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fTrrmy hulJitciriTOfb NATIONAL BUREAU OF STANDARDS REPORT

8365

EFFECT OF MOISTURE ON SURFACE FLAMMABILITY OF

COATED AND UNCOATED CELLULOSIC MATERIALS

by

T. G. Lee, J. J. Loftus, D. Gross

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring

maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. Its responsibilities include development and maintenance of the national stand- ards of measurement, and the provisions of means for making measurements consistent with those standards; determination of physical constants and properties of materials; development of methods

for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; assistance

to industry, business, and consumers in the development and acceptance of commercial standards and

simplified trade practice recommendations; administration of programs in cooperation with United

States business groups and standards organizations for the development of international standards of

practice: and maintenance of a clearinghouse for the collection and dissemination of scientific, technical. and engineering information. The scope of the Bureau’s activities is suggested in the following

listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials. Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere

and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics.

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Transport Systems. Office of Technical Services. Office of Weights and Measures. Office of Engineering Standards. Office of Industrial Services.

* NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado. ** Located at Boulder, Colorado.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1002-11-10427 June 1, 1964 8365

EFFECT OF MOISTURE ON SURFACE FLAMMABILITY OF

COATED AND UNCOATED CELLULOSIC MATERIALS

by

T. G. Lee, J. J. Loftus, D. Gross

for

Office of Civil Defense

Contract OCD-OS-62-89

NATIONAL BUREAU OF S

for use within the Government

and review. For this reason, 1 whole or in part, is not auth Bureau of Standards, Washing

the Report has been specifical

IMPORTANT NOTICE

ress accounting documents intended Approved forpublic release by the

Director of the National Institute of he Office of the Director, National Standards and Technology (NIST) on October 9, 2015.

, by the Government agency for which

copies tor its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Effect of Moisture on Surface Flammability of

Coated and Uncoated Cellulosic Materials

T. G. Lee, J. J. Loftus, D. Gross

ABSTRACT

A method is described for the rapid in situ determination of the "thermal inertia for surface heating" (kpc product)

of materials using a sensitive infrared detector. Experimental

measurements are given of the effect of moisture content on

the thermal inertia and on the surface flammability of selected

cellulosic materials conditioned to equilibrium at relative

humidities ranging from 0 to 99 percent. It is shown that

(1) the thermal inertia of uncoated hardboard and fiberboard

material can be represented as a linear function of its

moisture content, (2) that if the appropriate thermal properties are used, the flame-spread factor is Inversely proportional

to thermal inertia, and (3) the unbroken surface film of coated

materials results in a lower ignition sensitivity than that

predicted on the basis of thermal inertia.

1„ Introduction

The flame-spread index resulting from the performance of a standardized

flame-spread test on a material [1, 2] has been shown to be composed of two

multiplicative components: (a) a flame-spread factor representing the ignition

sensitivity of the material, and (b) a heat evolution factor representing the

maximum rate of heat generation [3]. A recent study of surface flame propagation on cellulosic materials showed that, except for very thin veneers, the

flame spread factor was inversely proportional to the kpc product, the

"thermal inertia for surface heating" [4], Here k, p, and c are the thermal

conductivity, density and heat capacity, respective ly „ These results

appeared to support a simple concept for the spread of flame on the surfaces

of cellulosic materials exposed to thermal radiation, namely that flame

propagation' consists of progressive ignition of the solid when a characteristic surface temperature is reached.

The correlation between the flame spread factor and the kpc product

was based upon a measured value for p and individual values of k and c obtained from the handbook . The present paper describes a simple method for

determining the thermal inertia of a material from a recording of its sur- face temperature history during surface irradiation* This technique was originally used for measurement of rapid changes of human skin temperature

[5] and is particularly attractive for in situ measurements on building

materials, including wood and other inhomogeneous materials.

