experiments:Below is the design of the experiment (DOE):

31

Table 2.2 Design of Experiment

Flame Retardant g/l Cross linker g/l Temperature C

450 80 170

350 70 190

450 70 190

450 60 190

400 70 150

350 80 190

450 60 170

350 70 150

400 60 150

400 70 190

350 80 150

400 80 190

400 60 170

350 80 170

400 80 170

450 60 150

450 80 190

350 70 170

450 70 150

350 60 150

350 60 170

400 70 170

450 70 170

350 60 190

400 60 190

400 80 150

450 80 150

Note:Wetting Agent = 10g/lSoftener = 15 g/lPhosphoric Acid 25 g/l

32

Figure 2.1 Recipes keeping Flame Retardant Concentration 400 g/l

Figure 2.2 Recipes keeping Flame Retardant Concentration 350 g/l

Figure 2.3 Recipes keeping Flame Retardant Concentration 450 g/l

33

Chapter 3 3. Results and discussions:3.1. Results3.1.1. Results for Flame Retardancy:

Unwashed:

Table 3.1 Results for Flame Retardancy

Flame Retardant g/l

Cross linker g/l TemperatureC

Char Length unwashed (cm)

After Flame

450 80 170 12 No350 70 190 15 Yes450 70 190 11 No450 60 190 12 No400 70 150 13 Yes350 80 190 16 Yes450 60 170 10 No350 70 150 14 Yes400 60 150 10 No400 70 190 11 Yes350 80 150 16 Yes400 80 190 13 Yes400 60 170 10 No350 80 170 15 Yes400 80 170 13 Yes450 60 150 11 No450 80 190 13 Yes350 70 170 15 Yes450 70 150 12 Yes350 60 150 13 Yes350 60 170 13 Yes400 70 170 13 Yes450 70 170 12 No350 60 190 15 Yes400 60 190 12 Yes400 80 150 13 No450 80 150 12 No

Note:Wetting Agent = 10g/lSoftener = 15 g/lPhosphoric Acid 25 g/l

34

Fig 3.1 Effect of Flame Retardant on Char Length

Discussion:

The unwashed samples that were tested after neutralization showed Flame

Retardancy. The Figure 3.1 shows that by increasing the concentration of Flame

Retardant the char length is decreasing i.e. less burning. Although the unwashed

samples showed the Flame Retardancy in acceptable limits but in most of the samples

an After Flame was there.

Fig 3.2 Effect of Cross Linker on Char LengthDiscussion:

In the Figure 3.2 the relation between the concentration of cross linker and char

length is shown. We can see that by increasing the concentration of cross linker there

is a slight decrease in the Flame Retardancy i.e. increase in char length. So from this

35

graph we can say that cross linker helps in fixation but at the same time reduces the

Flame Retardancy.

Fig 3.3 Effect of Temperature on Char LengthDiscussion:

The Figure 3.3 shows the relation between the increasing curing temperatures and

the char length. The above graph shows an irregular pattern where by increasing the

temperature to 170ºC decreases the char length i.e. increases the flame retardancy, but

then increasing the temperature further more decreases the flame retardancy of the

fabric i.e. char length increases slightly.

Note: The samples which were burnt for testing became more like a

membrane after burning.

Washed:

All the samples were given 5 washes and then tested for flame retardancy.

Discussion:

Unfortunately not even a single sample turned out to be durable to washing. Some

of the samples were completely burnt, but samples with the higher concentrations of

Flame Retardant burnt slowly due to the After Flame.

The appearance of the sample after being burnt was like a mesh with polyester

content being burnt and cotton content left.

36

Although no significant results were obtained from the tests after washing but still

the conclusions obtained from these tests can help in future studies on Polyester

Cotton Flame Retardant fabrics.

3.1.2. Results for tear strength:

Table 3.2 Results for Tear Strength

Flame Retardant g/l Cross linker g/l Temperature ºC Tear Strength (g) Warp Weft

450 80 170 1480 1320350 70 190 1520 1180450 70 190 1480 1200450 60 190 1640 1040400 70 150 1820 1360350 80 190 1440 1100450 60 170 1520 1380350 70 150 1780 1340400 60 150 2000 1440400 70 190 1720 1300350 80 150 1640 1280400 80 190 1480 1160400 60 170 1840 1520350 80 170 1480 1140400 80 170 1560 1380450 60 150 1550 1100450 80 190 1200 900350 70 170 1580 1220450 70 150 1440 1240350 60 150 2460 1800350 60 170 2020 1620400 70 170 1520 1360450 70 170 1440 1260350 60 190 1400 1280400 60 190 1380 1160400 80 150 1840 1440450 80 150 1920 1520

* Untreated fabric tear strength: Warp = 2440, Weft = 2040

Note:Wetting Agent = 10g/l

Softener = 15 g/l

Phosphoric Acid 25 g/l

37

Fig 3.4 Effect of Flame Retardant on Warp wise Tear Strength

Discussion:

The Figure 3.4 shows the relation between the concentrations of Flame

Retardant and Warp Tear Strength of the Fabric. It can be seen in the above graph

that on increasing the concentration of Flame Retardant there is a loss in the Warp

Tear Strength of the Fabric. At higher concentrations of the finish the strength loss is

high.

