NATL INST. OF STAND & TECH MIST

PUBLICATIONS

REFERENCE

NBSFR

An Evaluation of Fire Properties

of Generic Gypsum Board

Products

J. Randall Lawson, Research Associate

Gypsum Association

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 1977

Final Report

**'»eAu of *

S. DEPARTMENT OF COMMERCE

nONAL BUREAU OF STANDARDS

NBSIR 77-1265

AN EVALUATION OF FIRE PROPERTIES

OF GENERIC GYPSUM BOARD

PRODUCTS

J. Randall Lawson, Research Associate

Gypsum Association

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 1977

Final Report

U.S. DEPARTMENT OF COMMERCE. Juanita M. Kreps. Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistartt Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Acting Director

CONTENTS

Page

LIST OF FIGURES iv

LIST OF TABLES iv

Abstract 1

1. INTRODUCTION 1 1.1. Potential Heat 2 1.2. Rate of Heat Release 2 1.3. Ease of Ignition 3 1.4. Flame Spread 3 1.5. Material Examination by Scanning Electron Microscope —

13 mm (1/2 in) Type-X Gypsum Board 3

2. TEST SPECIMENS 3 2.1. Sampling and Conditioning 5 2.2. Specimen Preparation for the Potential Heat Test 5 2.3. Specimen Preparation for the Scanning Electron

Microscope Observations 6

3. TEST APPARATUS AND PROCEDURES 6 3.1. Standard Test Method for Potential Heat of Building

Materials — NFPA Standard 259-1976 6

3.2. Test for Measuring the Rate of Heat Release of

Building Materials — NBS Method 7 3.3. Ease of Ignition by Flame Impingement Test Method 8 3.4. Surface Flammability of Materials Using a Radiant Panel

(ASTM E 162) 10

4. TEST RESULTS AND DISCUSSION 11

4.1. Potential Heat Test 11

4.2. Rate of Heat Release 13

4.3. Ease of Ignition 15

4.4. Flame Spread 17

4.5. Scanning Electron Microscope Study of 13 mm (1/2 in)

Type-X Gypsum Board 19

5. SUMMARY 2 3

6. ACKNOWLEDGMENTS 23

7. REFERENCES 24

APPENDIX - COMPONENT WEIGHT FRACTIONS USED IN THE CALCULATIONS

OF POTENTIAL HEAT SHOWN IN TABLE 1 25

iii
LIST OF FIGURES

Page

Figure 1. Schematic Diagram of Test Procedure for Potential

Heat Measurements 7 Figure 2. NBS Heat Release Rate Calorimeter 8 Figure 3. Sketch of Ignition Apparatus 9 Figure 4. Diagrammatic Drawing of a Radiant-Panel Test Method .... 10

Figure 5. Average Ignition Time (Ignition Test) vs. Heat

Contribution Time Piloted 4 W/cm^ Exposure (Calorimeter) . . 16

Figure 6. Variation in Flame Spread E 162 versus E 84 19

Figure 7. SEM Picture 120X Type-X Board Core before Fire Exposure . . 21

Figure 8. SEM Picture 800X Type-X Board Core before Fire Exposure . . 21

Figure 9. SEM Picture 2700X Type-X Board Core Gypsiam Crystals Not

Exposed to Fire 21

Figure 10. SEM Picture 120X Type-X Board Core after Fire Exposure. . . 21

Figure 11. SEM Picture 500X Type-X Board Core after Fire Exposure. . . 22

Figure 12. SEM Picture 160X Expanded Vermiculite and Melted End

of Glass Fiber after Fire Exposure 23

Figure 13. SEM Picture 2600X Gypsum Crystals of Board after Exposure

to Fire 22

LIST OF TABLES

Table 1. Gypsum Board Potential Heat Test Results — NFPA 2 59

Method 12

Table 2. Gypsum Board Peak Rate of Heat Release 14

Table 3. Gypsum Board Ease of Ignition Test Results 15

Table 4. Gypsum Board Surface Burning Characteristics 18

iv
AN EVALUATION OF FIRE PROPERTIES OF GENERIC

GYPSUM BOARD PRODUCTS

J. Randall Lawson^

Abstract

An evaluation of the fire properties of generic gypsum board

products was made in order to obtain a better understanding of the

material's reaction to a fire environment. These gypsum board

products are typically used in wall and ceiling assemblies throughout the United States. Four small-scale fire test methods were

used in the examination of the materials' fire properties. The

tests conducted were for potential heat, ease of ignition by flame

impingement, rate of heat release, and rate of flame spread. All

of these properties are of major importance in the design of a building. They influence the potential rate of fire growth in a room. Standard fire test methods were used for the development of

data on rate of flame spread and potential heat characteristics.

The ease of ignition and rate of heat release characteristics were

determined by fire tests recently developed at the National Bureau

of Standards. Test results showed that the potential heat for the

materials examined ranged from 510 J/g (220 Btu/lb) to 2670 J/g

(1150 Btu/lb) . The ignitability of the materials spanned from

42 to 171 seconds, while the peak heat release averages ranged from

a 2.5 to 4.8 W/cm^ on an unpiloted 4 W/cm^ exposure and 3.9 to 8.2

W/cm^ on an unpiloted 6 W/cm^ exposure. The flame spread index for

the materials ranged from 8 to 38.

Key words: Buildings; ease of ignition; fire tests; rate of flame

spread; gypsum board; potential heat; properties; rate of heat

release; scanning electron microscope (SEM)

.

1. INTRODUCTION

Gypsum board was first used in construction in the early 1900's. The

production and use of the material in building construction grew at a slow

rate until the mid-1940' s when the demand for housing rapidly increased. At

this time, gypsum wallboard (drywall) became the major interior finishing

component for walls and ceilings in various types of buildings. Over the

last three decades, a family of nine generic board products have evolved with

special characteristics in order to meet the needs of the building industry

and code regulations (see section 2). At the present time, conventional

construction utilizes gypsum board in 90 percent of all buildings in the

United States. Gypsum wallboard is generally known for its fire resistive

characteristics; however, little technical information is available on the

specific fire properties [1] . Pure Gypsum is "hydrous calcium sulphate," CaS0i+'2 H2O, a monoclinic

shaped crystalline mineral that contains chemically combined water. The

gypsum crystals contain about 50 percent water by volume and about 21 percent

by weight. This water of crystallization plays a major role in the thermal

properties of the material and controls how it will react to heat and flame.

This work was conducted while Mr. Lawson was a research associate for The

Gypsum Association at the National Bureau of Standards.

Numbers in brackets refer to the literature references listed at the end

of this paper.