Because of the strong influence which moisture content has upon

surface flammability, a study was made of the effect of moisture content on

(a) the thermal inertia, and (b) the flame spread behavior of selected

cellulosic materials. The main objective of this study was to evaluate the

overall effect of moisture content and to illustrate the importance of the

thermal inertia property on surface flammability without consideration of

the effects of diffusion and phase change of moisture.

2. Theory

The surface temperature rise 0

g of a homogeneous semi-infinite solid

which is inert, opaque and totally absorbing, subjected to constant

irradiance X on the surface and losing heat by Newtonian cooling at the

surface is given by the relation [6]:
2

6

s =5 t 1 t? . ... e erfc b ( 1 )

where b = H

kpc , erfc is the complementary error function,

H is the surface heat loss coefficient,

t is time , and k,p and c are the thermal conductivity,

density and heat capacity, respectively. It is assumed that heat flow

is one -dimensional and that the thermal properties, which may represent

effective values for moist solids, are independent of temperature.

For sufficiently short times or for low values of the heat transfer

coefficient (see Appendix 1), an approximation to the surface temperature

rise is the more common expression:

0 = 21 ( 2 ) s / rrkpc

To account for specimen absorptivity less than unity, it is only necessary

to prepare all surfaces in a similar manner and to consider the "absorbed"

irradiance I = ryl , where ot is surface absorptivity and I is the incident

surface irradiance. While the assumption of opacity is s§tisfactory for

many materials, natural wood is considered partly diathermanous . It has

been found, however, that blackened wood surfaces are essentially opaque [7].

Equation (2) may be rearranged to obtain:

4 ft / o \ kpc = ^5 (3a)

s

It is sometimes desirable to supply incident radiation periodically

in order to eliminate energy reflected directly from the irradiated surface

to the detector when there is a spectral bandwidth overlap. In this case,

a time factor f, which represents the ratio of irradiation time to total

time, must be introduced. Using this factor, a simplified expression may

be written for the surface temperature rise (see Appendix 2) of an inert,

opaque semi-infinite solid subject to periodic application of a constant

effective irradiance with no heat losses:

4f® I

s

t

s

kpc = (3b)
-3-

Detennination of kpc, the thermal inertia for surface heating,

simply requires (a) a sufficiently rapid recording of the temperature

rise history of a blackened surface and (b) knowledge of the magnitude

of the effective irradiance, and its application period, when appropriate.

For measurement times exceeding those listed in Table 4, knowledge of the

surface heat loss coefficient is also required, and the value of kpc is

b

2 then obtained from equation (1) by using the plot of (1 - e erfc b)

versus b.

3. Experimental Method

3.1 Surface Temperature

A non-contact radiometric technique was used successfully by Hardy

and his associates [5, 8] for the rapid measurement of the surface

temperature of the human skin and for determination of its thermal

properties. This technique involves comparison of the infrared radiation

from the object with that from a blackbody source of known temperature.

The experimental arrangement for measuring surface temperatures

used in the present study is shown schematically in Fig. 1. The source

of radiant heat was a 300 watt projection lamp mounted in a ventilated

housing. A line-voltage regulator and autotransformer supplied power

to the lamp and permitted close control of the radiant intensity. The

radiation from the lamp passed through a 2 micron low pass filter and

impinged on a circular area, 8 cm in diameter of the specimen. The

irradiation, which was typically of the order of 0.02 Watts per square

centimeter (w/citP), was found to be uniform to within ±3 percent on a circular area 2 cm in diameter with a gradual fall off to the edges of

the irradiated area. An opaque shutter mounted between the lamp and the

specimen was used to control exposure duration.

The radiometer used for indicating temperature changes was a com- mercial infrared "radiation thermometer" containing a thermistor bolometer

detector with high sensitivity through the spectral bandwidth of the

instrument. The instrument employed germanium lens optics giving a 3-degree

field of view and a spectral response from 2 to 22 microns. The system

response time was 50 milliseconds and the sensitivity under the conditions

of use was on the order of 0.1°C. The radibmeter was focused on a circular

area of about 1.2 cm in diameter in the center of the irradiated area where the effect of lateral heat conduction was negligibly small.