Fig 3.5 Effect of Flame Retardant on Weft wise Tear StrengthDiscussion:

38

The Figure 3.5 shows the relation between the concentrations of Flame Retardant

and Weft Tear Strength of the fabric. All the values of Weft tear strength are less than

the Warp Tear strength. On increasing the concentration of Flame Retardant the Weft

Tear Strength decreases and on higher concentrations the strength is the most.

Fig 3.6 Effect of Cross Linker on Warp wise Tear Strength

Fig 3.7 Effect of Cross Linker on Weft wise Tear Strength

Discussion:

The Figures 3.6 & 3.7 shows the relation between the concentrations of cross

linker and Warp and Weft tear strength respectively.

39

It can be seen in the graphs that Warp Strength values are much higher than the

Weft strength values. But in both the graphs on increasing the concentration of cross

linker the tear strength of both warp and weft decreases.

Fig 3.8 Effect of Temperature on Warp wise Tear Strength

Fig 3.9 Effect of Temperature on Weft wise Tear StrengthDiscussion:

The Figures 3.8 & 3.9 shows the relation between the increasing curing

temperature and warp and weft tear strength of the fabric respectively.

It can be seen in the graphs that on increasing the curing temperature from 150 to

170ºC, the strength loss is more on warp of the fabric compared to the strength loss

on weft of the fabric. But in both the cases on increasing the curing temperature

40

strength loss is lost. And on higher curing temperatures i.e. 190º C the strength loss is

the most.

3.1.3. Results for Tensile Strength:

Table 3.3 Results for Tensile Strength

Flame Retardant g/l

Cross linker g/l

TemperatureºC

Tensile Strength (kg)Warp Weft

450 80 170 36 22350 70 190 30 21450 70 190 34 22450 60 190 31 18400 70 150 36 18350 80 190 31 20450 60 170 34 20350 70 150 34 23400 60 150 34 22400 70 190 31 23350 80 150 33 22400 80 190 33 22400 60 170 32 21350 80 170 32 21400 80 170 34 20450 60 150 33 22.5450 80 190 33 21.5350 70 170 32 22450 70 150 35 18350 60 150 30 19350 60 170 28 23400 70 170 35 21450 70 170 34 21350 60 190 28 22400 60 190 31 20400 80 150 37 22450 80 150 38 21.5

* Untreated fabric Tensile Strength: Warp = 33, Weft = 24

Note:Wetting Agent = 10g/l

Softener = 15 g/l

Phosphoric Acid 25 g/l

41

Fig 3.10 Effect of Flame Retardant on Warp wise Tensile Strength

Fig 3.11 Effect of Flame Retardant on Weft wise Tensile StrengthDiscussion:

The Figures 3.10 & 3.11 shows the relation between the Flame Retardant

concentration and Warp and Weft Tensile Strength of the fabric. It can be seen in the

above two graphs that on increasing the concentration of flame retardant the Warp

tensile Strength increases while the Weft tensile strength decreases.

42

Fig 3.12 Effect of Cross Linker on Warp wise Tensile Strength

Fig 3.13 Effect of Cross Linker on Weft wise Tensile StrengthDiscussion:

The Figures 3.12 & 3.13 shows the relation between the concentrations of cross

linker and Warp and Weft Tensile strength of the fabric. It can be seen in both graphs

that tensile strength increases with the increasing amount of cross linker. The increase

in the Warp tensile strength is more as compared to the increase in Weft tensile

Strength.

43

Fig 3.14 Effect of Temperature on Warp wise Tensile Strength

Fig 3.15 Effect of Temperature on Weft wise Tensile StrengthDiscussion:

The Figures 3.14 & 3.15 shows the relation between the increasing curing

temperature and Warp and Weft tensile strength of the fabric. In case of warp tensile

strength the tensile strength decreases by increasing the curing temperature. In case of

Weft tensile strength an irregular graph is obtained, on increasing the temperature the

weft tensile strength increases but on further increases the Weft tensile strength

decreases.

44

3.2. Overall discussion:

From all the test results, values and graphs it has been observed that Flame

Retardant applied to the Polyester Cotton blended fabric (50/50) gives some resistance to

burning before washing. The cross linker, higher finish concentrations and higher curing

temperatures don’t help much in making the fabric durable to washing.

By increasing the Flame retardant concentrations the fabric Flame retardancy does

improve but at the cost of loss in tear strength. The cross linker used also reduces the tear

strength but at the same time both Flame Retardant and cross linker when fixed to the

fabric increases the Tensile strength of the fabric.

This is because cross linking of the finish with the fabric makes the polymer

chains brittle and hence they are easy to tear. But in case of tensile strength the surface

coating due to the cross linking of finish increases the tensile strength of the fabric.

The increasing curing temperatures do help in fixation but at the same time a lot

of strength loss occur and even the fabric becomes yellow. But after neutralization wash

this yellowness of the fabric reduces.

