Reference

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NBS

Publications

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NBSIR 78-1465

Urea-Formaldehyde Foam Insulation

Subjected to High Humidity

Conditions at Elevated Temperatures

E. T. Pierce

D. M. Burch

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

July 1978

rQC

100

,U56

78-1465

S. DEPARTMENT OF COMMERCE

TIONAL BUREAU OF STANDARDS

SSatioital Bureac of Standards APR 1

7

1979

, US

NBSIR 78-1465

\ 4 1 UREA-FORMALDEHYDE FOAM INSULATION

SUBJECTED TO HIGH HUMIDITY

CONDITIONS AT ELEVATED TEMPERATURES

E. T. Pierce

D. M. Burch

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D. C. 20234

July 1978

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

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

UREA-FORMALDEHYDE FOAM INSULATION SUBJECTED

TO HIGH-HUMIDITY CONDITIONS AT ELEVATED TEMPERATURES

by

E. T. Pierce and D. M. Burch

ABSTRACT

Cured specimens of urea-formaldehyde foam insulation from four major manufacturers

were exposed to high-humidity conditions at two moderately elevated temperatures

in a temperature and humidity chamber. These conditions were 40°C (104°F) at

92% rh and 50°C (122°F) at 92% rh. The occurrence of moisture absorption, shrinkage, weight loss, and crumbling of the specimens during the exposure periods

was examined.

Key Words: Insulation properties; moisture in insulation; shrinkage of foam

insulation; urea-formaldehyde foam insulation.

i
CONTENTS

Page

ABSTRACT i

1. Introduction 1

2. Experimental Procedure 2

3. Properties of the U-F Foam Insulations 6

4. Experimental Results 7

5. Conclusions 13

REFERENCES 14

ii
UREA-FORMALDEHYDE FOAM INSULATION SUBJECTED

TO HIGH-HUMIDITY CONDITIONS AT ELEVATED TEMPERATURES

by

E. T. Pierce and D. M. Burch

1. INTRODUCTION

The costs of fuels for space heating of residential buildings have been increasing

at a rapid rate. As a result, home owners recently have become interested in

reducing the heating energy requirement for their homes by installing thermal

insulation in walls, ceilings, and floors. A common method used to install insulation in an uninsulated cavity wall is to drill holes in the top and bottom of

each wall cavity and then to inject either a loose-fill or wet-foam material

into the cavities of the walls.

A material used to retrofit exterior cavity walls and ceilings is urea-formaldehyde

foam insulation. As a building insulation, urea-formaldehyde-based foam is generated on-site using portable equipment to foam a partially polymerized urea-formaldehyde-based resin which then reacts chemically (cures) in place. Three major

ingredients are used in the generation of the foam: urea-formaldehyde-based resin,

a surfactant (generally called a foaming agent) which includes an acid catalyst

or hardening agent, and air. A wet foam is dispersed from the apparatus through

a flexible hose into the wall cavity. A chemical reaction between the resin and

the hardening agent begins to take place immediately. Initial curing of the foam

is reported to begin within one minute. Complete curing of the foam, however,

usually requires several weeks. After the foam has cured and dried, it is reported

to have good insulating properties due to the many small air pores within its

cellular structure [1]*.

The National Bureau of Standards recently conducted an extensive literature survey

[1] on urea-formaldehyde foam to assess its thermal and acoustical properties.

This report identified two possible problem areas with regard to the use of urea- formaldehyde foam as a thermal insulation in cavity walls and ceilings. These

possible problem areas include long-term shrinkage of the foam after it has cured,

and the effect of high-humidity conditions at elevated temperatures on the performance of the foam.

In a recent test [2] carried out at a commercial laboratory, cured urea-formaldehyde

foam specimens were exposed for 10 days to a near-saturated condition (95 to 100% rh)

at an elevated temperature of 70°C (158°F). At the end of the test period, the

specimens exhibited a 9.6% weight loss and a linear shrinkage of approximately

30%. It was further reported that the specimens had warped severely, were friable

and very powdery, and could not be handled.