1
In order to better relate how gypsum reacts to heat, it is necessary to understand its degradation process. The mineral gypsum CaSOi+ • 2 H2O at temperatures

between 0 to 66 °C (32 to 150 °F) usually contains a small amount of free

moisture absorbed to the surface of the pores. Around 100 °C (212 °F) the

moisture leaves the pores (desorption) , then at about 125 °C (257 °F) gypsum

becomes unstable and loses 3/4 of its chemically combined H2O from the crystal

lattice (dehydration) . This yields the material commonly known as Plaster of

Paris CaS04-l/2 HjO.

125 °C

CaS04*2 H2O CaSOij-1/2 H2O + 1-1/2 H2O AH - Heat of Hydration

heat steam 15,900 to 17,160 Joule/Mole

Through continued heating, the remaining H2O is released through the cell

lattice. The water driven off during the heating process carries away heat

and helps to retard the flow of heat through the remaining gypsum. At about

360 °C (680 °F) the soluble anhydrous CaSOi^ transforms into an insoluble modification which is stable up to 1227 °C (2240 °F) when a small amount of CaSOi^

dissociates into CaO and SO3. Finally, at 1382 °C (2520 °F) the melting of

CaO—CaSOi+ eutectic mixture takes place [2] . Physical properties change as the calcination of gypsum takes place.

Some of the most apparent modifications are the reduction in strength, heat

capacity and volume.

The goal of this project was to evaluate the fire resistive properties

of the nine generic gypsum wallboard groups. Tests were conducted to determine the potential heat, rate of heat release, ease of ignition, and rate of

flame spread of these gypsum materials so that their fire resistive properties

may be better understood. These properties were chosen because they provide

a broad base for additional analysis of the materials and lead to a better

understanding of how the materials may react in a fire situation. A scanning

electron microscope was used to examine the effect of fire on the modified

gypsum core of 13 mm (1/2 in) type-X gypsum board. A discussion of these

property tests and the microscopic investigation follows:

1.1. Potential Heat

The objective of the potential heat test is to provide a reasonable

estimate of the total amount of heat which could be released during a building

fire. Information concerning potential heat enables certain regulatory

groups to control materials used in building construction based on the

quantity of heat or "fuel" contribution.

The potential heat of a material may be defined as the difference between

(a) the heat of combustion of a representative sample of material and (b) the

heat of combustion of the residue remaining after exposure to a simulated

standard fire using combustion calorimetric techniques [3] . The potential

heat of a material is a major indicator that can be used to determine the

extent to which a building material may contribute heat to support active

combustion during a fire. The value of this property is of great importance

in the design of a building and specification of materials and furnishings to

be used in the structure

.

1.2. Rate of Heat Release

In addition to the total available heat, the rate at which a burning material releases heat plays a major role in the growth of a fire. In a room fire,

a large portion of the heat released collects in the upper portion of the room

and may be absorbed by the walls and ceiling. The attendant rise in air and

2
surface temperature creates thermal radiation levels which serve to produce

new ignitions, increase flame spread, and further increase the rate of heat

release of the building materials and furnishings. Therefore, the rate of fire

buildup in a room depends on the rate of heat release of the room contents and

construction materials [4] .

1.3. Ease of Ignition

The ease with which a material ignites by flame contact is another

property which may also influence fire buildup. For example, if a fire

develops in a waste paper basket, the objects around it may be impinged upon

by the flame. If the adjacent materials ignite rapidly, the fire will quickly

grow larger. However, if the ignition time for a material is longer than the

duration of the fire in the waste basket, the fire will die out.

1.4. Flame Spread

The rate and extent to which flames travel across the surface of a material is controlled by the properties of the material and the environment around

the involved area. The important properties of a material are its thermochemical and thermophysical properties, thickness, and orientation. The

environmental factors which may influence the flame spread rate are the level

of incident thermal radiation, temperature, air movement and oxygen concentration.

Flame spread tests are designed for the determination of flame spread

rates and distances over a surface of a material while it is exposed to a standardized fire environment. The tests also attempt to classify the material and assign a flame spread index number which reflects the rate or distance of flame spread over the surface.

1.5. Material Examination by Scanning Electron Microscope

13-min (1/2-in) Type-X Gypsum Board

Because gypsum board changes significantly during the exposure to fire,

it was felt that a microscopic analysis of the burned gypsum core would be

useful in improving the understanding of this degradation process

.

It is known that gypsum contains chemically bound water and that it can

be removed by applying heat. The application of heat results in the calcination of the gypsum and the reduction of physical strength. The type-X board

contains other materials which are introduced into the board core to provide

a means of maintaining strength and stability during prolonged fire exposures.

Two of the components usually added to the core are vermiculite and short

strands of fiber glass. An objective of this microscopic observation was to

view any changes which take place in the core as a result of it being exposed

to fire.

2. TEST SPECIMENS

Nine gypsum board products were selected for test in this project. The

materials are currently used in typical residential and commercial structures.

These materials are manufactured by all of the major producers of gypsum

board products, and are considered to be generic by the Model Building Codes.

3
The products chosen for this study were selected at random from typical production and supplied by four manufacturers. The following is a list of the

materials studied:

8 mm (5/16 in) MH Gypsum Board

13 mm (1/2 in) Regular Gypsum Board

13 mm (1/2 in) Gypsum Formboard

13 mm (1/2 in) Regular Gypsum Board with .2 mm

(.008 in) Vinyl Coating

13 mm (1/2 in) Gypsum Sheathing

13 mm (1/2 in) Water Resistant Gypsum Backer Board

13 mm (1/2 in) Type-X Gypsum Board

16 mm (5/8 in) Type-X Gypsum Board

25 mm (1 in) Gypsum Core Board

A description of each material and use follows:

8 mm (5/16 in) MH Gypsum Board — This board is designed for use

in mobile home construction with or without further

, . .. surface decoration. Its composition is essentially a

. reinforced noncombustible gypsum core. 3 Glass fiber is

generally used for reinforcement. The core is incased

in paper. It meets the requirements of ASTM C36-76A

Standard Specification for Gypsum Wallboard and Glass

Fiber Reinforcement not exceeding 15 weight percent of

the core.

13 mm (1/2 in) Regular Gypsum Board — This board is designed

to be used for the surface layer on interior walls and

ceilings that provide a smooth even surface suitable for

decoration. Its composition is a noncombustible gypsum

core with paper on the face, sides and back of the board.

It meets requirements of ASTM C3 6-76A Standard Specification

for Gypsum Wallboard.

13 mm (1/2 in) Gypsum Formboard — This is used as a support and

permanent form to hold gypsum concrete in poured gypsum

roof decks. The material consists of a noncombustible

gypsum core, with or without fiber. The surface is covered

• -' with sheets of fibrous materials, usually paper. The

exposed surface is chemically treated to resist fungus

growth. It meets the requirements of ASTM C318-67 Standard

Specification for Gypsum Formboard.