Overall adding a cross linker to the Flame Retardant finish doesn’t help much in

increasing its durability and at the same time gives strength loss

45

Chapter 4 4. Summary:4.1. Key findings of the project:

Though the Flame retardant finish didn’t prove to be durable on Polyester Cotton

blended fabric after washing, but still there were some findings and conclusions made

from this project:

Addition of the cross linker to the Flame Retardant recipe i.e. Pyrovatex CP

can only help finish to crosslink with the cotton content of the fabric.

The Finish applied to the Polyester Cotton blended fabric can give Non

durable finish on the fabric.

The fabric when burnt gives a mesh like appearance, half of the content

being burnt and half of the content remaining.

In some recipes where the concentration of Flame Retardant was high, the

fabric didn’t burn at once but due to the after flame.

Increasing the Concentrations of both Flame Retardant and cross linker

results in strength loss of the fabric.

Increasing curing temperatures also reduces the strength of fabric and

makes the fabric yellowish at higher curing temperatures.

After the neutralization wash, the yellowness of the fabric was reduced.

The best results were obtained at 450 g/l Flame Retardant, 70g/l Cross

Linker and 170 ºC curing temperature.

Overall the addition of a cross linker and raising the curing temperatures

doesn’t really help in improving the durability of the fabric and also

reduces the strength of the fabric.

4.2. Implications of the findings:

As polyester cotton blended fabric is mostly used in apparel and kids wear, this

finish can be applied on polyester cotton blended fabrics which are to be used for such

purposes. But this can only give a non durable finish, can not withstand washing.

46

But still work should be carried on to make the polyester cotton blended fabrics to

make them durable to washing because there is a demand of such fabrics these days in

apparel and kids wear industry.

4.3. Suggestions for the future work:

As the two fibers Polyester and Cotton differ a lot in their properties and Nature,

also the ignition temperature of cotton is 350ºC where as the ignition temperature of

polyester is 480. Keeping these properties and the try I have made to make the Flame

Retardant finish durable on Polyester Cotton Blended fabric, I have the following

suggestion for future work:

Instead of adding other auxiliaries with the finish, the chemistry of the

finish should be looked into and work should be done to make a durable

finish for Polyester Cotton Blended fabric.

The finish should be applied with a suitable binder to check if it improves

durability.

A two bath process can be done too, with first padding the fabric with the

finish suitable for cotton, drying and curing it. After curing the fabric

should be padded again with the finish suitable for polyester and then

giving the required drying and curing. Though the process will prove to be

an expensive one but it gives some acceptable results.

5. References:

1. http://www.ehow.com/about_5114277_polyester-cotton-blend.html (Accessed on

16th February,2011)

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2. A. R. Horrocks, Flame Retardant Finishing Of Textiles, Review Progress

Coloration, Vol. 16, 62-100 (1986).

3. Textile Finishing edited by Derek Heywood, Society Of Dyers And Colorists,

2003,351-371.

4. Finishing by Pietro Bellini, Ferruccio Bonetti, Ester Franzetti, Giuseppe Rosace

and Sergio Vago, ”Textile Reference Book For Finishing”, (2002), 144-147.

5. Peter J of Schill & Seilacher, Achieving a flame retardant performance,

International Dyer, JULY 1994

6. Thomas Paulini, Durable flame retardant for Polyester, Technical Fabrics,

International Dyer, JUNE 2005

7. Modern Flame Retardant Systems and Selected Test Methods for Textiles by

Herbert Rosch, from International Dyer.

8. W.D. Schindler and P. J. Hauser, Chemical Finishing Of Textiles.

9. Judi Barton, A choice of Treatments, Flame Retardancy, International Dyer,

JULY 2001.

10. Anderson J J, Camacho V G and Kinney RE, ‘Fire retardant polymers containing

thermally stable phosphonate esters’, US Patent 3,849,368, 1974; both patents

assigned to Albright & Wilson Inc

11. Anderson J J, Camacho V G and Kinney R E, ‘Cyclic phosphonate esters and

their preparation’, US Patent 3,789,091, 1974;

12. www.zeusinc.com , A Technical Paper by ZEUS Industrial Products Inc,

(Accessed on 26th June, 2010).

13. Web page, Short articles on combustion of polymers: Oxygen-Index Methods.

14. HALL, Flame Retardants Chemistry, Textile Finishing.

15. “Flame Retardants”, www.bromine-info.org (Accessed on15th June, 2010)

16. Web page of “Bolton’s Fire Materials Laboratory” (Accessed on 3rd July, 2010)

17. Levin M, Handbook of Fiber Science and Technology, Vol. II, Chemical

Processing of Fibers and Fabrics. Functional Finishes, Part B, Levin M and Sello

S B (Eds), New York, Marcel Dekker, 1984, 1–141.

18. Wakelyn P J, Rearick W and Turner J, ‘Cotton and flammability – overview of

new developments’, American Dyestuff Reporter, 1998, 87(2), 13–21.

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19. Benisek L, ‘Antagonism and flame retardancy’, Textile Research Journal, 1981,

51, 369.

20. Hauser P J, Triplett B L and Sujarit C, ‘Flame-resistant cotton blend fabrics’, US

Patent 4,732,789, 1988, assigned to Burlington Industries.

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