* See references at end of paper.

1
The purpose of the present study was to investigate the effects of high-humidity

conditions at moderate temperatures on the physical characteristics of urea-formaldehyde foam. The original plan was to expose cured foam specimens to high-humidity

conditions at 20, 30, 40, and 50°C. The 20 and 30°C conditions would be representative of residential applications, whereas the 40 and 50°C conditions would not.

Work for the 40 and 30°C conditions was completed. However, due to conflicts*

with other research efforts, work was not carried out for the 20 and 30°C conditions. While the results of this report are not indicative of urea-formaldehyde

foam performance in residential applications, the report does provide physical performance data for the foam at 40 and 50°C conditions. The properties investigated

include weight loss, moisture absorption, shrinkage, and fissuring. The test procedure is documented.

2. EXPERIMENTAL PROCEDURE

To obtain a variety of specimens of urea-formaldehyde (U-F) foam, four major

manufacturers were contacted, and foam from these manufacturers was injected into

wooden enclosures. In two cases, the manufacturer's personnel did the foaming.

In the other two cases, foaming was carried out by local contractors with the

manufacturer's knowledge. The enclosures were then stored in the laboratory, which

was maintained at approximately 23°C (73.4°F) and 40% rh, for approximately one month

in order to permit the injected foams to cure. Specimens of each of the foams were

then removed and exposed to the same ambient conditions for a period of ten days

to permit further curing to take place. Specimens of the insulations were then

placed in a temperature and humidity chamber for a 7-week exposure period at 30 °C

(122°F) and 92% rh. Other specimens, which had been kept in the laboratory during

the 7-week interval, were placed in the temperature and humidity chamber and were given a 14-week exposure period at 40°C (104°F) and 92% rh. Changes in weight,

dimension, and appearance were periodically observed and recorded during both the

exposure periods. Details of this procedure are described in the following

paragraphs

.

The wooden enclosures consisted of 1.22 m (4 ft) high wall cavities fabricated

from two nominally 2x4 studs placed 0.406 m (16 in) on center with 0.635 cm

(1/4 in) plywood attached to the front and back. A 2 x 4 plate was placed at

the top and the bottom. A photograph of several of the wooden enclosures is shown

in Figure 1.

Three of the suppliers used a hose-insertion technique to inject the foam into the

wooden enclosure. They inserted a hose for dispersing the foam into the cavity

of the enclosure and then gradually withdrew the hose as the cavity was filled with

foam. One manufacturer's representative simply squirted the foam from the top

of the cavity without inserting the hose. After the cavities were filled, the excess foam was partly struck off with the 2x4 top plate. The top plate was then fastened across the top of the wooden enclosure. Light compression of the

foam helped assure an initially full cavity.

* The temperature and humidity chamber used to condition the specimens belonged

to another organizational unit of NBS. Tests could not be performed at the 20 and

30°C conditions because the temperature and humidity chamber was needed for other

research studies.

2
f 3
After the foaming process was completed, the wooden enclosures were placed in a vertical (upright) position for approximately one month in the laboratory, which

was maintained at approximately 23°C (73.4°F) and 40% rh. The purpose of this one- month conditioning period for the installed U-F foam insulations was to permit the

foam insulations to cure at rates consistent with typical cavity-wall applications.

During the curing process, the U-F foam loses moisture to adjacent materials or air

spaces. The rate of the curing depends on the rate at which moisture is transferred, which in turn depends on the water-vapor transmission characteristics of the

materials comprising the cavity. After U-F foam reaches a dry density of approximately 11 kg/m^ (0.7 lb/ft^), it is generally considered to have reached a cured

state

.

One of the wooden enclosures was weighed periodically during the curing period.