I 13 mm (1/2 in) .2 mm (.008 in) Vinyl Gypsum Board — This

I material is regular gypsum board that has been predecorated

with .2 mm (.008 in) vinyl. It meets the requirements of

ASTM C36-76A.

13 mm (1/2 in) Gypsum Sheathing — This is used to stiffen exterior

frame walls against the forces of wind and vibration and to

provide fire resistance. Sheathing is covered with an exterior finish, such as siding. Sheathing board consists

of a noncombustible core, essentially gypsum with or without fiber. The core is treated with water-repellent chemicals and the surface is covered with a water-repellent paper.

' -• - It meets the requirements of ASTM C79-67 (73) Specification

for Gypsum Sheathing Board.

3 The basxc gypsum board core is considered to be noncombustible on the basis

of ASTM E 136-73 Noncombustibility of Elementary Materials test results.

4
13 nun (1/2 in) Water-Resistant Gypsum Backer Board — This product

serves as a base for the application of wall tile in baths,

showers, and other wet areas. It consists of a waterresistant gypsum core, with or without fiber or aggregates.

The surface is covered with water-resistant paper bonded to

the core. It meets the requirements of ASTM C6 30-74A

Specification for Water-Resistant Gypsum Backing Board.

13 mm (1/2 in) Type-X Gypsum Board — This material is similar

in all respects to regular gypsum board except that the core is made more fire resistant by the addition of glass

fiber reinforcement and other materials. This product is

designed to provide a 3/4-hour fire rating in the ASTM E

119 Fire Endurance Test when used in the construction of

a specified wall assembly [5] . It meets the requirements

of ASTM C36-76A and contains glass fiber reinforcement not

exceeding 15 weight percent of the core.

16 mm (5/8 in) Type-X Gypsum Board — This material is similar

in all respects to 13 mm (1/2 in) regular gypsum board

except that the core is thicker and is made more fire

resistant by the addition of glass fiber reinforcement

and other materials. This product is designed to provide

a one-hour fire rating in the ASTM E 119 Fire Endurance

Test when used in the construction of a specified wall

assembly [5] . It meets the requirements of ASTM C36-76A

and contains glass fiber reinforcement not exceeding 15

weight percent of the core.

25 mm (1 in) Gypsum Core Board — It is used as a wall base, as a self-supporting gypsum wall errected without framing, and

in demountable walls. It consists of a noncombustible core,

essentially gypsum, with and without fiber. A paper surface

is bonded to the core. It meets the requirements of ASTM

442-72 Specification for Gypsiam Backing Board.

2.1. Sampling and Conditioning

In all cases except one, specimens were taken from the center third of

1.2 by 2.4 m (4 by 8 ft) board products. The specimens taken from core board

came from the center third of a board measuring 0 . 6 by 1 . 2 (2 by 4 ft).

Specimens were cut to the various dimensions specified by the appropriate test.

All specimens were cut with their long dimension parallel to the paper grain

of the gypsum board. The specimens were then conditioned in an atmosphere of

50% relative humidity at 23.8 °C (73 °F) until they reached weight equilibrium.

When test methods required special conditioning, the test specimens were

subjected to the conditions specified. No finishes were applied to the

surface of the samples; however, it should be noted that the 13 mm (1/2 in)

vinyl gypsum board is a factory finished product.

2.2. Specimen Preparation for the Potential Heat Test

The specimens prepared for the potential heat test were handled in the

following way:

Representative rectangular samples of known area 968 mm^ (1.5 in^) were

taken from the field of the various gypsum board products. The face and back

paper was removed by cutting the paper away from the core and ground with a mechanical mill until all material passed through a 60 mesh sieve screen. Care was taken to prevent segregation. The board core material was then

ground by hand using a mortar and pestle until it also passed through the 60

5
iTiesh screen. Special care was taken to insure that calcination of the gypsum

did not occur during the grinding process. The core and paper corresponding

to the original sample area was then combined and thoroughly blended. The

specimen was then exposed to a 50% relative humidity 23.8 °C (73 °F) atmosphere until it reached weight equilibrium. This method of specimen preparation was used on all of the standard tests conducted; however, two special

potential heat tests were conducted on 13-mm (1/2- in) regular gypsum board.

The specimens for these tests were prepared as follows:

The requirements for the first of the two additional tests performed

stated that the core material, face, and back paper be tested as individual

units. The face and back papers were tested in their original state as shipped from the paper mill. These samples did not come into contact with

the gypsum board core at any time. The potential heat of the gypsum board

core was also ascertained as an individual item.

The second set of special tests required that a specimen be taken from

the 13-mm (1/2-in) regular gypsum board in the following manner. A specimen

was removed from the board that consisted of a 3-mm (1/8-in) thick section of core with the face paper attached, and then it was ground into the minus 60

mesh homogeneous powder. The potential heat test was performed on this

composite. A core/back paper specimen of the same geometry was also prepared

and tested.

2.3. Specimen Preparation for the Scanning

Electron Microscope Observations

A 13-mm (1/2-in) by 76-mm (3-in) specimen was removed from a 13-mm (1/2-

in) type-X gypsum board. The specimen was cut in half and one-half of the

sample was fired in a muffle furnace for one hour at 750 °C (1382 °F) . The

specimen was then removed from the furnace and cooled to room temperature in

a desiccator.

The second half of the original sample was handled in the following way.

It was not exposed to any fire condition; however, the face and back paper

was removed so the core could be directly viewed.

Representative samples were then taken from these two materials, mounted

on specimen stubs, and sputter coated with .01 microns (100 A) of gold. The

specimens were then viewed with a commercial scanning electron microscope

(SEM)

.

3. TEST APPARATUS AND PROCEDURES

3.1. Standard Test Method for Potential Heat

of Building Materials —

NFPA Standard 259-1976

Two samples are removed from the material to be tested. One is pulverized, pelleted, and then burned in an oxygen bomb calorimeter. This yields a measure of the gross heat of combustion of the material. In the case of

materials of low combustible content, a combustion promoter is added prior to

pelleting the specimen for test in the combustion calorimeter.

The second specimen of approximately 13 by 19 by 76 mm (1/2 by 3/4 by

3 in) size is "fired" in a muffle furnace. The firing of the specimen is

accomplished by heating it in air for two hours at a temperature of 750 °C.

The weight loss of the specimen is noted, and the residue remaining, if it is

more than five percent of the original weight, is pulverized into a homogeneous powder. A portion of the resulting powder is mixed with a corresponding weight of combustion promoter, pelleted, and burned in the combustion

6
calorimeter as previously described. After correcting for the heat produced

by the combustion promoter, the difference in heating values of the two

specimens is reported as the potential heat [6]

.

