-Bus report has been prepared

Jot Information and record

purposes and is not to be referenced

?n any

° ; -ri

NATIONAL BUREAU OF STANDARDS REPORT a 6885 Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) - on October 9, 201 5.

SURFACE FLAMMABILITY

of

FIRE RETARDANT AND CONVENTIONAL PAINT

ASSEMBLIES

by

J. J. Loftus

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL

NIBS PROJECT

BUREAU OF STANDARDS REPORT

NBS REPORT

1002-12-10120 June 27, I960 6885

SURFACE FLAMMABILITY

of

FIRE RETARDANT AND CONVENTIONAL PAINT

ASSEMBLIES

by

Jo J, Loftus

IMPORTANT NOTICE

NATIONAL BUREAU OF STANDARDS REPORTS are usually preliminary or progress accounting documents

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to reproduce additional copies for its own use.

U. S. DEPARTMENT OF COMMERCE

SURFACE FLAMMABILITY

of

FIRE RETARDANT AND CONVENTIONAL PAINT

ASSEMBLIES

by

J. J. Loftus

ABSTRACT

Surface flammability measurements using the

radiant panel test method have been made on three

conventional paints and five fire-retardant coatings

applied to four common combustible interior linings.

With the exception of one intumescent type fireretardant system, the performance of conventional

paints of the flat alkyd and latex emulsion types

tested, was comparable to that of the fire-retardant

coatings, at the same coverage rate. It is shown

that the fire retardant effectiveness of coatings

depends to a very large extent upon the coverage

rate, the type and density of the substrate material

and the application of overcoats. Of the four substrates tested, tempered hardboard exhibited the

lowest coefficients of variation and is considered

to be a suitable choice as a standard substrate

for measuring the fire-retardant effectiveness of

paints and other thin surface coating materials

intended to reduce the flammability of combustible

interior linings.

INTRODUCTION

The results of a previous study [l] have shown that

paints and other thin coverings applied to a flammable base

material can provide a new surface of substantially lower

flammability than that of the untreated base. Although with

coatings of more than 0 . 05-inch thickness the particular base

material used did not appreciably affect the flame spread index

it appeared that with thinner finish coatings the base material

had an important bearing on the flame spread results obtained.

2

In another study, in which non-flammable substrates were

used, it was found that the flame spread index increased with

increasing thickness of a paint coating applied on steel sheet.

For example, the flame spread index of a No. 18 gage, red lead

primed steel sheet had values of 1, 7? 69? and 110 for oilbase paint coatings of 5? 10, 15 ? and 20 mils, respectively.

An assembly of a 10 mil coating of the same paint applied to

1/8 inch thick asbestos-cement board had a flame spread index

of 2. Thus it appears evident that the flame spread behavior

of coatings applied to either flammable or non-flammable substrates depends not only on the type and thickness of the

paint film but also on the characteristics of the substrate.

In choosing a standard substrate for surface flammability

evaluation of paints, the use of an incombustible material such

as asbestos cement board would obviously restrict the range of

measurements. A study was therefore undertaken for evaluating

the surface flammability of a number of conventional paints

and fire retardant coatings as applied to four common combustible interior lining materials. The primary objects of the

investigation were to evaluate those characteristics of the

substrate material which were important in surface flammability

measurements on painted assemblies and to select, if possible,

one substrate as a standard for paint flammability measurements.

2. MATERIALS

Five fire retardant and three conventional paint finishes

were applied to each of four substrates; paper wallboard, plywood, fiberboard and tempered hardboard. The coatings were

applied to the smooth finished side of each substrate. Table 1

lists and briefly describes the substrates and Table 2 gives

the schedule employed in the preparation of the test assemblies.

