NISTIR 88-3893

Report of Roof Inspection:

Partial Delamination of

Adhesive-Bonded Seams at an

Army Facility

Walter J. Rossiter, Jr. and James F. Seiler, Jr.

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1988

Prepared for:

U.S. Army Engineer District, Baltimore

PO Box 1715

Baltimore, MD 21303-1715

NISTIR 88-3893

Report of Roof Inspection:

Partial Delamination of

Adhesive-Bonded Seams at an

Army Facility

Walter J. Rossiter, Jr. and James F. Seiler, Jr.

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1988

National Bureau of Standards became the

National Institute of Standards and Technology

on August 23, 1988, when the Omnibus Trade and

Competitiveness Act was signed. NIST retains

all NBS functions. Its new programs will encourage

improved use of technology by U.S. industry.

Prepared for:

U.S. Army Engineer District, Baltimore

POBox 1715

Baltimore, MD 21203-1715

U.S. DEPARTMENT OF COMMERCE

C. William Verity, Secretary

NATIONAL INSTITUTE OF STANDARDS

AND TECHNOLOGY

Ernest Ambler, Director

ABSTRACT

This document was prepared at the request of U.S. Army Engineer

District, Baltimore, to provide assistance in obtaining data on

the delamination of seams of an EPDM roofing system at Fort

Belvoir, Virginia. The investigation was beneficial to NIST,

because it provided an opportunity to characterize adhesivebonded seams in service and to obtain data relative to NIST

laboratory research on the effect of surface contamination on

seam performance.

Seam specimens were taken from the roof and analyzed for peel

strength and surface condition of the rubber. In addition, seams

were prepared in the laboratory using the same brand name

rubber/ adhesive system to obtain peel-strength values for

comparison with those measured for the field specimens. The

results of the study indicated that the field specimens had low

T-peel bond strengths in comparison to the strengths achieved by

the laboratory-prepared seams. Small voids in the adhesive layer

of the seams of the field seams may have contributed, in part, to

the low bond strength. SEM analysis of the field-formed seams

indicated the presence of a talc-like contamination on the rubber

surface which may have also contributed to the low strength. In

addition, SEM analysis of some laboratory specimens cleaned with

the proprietary wash solution showed a talc-like contamination

which was not visible to the unaided eye. Other laboratory

specimens cleaned using the wash solution did not show such

contamination

.

Key words: adhesive-bonding, bond strength, contamination, EPDM,

field inspection, low-sloped roofing, membranes, roofs, seams,

SEM analysis, surface condition

111
TABLE OF CONTENTS

Page

ABSTRACT iii

LIST OF TABLES ...... v

LIST OF FIGURES v

1. INTRODUCTION 1

2. OBSERVATIONS FROM THE FIRST FIELD INSPECTION 2

2.1 Roof Construction 2

2.2 Observations and Notes 3

3. OBSERVATIONS & TESTS ASSOCIATED WITH THE SECOND

FIELD INSPECTION. 7

3 . 1 Test Samples and Observations Noted During

Field Sampling .....

3.2 T”peel Tests of the Field Seam Samples

3 . 3 Observations on the Condition of the

Field Seam Samples 10

3.4 Laboratory Specimens for T-peel Testing 12

3.5 Nature of the Adhesive 17

3.6 Scanning Electron Microscopy 19

4. SUMMARY AND CONCLUSIONS 23

5. ACKNOWLEDGMENTS 2 5

IV

VO

"vj
LIST OF TABLES

Page

Table 1. Observations Noted During Sampling of the Seams. 26

Table 2. Results of T-Peel Tests of the Field Samples . . 27

Table 3 . Observations on the Condition of the Field Seam

Specimens 28

Table 4. Variables Studied for Their Effect on the Bond

Strength of the Laboratory Specimens ...... 31

Table 5. Results of T-Peel Tests of the Laboratory

Specimens 32

Table 6. Modes of Failure of Laboratory Specimens

During T-Peel 3 3

LIST OF FIGURES

Page

Figure 1. ‘ Cross Section of the Roof Construction

Including a Seam and the Lap Sealant at

the Seam Edge (Not to Scale) 34

Figure 2. Plan Indicating Approximate Dimensions of the

Roof and Locations of the Test Cuts 35

Figure 3. Results of the T-peel Tests for the Laboratory

Samples in Comparison With Those of the

Field Samples 36

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1 . INTRODUCTION

In September, 1987, the U.S. Army Corps of Engineers (COE),

Baltimore District, requested the NIST Center for Building

Technology to provide information on the performance of adhesivebonded seams in EPDM (ethylene-propylene-diene terpolymer)