See figure 1 for the flow diagram of the test method which illustrates

the steps involved [3] .

MATERIAL

TO BE TESTED

'combustion promoter"} correction JCOMBUSTION promoter]

correction

potential heat

by difference

Figure 1. Schematic Diagram of Test Procedure

for Potential Heat Measurements

3.2 Test for Measuring the Rate of Heat

Release of Building Materials — NBS Method

The National Bureau of Standards rate of heat release calorimeter [4]

consists of three chambers which are classified as follows: (1) Combustion

Chamber; (2) Control Chamber; and (3) Mixing Chamber.

The tests conducted for this study were run with thermal radiation

levels of 6 W/cm^ and 4 W/cm^ . The 4 W/cm^ exposure required the use of a gas pilot flame for ignition of the gypsum board paper; with the 6 W/cm^

exposure the paper ignited rapidly without a pilot flaime.

After the calorimeter has been stabilized and calibrated, a 115 by

152 mm (4.5 by 6 in) specimen is placed in a vertically oriented holder

which is located at the center of the combustion chamber. Only the speci- mens finished surface is exposed to radiation from the radiant panels which

are located on three sides of the combustion chamber. The edges of the speci- men are shielded by the insulated holder, and the rear surface is separated

from a water-cooled brass block by an approximate 13-mm (1/2-in) air space.

7
The air space behind the specimen represents a small section of wall cavity.

The heat transferred from the rear surface of the specimen to the brass block

is measured by a thermocouple which registers the rate of temperature rise of

the cooling water circulating through the block.

A propane burner located inside the control chamber of the calorimeter

produces heat at a considerably greater rate than that of the burning specimen. As the specimen burns, the propane flow is automatically reduced by the

amount necessary to maintain the flue gas in the mixing chamber at a constant

temperature. The rate of heat release through the front surface of the

specimen is determined from the reduction in propane flow. Only the heat

released at the front surface of the specimen is stated in this report. A

drawing of the calorimeter is located in figure [4]

SIDE VIEW

Figure 2. NBS Heat Release Rate Calorimeter

3.3. Ease of Ignition by Flame Impingement Test Method

An ease of ignition by flame impingement test method, recently developed

at NBS , was used to evaluate the ignition characteristics of the gypsum board

products (see fig. 3)

.

8
The test apparatus consists of two specimen holders 140 nun (5-1/2 in)

wide and 152 mm (6 in) high that position the specimens 50 mm (2 in) apart.

The burner is constructed out of two brass blocks that are water-cooled,

and they support the specimen holders located on top. The brass blocks are positioned vertically and on the same plane as the specimen holders. A

horizontal row of 2 mm (1/16 in) holes spaced 13 mm (1/2 in) apart located

near the bottom of the brass blocks allows methane gas to pass into the

opening between the blocks and specimens. The gas is ignited by an electrical

spark ignition system located near the gas ports. The exposure flame develops

rapidly and passes between the two specimen surfaces and extends about 152 mm

(6 in) above the test frame. Almost 3/4 of the specimen's surface is impinged

upon by this flame and ignition of many organic materials generally occurs

as a result of this exposure. The average incident heat flux, radiant and

convective, on the specimen surface is about 3.3 W/cm^

.

The test begins by mounting two identical samples in the specimen test

frames. A dual pen chart recorder is started. The recorder receives an output from a photo tube which views the specimens and records the amount

of light emitted as the test material contributes energy to the exposure

flame. The second channel of the recorder is connected to a push button

actuated time marker circuit for observations made by the operator. The

electrical spark igniter is turned on, and the solenoid gas control valves

are opened. The exposure flame develops between the specimens, and

9
observations are made by the operator and marked on the recorder chart

throughout the test. The following events are logged during the test: time

of surface degradation, ignition time, contribution time, and time of flame

persistance. The time of surface degradation is determined by observing the

specimen and recording the time at which visible changes are noticed. Ignition

is considered to be the time of flame attachment to the surface. The contribution time is determined by a 25 percent rise in light output of the photo

tube and indicates when the specimen is contributing to flame intensity. The

time of flame persistance is determined by cutting off the exposure flame

when it appears that the specimen will sustain a flame without external

support. The flame persistance time is the difference between exposure flame

cut off the end of self sustained flaming.

Six tests were conducted using the above procedure to provide an average

ignition time and replication.

The test apparatus used in this method consists of a radiant panel, a frame to support the test specimen, and associated measuring equipment

(see fig. 4)

.

The radiant panel consists of a cast iron frame enclosing a 305-by

457-mm (12-by 18-in) porous refractory material. The panel is mounted in a vertical plane and a premixed gas-air mixture supplied from the rear is

burned in intimate contact with the refractory surface, providing a radiant

heat source. The energy output of the panel equals that obtained from a black body of the same dimensions operating at a temperature of 670 °C

(1264 °F) . A stack placed under the vent hood above the test specimen receives

the hot products of combustion and smoke. The heat liberated by the specimen

is measured at this location by a group of thermocouples.

The test specimen, measuring 152 by 457 mm (6 by 18 in) is dried for

24 hours at 60 °C (140 °F) , and then conditioned to equilibrium at an ambient

temperature of 23 + 3 °C (73 + 5 °F) and a relative humidity of 50 + 5 percent.

It is then placed in the metal holder and hung on the test frame. The orientation of the specimen is such that ignition is forced near its upper edge by

the gas pilot, and the flame front progresses downward.

A factor derived from the rate of progress of the flame front (ignition

properties) and another relating to the rate of heat liberated by the material

under test are combined to provide a flame spread index [7,8].

3.4 Surface Flammability of Materials

Using a Radiant Panel (ASTM E 162)

Stack Thermocouple

Temperature Pvise

Radiant

Heat

Source

Figure 4

.

Diagrammatic Drawing of a RadiantPanel Test Method

10
4. TEST RESULTS AND DISCUSSION

4.1. Potential Heat Test

A total of seventeen tests were conducted during this test program.

Single determinations were made on six (6) of the nine (9) materials. Two

determinations were made on three (3) of the materials in order to check the

repeatability of the test results. A special set of tests involving seven

(7) determinations on board components was also conducted on 13-mm (1/2-in)

regular gypsum board. This was done to determine if the testing of individual

board components (paper and core) would actually yield the same results as obtained from the composite specimen. During this study, it was decided to

also compair the weight of chemically bound water in the gypsum board core with its theoretical weight (21.0%). The board core specimen after being

calcined in the muffle furnace provided a favorable comparison with a weight

loss of 20.6%. A second objective was to check the feasibility of obtaining

the values of each component and using them to calculate the potential heat

value of other materials that contain the same components but in different

proportions.