With the exception of coating systems 7? 7a? and 7b, the

coverage rate employed in the preparation of the assemblies

was 125 ft 2 /gal (two coats at 250 ft 2/gal) . This rate, unusually

heavy for normal paints, was fairly represnetative of the

coverage rates commonly used and recommended for fire retardant

coatings. The paints consisted of two alkyd flat paints (Nos. 3

and 8), one latex water emulsion paint (No. 6), four fire

retardant paints (Nos. 1, 2, 4, and 5)? and one coating system

consiting of an intumescent fire retardant undercoat plus top

coat (No . 7)
.
- 3

-

3- SAMPLE PREPARATION

The first step in preparing the test assemblies was to

coat the substrate boards, at 4-50 ft^/gal coverage, with a white pigmented primer-sealer conforming to Federal Specification TT-P-56. After 72 hours the primed substrates, with

the exception of those reserved for coatings 7, 7a and 7b,

received two coats of paint at 250 ft2/gal coverage each,

allowing 72 hours between coats. Sample 7 received one coat

of flat interior fire retardant paint and one top coat of an

interior gloss fire retardant paint, at the same 250 ft^/gal

coverage. Sample 7a received only one coat of the flat interior fire retardant paint at a 350 ft^/gal coverage. Sample

7b was coated with the same paints as Sample 7 but with

coverages of 350 ft2/gal and 500 ft^/gal for the undercoat

and top coat, respectively. The coatings on samples 7, 7a

and 7b were purposely varied to study the effect on flame

spread behavior of different rates of coverage of the same

paints

After the application of the finish materials, the

assemblies were dried for not less than 72 hours and then cut

to produce five specimens, each 6 by 18 inches. The specimens

were then dried in an oven at 160°F for 24 hours and again

conditioned, in a room maintained at 73°F and 50 per cent

relative humidity, for not less than one week prior to testing.

4. METHOD OF TEST

Surface flammability measurements were made using the

radiant panel flame spread test method as described in detail

by Robertson, Gross and Loftus [2]. The equipment and test

procedure are further described in an Interim Federal Standard [.3 ]•

5. RESULTS

Four replicate tests were run on each test assembly.

The individual and averaged flame spread indices and the

coefficients of variation are listed in Table 3* The weight

of the smoke deposit listed is the average for replicate tests.

Intumescence was exhibited by paints 1, 7a, and 7b.

Paints 2, 4, 6, and 7 blistered, whereas the conventional paints

3 and 8 did not blister or intumesce. Paint 5 flaked off from

the substrate during test.
f

,
Blister and intumescent formations were responsible for

a wide variation in flame spread indices for the paints which

exhibited these properties. The conventional paints 3 and 8

showed better reproducibility between replicate tests than

those which blistered or intumesced.

Of the four substrates used, the plywood and the hardboard showed the widest range in flame spread index values,

affording good opportunity for discrimination between coatings.

The hardboard values, however, had lower coefficients of

variation than the plywood values, and much lower than those

obtained with the other two substrates. Considering the results

obtained with the hardboard, the conventional paints 3? 6, and

8 appeared to be comparable to the fire retardant paints 1, 4,

and 5) when applied to this substrate at the same coverage rate

of 125 ft^/gal. The intumescent fire retardant coating, 7a,

showed both the lowest flame spread index and the lowest smoke

deposit value of any of the coatings.

For the coverage rate employed in this investigation,

(125 ft^/gal) the average flame spread index was found to be

related to the density of the substrate material. This is shown

in the lower curve in Figure 1. The upper line indicates a similar effect for two conventional paints (latex and alkyd

flat) applied at a coverage of 370 ft^/gal in a previous study.

Although the lower curve includes values for fire retardant as

well as conventional paints, the two curves also indicate the

effect of rate of coverage (and therefore coating thickness)

on the flame spread index. A more direct demonstration of this

effect is given in Table 4 which lists the flame spread indices for the two conventional paint types at the two coverage

rates and on two substrate materials.

5-1 STATISTICAL ANALYSIS

An analysis of the data was made to provide a statistical

measure of variability. Particular attention was directed

toward evaluation of the four substrate materials both from the

standpoint of (a) selection of a standard material for paints

and other liquid coatings and (b) interpretation of previous

and subsequent flame spread data on coated assemblies employing

a variety of substrates.