roofing systems. The request centered on the roofing of the new

State-of-the-Art Medium Terminal (SAMT) Building at Fort Belvoir,

Virginia. The system had a fully-bonded EPDM membrane constructed

in the late summer of 1986. During a COE inspection of the roof

conducted shortly prior to the request, hairline cracks were

found in the lap-sealant applied along the outside edge of the

seams. Some delamination of small sections of seams was also

observed. The COE asked that NIST research staff inspect the

roof for purpose of assisting the COE in analyzing the problem

occurring with the roofing, and in particular the lap-sealant.

Two NIST researchers visited the roof twice accompanied by a COE

representative. The first visit was on 10 October 1987 to

observe the roofing, and, if warranted, to suggest plans for

further investigation. It was decided to conduct further

investigation concerning the seam condition, particularly

regarding contamination of the surface of the EPDM rubber at the

seams. Thus, a second visit was made on 24 November 1987 to take

samples of the seams for laboratory testing and analysis. Other

observers from NIST, COE, and the Navy were present during the

second visit.

1
This report presents a summary of the field inspections and

laboratory testing. The investigation was beneficial to NIST,

because it provided an opportunity to characterize adhesivebonded seams in service and to obtain data relative to NIST

laboratory research on the effect of surface contamination on

seam performance.

2.

OBSERVATIONS FROM THE FIRST FIELD INSPECTION

2 . 1 Roof Construction

At the time of this inspection, COE staff described the specified

roof construction (Figure 1) as follows:

1. A monolithic steel deck constructed from steel plates welded

at the seams. The thickness of the plates was not given.

The steel could not be penetrated which precluded mechanical

attachment of the insulation and/or membrane.

2. A single layer of polyisocyanurate cellular plastic board, 2

in. (50 mm) thick. The insulation was secured to the deck

using hot asphalt.

3. A single ply of EPDM membrane, 0.060 in. (1.5 mm) thick,

totally adhered to the insulation using a contact adhesive.

Seams bonding adjacent sheets were about 10 ft (3 m) apart.

A lap-sealant was applied to the outside edge of the field

seams after installation of the roofing (Figure 1)

.

4 . Field seams were prepared by cleaning (washing) the rubber

sheets at the overlap areas with a proprietary solvent

(wash) solution. This was a hydrocarbon-based solvent that

was black in color. After cleaning, a proprietary contact

adhesive was used to form the bonds.

2
4. The building was about 38,000 ft^ (3500 m^) , with few

penetrations. Figure 2 shows a plan-view outline of the

roof without indicating the penetrations.

2 . 2 Observations and Notes

The following observations were noted during the inspection of

10 October 1987:

o The membrane was black rubber, typical of EPDM. The

membrane was totally adhered and, in general, was flat on

the substrate without wrinkles and buckles. One small area

at the southeast corner showed some wrinkling for reasons

which were not determined. Field seams between sheets were

generally 6 in. (150 mm) wide. Lap sealant had been applied

to all edges of the seams (Figure 1) . In some areas, the

lap-sealant was re-applied by the contractor because of

hairline cracking that had occurred in the original lapsealant (see discussion that follows)

.

o The slope was apparent and considered to be generally

adequate. The specification reportedly required 1/4 in. /ft

(20 mm/m) . One minor area of ponding of water was observed

near a parapet wall at the northwest corner of the building,

o There was some "picture-framing^" of insulation boards.

While walking across the roof, some of the boards could be

felt to -move when they were stepped on. This indicated that

some boards were not well adhered to the deck. COE staff

explained, when construction began, many insulation boards

^Imaging of the outline or edges of the insulation board

through the membrane.

