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NATIONAL BUREAU OF STANDARDS REPORT

NBS Project NBS Report

1002-^-3-1029 January 30, 1952 1422

Fire Research Infomoiion Services

hanonai Bureau of StondoMs

Bldg. 224, Rm. A252

Washington, D.C. 20234

TESTS ON FUMMABLE SWEATERS

by

Marjorie V/, Sandholzer, Chemist

Fire Prevention Section

Building Technology Division

Requested by

D. C, Engineer Department

for

Fire Marshal

District of Columbia

<^BS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

This report is issu

production in any f writing is obtained

Washington 25, D. C

Approved for public release by the • T-»- n TWT • , ation, reprinting, or re- Director of the National Institute of bited unless permission in Standards and Technology (NIST) )nal Bureau of Standards, on October 9, 2015.

TESTS ON FLAMMABLE SWEATERS 1.

INTRODUCTION

The Fire Marshal of the District of Columbia has requested that certain sweaters, which have caused current

widespread public concern because of extreme flammability,

be inspected and tested to determine their burning characteristics and flammability as compared with other materials

commonly used in clothing,

2,

TEST MATERIAL

For test purposes, the Fire Marshal submitted a sweater

set consisting of a sleeveless, slip-over style sweater and

a long-sleeved jacket sweater with front button closure.

Both sweaters v/ere made of a maroon tricot knit rayon with

brushed outer surface, and were trimmed by front and neck

bands of the same material in gray. The long-sleeved

sweater bore a label inscribed ’’Designed for Comfort,

Genuine Embassy Sportsv/ear”, No further identification

appeared on the sv/eaters or the box in which they were received,

3.

TESTS AND RESULTS

3,1 Composition of the Fabric

Investigation by the Testing and Specifications Section of the Bureau determined that the fabric in the

sv/eaters had been knit entirely of delustered viscose rayon.

The delustering process is a common treatment ana leaves

a small amount of the delustering agent (frequently titanium dioxide) in the fibers, but there was no evidence of

other special finishing materials present in the cloth.

The outer surface of the fabric had been brushed to a soft,

fuzzy texture similar to that of a woolen blanket while

the inner surface had been left with the smooth finish of

the knitted threads.

- 2-

3.2 Flammability Tests

Samples of the material were subjected to three

different flammability tests, an inclined test developed

by the American Association of Textile Chemists and

Colorists, a horizontal test developed by the National

Bureau of Standards, and a vertical test developed by the

office of the California State Fire Marshal. No one of

these tests has yet been accepted as an established standard, though both the Inclined test and the horizontal test

were included as criteria in Federal legislation proposed

in 19^9. However, since the inclined test, which is fully

described in the 1951 Yearbook of the A.A.T.C.C., has had

the widest usage among textile interests, the major part

of the present testing was done by that method. The horizontal test equipment and procedure are described in

National Bureau of Standards Circular C455 on “Flameproofing of Textiles”, and mimeographed material describing the

ertlcal test is available from the office of the California

State Fire Marshal.

(a) Inclined Test

A 2 by 6 in. sample of the material is clamped in a

specij^en holder which leaves a 1 by 6 in. strip of the

fabric exposed, and is conditioned at 105° G, After

cooling in a desiccator over anhydrous calcium chloride,

the mounted sample is supported at an angle of degrees

in the test cabinet, and the flame from a microburner is

applied for one second to the surface of the fabric near

the lower end of the sample. The time required for the

flame to progress upward over a five inch length of the

sample is recorded by an automatically operated stopwatch.

It is suggested by the A.A.T.C.C, that a fabric for which

the recorded time of flame spread, based on an average of

five samples, is less than four seconds should be considered

dangerously flammable.

Tests were made on the brushed surface of the sweater

material, both in its original condition and after being

subjected to normal dry cleaning in perchi or ethylene at

the National Institute of Cleaning and Dyeing, Silver Spring,

Md, The average flame spread times obtained were 1.2 seconds and 1,1 seconds respectively, indicating that the dry

cleaning had no appreciable effect on the flammability,

- 3-

though it had somewhat altered the hand of the fabric.

In every test the body of the fabric v/as ignited from

the surface flames and burning continued until the entire material was destroyed.