The analysis showed that the wallboard and fiberboard

substrates gave a much more consistant behavior of dispersion

about the mean than the plywood and hardboard substrates.
,
- 5 -

The performance of the wallboard was found to he significantly

better than the fiberboard when compared according to the

following criteria:

a. Better discriminating power, as evidenced by a greater range of flame spread index values for the

eight coating materials,

b. More consistent dispersion behavior, as evidenced

by a smaller range in coefficient of variation, and

c. Consistency in the ranking of the coating materials

with respect to the rankings using other substrates.

Further inspection of the results with the hardboard

reveals the following facts. Although coated hardboard assemblies did not show as good' conformity to the assumed proportionality between the standard deviation and the mean flame spread

index as those of wallboard and fiberboard, they did exhibit:

a. A substantial range of flame spread index values

for the eight coating materials, and

b. The lowest coefficients of variation.

It should be noted that considerable variation was observed

in the rankings of the eight coatings on the four substrates.

In addition, the coefficients of variation were considerably

higher than those obtained in an earlier investigation of

conventional paints on the same or similar substrates [l].

This is not unreasonalbe when consideration is given to the

special types of coatings and rates of application employed here.

In view of this, too much weight should not be placed upon the

relative rankings of the coating materials. The fact that the

coefficient of variation is consistently lower when using a particular substrate is considered to be of much more significance from the standpoint of selection of a standard substrate

material. Inasmuch as the hardboard did result in the lowest

coefficients of variation and provided a substantial range of

flame spread index values for the coating materials tested,

its choice as a standard substrate is indicated.

6. CONCLUSIONS

On the basis of the work reported, the following conclusions seem justified:

1. Tempered hardboard may be considered a suitable

choice as a standard substrate for evaluating the fire retardant effectiveness of paints and other thin surface

coatings. Of the substrates tested, it gave results with

the lowest coefficients of variation, and it provided a substantial range in flame spread index values.

2. The fire retardant effectiveness of paints and

other coatings is highly dependent upon the coverage rate of

application and the type and density of the substrate material

as well as the coating composition and the undercoat-overcoat

combination employed.

3. In general, conventional paints of the flat alkyd

and latex emulsion types tested, when applied at the heavy

rate common for fire retardant coatings, appear to have flame

spread indices comparable to those of typical fire retardant

coatings. However, one intumescent fire retardant coating

showed a flame spread index significantly lower than that of

any other covering tested.

7. ACKNOWLEDGEMENTS

Mr. Neil B. Garlock of the National Paint, Varnish and

Lacquer Association took a strong interest in the work and

kindly provided all the paint coating systems. Mr. Harry Ku

of the National Bureau of Standards, Statistical Engineering

Section, made the statistical analysis.

USCOMM-NBS-DC
*

.
- 7

-

[1] D. Gross and J. J. Loftus, Flame Spread Properties of

Building Finish Materials, Am. Soc. Testing Mats

Bui. No. 230, 56-60, May 1958.

[2] A. F. Robertson, D. Gross and J. J. Loftus, A Method

for Measuring Surface Flammability of Materials Using

a Radiant Energy Source, Proceedings, Am. Soc. Testing

Mats . , 16 ? ( 1956)

[ 3 ] Interim Federal Standard No. OOI36 (Com-NBS) July 31? 1959*
-

'
Table 1

Substrate Materials

Symbol Substrate

A Paper Wallboard - Factory Finished

one side

B Plywood - Douglas Fir, interior

grade

C Fiberboard - Building Board, Class D

finish

Thickness Density

in. lb/cu ft

3/16 35.0

1/4- 39-0

1/2 19 A

D Hardboard - Tempered 1/4 67.6

Table

2.