After 35 days, the wooden enclosure stopped losing weight. At this point, the

calculated density of the foam determined from the volume of the wooden enclosure

and the weight of the foam was very nearly equal to the dry density of foam. These

results suggest that curing of the foam within the wooden enclosure took place in

approximately 35 days.

After the insulation was cured in the wooden enclosures, a plywood panel was removed from each of the wooden enclosures and the linear shrinkage in the height

and width directions was measured. Next, three large pieces, approximately

23 x 28 cm (9 x 11 inches), were cut out with a bread knife from the U-F insulation

contained in each of the wooden enclosures. Differences in fragility or coherence

were observed. The insulation from some of the wooden enclosures could be cut

neatly, while that from others was very fragile and tended to fracture when cut.

The three specimens from each of the wooden enclosures were then placed in a cardboard carton and stored at ambient conditions of approximately 23°C (73.4°F) and

40% rh for six days. The purpose of the second conditioning period was to permit

additional curing of the specimens to take place. Shrinkage was not measured during

this period.

Test specimens of final size were then cut from the larger specimens and stored

for an additional four days. The small specimens were first cut about 1 cm larger

in width and height than the desired final size. Thin layers were then shaved off

until the final size was reached. An attempt was made to produce final specimens

with square sides and flat surfaces in the direction of height and width. The thickness of the specimens was not altered from the thickness as installed. The size

of the final specimens for test was approximately 10 x 12 x 9 cm (3.9 x 4.7 x 3.5 in).

Specimens were then placed in a temperature and humidity chamber (see Figure 2) and

exposed to 50°C (122°F) and 92% rh for a 7-week period. Shrinkage, weight loss,

and appearance of the specimens were periodically observed and recorded. Shrinkage

and weight loss were also observed for control specimens of the four insulations

which were not placed in the temperature and humidity chamber but were instead exposed

to laboratory conditions of 23°C (73.4°F) and 40% rh. Differences in physical performance of the two control groups would be due to differences in the ambient conditions to which the two groups were exposed.

Other specimens from the four manufacturers, which had been exposed to laboratory

conditions of 23°C (73.4°F) and 40% rh during the 7-week period, were then placed

in the temperature and humidity chamber and exposed to 40°C (104°F) and 92% rh for

4
Figure 2. U-F foam specimens ready to be placed

in temperature and humidity chamber.

5
a 14-week period. As in the case of the previous test, shrinkage, weight loss,

and appearance of the foam specimens were observed and recorded.

3. PROPERTIES OF THE U-F FOAM INSULATIONS

The wet densities as foamed, the dry densities as tested, the curing times in the

wooden enclosures, and the observed shrinkages during this curing process for the

four foam insulations are given in Table 1.

TABLE 1. PROPERTIES OF U-F FOAM INSULATIONS

Manufacturer

Type

Wet Density

as Foamed

kg/m3 (lb/ft 3

)

Dry

as o kg/ nr

Density

Tested

(lb/ft 3

)

Curing Time in

Wooden Enclosure

days

Shrinkage

During Cure

%

A 40 (2.5) 8.1 (0.51) 24 2.0

B 45 (2.8) 16.8 (1.05) 38 2.7

C 58 (3.6) 16.1 (1.01) 39 2.4

D 51 (3.2) 12.3 (0.77) 44 2.5

AV—^ =2.5

1 / 1/ Average of linear shrinkage in the height and width directions.

Since foam A may not have completed the curing process, it is not included

in the average.

The wet densities of the foams were determined by dividing the weight of the

insulation in the enclosure by the volume of its cavity. The dry density for

materials as tested was determined by dividing the weight of the specimens by

their volumes.

Foams B, C and D were cured in the wooden enclosure for more than 35 days, which

is the estimated curing time based on periodic weighing during the curing process.

Foam A was cured in the wooden enclosure for only 24 days, which is 11 days less

than the estimated curing time. Therefore, at the time of cutting out specimens

from the insulation in the wooden enclosure, foam A may not have reached a cured

state. Since specimens of foam A, after being removed from the wooden enclosure,

were conditioned for an additional 10-day period in the laboratory air and attained

a dry density of 8.1 kg/m (0.51 lb/ft 3 ), it is likely that foam A was at a cured

state at the time of the exposure tests in the chamber.