3
did not lie flat on the steel deck. This was due to the

raised welds between some deck panels. During roof construction,

grooves were cut in some insulation boards to accommodate

the welds in an attempt to allow the boards to set flat on

the deck.

o In observing the in-place lap-sealant, many areas were seen

where a hairline crack had formed parallel to the seam. The

crack was along the edge of the upper sheet comprising the

seam (Figure 1) . (The hairline cracks were as described in

the COE request for assistance, and were the reason for

inspecting the roof.) In two small areas, a sample of

sealant was removed from the seam using a knife. The

removed sealant samples were judged to be pliable. Although

the evidence from this observation was limited and subjective,

it suggested that embrittlement of the lap-sealant had not

occurred. Further testing of the lap-sealant was not performed.

o Many areas of the seam where hairline cracks were observed

in the lap-sealant were probed using the tip of a jack-knife

blade. The blade tip was inserted into the hairline crack

and into the edge of the seam. It was found that, in many

areas probed in this manner, the lap seam had delaminated

along its edge. The extent of delamination varied from

location to location on the roof. No consistent pattern was

observed. The amount of delamination into the seam ranged

from tenths of inches to a couple of inches or more (a few

millimeters to 50 mm or more) . No areas were found where

the seam had completely delaminated across its entire width.

However, not all the seams of the roof were probed. ’ Dirt

4
was generally observed in the delaminated seam areas. The

dirt was found on top of the adhesive, which was taken as an

indication that it entered the delamination after adhesive

application to the rubber sheet, and after seam formation.

o In considering reasons for the hairline cracks in the lapsealant, the question was asked whether they were symptomatic

of some delamination of the seam. This was raised because

of the observation that some seam delamination at the edge

of the lap was generally present where the cracks in the

lap-sealant were found. Whether a cause and effect relationship

existed between the cracks in the lap-sealant and the

delamination of the seams was not known. Further, the

question was not investigated in this brief investigation.

Nevertheless, because some delamination was occurring in the

seams, it was decided to conduct a laboratory investigation

of the seam condition.

o During this first inspection, the COE representative had

informed NIST staff that the roofing contractor had planned

to re-apply the lap-sealant in the areas where cracking had

occurred (see authors' note below) . However, it was

considered that such a repair might not eliminate the

hairline cracks, if they were not due to poor lap-sealant

performance, but were symptomatic of seam delamination.

With that in mind, some areas of seams where a second

application of lap-sealant had been applied over that

originally installed were closely examined for the presence

of cracks. In some locations, cracking of the second

application of the lap-sealant had occurred.

5
o (Authors* note: Subsequent to the first inspection of the

roof and prior to preparing the present report, COE had a

Washington-based roof consultant perform an inspection of

all areas of the seams. The consultant recommended that the

seams should be repaired. The COE representative indicated

that the seams were to be re-covered with strips of EPDM

rubber, and that further application of lap-sealant to

existing seams was not to be done.)

6
3. OBSERVATIONS & TESTS ASSOCIATED WITH THE SECOND FIELD INSPECTION

The second inspection was conducted to obtain seam samples for

laboratory testing of strength and observation of the surface

condition of the rubber sheets from the delaminated samples. The

following tasks were associated with this part of the investigations

o Taking seam samples

o Conducting T-peel tests of the field seam samples

o Noting condition of the rubber surface of the delaminated

seam samples

o Preparing new laboratory specimens for T-peel testing

o Determining the type of adhesive used to prepare the seams

o Conducting scanning electron microscopy analysis of selected

samples

.

3 . 1 Test Samples and Observations Noted During Field Sampling

Test samples of the lap seam were taken from five general

sections of the roof: each corner and in the center of the

building (Figure 1) . Before cutting the membrane, it was decided

to take both "good" and "bad" samples from each of the 5 sections.

Good samples were those having no hairline cracks visible in the

lap-sealant; whereas bad samples had a crack in the lap-sealant

and some delamination of the bond along the seam edge, though not

across the entire width of the seam.

Four replicate good and bad specimens were cut at each sample

location, providing a total of 40 specimens. At each location,

the specimens in each set (whether good or bad) were sampled

within a few inches of each other to allow repair of the cut with

a single patch. Samples of the insulation board were not taken

during the inspection.