From the data listed in table 1, it can be seen that both of the special

battery of tests performed on the components of the regular gypsum board com- pare favorably (410 vs 390) to the test results obtained from the composite

samples. This indicates that both methods of specimen preparation are reliable

if good laboratory techniques are used. It also indicates that the second

objective mentioned above is feasible when making the following assumptions.

In order to calculate the potential heat of the various gypsum board products

that occur in specific generic groups such as regular board, it must be

assumed that the paper and board core formulations are relatively uniform.

On this basis, the potential heat values can be calculated for boards of

various thicknesses. Using the potential heat results developed on the

components of 13-mm (1/2-in) regular gypsum board, potential heat values were

calculated on three regular board products which varied in cross-sectional

dimensions. These values have been included in table 1. The component

weight fractions used for the calculation of each of the three materials is

located in the Appendix.

Some problems were experienced in performing the oxygen bomb test. These

problems occurred while attempting to test the individual paper specimens.

The test method requires that a one (1) gram pellet be formed for oxygen bomb

firing. This procedure was followed in preparing the paper materials. However, it was found that the paper was very resilient and after being compressed

as tightly as possible the pellet height was equal to the height of the test

crucible sides. Upon igniting the specimen in the bomb, it became apparent

that violent burning occurred which caused a portion of the specimen to be

thrown from the crucible where it fell to the bottom of the bomb and was

quenched. This action resulted in the lack of combustion of a large percentage of the specimen and this required the retesting of the sample material.

A second test was run which ended with the same results. It was decided at

this time to perform the test on a 0.5-gram specimen pellet. During this

test, all of the specimen remained within the crucible and burned to completion.

It was then found that the paper left a residue which was in excess of one

percent. This finding required that a second oxygen bomb test be conducted

using a 0.5-gram paper sample blended with 0.5 grams of benzoic acid combustion

promoter. This method of specimen preparation worked well and produced acceptable results with approximately the same amount of residue remaining.

As can be seen in table 1, core board has the lowest potential heat value

of all materials tested. This is attributed to an increase in the core to

paper ratio. The influence of core to paper ratio is exhibited throughout

the range of board thicknesses.

11
** Table 1. Gypsum Board Potential Heat Test Results NFPA 259 Method

Specimen "eat Residue Heat Potential Heat Material of Combustion of Combustion

J/g Btu/lb J/g Btu/lb J/g J/cm2 Btu/lb Btu/ft^

6mm (1/4") Regular Board Calculated 9770

* 960 RAH

Smm (5/16") MH Board 140 60 -1900 -817 1510 8860 650 780

10mm (3/8") Regular Board Calculated 1390 9200 600* 810

13mm (1/2") Formboard 12 5 -1710 -735 12270 540

37 16 -1765 -759 1330 12950 570 1140

13mm (1/2") Sheathing 1214 522 -1714 -737 2440 23850 1050 2100

ISrnm (1/2") Water Resistant Backer Board 1772 762 -1284 -552 2670 24870 1150 2190

13mm (1/2") Regular Board -302 -130 -1610 -692 910 7950 390 700 -254 -109 -1770 -761 1070 9430 460 830

13mm (1/2") Type-X Board -188 - 81 -1710 -735 1090 10110 470 890

13mm (1/2") Vinyl Board

0.2mm (.008") Vinyl -88 - 38 -1677 -721 1090 10110 470 890

16mm (5/8") Regular Board Calculated 700 7720 300* 680

16mm (5/8") Type X-Board -335 -144 -1200 -516 560 6590 240 580 -400 -172 -1451 -624 700 8180 300 720

25mm (1") Core Board -837 -360 -1779 -765 510 10220 220 900

Special Tests

13mm (1/2") Regular Board Calculated from Component Values 950 8400 410* 740 Face Paper 17000 7300 17000 5220 7300 460 Back Paper 18000 7700 17900 5790 7700 510 Core -1784 -767 -1845 -793 -330 -2610 -140 -230

13mm (1/2") Regular Board 910 7950 390* 700

3mm (1/8") Core/Paper

Sections

Core/Face Paper 942 405 -1796 -772 2190 4770 940 420 Core/Back Paper 889 382 -1731 -744 2090 4540 900 400

Calculated values on basis of estimated board weights and results of 13mm (1/2") regular board core and paper components

.

Results listed are not average but are single determinations.

Because this test method is relatively sensitive to sampling procedure,

specimen preparation, and laboratory technique, special care was taken to

stay within the recommended reproducibility limits. Duplicate measurements

of potential heat are expected to agree within 460 J/g (200 Btu/lb) in the

same laboratory and within 1160 J/g (500 Btu/lb) at different laboratories [9],

In this study, duplicate tests were conducted on gypsum formboard, 13 mm (1/2")

regular board, and 16 mm (5/8") type-X board. The results of these tests

indicate a reproducibility of less than 175 J/g (75 Btu/lb)

.

12
4.2. Rate of Heat Release

Three sets of tests were conducted on the nine gypsum board materials

using the NBS Rate of Heat Release Calorimeter. This was done in order to

obtain an indication of how the materials would react in various radiant flux

environments. There were two sets tested with an exposure of 4 W/cm^ (see

table 2), one with a pilot flame above the specimen and one without. Only

the vinyl board exhibited a flaming ignition when tested without the pilot

flame. When the pilot was present, all of the materials exhibited a flaming

ignition except one type-X board specimen and two core board specimens

.

However, the 25-mm (1-in) core board had a flaming ignition on only one of

the three specimens tested. All of the samples exposed at the 6 W/cm^

radiant energy level ignited and exhibited flaming.

Generally, all of the gypsum board products performed within a narrow

peak heat release range on the battery of tests conducted. It was observed

however, that a few of the specimens did vary somewhat from the norm. The

only material which showed a significantly higher heat release compared to

the others was the 13-mm (1/2-in) vinyl covered gypsum board. This is most

apparent in the unpiloted 4 W/cm^ and 6 W/cm^ exposures. The higher heat

release during the unpiloted 4 W/cm^ test is attributed to the ignition of

the vinyl finish.

The peak release rate of the unpiloted 4 W/cm^ test resulted in the

greatest degree of variation with a range of within + 25% between all materials tested except the vinyl which exhibited flaming. The type-X board

products had low peak heat release rates at 6 W/cm^ . However, the peak

was reached earlier as compared to the 4 W/cm^ exposure. The reduction in

heat release at 6 W/cm^ was probably due to the absence of the pilot flame.

Another point of interest which is seen in table 2 is that the percent weight

loss was approximately the same in each test series on all of the materials

tested. This resulted from the chemically combined water in the gypsum board

core being removed at a controlled rate which is established by the total

heat flux interacting with the specimen.