In operation, a motor-driven reflective chopper wheel, within the

radiometer, interrupted radiation from the target and reflected radiation

from a controlled internal blackbody on to the detector at a rate of 90

cycles per second. Thus, a 90 cps signal was generated whose amplitude

was proportional to the difference in radiance betwen the target and the

internal source. This signal was amplified, rectified and recorded.
4

The radiometer was calibrated at the start and end of each day by

substituting for the specimen a large copper block with a black” coate d

cylindrical cavity. The temperature of the block was raised by means

of an imbedded electrical heater and monitored by means of a precision

thermometer also imbedded in the block, A series of measurements of

detector output readings and copper block temperatures was made over the

operating temperature range (20° to 30°G) . Since the same flat black

coating was used on the copper block cavity as on the test specimens,

the calibration provided a means for measuring the surface temperature

of the specimen.

For applications in which energy reflected from the irradiated

surface to the detector may introduce a spurious response (i.e., when

the spectral bandpass of the detector overlaps the wavelength region of

the incident radiation) , a second chopper wheel can be placed so as to

periodically interrupt radiation incident on the specimen. Exact out-ofphase synchoronization with the similarly interrupted target radiation

would thus avoid the receipt of any reflected energy. A synchronous

chopping arrangement of this sort was employed for measuring the thermal

inertia of human skin during exposure to far infrared radiation [8].

3.2 Flame Spread

The apparatus and experimental procedure for performing a standardized

flame-spread test has been described in detail [2, 3], The test requires

a 6- by 18-in. specimen facing and inclined 30 degrees to a verticallymounted, gas-fired radiant panel. Ignition was initiated at the upper

edge of the test specimen and observations were made of the progress of the

flame front down the specimen surface as well as of the temperature rise

of thermocouples in a stack supported above the specimen. The test duration

was 15 minutes, or until sustained flame propagated downward the entire

18-in. length of the specimen, whichever time was less. The flame-spread

index I was computed as the product of the flame-spread factor F and the

heat evolution Q e or I = F Q

s s (4)

where F = l + —

s t. + —— + —— + ——- +

£ - £ £ — fc £ «. £ £ — £ 6 3 9 6 12 9 15 12

(5)

The symbols t^ . . . t ^

correspond to the times in minutes from

specimen exposure until arrival of the flame front at a position 3 , . . 15 inches, respectively, along the length of the specimen. The heat

evolution Q is proportional to the observed maximum temperature rise of

the stack thermocouples.
5

3.3 Specimen Preparation

Although values of thermal inertia of other types of cellulosic

materials have been determined by this method, the present study on

the effect of moisture was confined to only two materials - cellulose

fiberboard and tempered hardboard. These were chosen for the initial

study in order to minimize the effect of structure inhomogeneity which

is characteristic of natural woods. Table 1 lists the thickness,

density, humidity condition and corresponding equilibrium moisture content

for each specimen. The relative humidity-equilibrium moisture content

relationships are shown graphically in Fig. 2.

A test specimen was prepared by applying a flat black enamel to a circular area of 7.5 cm diameter near its center. This coating was spray-applied and contained approximately 8% pigment, principally carbon

black, and 8% non-volatile modified styrene vehicle. The normal paint

coating, when dry, weighed 0.002 g/cn? and this produced a surface of

high absorptivity (>0.94) to visible and near- inf rared radiation. The

6 by 18 in. specimen was then dried in an oven at 105°C for 24 hrs,

allowed to cool in a desiccator, weighed, and then placed in a series

of controlled humidity chatnber to reach constant weight.