During sampling, observations concerning the condition of the

specimens and the roofing were noted. These observations are

7
summarized in Table 1. A major observation was the presence of

small voids (1-2 mm) in the adhesive layer, which were readily

seen when many of the cut seam specimens were viewed on edge.

Reasons for the presence of the voids were not ascertained. One

suggestion is small air pockets were entrapped between the

individual sheets mated to form the seam. Another suggestion is

that the solvent had not totally evaporated from the contact

adhesive before formation of the seams. Then, after mating of

the seam sheets, the residual solvent volatilized to create the

voids

.

From Table 1, it can be seen that most of the sampled areas of

the roof under the cut membrane appeared to be dry. Water was

found under sample location No. 2 where the good samples were

cut. Assuming that the roof was applied in a dry state, then the

water apparently entered the system through a delamination that

totally traversed the seam. No puncture or other defect was

observed in the membrane in the location of the test sample cut.

Another important observation made during seam sampling was the

poor adhesion of the facer sheet^ to the insulation board

observed at two locations (G2 & G4)

,

Although the observation

was limited to two locations, it suggested that, in some areas of

the roof, the attachment of the membrane to the substrate was

less than expected. The observation was taken as evidence of the

importance of routine periodic inspection of this roof to assure,

^Mat that was factory-bonded to the face of the insulation

board.

8
among other factors, that the roof membrane remains adequately

secured to the substrate.

3 . 2 T-peel Tests of the Field Seam Samples

The T-peel strengths of the lap seam specimens were determined

using a portable testing machine^. The tests were based on ASTM

Standard Method D 1876 and conducted at room temperature, 70 to

72 “F, (21 to 22 °C) at a rate of 2 in./min (50 mm/min) . Samples

G1 and B1 were tested in a room of the SAMT Terminal Building

shortly after they were cut from the roof. This was to demonstrate

the applicability of the portable test machine to obtaining data

in the field, and its usefulness in addressing a practical

problem. The remaining samples were tested in the NIST laboratories

with the portable test machine.

The results of the T-peel tests are given in Table 2 for the

individual sample sets and also the pooled sets of all specimens

described as good and bad. The data for each set of good and bad

samples, as well as the pooled data for all specimens, were

compared using the statistical t-test technique. The comparisons

were made at the 0.05 percent significance level. The results of

the t-test comparisons are given in the right column of Table 2.

As is evident, the average values of the peel strength were only

significantly different for the good and bad specimens of Sample

Set 1. The other sets (nos. 2-5) showed no significant difference.

^Model SP-103A, Instrumentors , Inc. The brand name is given

to specify adequately the equipment used. In no case does such

identification imply recommendation or endorsement by NIST.

9
In the case of Sample Sets 1, 2 , and 4, the bad specimens had an

average strength less than that. of the good specimens. Sample

Sets 3 and 5 were the opposite with the bad specimens having

greater average strengths.

The average peel strength for all good and bad specimens were 2.4

and 1.9 Ibf/in. (0.42 and 0.33 kN/m) , respectively (Table 2).

This difference was statistically significant at a significance

level of 0.05%, even though four of the individual sets were not

significantly different. The pooled data is more sensitive to

differences because of the larger number of points involved in

the comparison. No practical significance is assigned to the

difference in strength of the pooled good and bad samples at this

time. Nevertheless, the data indicate that, on the average, the

samples cut from seam areas where the lap-sealant displayed

hairline cracks had lower strengths than those areas where no

cracking was present.

3 . 3 Observations on the Condition of the Field Seam Samples

After delamination of the T-peel specimens, each was examined

visually in the laboratory for evidence of contamination or other

factors that may affect bond strength. A summary of the comments

recorded during the examinations is given in Table 3 . Three

major observations from the examinations may be noted.

First, the majority of the specimens (23 cases) showed little or

no surface contamination as seen by eye. Some limited light

microscopy was conducted on selected specimens at 25 magnification.

10
but the results gave no further evidence of the surface condition.

Although extensive surface analysis of surface contamination was

beyond the scope of this investigation, limited analyses using

scanning electron microscopy were performed and are discussed in

Section 3.6.