Coating

Schedule o 0 P 0 0 0 P o P P 0 0 •rH 1—1 P p 0 0 o O ft VO 0 0

•H z •H 0 • •H o 0 0 0 0 0 VO P 0 o o Ph P Ph i—1 a p 0 O ft 0 0 0 0 •H •H p

-p P •rH P a

pp

p

p P 0 p 0 0 0 tn 0 ft 0 0 0 •H 0 Ph 0 •H o p 0 0 p ft P p i 0 0 P Ph o P P P z 0 p 0 •H P 0 Ctf 0 0 p 0 0 p i 0 o- O- 0

CD

p 1 1 P 0 o 0 0 p P 1 1 Q 0 pL, 0 ft o ft 0 0 0 0 0 (ft ft ft 1 p o P 0 0

ft

p 0 p o P 0 t>* 0 0 0 •H 0 0 0 0 >> P P P p •H 0 p p P a a ft

j: 1 1 •H z 0 0 0 0 o •H 0 0 rH

ft <=tf Ph ft Ph P P EH <p CO CO 1—1 0 0 VO O o

ft \ Va o

Ctf AJ 1 i l 1 1 1 CM 1 Va !

(ft P

<P

ft 0 o -p • ctf 1 i 1 1 1 1 1 1 1 1 1 1 o o s o

-P Va Va

•H 0 On On c

VO 1 i l 1 1 1 • 1 * 1 Pi \ 1 1 1 CD ft 1 1 I 1 Q 1 1 1 1 0 0 VO

ft \ o o O o o o O o O o

ctf OJ VA VA Va Va Va Va Va Va Va Va

ft P CM CM CM CM CM CM CM co co CM ft

Cm 0 O p•

ctf CM CM CM CM CM CM 1

1—

1 1 CM o OOP 0 0 o 0 P

ft 1—1 0 •rH z 0 o P p o o P O

-P ft 0 p rH

•H •H 0 OA co CM vO vO VA co CO co 1 1

ctf CO VO • • • ® • • * • * Ph 0 \ 1 1 CM CM O co 1 1 CM CM CM CM 0 ft 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Q 1 1

tuo

a 0 0p 0 ft

ft 0 1 1 CM CO Va nO [>- O- co

ctf O CO o

Note: A

primer-sealer

(10.8

lb/gal

density)

was

applied

to

all

substrates,

ata

coverage

of

ft 2

/gal,

before

coating.

FLAME

SPREAD

INDEX

OF

COATED

ASSEMBLIES

Coating

System

O O' O

+ coo X xOOH oncoj-oo CM nO 1— ONJ- XX x_t 0 O XlAj- X ip CP co Jr no xj- J- co CM co H X it N 1—1 1—1 r— H Cp XXCMCM CM 1—

J- O X lo O' >-* O

,0 lr\0 O CM On co 1—

NXNCM nj- h O H Xcc OnnO 1— ONXJ- 0 X pt H N c0 OO 1—1 ON CM 1— ON 1—1 IP

1—1 pt C\J CM cc X CM IP IP CM 0 * • • • • *• •

f

*• N CMCMOO H nO H J-HHCM CM 1—1 1— P~ O O 1— 1—1

1—1 1— CM 1—I CM 1—

H XH

CO IN- UA N

1—

1—1 IN Pt CM

1 XXJ- X) J- CM XX CM CM ON ON C\ X N O CM ON X H XX CM CM OJ-cc N 1 1—1 NO 1—1

1—1 X H H O CM H IPX J1—1 CM X IP 1—1 CP CM i—| O O On CM H H CMX X O CM XJ- X X IPX CM OnNNJ- CM IP CP X J- OXJ- X co Cpx cOH J-x XH H O XlPXX J- CM