4.3. Ease of Ignition

Six individual tests were conducted on each of the nine materials. Data

from these tests are included in table 3. The time of degradation relates to

the time that the first signs of surface change or discoloration occurs on

the specimen. All of the recorded times, except the one on 13 mm (1/2 in)

vinyl covered gypsum board, relate to the browning or charring of the paper

exposed to the test flame. The vinyl covered board exhibited the development

of small bubbles before charring occurred and the time of degradation was taken from the time the first bubbles were observed.

Ignition is determined by observing the specimen during the flame

exposure period and marking the chart record when flame attachment occurs.

The flame exposure time required to obtain flame attachment to the specimen

is cataloged as the ignition time (see table 3) . The average ignition times

on the basis of six determinations of the materials tested, varied from a mini- mum of 27 seconds for vinyl covered gypsum board to a maximum of 83 seconds

for gypsum formboard and water resistant backer board. The average ignition

time for regular board was 50 seconds.

13
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14
Table 3. Gypsum Board Ease of Ignition Test Results

Material

Average

Surface

Degradation

Time (s)

Average

Time of

Ignition

(s)

Minimum Exposure

Time Required for

Sustained Flaming

(8)

Period of

Sustained

Flaming

(s)

8 mm (5/16")

MH Board

22 74 120 78

13 mm (1/2"

Formboard

22 83 143 19

13 mm (1/2"

Sheathing

37 82 171 13

13 mm (1/2"

Water Resistant

Backer Board

18 83 125 19

13 mm (1/2 ) Regular Board

14 50 78 43

13 mm (1/2")

Type-X Board

15 61 117 19

13 mm (1/2"

Vinyl Covered Board

.2 mm (.008") Vinyl

6 27 42 80

16 mm (5/8")

Type-X Board

16 60 128 26

25 mm (1")

Core Board

40 71 102 3

* The average values shown were developed on the basis of six determinations.

The time of contribution is normally recorded as part of this test procedure; however, during this test series the gypsum board products did not

contribute sufficiently to cause an increase in the photo tube output.

Because the low contribution level did not provide any comparative information about the materials, it was decided to test for sustained flaming

characteristics. This was accomplished by observing the specimen after

flame attachment occurred. The exposure flame was allowed to continue and

was shut off at random intervals when it appeared that the specimen would

sustain a flame without external support. The flame persistance time was measured and the average from six determinations is listed in the table. The

flame persistance time provides some information about how long a material

will sustain flaming after the primary ignition flame is removed.

A review of the various test results indicated that there is a correlation between the average ignition times from the ease of ignition test and

the average heat contribution times obtained from the rate of heat release

calorimeter with the piloted 4 W/cm^ exposure. Eight (8) of the nine (9)

materials (89%) tested had ignition times within 20 percent of the contribution times experienced with the calorimeter. Six (6) out of the nine (9)

materials (66%) had ignition and combustion times that differ less than 10

percent (see fig. 5)

.

15
100 r

Ignition

( Ignition

Test

)

Seconds

0 10 20 30 40 50 60 70 80 90 100

Heat Contribution

(Calorimeter)

Seconds • 8 min (5/l6") MH Board

O 13 mm (1/2") Formboard

13 mm (1/2") Sheathing

13 mm (1/2") Water Resistant Board ^ 13 mm (1/2") Regular Board

O 13 mm (1/2") Type-X Board

A 13 mm (1/2") Vinyl Board

A 16 mm (5/8") Type-X Board

# 25 mm (1") Core Board

Figure 5. Average Ignition Time (Ignition Test) vs. Heat

Contribution Time Piloted 4 W/cm^ Exposure (Calorimeter)

The time it takes sustained ignition to occur is recorded to indicate

the point at which a material will support a self-sustaining flame. As

mentioned earlier, sustained ignition is defined as having occurred if a flame persists any place on the specimen three seconds after the gas has been

cut off. As can be seen in table 3, vinyl covered gypsum board exhibited the

earliest ignition time of 42 seconds. The longest period of exposure for

obtaining ignition was experienced by gypsum sheathing with a time of 171

seconds.

The sustained flaming times which indicate the burning time after the

exposure flame is removed are also listed. Transient ignitions also occurred

and are considered to be any flaming that remains on the surface of a specimen for periods of less than three seconds.

16
4.4. Flame Spread

Most of the materials tested using the ASTM E 162 method exhibited

uniform burning characteristics. Four determinations were made on each

material; the results are presented in table 4. Three specific materials

tested showed a significant variation from the burning characteristics

experienced with the other materials. These materials were 13 mm (1/2 in)

gypsum sheathing, 13 mm (1/2 in) water resistant gypsum backer board and 13 mm (1/2 in) vinyl covered gypsum board.

The tests reported show that gypsum sheathing and water resistant gypsum

backer board had samples which resulted in a fairly short distance of flame

travel as compared to the other specimens. Both of these materials had a water resistant treated core and paper. It is believed from the observations

made that the paper and core treatment had an influence on the surface flame

spread. Each of the specimens exhibited a gas phase flash ignition at the

top, and the paper burned at a slow rate until the flame went out. A glowing

ignition of the paper was apparent for several minutes after the flame died.

When these materials were retested, a similar form of burning was experienced.

It is also apparent in table 4 that the vinyl covered gypsum board had

the highest flame spread index number of all of the materials tested. However,

the flame distance traveled and time was approximately equal to the distance

traveled and time on the unfinished paper surfaces. The higher index number

can be attributed to the burning of the vinyl which resulted in a significantly

higher stack temperature. The average net stack temperature rise for the

13 mm (1/2 in) regular gypsum was 18.3 °C, whereas the average net stack

temperature rise for the vinyl finished board was 36.16 °C. The vinyl finish

thus resulted in an approximate increase of 100% in heat release over the

regular unfinished board.

Standard ASTM E 84 tests were conducted on the same generic materials

(but not the same batch) addressed by this report during the past years as the materials were marketed. These tests were conducted at Underwriters'

Laboratories, Inc. and the test results have been included in table 4 to show

the flame spread characteristics of the specimen as it relates to the E 84

test method. The UL test report niombers are also included in table 4 for

reference. The average E 162 flame spread index varied considerably on

several of the materials as compared to the results obtained on the E 84.

There is a limited correlation between the results. This can be seen in fig- ure 6 and can also be observed in Underwriters' Laboratory Report "Flammability Studies of Cellular Plastics and Other Building Materials used for

Interior Finishes." The E 162 test method was designed as a research tool

and is not currently used by the model codes as a means of classifying building materials for code purposes.

Another point of interest is that the majority of the specimens tested

exhibited a flame travel distance of between 254 mm (10 in) and 356 mm (14 in)

in the E 162 test before the flame went out. This would indicate that the

approximate heat flux from the radiant panel at the flame out point for these

gypsum board products ranged between 1.58 W/cm^ and .90 W/cm^ as determined

from the energy flux per unit area profile given in the paper by Robertson,

Gross, and Loftus entitled "A Method for Measuring Surface Flammability of

Materials Using a Radiant Energy Source." The values given in the table

are based on interpolation of data from the above report.