Second, six specimens (Bl-1 through Bl-4, B2-2, and B2-4) were

found by eye to have noticeable surface contamination, which

appeared as a brownish oil-like film on the rubber surface. The

source of the film was not ascertained, and the oil-like material

was not identified. Possible reasons for the presence of the

film include random contamination of the rubber during seam

formation, perhaps due to use of an unclean cloth in cleaning

(wash solution) the rubber surface in the field, or maybe the

migration of a foreign substance from the rubber to the sheet

surface. If the latter were the cause, it is thought that the

oil-like film would have been more wide spread. The finding of

some obvious surface contamination raises questions as to whether

adequate cleaning of the rubber surfaces was accomplished during

fabrication of the field seams, and if other non-visible contaminants

were present on the seam specimens.

The third significant observation was the presence of pockmarks

in the adhesive layer. These pockmarks were numerous (see Table

3) and consistent with the observations made in the field that

the specimens had voids (i.e., areas of apparently no bond) in

the adhesive layer. It was considered that the pockmarks

contributed, in part, to the low bond strength of the samples

11
(see Section 3.4), because they represented areas of little or no

bond. In the areas of the pockmarks, the peel failure of the

seam was generally seen to be ”cohesive-like, " in that, in these

areas, the failure was by delamination through the void in the

adhesive and not by peeling of the adhesive from the surface of

the rubber.

3 . 4 Laboratory Specimens for T-peel Testing

COE staff provided NIST researchers with samples of the EPDM

sheet, contact adhesive, and wash solution (Section 2.1),

reported to be of the same generic type and brand names as those

e used to construct the Fort Belvoir membrane. The batches or lots

of these materials were different from those of the roofing

construction, because of the time that had elapsed between roof

construction and the present investigation.

The surfaces of the EPDM sheet were only lightly dusted with a

talc-like powder (release agent) . Thus, the surface color was

essentially black, unlike some new EPDM products which have a

silvery-gray appearance due to a heavy dusting of release agent.

The noted lack of excessive dusting raised a question as to the

type of process used to coat the sheet with release agent during

production. In particular: Was the process different than that

used to dust sheets that are silvery-gray in color? And does it

result in a dusting that is difficult to remove by cleaning with

the wash solution?

12
The generic type of contact adhesive, whether butyl- or neoprenebased, was not known, and the container only bore the brand name

identification of the product. COE construction records for the

roof indicated that a "new” seam adhesive was to be used. This

fact implied that the adhesive was butyl, because such adhesives

were replacing neoprene adhesives during the time the Fort

Belvoir roof was built.

3.4.1 T-peel Tests . Using the materials provided, seam specimens

were prepared in the laboratory for testing in T-peel at 2

in. /min (50 mm/min) , using the same procedure applied to the

field specimens. Six replicate specimens were tested for each

application condition under which the seams were prepared. Table

4 gives the various conditions used in the preparation of the

seams. The cleaned specimens were prepared using the proprietary

solvent wash provided by COE personnel. The bond strengths of

the laboratory specimens were compared with those of the field

specimens. The laboratory tests measured values of bond strengths

that might be expected for specimens cleaned using the solvent

wash, as well as those of uncleaned specimens.

Table 5 presents the results of the T-peel tests for the laboratory

specimens. The data are summarized in Figure 2 where a comparison

with the- field test results is also made. The maximum average Tpeel strength was achieved for a cleaned specimen, cured for 14

days at 73 °F (23 °C)

.

This value of 5.7 Ibf/in. (1.0 kN/m)

provides an indication of the expected maximum strength that this

rubber/adhesive system (including the wash solution) may reach

13
under close-to-optimum conditions of seam formation. (Longer

cure times may produce stronger bonds, but this parameter was not

further investigated in the present study.) The average maximum

value of 5.7 Ibf/in. (1.0 kN/m) was more than twice the average

value of 2.8 Ibf/in. (0.49 kN/m) found for all field specimens.

The value of 5.7 Ibf/in. (1.0 kN/m) was suggestive that the

adhesive was not neoprene-based, because neoprene adhesives for

EPDM membranes generally achieve T-peel strengths of about 2

Ibf/in. (0.4 kN/m.). On the other hand, some butyl-based

adhesives have been found to reach bond strengths of 8 Ibf/in.