This extremely rapid spread of flames over the

fabric closely paralleled previous experience with

heavily napped or fleeced fabrics both of rayon and

of cotton. Tests have been made on fabrics with a

long, fine rayon pile (such as the material in the

cowbov suit chaps whjch caused a number of fatal accidents), on brushed rayons, on highly fleeced cottons,

and on tufted cottons, which burned in a manner similar

to that of the present sweater material, and gave average flame spread times ranging from 1.1 to 2.0 seconds

in the inclined test. The evidence strongly indicates

that the type of fabrication is a more decisive factor in

producing unusual flammability than the particular combustible fiber used, and that fabrics of any cellulosic

fiber may become unusually hazardous if the pile is made

especially long and fine or the siarface is very heavily

fleeced or napped. On such surfaces the myriad fine

fibers, raised so that there is free access of air among

them, present ideal conditions for instant ignition and

rapid spread of flame.

Further evidence of the importance of surface condition in relation to flammability was provided by an additional test, made on the sweater material with the fabric

reversed so that the igniting flame was applied to the

smooth back or inner surface. In this position, a four

second application of the microflame was necessary to

ignite the fabric, and the time of flame spread over the

five inch length was 22 seconds. Since the fabric was

knit of the same rayon fibers throughout, the difference

was apparently in the surface condition.

(b) Horizontal Test

A 4 by 12 1/2 in. sample of the material, after

conditioning at 60° C, is placed in a specimen holder

which leaves a 2 by 12 1/2 in. strip of the fabric exposed, and the holder is supported in a horizontal position in the test cabinet. The exposed edge of one end of

the sample is ignited by a low gas flame or match flame and,

after 1 1/2 inches of the sample have burned, the time required for the flames to progress over the next ten inches

is recorded with a manually operated stopwatch. From

the recorded time, the rate of flame travel in inches

per minute is calculated. The proposed Federal legislation which referred to this test, defined as highly

flammable a fabric which shows a rate of flame spread

greater than 60 inches per minute, based on the average

of five tests.

Two samples of the sweater material in its original

condition were tested, and an average rate of flame

spread of 270 inches per minute was obtained. This

value also compared closely with flame spread rates previously determined by the same method on other highly

flammable fabrics,

(c) Vertical Test

A 6 by 8 in, sample of the material is clamped

between two vertically mounted, convexly curved metal

plates which have a 2 by 7 in, spiral opening or window

cut diagonally across the center. Thus, the exposed test

area of the vertically held sample is 2 by 7 inches and

spirals upward at an angle of about 45 degrees. The

fabric is ignited by a microflame applied to the surface

at the lov/er end of the test area, and the time required

for the flames to progress over a designated five inch

length is recorded by an automatically operated stopwatch.

Performance requirements which might suitably define a

highly flammable fabric have not been suggested, but,

since most fabrics appear to burn somewhat more rapidly

in this test than in the inclined test, a time limit

slightly lower than the four seconds proposed for the inclined test would perhaps be reasonable.

Four samples of the sweater material, in its original

condition, were tested and showed an average flame spread

time of 0,7 second. Though our experience with this test

has not been as extensive as with the other two, it has

included some heavily fleeced cottons which had flame spread

times comparable to the value obtained for the sweater fabric.

3,3 Ignition by Cigarettes

Six attempts to ignite the sweater material by pressing

a lighted cigarette into the brushed surface, failed to
J ):

)

)
-5

produce flames or continuing glow in any instance. Glow

usually appeared around the edges of the hole burned by

the cigarette, but was always self -extinguished in a few

seconds.

In a further test, a burning cigarette was buried

within a deep fold of the fabric and left undisturbed

until all smoke and evidence of burning had ceased.

Examination of the fabric after the cigarette had

burned out, showed that the char did not extend beyond

the area in contact with the cigarette.

h, SUliMARY

The fabric used in the sweaters was knit of delustered viscose rayon, with the inner surface left

smooth and the outer surface brushed to a soft, fuzzy

texture resembling that of a woolen blanket.

In flammability tests the material compared closely,

in both manner and rate of flame spread, with highly

flammable napped and pile fabrics previously tested.

These have included cottons as well as rayons and there is

strong evidence that the type of fabrication of a cellulosic material, particularly of the surface, is a more

decisive factor in pi'-oducing extreme flammability than is

its fiber composition. Specific evidence that the high

flammability shown by the sweater material resulted primarily from the brushing of the outer surface was provided

by a test which demonstrated that the smooth back of the

fabric did not ignite or spread flame with unusual rapidity.

The sweater material was not ignited by application

of a burning cigarette, either on a single thickness of

the fabric or v/ithin a pocket formed by deep folds of the

cloth.

No, TG 10210-1808 JFP3096

G/863>+