The linear shrinkage that occurred when the specimens were cured in the wooden

enclosures ranged between 2.0 and 2.7%. The 2.0% figure for specimen A is less

than the other specimens, perhaps because this specimen experienced a shorter curing

period. Neglecting foam A, the average amount of linear shrinkage observed during

the curing process was found to be 2.5%.

6
4. EXPERIMENTAL RESULTS

4.1 14-WEEK EXPOSURE TEST* AT 40°C (104°F)

A plot of the relative weight gain of the four specimens placed in the temperature

and humidity chamber as a function of time is given in Figure 3. The relative

weight gain (<f> ) is defined by the relations:

<j> = (W - w

i )/w..

Here W and W^ are the current weight and initial weight of the specimens, respectively. Note that all the specimens gained weight after being placed in the

temperature and humidity chamber. This weight gain was attributed to the acquisition of moisture by the specimens. From the third to the fourteenth week, the

specimens tended to lose weight. It was hypothesized that this latter weight loss was due to a chemical reaction involving the acquired moisture and constituent(s)

of the specimens.

After the specimens were removed from the temperature and humidity chamber, the

weight of the specimens declined markedly as they reached equilibrium with the

ambient conditions of the laboratory (23°C (73.4°F) and 40% rh). Note that the

final weight of the specimens after being removed from the chamber was seen to

be less than the initial weight of the specimens.

The test results for the 14-week 40°C (104°F) exposure test are summarized in

Table 2. The linear shrinkage for the various U-F foam insulations is given in

column 3. After the fourth week, specimens B, C and D began to fissure and fall

apart. It was therefore not possible to record linear shrinkage for these specimens after 4 weeks. The specimens of foam A did not fissure and fall apart during

the exposed period. Photographs showing the condition of the specimens placed in

the chamber and those not placed in the chamber are given in Figure 4. While

placed in the temperature and humidity chamber, specimen A underwent a linear

shrinkage of 5.1% in addition to the 2.0% shrinkage observed during the curing

process

.

The average linear shrinkage of the control specimens exposed to ambient conditions

of 23°C (73.4°F) and 40% rh during the 29-week period was only 1.6%. In addition,

none of the control specimens crumbled and fell apart.

* This exposure test was conducted after the 7-week exposure test at 50°C (122°F).

It is presented first because weight changes of the specimens were monitored on

a weekly basis, permitting a more detailed discussion of the processes taking

place in the temperature and humidity chamber.

7
SPECIMEN C 8

Figure

3-

Relative

weight

change

of

specimens

asa

function

of

time

during

the

lU-week

U0° C

(lOi*°

F)

exposure

test.
9

Figure

1+.

Appearance

of

U-F

foam

specimen

after

exposure

to

U0° C

(10H°

F)

at

92%

rh

fora

lU-week

conditioning

period.

For

each

pair

of

frays:

righttray

contains

the

control

specimen

left

tray

contains

the

specimen

which

was

conditioned

in

the

chamber.
TABLE 2. SUMMARY OF TEST RESULTS FOR 14-WEEK 40°C (104°F) EXPOSURE TEST

Manufacture

Type

Linear Shrinkage^

after 1 week after 4 weeks

% %

Weight Loss^

%

Moisture

Loss after removal

from chamber^

%

A 3.3 4.1 14.5 9.7

B l.l

4

1.9 4 11.5 20.1

C 3.0 3.4 10.8 38.7

D 3.4 4.4 12.3 27.9

-^Average of linear shrinkage in the length, width, and thickness directions. ^ (W^ - Wf)/W. , where W^ = initial weight of specimen prior to exposure test and w

f

1 is the final weight of the specimen after it was removed from chamber and

reached equilibrium with ambient air at approximately 23°C (73.4°F) and 40% rh.