(1.4 kN/m), when applied to carefully cleaned EPDM sheet and

cured for 7 days at room temperature.

The importance of the three application conditions (Table 4) on

seam strength is evident from Figure 2. For every comparable

instance of cure time and temperature, the uncleaned specimens

displayed lower bond strengths than the cleaned specimens. The

reduction in strength was of the order of 40 percent. The

finding was not unexpected, since previous studies using T-peel

tests had indicated loss in T-peel strength due to uncleaned

surfaces. Moreover, in the present study, the average bond

strength of any set of uncleaned specimens had lower strength

than all cleaned specimens. In fact, the averages for specimens

representing three of the four uncleaned conditions (Figure 2)

were between 2 and 3 Ibf/in. (0.4 and 0.5 kN/m), which was the

approximate range for the average values of all field samples

14
(Table 2). Only the uncleaned specimens cured 14 days at 73 °F

(23 °C) had strength values higher than those of the field

samples

.

It is also evident from Figure 2 that, as the cure time lengthened

from 7 to 14 days, the bond strength generally increased. This

result was also consistent with previous NIST findings regarding

a butyl-based contact adhesives which cures over time. An

exception was for the uncleaned specimens cured at 158 °F (70

°C). In this case, a slight decrease in strength was observed in

time. No reason for the observation was apparent.

From Figure 2, the effect of cure temperature was quite apparent.

For every comparable instance of cure time and surface condition,

the average bond strength of specimens cured at 158 °F (70 °C)

was less than that for specimens cured at 73 “F (23 °C)

.

The

finding was not expected. Rather, it was expected that higher

bond strengths would be found with increased cure temperatures

due to an acceleration of the curing reaction. Although the data

were limited for this observation, they did suggest that the

adhesive/rubber system used to prepare the laboratory specimens

tended to give lower strengths when cured at high temperatures.

The data for. the T-peel strengths of the laboratory specimens

were compared using the statistical 3-way analysis of variance

procedure. As just discussed, the effects of the three application

conditions analyzed were: (1) lower bond strength due to lack of

cleaning of the rubber, (2) greater bond strength due to longer

15
cure time, (3) lower bond strength due to higher cure temperature.

The analysis showed that all three factors were statistically

significant. In addition, it was found that an additive model

for the effects of the factors was reasonable, indicating that

the factors act independently.

Finally, in discussing the effect of the specimen preparation

conditions, it is noted that the two lowest average bond strengths

were found for specimens prepared using uncleaned rubber, and

cured at 158 “F (70 ®C). These strengths were about 2.1 to 2.3

Ibf/in. (0.37 to 0.40 kN/m) , which, perhaps coincidentally, were

comparable to the average values found for the field specimens

(Figure 2) . Although the evidence was limited, it raised

questions as to what extent the cleaning procedure in the field

and the cure temperatures contributed to the observed values of

strengths of the field specimens. The roof with a black EPDM

sheet was installed in the summer in Washington, DC. which could

have provided some periods of high temperature during curing. In

addition, as discussed previously, a few of the field samples

exhibited noticeable surface contamination. More importantly, as

will be discussed in Section 3.6, SEM analysis indicated a talclike substance on the surfaces of the rubber.

16
3.4.2 Appearance of the Adhesive of the Delaminated Specimens . Each of the laboratory specimens was examined after T~peel

testing to observe the condition of the adhesive and to note the

type of failure, whether adhesive or cohesive"^. Another point of

interest was to see if pockmarks were present in the adhesive

layer, as was found for the field specimens. In the case of the

laboratory specimens, pockmarks were not observed. A summary of

the types of failures is given in Table 6. Note that the

majority were adhesive failures even for the cleaned specimens,

indicating that the weak link in the seam was at the interface of

the adhesive and rubber sheet.

3 . 5 Nature of the Adhesive

Fourier Transform Infrared Analysis (FTIR) was conducted on the

adhesive present in the field samples, and that used to prepare

the laboratory samples. The intent was to determine whether the

adhesives were the same, and if possible, to identify the generic

type of adhesive, butyl-based or neoprene-based. This was done

because the construction records did not indicate the type of

adhesive.

