This document discusses fabric flammability and flame resistance. It defines key terms like flammable, flameproof, and flame resistant fabrics. It also discusses factors that affect flame resistance like fiber content, yarn type, fabric structure, and weight. The document describes several test methods used to measure flame resistance, including the torsion balance procedure, visual timing test, 45 degree test, and hoop test. It provides data on flame resistance ratings for various fabric mixtures and chemically treated fabrics. Finally, it discusses recent test method developments and flameproofing finishing processes.

1. MD MAZBAH UDDIN
BANGLADESH UNIVERSITY OF TEXTILES
YARN ENGINEERING
BATCH 08
FABRIC FLAMMABILITY

2. Flammability
Flameproof fabrics are absolutely necessary for
protective clothing in many industrial processes
where chances of inflammable fabrics being ignited
are high. In domestic sphere many serious and
tragic accidents are the results of clothing catching
fire.

3. Flammable: A flammable fabric is one which propagates
flame, i.e. it continues to burn after the igniting flame has
been removed.
Flameproof: A flame proof fabric is one which doesn’t
propagate flame, i.e. any flame goes out quickly when the
igniting flame is with-drawn.
Flame resistance rating: The time in seconds necessary for
the propagation of flame in a vertical strip of 100 inch.
Flame resistant: A flame resistant fabric is one whose flame
resistance rating is high, i.e. above 150.
Some definition and terms relating
flammability

4. Inherently flame proof material: A material that has not been
subjected to any flameproof processing's yet it has the
flame-proofing ability.
Durably flame-proof material: The ability of a flameproof
material to retain its flame proof quality even after being
submitted to washing treatments.
Temporarily flameproof material: Material which complies
with the requirements of Clause 3 of B.S. 3120, before, but
not after, the prescribed washing treatment.
Some definition and terms relating
flammability

5. Fibre content: The flame resistance of a fabric is partly
dependent on the fibre from which it is made. Cellulosic
like as cotton, flax, viscose rayon give fabrics of low
flame resistance. Wool fabrics are difficult to ignite.
Nylons and Terylene(polyester), both are thermoplastic
fibres, shrink from the flame and tend no to ignite.
Although some stiffening treatments and certain dyes
can may result in the ignition of nylon and terylene.
Factors affecting flame resistance

6. MD MAZBAH UDDIN
BANGLADESH UNIVERSITY OF TEXTILES
YARN ENGINEERING
BATCH 08
Fabric Flammability

7. Yarn types: Yarn structure does not affect the flame
flammability of a fabric.
Fabric structure: Flammability is largely independent of
fabric structure. It doesn’t matter whether it is weaved,
knitted, laced, bonded, or felted fabric.
Fabric weight: Fabric weight influences the flammability
of the fabric. For a given fibre the flame resistance
rating of the fabric has been found to be directly
proportional to its weight in ounces(Oz) per Yd2.
Factors affecting flame resistance

8. It is not easy to measure directly the vertical flame speed
over rapidly burning fabrics as the flame front is not well
defined. It is, however ,possible to measure the vertical
flame speed indirectly by weighing the fabric continuously
on a torsion balance while it is burning. The vertical flame
speed is then readily calculated from the rate of wt. loss,
the initial wt. of the fabric and the wt. of the residue .
Although torsional balance procedure is valid for all types
of fabric, but it is unsuitable for practical purposes in
industrial conditions. This fact led to the development of
alternative procedures:
Torsion balance procedure

9. The visual timing test: A fabric strip is suspended vertically and
ignited from the bottom edge, then the rate of flame spread is
determined . This method is applicable for slow burning fabrics but
not for highly flammable fabric.
The 45 test: In which the time (t), for the flame to travel 5 inch over
fabric sloping at 45 degree angle is measured in seconds. The flame
resistance rating , M, is then given by 2.5 x t. This method doesn't
show statistical correlation with those of torsion balance method
throughout the whole range of fabrics.
The hoop test: In which the rate of flame spread is determined over
the fabric mounted on a semicircular frame.
Method 2&3 are not suitable for fabrics which ‘drip’ while burning.
Test Methods

10. Description Wt. per unit area (
Oz/yd2)
Rating
20% wool, 80% cotton 3.7 56
20% wool, 80% cotton 4.0 48
40% wool, 60% cotton 3.5 45
50% wool, 50% viscose 7.7 149
50% wool, 50% nylon 8.5 Infinity
50% wool, 33% viscose,
17% nylon
7.7 213
50% wool, 33% nylon,
17% viscose
8.6 Infinity
Table: Data for mixture fabrics

11. Description OZ/yd2 Rating
Cotton, Erifon
(Lifeguard) treated
5.9 Infinity
Cotton, Proban treated 5.1 Infinity
Cotton, Antiflamm
treated
5.7 Infinity
Viscose, Proban treated 5.1 Infinity
Cotton, Antiflamm
treated
5.5 Infinity
Data for fabrics treated with flame resistant
processes

12. Recent tests are modification of vertical strip and 45
degree test , are found in British Standard .Three test
methods are given below:
Method A: Basically, this method is the vertical strip test
in which the rate of propagation of the flame is
measured in terms of the distance in millimetres per
minute that the base of flame travels up a strip of 900
mm x 75mm. The time to travel between two markers
500 mm apart is observed . The rate of propagation is
then given by (500/t x 60 mm/min), where t is in
seconds.
Recent Progress in flammability test

13. Some other information's like after-flame, after-glow, char
length are also derived and reported:
After-flame: The time in seconds that elapses between the
removal of the std. gas lighting fame and the flame
extinction.
After-glow: the time in seconds between flame extinction
and the end of any glowing.
The charring: the extent of charring is given by ‘char length.
This is the difference in mm between the original specimen
length and the undamaged length of the specimen.
Recent Progress in flammability test

14. Method B: Fabrics made from thermoplastic materials don’t
burn in a convenient manner for a satisfactory strip test to be
made. They melt, shrink, curl away from the flame. In method
B the test specimen is hung in the sheet form and the igniting
flame applied at right angles to the sheet and near to the
bottom edge. The amount of damage and time taken is
observed and reported.
Method C: This test is concerned with the transmission of
flame across pile fabrics.
To determine the durability of any flame resistant treatments
the following tests are repeated after washing, drying
cleaning or leaching.
(The lower speed of propagation of flame over wool, silk, acetate fabrics is
due to the fact that they melt and drip during burning)
Recent Progress in flammability test

15. Special chemical finishing processes have been developed
which reduce the flammability of the treated fabrics. Some
recent developments have led to the introduction of such
finishes as Proban, Antiflamm, and Lifeguard. Such finishes
should have following properties:
1) Be permanent and not disappear at the first laundering
or cleaning.
2) Be non-toxic .
3) Be non-irritant to the skin
4) Leave the handle and the other desirable properties
unaffected.
Flame proofing and Flame resistant finishing

16. Ref. Book : JE BOOTH