/* N 1—1 XC\l nO X X O' H • • • CMX CM cc OnCp 1—

|

0 OXX J- CM CM OJ- HX N0 O 1—1 CM CMX 1 XN4-

CP H H CP 1—1 CM 1—1 HU H N XXX 1 X

0 '"N 0 X O

0 NO CM X On Ip X

O # * —

. 1—1 « pq H COJ- N J- CM CM NJr j-x O J H CM NON NO X 1—1 1—1 '—

XX ON 1 NCpX

Jr XX H CM cOnO \0 J- XCM X X CM X CM X H N XXX 1 X

1—l 1—1 0 X

1—1 0 0

0 1—1 J- 0 N 0 O

• 0 • X * O • Jr NX CM O nQ 1—

|

0 CPX NO NX i—

0 CM NNX N CM O XtxxipX IPCP cO 0 1—1 cO |—|

|—

|

CM ITN 0 CM CM CM CM CM 0 1—1 X X XCM CM CM CM H

CD [3 X 0

P !> •H 0

0 CP 1—

N (in O w CP

Ph . P • • • CPXJ" CM =ONH CMJ- J- H CpCPH JrJ- On CM NX 1—

NlPO on IPH-t

cm xcpxn p- cO NX OMo N CM O X CM H ON Q XX ON ip N CM pq 0 0

CD 10 0 1—X 1—

X 1 1 X • -p * 0 • 0 • 0 J-vOOIT j- CO CM 0 X XXX H CPX 0 H Cp CM CM ipIPX 0 X CM N CM OnOnJ1—1 0 X CMX CM -t J- 0 1—l_d" 1—

CMX X CM On 1—| 1—

|

XH X 4- CM CM CM CM X

-P x 0 H 0

0 w X X

X X p P

P p co CO

CO rv CO 0 P) rs rs X 0 X O 0 0

0 H W 0 H W X O X O 0 p> a x -p a 0 H PC (1) *H W

0 0 0 0 x x a 0 x a M H • 1—1 'H * 0 0 0 0

0 -P 0 -P H H » H H * X 0 H d 0'H 0 X 0 X

0 > 0 0 > 0 X 0 H 0 0 H

0 O 0 O 0 >. 0 0 > 0

0 Ph P 0 H P 0 O 0 O

Ph O 0 CL O 0 0 Ph P 0 Ph P

co q CO Q Ph O 0 Ph O 0

x > -P CO Q (O Q

0 p 0 0 0 0 X X

a 0 44 a 0 Li 0 0 0 0 0 0

0 H 0 0 H O a 0 44 8 0 44 HOE h 0 a 0 H O 0 *H O

IP H CO fn H X h 0 a rh ° a

Ch Ph x h co fxh <H CO 0 Ph 0 0 Ph 0 Ph Ph -

0 0 0 0 0 0 0 Ph 0 0 Ph 0 0O0 0O0 0 0 0 0 0 0

S O S| S O s 0O0 0O0

S O S SuS

Note:

Numbers

in

parentheses

are

mean

flame

spread

indices

of

uncoated

substrates.

Table 9-. Flame Spread Index of Painted Substrates

Substrate

Coverage Fiberboard Plywood

Paint Type Rate (19.9- lb/ft3) (39*0 lb/ft3)

f

t

2/gal

Alkyd Flat 125 10* 3

i+*

n n 370 ko 69

Latex 125 15 9-6

!! 370 66 93

* Average for two paints

Figure

1.

EFFECT

OF

SUBSTRATE

DENSITY

ON

FLAME

SPREAD

INDEX

co -p

•H

cti CO Ph g

CD rH -P

cd co C t>> O co •H

-P tU3 £ £

CD *P > -p £ cd o o

o o

c\i co P p

o o p p

txO tuO > >

cd cd

CD 0)

p p

(D CD P ^ P O

xepuj peards atuex^ aSejaAy

Density

of

wood

base

substrate,

lb/ft^

U jS. department of commerce

Frederick H. Mueller, Secretary NATIONAL BUREAU OF STANDARDS

A. V, Aslin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

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its title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover, WASHINGTON, D.C,

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a • »

'

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)

*

I