FTIR spectra of selected field and laboratory samples were

compared with those of a known neoprene adhesive and a known

butyl adhesive. These known adhesives were commercially-used

products available in the NIST laboratories. In this limited

investigation, the FTIR evidence was not sufficient to provide

^Adhesive indicates failure at the interface of the adhesive

and rubber surface; whereas cohesive indicates failure within the

bulk of the adhesive.

17
conclusive identification of the adhesive. The observations made

were:

o The FTIR spectra for the known neoprene and butyl adhesives

were distinctly different.

o The spectra of the field and laboratory samples were very

similar. The comparison suggested that the adhesives might

be the same. The finding was consistent with the fact that

NIST staff were given a sample of adhesive reported to be

the same generic type as that used in the field.

o No conclusions were made from the comparisons of the spectra

of laboratory adhesive with that of the known neoprene or

butyl adhesives, because the spectra of the materials in

question were not clearly distinctive.

3.5.1 Beilstein Tests of the Adhesives . A classical qualitative

analysis procedure for the identification of halide-containing

organic compounds is the "Beilstein Test." In this test, a small

sample of the compound is burnt on a piece of copper using a

laboratory gas flame. If a halide is present, a green flame is

produced.

The test was applied to the known adhesives and that from the

roof in question. A difference in the flames of the known

neoprene and butyl adhesives was apparent. The neoprene produced

a strong, bright green flame. The butyl gave a strong yellow

flame with a trace of green when initially ignited. The green

color may have been generated by a trace of chlorinated polymer

or solvent in the adhesive. The adhesive used to prepare the

laboratory samples behaved almost identically to the known butyl

adhesive. The adhesive from the field samples gave only a yellow

flame. The conclusion was that the adhesives from the field and

laboratory samples were not neoprene-based. This was consistent

18
with the T-peel data for some laboratory specimens that suggested,

on the basis of strength values, that it was not neoprene.

3 . 6 Scanning Electron Microscopy

Scanning electron microscopy (SEM) analysis of selected rubber

sheets including that received by COE personnel, those taken from

delaminated field seams (Section 3.2), and those from laboratoryprepared seams (Section 3.4) was conducted to obtain information

on the rubber surfaces. The SEM samples from delaminated seams

were as follows: two field samples (B3-2 and B2-3)

,

and two

laboratory samples (one using rubber cleaned with the solvent

wash, C4 , and one using uncleaned rubber, UC4 ; both cured two

weeks at 158 ‘’F/70 “C) . The samples of the rubber sheet received

from COE personnel were as follows: one uncleaned sample (in the

"as-received" condition) , and one cleaned (brushed using laboratory

detergent and water followed by a hexane wash and air drying)

.

Photomicrographs were obtained for all analyzed samples at lOOX

and 500X magnification.

The SEM analysis, performed on the top surfaces of these samples,

provided information concerning the condition of the rubber

surfaces. The results were that, with the exception of the

rubber sheet sample cleaned with soap and water and then hexane,

the samples showed surfaces of rubber contaminated with a talclike substance. Even the specimens cleaned using the proprietary

wash solution showed the presence of talc-like particles across

the surface. For all samples showing these particles, the

coverage of the rubber surfaces was comparable. The particles

19
were clearly visible as platelets, having variable size ranging

from less than 10 m to more than 100 m, that appeared to cover

the rubber surface totally. Energy-dispersive X-ray analysis

gave a strong indication of silicon in the substance. Silicon is

a predominant element in talc, mica, or clay. In contrast to the

specimens showing the talc-like particles, that cleaned with soap

and water and then hexane was found to have little talc-like

particle contamination. Apparently, for the initial laboratory

samples under investigation, the cleaning technique using the

wash solution provided by COE personnel did not totally remove

the talc-like substance from the rubber surface.

Because the finding of the talc-like contamination on specimens

cleaned using the proprietary wash solution was not expected, it

was decided to clean (using the was solution) four other specimens

of rubber for additional SEM analysis. Two of these specimens

were cleaned one day and two were prepared another day in case

the cleaning technique varied over time. Unlike the case of the

initial specimens, the SEM photomicrographs of the additional

four specimens showed the surfaces of the rubber to be generally

free of the talc-like contamination. One of the four had some

contamination, but it was not considered as extensive as for the

initial specimens investigated.