The humidity chambers (Table 2) consisted of (a) moisture- tight

drums containing either calcium chloride or various saturated salt

solutions [9] for maintaining a series of specified relative humidities,

(b) a commercial room air conditioning system for maintaining 50±5 percent

relative humidity (rh) and (c) a commercial controlled humidity chamber

especially suitable for controlling humidity in the 80 to 100 percent

rh range. The relative humidity in all chambers was monitored by means

of commercial moisture-sensitive resistance elements calibrated to ± 2 percent rh.

Specimens were transferred in polyethylene bags from their humidity

chambers for weighing and thermal inertia determination. Prior to removal

from the bag, specimens were permitted to adjust to the temperature of

the laboratory ambient air, when necessary. Thermal inertia determinations

were then made as quickly as possible. Although the effect of variations

in laboratory ambient humidity ranged from 35 to 50 percent rh) was not studied, some exchange of moisture between specimen and ambient

atmosphere would be expected.

After the thermal inertia determination # the specimen was returned

to its controlled humidity chamber for reconditioning prior to a flamespread test. Additional specimens were conditioned and tested for sur- face flammability only to provide sufficient flame-spread replication

data.
- 6 -

4. Results and Discussion

Figo 3 illustrates typical surface temperature- time records for

fiberboard and tempered hardboard of various moisture contents. When

plotted as a function of/’t, as shown in Fig. 4, the data appea-r as straight lines, and the initial slopes may be used to calculate values

of kpc using equation (3a)

„

For times exceeding those listed in Table 4, equation (1) was used

to evaluate kpc. The surface heat transfer coefficient was calculated

from the following equation:

^ a e (T

4 - T

4

) + h (T - T)

H = —

y-Tt

S — (6)

Where T

s T

a o

e

h

surface temperature °K

ambient temperature, °K

-is

Stefan-Bo ltzmann constant, 5.67 x 10 w/cnP “K4

,

surface emissivity, assumed equal to 1,

convective cooling coefficient.

For typical values of T = 300°K(27°C), T = 296°K(23°C) and

-4 S 3

h = 1.8 x lCfo w/crrP C K (for laminar conditions on a vertical plane,_^

surface with a small irradiated area) ,' the value for H is 8.4 x 10 w/ cttP

' j K.

Because of uncertainties associated with surface emissivity,

absorptivity and diathermancy, all specimens for thermal inertia determination were painted with a flat black enamel which provided a uniformly

high absorptivity and opacity* However, the actual value of the absorptivity is not necessary since a measurement was made of the effective

or absorbed, rather than incident, irradiance using selected specimens

of known thermal properties. The calculation of the effective I was based upon temperature -time records and independently-determined values

of k, p and c on a variety of materials, using equation (1). Results

of these measurements are given in Table 3. All subsequent computations

of kpc were based on the average effective I value of 0.018 w/cnP .

Linear relations between moisture content and the computed values

of kpc based on the present method for fiberboard and hardboard are indicated by the data plotted in Fig. 5. The dotted portion of the line

shows some deviation from linearity. Natural woods of intermediate densities would be expected to have values of kpc between the two curves.

The linear relationship as well as numerical values are in agreement with

the findings of a previous literature survey of available data which was based on individual measurements of k, p and c [10].
7

The computed kpc values take into account changes in each propertydue to moisture. Whereas specific heat and thermal conductivity both

increase with increasing moisture content, the swelling of common woods

due to moisture results in a decrease in density. This was particularly

noticeable for hardboard at high moisture contents (see Table 1).

It may be noted that the presence of a thin factory-applied white

paint coating on the thermal insulation fiberboard which conformed to

Fed. Spec. LLL-I-535, Class D, had no appreciable effect upon the

computed values of kpc.

The measured flame spread factors for hardboard and for painted and

unpainted fiberboard are shown in Fig. 6 as a function of the corresponding

thermal inertia values. The flame spread factor is seen to be inversely

proportional to thermal inertia. The plotted data include measurements

over the entire range of moisture content.