(W

z - W^)/W^, where W

z = final weight of specimen while still in chamber.

W^ and W^ are as above. It is assumed that this weight loss results from

reduced moisture content.

Shrinkage in width direction only. Shrinkage in other directions could not be

measured because of the physical condition of the specimen.

Therefore, it was concluded that the combination of moderately elevated temperatures

and high humidity conditions at 40°C (104°F) was the cause of the crumbling and

fissuring of the specimens placed in the chamber.

The percentage weight losses for the specimens placed in the chamber are given in

column 4 of Table 2. The weight loss for each specimen was determined by taking

the difference between the initial weight of a specimen and its final weight after

being removed from the chamber and reaching equilibrium with ambient air at 23°C

(73.4°F) and 40% rh. Note that the percentage weight loss for all the specimens

does not differ significantly. The average weight loss is 12.3%. On the other hand,

the weight loss for the control specimens exposed to ambient conditions 23°C (73.4°F)

and 40% rh for a 16-week period ranged between 4.2 and 5.6%.

The percentage of moisture in the specimens which was lost when they were removed

from the chamber is given in column 5 of Table 2. This amount of moisture is

assumed to be due to the differences between the equilibrium moisture contents

for the separate exposure conditions. Note that specimen A, which did not fissure

and fall apart, lost much less moisture after being removed from the oven than

the other specimens.

10
4.2 7-WEEK EXPOSURE TEST AT 50 °C (122°F)

For this exposure test, specimens of foam insulations B, C and D began to fissure

after the second week. A photograph showing the condition of the test and control

specimens at the end of the 7-week exposure period is given in Figure 5. Note

that as in the case of the previously discussed 14-week exposure test, specimen A

did not fissure and fall apart.

The test results for the 7-week exposure test at 50°C (122°F) are summarized in

Table 3. The average linear shrinkage at the end of the second week for this

* exposure test was approximately the same as the amount observed at the end of the

fourth week for the 14-week exposure test at 40°C (104°F). The percentage weight

losses tended to be slightly lower than values for the 14-week exposure test at

40°C (104°F). As in the case of the other exposure test, the moisture loss for

specimen A after it was removed from the chamber was much less than that for the

other specimens.

-

TABLE 3. SUMMARY OF TEST RESULTS FOR THE 7 -WEEK 50 °C ( 122 °F) EXPOSURE TEST

Manufacture

Type

Linear

Shrinkage^

after 1 week

%

Linear

Shrinkage^

after 2 weeks

%

Weight Loss

%

Moisture

Loss after removal ^ from chamber-^

%

A 3.9 4.9 15.6 3.6

B 2.0 4.0 10.5 9.1

C 2.9 3.6 11.0 18.1

D 3.1 4.6 11.9 18.8

Av = 4.3

-^Average of linear shrinkage in the length, width, and thickness directions. ^ - Wj)/W^, where W^ = initial weight of the specimen prior to exposure

test and W^ is the final weight of the specimen after it was removed from

the chamber and reached equilibrium with ambient air at approximately

23°C (73.4°F) and 40% rh.

(W - Wf)/W^, where W

z - final weight of specimen while still in chamber. W^ ana W^ are as above. It is assumed that this weight loss results from reduced

moisture content.

11
12

each

pair

of

trays:

right

tray

contains

the

control

specimen

left

tray

contains

the

specimen

which

was

conditioned

in

the

chamber.
5. CONCLUSIONS

Urea-formaldehyde foam from four major manufacturers was cured in wooden enclosures

and underwent a linear shrinkage of approximately 2.5%. Specimens from these four

foams were exposed in a temperature and humidity chamber for a 14-week period at

40°C (104°F) and 92% rh, and other specimens for a 7-week period at 50°C (122°F)

and 92% rh. For both exposure tests, three out of four of the specimens fissured

and fell apart. The specimen which did not fissure and fall apart for either

exposure test did not take on as much moisture as the other specimens when it was placed in the temperature and humidity chamber. All the specimens underwent

\ linear shrinkage of approximately 4% during the first two to four weeks of the

exposure test. All test specimens also underwent a weight loss between 10 to 16%.