17
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18
Materials

• 8 mm (5/16") MH Board

O 13 mm (1/2") Pormboard

13 mm (1/2") Sheathing

13 mm (1/2") Water Resistant Board

13 mm (1/2") Regular Board ^ 13 mm (1/2") Type-X Board

A 13 mm (1/2") Vinyl Board

A 16 ram (5/8") Type-X Board ^ 25 mm (1") Core Board

Flame

Spread

Index

ASTM E 162

Flame Spread Classification,

ASTM E 84

Figure 6. Variation in Flame Spread E 162 versus E 84.

4.5. Scanning Electron Microscope Study of

13 inin (1/2 in) Type-X Gypsum Board

The study was composed of two different sets of observations. The first

specimen studied was not exposed to heat or fire, while the second specimen

was exposed to a temperature of 750 °C (1382 °F) for one hour in a muffle furnace. The gypsum board paper ignited and burned away. The unfired board core specimen was viewed in order to determine the material's natural characteristics. The first observations of the core at 120 magnification indicated that

strands of glass fiber and particles of unexpanded vermiculite were relatively

evenly distributed throughout the material. Spherical voids were prevalent

throughout the core. These voids varied in size from 25 to 10 0 microns in

diameter. However, the majority of these voids averaged at about 50 microns.

The average vermiculite particle size was about 200 microns square and 5 to 10

microns in thickness. The glass fiber thickness was approximately 10 microns.

This can be seen in figure 7.

19
After scanning the surface of the specimen at 120 power, the magnification was increased to 800 power. At this level, it was found that gypsum

crystals do actually bond to the surface of the glass fiber. Gypsum crystals

were also found to be bonding to the compressed edges of the vermiculite but

it did not appear to be bonded very well to the smooth end surfaces (see fig.

8). The ends of the glass fiber strands appear smooth in the 120 power picture,

but at 800 power the ends of the fiber exhibited a rough appearance. The

gyps\im crystals which make up the major portion of the board core appeared to

be quite random in length and diameter. Crystal sizes ranged from about 3 to

10 microns in length. The crystal diameter ranged between 0.25 to 0.50 microns.

These crystals were bonded together into a random directional polycrystalline

mass. The gypsum crystals were also viewed at 2700 power, and they appeared

to have sharp well defined edges (see fig. 9)

.

After observing the unfired specimen, the fired specimen was viewed at

120 power as shown in figure 10. There was a vast difference between the

fired and unfired specimens. The most apparent difference did not show on

the surface of the crystal but was a physical change which took place within

the individual crystals as a result of being exposed to the fire.

In order to evaluate this property change, it is necessary to understand

the operation principal of the SEM. Upon viewing the specimen it could be seen that the crystals were receiving an electrical charge from the SEM's

electron beam which impinges on the surface and penetrates the specimen. The

beam interacts with the specimen and this results in the back scatter of some primary electrons and the release of secondary electrons. These free electrons

are picked up by a sensor and converted into an image which is viewed on a cathoderay tube [10]. With materials that are good insulators, electrons are captured and charging occurs. Charging was not noticed on the unfired specimen. The .01 micron (lOOA) coating of gold on the surface of the unfired

specimen successfully conducted the excess electrons to ground. It is believed

that because the chemically combined water was removed from the gypsum crystals

during the fire exposure, the material became a better electrical insulator

which allowed it to absorb (hold) a charge. This caused the surface to

become extremely bright and washed out almost all surface detail. To correct

this condition another .025 microns (250^) of gold was sputter-coated onto

the surface of the specimen before an acceptable pigture was obtained. This

resulted in a total thickness of .035 microns (350 A) of gold coating. When

the specimen was viewed again only very small bright patches appeared, and

this can be seen in figure 10. Several interesting observations can be made

from this picture. It is evident that visible changes did occur in the crystal

structure as a direct result of the specimen being exposed to a fire. In the

upper right corner of the picture a vermiculite particle has expanded to a considerable length. The particle of vermiculite located at the center left

also expanded but was restrained by the core. This can also be seen in fig- ure 10 which is a 500 power magnification of the same area. This demonstrates

how the vermiculite expanded and receded after cooling.

In figures 11 and 12 it is apparent that the exposed ends of the glass

fiber melted into a smooth droplet shape and no longer exhibits the roughsheared surface. While examining specimens of glass fiber which were totally

surrounded by the core, no deformation was noted.

The surface appearance of the gypsum crystals after being exposed to the

fire showed little change in characteristics when seen at a magnification of

500 to 800 power. However, it was noted that in one area on the surface of

the fire specimen the crystals appeared to be slightly rounded on the edges.

This area was observed again at a magnification of 2600x and the surface

characteristic could be better defined (see fig. 13) . This picture shows

that the crystals become rounded on the edges and there is some indication

that the particles may have been fused. The large hole in the center of the

picture is an air void, and the influence of specimen charging is seen on the

right side of the picture. Two scan faults also appear on this picture which

resulted from the charging of areas outside the field of view.

20
Figure 7. SEM Picture 120X Type-X

Board Core before Fire

Exposure. (Unfired Type-X

13 mm (1/2 in))

Figure 8. SEM Picture 800X Type-X

Board Core before Fire

Exposure. (Unfired Type-X

13 mm (1/2 in))

Figure 9

.

SEM Picture 27 0 OX Type-X

Board Core Gypsum Crystals

Not Exposed to Fire

Figure 10. SEM Picture 120X Type-X

Board Core after Fire

Exposure
Figure 11. SEM Picture 500X Type-X

Board Core after Fire

Exposure

Figure 12. SEM Picture 160X Expanded

Vermiculite and Melted

End of Glass Fiber after

Fire Exposure

Figure 13. SEM Picture 2600X Gypsum Crystals

of Board after Exposure to Fire
5 . SUMMARY

This paper summarizes results from four test methods used to evaluate

the fire properties of nine generic gypsum board materials. The laboratory

tests conducted were for potential heat, ease of ignition by flame impingement, rate of heat release, and flame spread. The potential heat of these

materials ranged from 510 J/g (220 Btu/lb) for core board to 2670 J/g (1150

Btu/lb) for water resistant backer board. The majority of the materials

exhibited potential heat values that range between 700 to 1510 J/g (300 to

650 Btu/lb) . The ignition times experienced were from a minimum of 42

» seconds with vinyl covered board to 171 seconds with gypsum sheathing. There

is also an interesting correlation between the ignition time from the ease

of ignition test and the time of heat contribution based on the piloted 4 W/cm^ exposure in the heat release calorimeter. Generally, all of the gypsum

* board products fall within a narrow peak heat release span. The materials

were tested using two different radiant heat flux levels without a pilot

flame 4 W/cm^ and 6 W/cm^ . Tests were also conducted at 4 W/cm^ with a pilot

flame above the specimen. It was found that the paper on the gypsum board

would not produce a flaming ignition at an unpiloted incident flux level

of 4 W/cm^ . The highest average peak heat release obtained was 8.2 W/cm^

.