A relation of this type is in accord with the concept that a characteristic temperature at the surface must be reached prior to

ignition. A high kpc value, for example, would delay the attainment of

the characteristic temperature and thus lower the flame spread factor.

In a previous study [4], flame spread factors for a wide variety of thick

cellulosic materials conditioned to equilibrium at 50 percent relative

humidity only, were also found to be inversely proportional to the kpc

values. However, the thermal conductivity and specific heat values used

were "dry" values obtained from handbook sources and were not adjusted

for the appropriate moisture contents. When this adjustment is made,

the previous data can be represented by the equation:

F

s 4 +

.005

kpc (7)

which is also shown in Fig. 6 for comparison. Though the flame spread

factors for hardboards appears to deviate somewhat from equation (7),

they are actually within the data scattering on which the equation was

based.

The flame spread factors for painted fiberboard were significantly

different from the mean values represented by equation (7), even when

the appropriate kpc values were used. For flame propagation on surfacecoated cellulosic materials, therefore, it appears that a higher surface

temperature had to be attained in order to permit heat penetration and

rupture of the coating (approximately 0.002 cm thick) and subsequent

release of combustible vapors.
- 8 -

Figure 7 shows the measured flame spread index, I = F Q, as a function

of corresponding computed values of thermal inertia for the three types

of materials with various moisture contents. Since the heat release rate

Q depends on the thickness as well as the density of the cellulosic

specimens, a single continuous function is not expected to cover both the

hardboard and fiberboard which do not have comparable density or thickness.

But, for a given type of specimen, the correlation between I and kpc

appears to be reasonable. Accordingly, the effect of moisture on the

flame spread index may be interpreted in terms of the thermal properties

of the materials.

The

for this

principal sources of error involved in the kpc

study were?

determinations

(a) the uncertainties in the measurements of the surface

temperature rise and the effective irradiance,

(b) the modification of the surface conditions by the

application of a flat black enamel, and

(c) the use of

ment times

the approximate

(or high values

equation (2) at long measureof the heat transfer coefficient).

The coefficient of variation of the kpc computations was approximately

3 percent based on fifteen sets of duplicate determinations. The overall

uncertainty in kpc due to random and systematic errors is estimated to be

about ± 10 percent. A significant reduction in this uncertainty should

be possible by more precise measurement of the effective irradiance and

by the use of the exact equation in place of the approximate one. The

coefficient of variation of the flame spread factor computations was approximately 4 percent based on fifteen sets of four repeat determinations.

5. Conclusions

Inasmuch as the movement of hygroscopic moisture and the conduction

of heat are basically diffusion processes, no abrupt difference in flamespread behavior was expected with variations in the moisture content of

typical combustible materials. The results did, in fact, indicate that

the ignition sensitivity, or flame-spread factor, varied in a manner

closely approximating previous data-~for thick cellulosic materials

conditioned at a single relative humidity--when the effect of moisture

on the appropriate thermal properties was taken into account.
9

The radiometric method described for the direct and rapid in situ

determination of the thermal inertia for surface heating (kpc product),

is particularly attractive for bpilding materials, including wood and

other inhomogeneous materials. Although simple measurements are con- veniently made at ordinary temperatures, the method may be readily

applied to measurements at much higher temperatures. The application

of the method to the rapid non-contact measurement of moisture content

of materials also appears feasible. Finally, consideration could be

given to the use of the method for applications involving composite

materials with a thin surface veneer, for which the appropriate temperaturerise relationship (cf. ref. 11) should be employed.
AW "

6- References

tlj Interim fedstal Standard Ho . 00136b (COMM-NBS) -D@o. 26, 1962.

Available from General Services Ad»i» 1st rat loft Regional Offices.

|2J A..F. Robertson, B. Gross and J. J. Loftus, "A Method for Measuring

Surface Flammability of Materials Using a Radiant Energy Source,"

ASTM Proc. 56, pp. 1437-^3, 1956.