The total linear shrinkage due to the curing process and the exposure test was approximately 6.5%. For cavity wall application, this amount of shrinkage corresponds to a reduction in insulated area of approximately 13%. The uninsulated

regions created by the shrinkage constitute high conductance air spaces which will

result in increased heat transmission. Another mechanism by which the heat transmission may be increased is air circulation around the insulation.

The experiments did not determine a threshold condition of temperature and

humidity below which the U-F foam insulation would not lose its structural form

and disintegrate. Neither did the test reveal why one of the four foam insulations

did not collapse structurally like the other three. The temperature conditions used

in the 7-week and 14-week exposure tests are frequently exceeded in the attic of

a residence, but a concurrent relative humidity of 92% would not be likely to occur after the initial curing period, unless occasional wetting occurred from rain

or other causes. Urea-formaldehyde foam insulation of one of the types used in

these tests has been periodically observed over a 35-month period in the wall of

a test house [3] exposed to natural weather conditions in Washington, D.C. The

foam has not collapsed structurally, but it did undergo a linear shrinkage of

about 8% during a 35-month period.

The results of these tests are not sufficiently comprehensive to provide reliable

criteria for the application of urea-formaldehyde foam insulation in buildings,

since they do not establish a threshold of temperature and humidity below which

structural disintegration will not occur, nor the long-term shrinkage under typical

conditions. They do serve as a caution in applying U-F foam insulation in temperature and humidity conditions near those used for the exposure tests. Although

one type of foam insulation maintained its structural shape, it did shrink sufficiently to reduce its overall insulating effect significantly.

• Further tests are needed to investigate physical and heat transmission characteristics

of U-F foam insulation at representative conditions for residential applications,

„ and to determine the causes for variations in physical performances for different

brands. If these tests were to show that urea-formaldehyde foam specimens undergo

physical degradation when exposed to representative conditions for residential applications, then such a test as outlined in the present report should be incorporated

as a test in a performance standard for urea-formaldehyde foam insulation.

13
REFERENCES

1. W. J. Rossiter, R. G. Mathey, D. M. Burch, and E. T. Pierce, Urea-Formaldehyde - Based Foam Insulations: An Assessment of Their Properties and Performance, NBS

Technical Note 946, July 1977.

2. Urea-Formaldehyde Foam, Report No. 39573, Owens-Corning Fiberglas Corporation,

Technical Center, Granville, Ohio, 43023, April 1973.

3. D. M. Burch and C. M. Hunt, Retrofitting an Existing Wood-Frame Residence for

Energy Conservation — An Experimental Study, NBS Interagency Report 77-1274

(July, 1977) and NBS Building Sciences Series BSS 105 (in press).

14
NBS-114A (REV. 7-73)

J

y

4

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 7 8- 1465 (R)

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

UREA-FORMALDEHYDE FOAM INSULATION SUBJECTED

TO HIGH HUMIDITY CONDITIONS AT ELEVATED TEMPERATURES

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S) 8. Performing Organ. Report No. NBSIR 78-1465 (R)

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 462 6l4i

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

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

bibliography or literature survey, mention it here.) Cured specimens of urea-formaldehyde foam from four major manufacturers were exposed

to several high-humidity conditions at moderately elevated temperatures in a temperature and humidity chamber. These conditions included 40° C (l04° F) at

92% rh and 50°(l22° F) at 92% rh. The occurrence of moisture absorption, shrinkage,

weight loss, and crumbling of the specimens during the exposure periods was

examined.

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) . . . . . Insulation properties; moisture m insulation; shrinkage

of foam insulation; urea-formaldehyde foam insulation.

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