Flame spread tests were conducted on the ASTM E 162 apparatus and the results

were compared with ASTM E 84 data. There is only limited correlation between

the data obtained from the two flame spread tests. The flame spread index

for the E 162 test method spanned from 8 to 38. The flame spread index for

E 84 went from 10 to 25.

A scanning electron microscope (SEM) study showed the changes which took

place in the core of 13 mm (1/2 in) type-X gypsum board when it was exposed

to fire. One of the most interesting findings was the change in electrical

characteristics of the gypsum crystals after being exposed to the fire environment. The removal of much of the chemically combined water resulted in the

crystals becoming better electrical insulators which allowed them to be

charged by the SEM's electron beam. It was also found that the sharp edges

of the crystals become rounded in the areas where there was direct flame

contact, and there was some indication that the particles may have fused.

This report attempts to provide basic information on the fire resistive

properties of gypsum board products. It is believed that the data presented

will help to improve the understanding of how gypsiam board materials react

during fire exposure.

6 . ACKNOWLEDGMENTS

Appreciation is expressed to Mr. William Kerry of the NBS , Electronics

Technology Division for his help in preparing the scanning electron microscope

photos used in this report, and to Mr. Roland Willard of the NBS, Center for

Fire Research, for his assistance in performing various tests.

23
7 . REFERENCES

[1] Abbey, C. E., Type-X Wallboard, What It Is and Where and When It

Originated, Southern Building Magazine (April 1966)

.

[2] Harmathy, T. , A Treatise on Theoretical Fire Endurance Rating, ASTM

STP 301, 10-40, American Society for Testing and Materials, Philadelphia,

Pennsylvania (1961)

.

[3] Gross, D. , Loftus, J. and Robertson, A., Potential Heat Method for

Measuring the Heat Release of Materials in Building Fires, Proceedings

ASTM, Vol. 61, 1336-1348 (A61)

.

[4] Parker, W. J. and Long, M. E., Development of a Heat Release Rate

Calorimeter at NBS, ASTM STP 502, 135-151, American Society for

Testing and Materials, Philadelphia, Pennsylvania (1972)

.

[5] Underwriters' Laboratories Incorporated, Building Materials Directory,

(223-225) Underwriters' Laboratories Incorporated, Chicago, Illinois

(1976)

.

[6] Standard Test Method for Potential Heat of Building Materials, NFPA

259-1976, National Fire Protection Association, Boston, Massachusetts

(1976)

.

[7] Gross, D. and Loftus, J., Flame Spread Properties of Building Finish

Materials, ASTM Bulletin (TP 134) , American Society for Testing Materials,

Philadelphia, Pennsylvania (1958) .

[8] Surface Flammability of Materials Using a Radiant Heat Source, ASTM

E 162-75, American Society for Testing and Materials, Philadelphia,

Pennsylvania (1975)

.

[9] Gross, D. and Natrella, M. , Inter laboratory Comparison of the Potential

Heat Test Method, Fire Test Performance, ASTM STP 4 64, 127-152, American

Society for Testing and Materials, Philadelphia, Pennsylvania (1970).

[10] Goldstein, J., Yakowitz, H. , Practical Scanning Electron Microscopy,

Plenum Press, New York, N. Y. (1975).

24
APPENDIX — COMPONENT WEIGHT FRACTIONS USED IN THE

CALCULATIONS OF POTENTIAL HEAT SHOWN IN TABLE 1.

Material Face Paper Back Paper Core

6 nun (1/4") Regular

Gypsum Board

.070 .073 .856

10 mm (3/8") Regular

Gypsum Board

.047 .049 . 904

16 mm (5/8") Regular

Gypsum Board

.028 .029 .943

SPECIAL TESTS

13 mm (1/2") Regular

Gypsum Board .035 .037 .928

Remaining Core

13 mm (1/2") Regular

Gypsum Board

3 mm (1/8") Core/

Paper Sections

.25 .25 . 50

25
NBS-lUA (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET NBSIR 77-1265

2* Gov't Access ion No.

3, Recipient's Acccs.sion No,

4. IlILh. ANL) i>Uo 1 H Lb

A XT T7TT A T TT A T" Tr\XT f\'X? 'I?TT>^ "DU A'DTTT) T TT? C AT? /^^Xn?DT/^ AN EVALUAiiON Or r IKii rKUrhKiibb Or (jhjNhKiL

GYPSUM BOARD PRODUCTS

5. Publication Date August 1977.

6» Performing Organization Code

7. AUTHOR(S)

J. Randall Lawson

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4926574

11. Contract/Grant No.

12, Sponsoring Organization Name and Complete Address (StreBtf City, StBte, ZIP)

Same as No. 9

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most sigpificant informatiort. If document includes a significant

bibliography or literature survey, mention it here.) An evaluation of the fire properties of generic gypsum board products was made

in order to obtain a better understanding of the material's reaction to a fire

environment. These gypsum board products are typically used in wall and ceiling

assemblies throughout the United States. Four small-scale fire test methods were

used in the examination of the materials' fire properties. The tests conducted were

for potential heat, ease of ignition by flame impingement, rate of heat release, and

rate of flame spread. All of these properties are of major importance in the design

of a building. They influence the potential rate of fire growth in a room. Standard

fire test methods were used for the development of data on rate of flame spread and

potential heat characteristics. The ease of ignition and rate of heat release

characteristics were determined by fire tests recently developed at the National

Bureau of Standards. Test results showed that the potential heat for the materials

examined ranged from 510 J/g (220 Btu/lb) to 2670 J/g (1150 Btu/lb) . The ignitability

of the materials spanned from 42 to 171 seconds, while the peak heat release averages

ranged from a 2.5 to 4.8 W/cm^ on an unpiloted 4 W/cm2 exposure and 3.9 to 8.2 W/cm2

on an unpiloted 6 W/cm^ exposure. The flame spread index for the materials ranged

from 8 to 38.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Buildings; ease of ignition; fire tests; rate of flame spread;

gypsum board; potential heat; properties; rate of heat release; scanning electron

microscope (SEM)

.

18. AVAILABILITY [x] Unlimited

1

' For Official Distribution. Do Not Release to NTIS

1

1 Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. C13

1 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22, Price

USCOMM-DC 29042-P74
I