{3] A. F. Robertson, ^Surface Flammability Measurement by Radiant Panel

Method," ASTM Special Technical Publication No. 344, pp, 33-46, 1962.

!A] 0. Gross and J. J. Loftus, "Surface Flame Propagation on Cellulosic

Materials Exposed to Thermal Radiation," NBS J. Research 67C,

pp. 251-258, Sept 1963.

[5] J« D. Hardy and I. Jacobs, "Method for the Rapid Measurement of Skin

Temperature During Exposure to Intense Thermal Radiation," J. Appl.

Physiology, 5_, pp. 559-566, March 1953.

[6] D . I. Lawson, L. L. Fox, and C. T. Webster, "The Heating of Panels

by Flue Pipes," Fire Research Special Report No. 1, Dept, of

Scientific and Industrial Research and Fire Offices' Committee,

London ,1952

.

[7] A. F. Robertson, Private Communication

[8] E, Hendler, R„ Crosbie and J. D. Hardy, "Measurement of Heating of the

Skin During Exposure to Infrared Radiation," J. Appl. Physiology, 12,

pp. 177-185, 1958.

[9] A. Wexler and S, Hasegawa, "Relative Humid i ty -Temperature Relationships

of Some Saturated Salt Solutions in the Temperature Range 0° to 50°CVl NBS J. Research 5^, pp. 19-26, July 1954.

[10] Ho Bo Nottage, "The Thermal Properties of Buildirfg Materials," ASHVE^

Research Bui. 53, 1947.

[11] Mo Vo Griffith and G. K. Horton, "The Transient Flow of Heat Through

a Two-Layer Wall," Proc. Phys. Soc . 58, pp . 481-87, 1946.

[12] J. C. Jaeger 8 "Pulsed Surface Heating of a Semi-Infinite Solid,"

Quart. Appl. Math. 11, pp. 132-37, 1953.
APPENDIX 1 2b b

y The error in using the approximation /tt = (1-e erfc b) will be

within 1, 5 and 10 percent for values of b = 0.011, 0.056 and 0.111,

respectively. For a range in thermal inertia values, and assuming a room temperature value for H (the effective heat loss coefficient for

radiation and convection) of 0.00084 w/cn/C, these correspond to the

maximum measurement times listed in Table 4.

Table 4: Error Introduced by Using the Approximation for

Various kpc Values and Maximum Measurement Times.

Thermal Inertia 1% 5% 10%

kpc (b = 0.011) (b = 0.056) (b = 0.111)

sec sec sec sec

°c? cm"

175 X io"

6

.03 00 0 3.1

700 X io"

6

o 12 3.1 12.

1750 X io"

6

.3 00

r*

s» 31.

7000 X

10~6

1.2 31. 120.

For very good insulating materials (low thermal inertia) , increased

accuracy may be achieved by continuing temperature-time observation for

an extended period. A plot of temperature rise vs 1 //1 becomes linear

for long times and the value of kpc may be determined from the slope

of the line 1 J&o c /tt ^ and the intercept (I/H).

V

/
APPENDIX 2

The surface temperature rise of a semi-infinite solid subjected ter a pulsed surface flux of rectangular wave form is equal to the sum of a periodic part superposed on the rising temperature due to the average

surface flux fl. The value of the transient part is given by:

e = 2fi/—~— (8)

t J rrkpc

and the periodic part at time bT , after the beginning of a heating

period [ 12 ] , by:

where T is the total time per cycle.

The ratio of the periodic to the transient parts is:

(1 - f) - ( 10 )

For f = 0.5, the average half-cycle value of the term

is less than 0.24, so that for a chopping frequency of 90

(T = 0.011 sec), the effect becomes small (<5%) for times

0.25

in brackets

cps

greater than

sec

.
3

TO H

1 o co 00 30 3) ON T—

1

00 3i o o 1“—

1

1—1 o

CO o o CM 3 CO ON co CN 3 ON ON CO CO M in CO CM r—

1

CM t—

1

\—

i

CM CN i—

4

1—

1

r—

4

CM r—

1

ON CO LP| i—4 co 00 3 00 o 3> m 00 On CO o

CO 3 r—

4

00 <J- T—

1

uo CO i—1"4 00 3 co

Em CN CM r—

1

r-l r—

4

r—

4

r—l r—l

M-l e o u 1

?n - Sb 10

4-J ca o •H o X

i—

1

Q- U

•H Psi TO 3 o m CO 30 r—

1

in

rO

cu t3

CO CM co CO <1* 3) CN co co 3 3 o <1- ON

1 1 r—

1

CM CN CM i to

TO O3

U-i T3 0) 3 3 4-J 4-J TO TO

TO PC D

4-) 3 c

TO TO 00 1—

1

a-' CM H ON CN CM O' ON r—

4

o O

CU CO 4-J CJ 3 TO 3 3 o CO 3 i—

1

in 1—4 co 3> r—l o r—

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LO ON 3

3 3 o O TO r—

1

CM r—

1

CM T—l 3 TO a U 3-

cn

T3

XI 3

3 TO TO kO

TO O > 4J 4-J 3 •H •3 3 o o o

<3 3 4-J "O cu o o o

»h a; CU •H U o CM o 30 r-4 O CM O 3 r—

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4-J X) t—4 g 3 i—

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in 1 i—

1

m 1 T—

1

3 1

J-i *H TO 3 TO ON ON CTn

cu PS 3= C- ON cM CO

CO r“

4

CU

cuc O' o CM 30 o ON o CM 3 o o O CN 3 o

£

r-4 CM CN CN CO 1—

1

CM CM CN co 3 3 3 3 00 u a •

(1) •H t—

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r—l r—

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r—

1

r—

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1 1 r—

4

r-l i—l I—

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o O O O o

3 3

H H

00 ON i—

1

00 ON i—"4 CO CN Cl TO CM CN CM CM CO CN CM CM CM co o o o o ON M O o o O o o O o o o H T“—

1

T“—

1

1—1 o

TO X) TO 3 TO 3 TO

r—

1

TO u TO TO 3

TO O c O TO TO •H 30 •iH 30 4-J O 3 3 TO 3 3 3

TO TO a TO •H TO

4-J 30 3 30 03 Pj CU •I—

1

3 *r—

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3- TO 2 Pm Pm N-/

co co 3 3

TO TO £ £

•r4 •H

TO u

TO TO CL a

CO CO CM3 3

O O 3 3

TO TO 00 00

TO TO 3 3

TO TO > >

<c <

'rol 3|
Table 2

Methods Used for Maintaining Various Relative Humidity

Conditions

Nominal

Relative Humidity

percent

0

12

50

76

80 - 100

Means of Achieving Humidity

Calcium Chloride (CaCls)

Lithium Chloride (LiCl’HsO) solution

Commercial Room Air Conditioner

Sodium Chloride (NaCl) solution

Commercial Humidity Chamber
Table 3

Effective Irradiance Measurements

Material Density

Thermal—^

Conductivity

Heat

Capacity

Thermal

Inertia

Effective

Irradiance

P g/cm3

k

w/ cm° C

c w sec/g°C

kpc

2 w sec

I w/ cm" “C^cm4

Rubber 0.97 15.2 x 10" 4

1.77 26 x 10

-4

.020

Insulating

Board, dry 0.23 5.03 1.21 1.4 .019

Rigid PolyVinyl Chloride 1.4 12.5 0.84 15 .018

Asbestos

Board 0.67 12.3 0.84 6.9 .016

GypsumVermicul ite

Plaster 0.63 18.9 1.02 12 .015

a/ Based on measurement in guarded hot plate apparatus (ASTM C117-42T)

at mean temperature of 23°C.


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