Reasons why the cleaning of the rubber using the wash solution in

the laboratory did not, in the one instance, remove all the talclike particles were not determined. It was felt that normal

caution was exercised in all laboratory cleaning operations, and

20
that the wash technique was expected to provide a surface

relatively free of the talc-like particles. The finding that the

talc-like substance was generally removed in the laboratory using

the wash solution in one case and not in another provided

evidence that a means for assuring the quality of the cleaning

procedure is needed.

The SEM examination of the samples taken from the Fort Belvoir

roof showed talc-like contamination. Although the observations

of this investigation were limited, a question raised was whether

the rubber sheets were improperly cleaned in the field (leaving

some residue of the release agent) , or whether the proper

cleaning technique was followed, but was not efficient and left a

residue on the surface (as appeared to occur in the laboratory)

.

In the case of the contaminated surfaces, the talc-like substance

was only observed by SEM analysis, which was in direct contrast

to the visual observations made using the naked eye. By eye, the

surfaces of all samples cleaned in the laboratory appeared to be

free of talc-like substance. Also, the delaminated field samples

were apparently talc-free. The finding that contamination was

not seen by eye (nor by light microscopy at 25x)

,

even though the

SEM showed it to be present, provided strong evidence that the

unaided eye is not adequate for characterizing surfaces. A

question is whether the black proprietary wash solution may have

darkened the rubber surface and prevented detection of talc-like

contaminants by eye.

21
The findings of the SEM analysis were considered in relation to

the results of the T-peel bond-strength tests for the cleaned

(C4) and uncleaned (UC4) laboratory seam samples (Table 5)

.

Although the rubber surfaces showed comparable SEM photomicrographs,

indicating surface contamination in both cases, the cleaned and

uncleaned seams displayed different average T-peel bond strengths.

For room temperature cure, the average peel strength of the

cleaned sample (C4) was 2.3 times that of the uncleaned sample

(UC4) . The presence of a layer of talc-like substance may

explain the earlier-mentioned observation that the strength of

the cleaned specimens (about 5 to 6 Ibf/in. or 0.9 to 1 kN/m)

were less than 7 to 8 Ibf/in. (1.2 to 1.4 kN/m), as has been

observed with other cleaned seams prepared by the authors with

butyl adhesive. The wash solution apparently promoted increased

adhesion in the case of cleaned specimens over that of the

uncleaned specimens even though the talc-like substance was not

totally removed. Perhaps partial removal of contamination during

the cleaning was sufficient to provide the greater bond strength.

These results raise questions concerning the understanding of

performance of the rubber, release agent, and adhesive system,

and suggest that further investigation of their surface chemistry

is needed. An important question is what effect any remaining

talc-like layer on the rubber may have on the long-term seam

performance. Another question is why the laboratory cleaning

with the wash solution did not apparently, in at least one case,

totally remove the talc-like release substance on the surface of

the rubber sheet.

22
4. SUMMARY AND CONCLUSIONS

This investigation was a limited study of problems occurring with

the seams of the EPDM membrane on the roof of the SAMT building,

Fort Belvoir, Virginia. Based on the results of the study, the

following summary of key observations is made:

o The seams of the membrane had experienced some delamination

within about a year of formation. In the areas observed,

the delaminations had not occurred across the entire width

of the seams.

o Specimens of seams removed from the roof had low T-peel bond

strengths in comparison to the strengths achieved by the

given adhesive/rubber system when the seams were prepared

under laboratory conditions using rubber washed with the

proprietary wash solution.

o SEM analysis of the field-formed seams indicated the , presence of a talc-like contamination on the rubber surface

which may have contributed to the low strength. The

contamination was not visible to the eye.

o Specimens of seams removed from the roof showed the presence

of small voids in the adhesive layer. The small voids in

the adhesive layer of the seams may also have contributed,

in part, to the low bond strength, because they represented

areas of little or no bond.

o Not cleaning the rubber surface and elevating the cure

temperature had a negative effect on the bond strength of

the laboratory-prepared seams. Seam strengths were reduced

about 40 percent when the rubber surfaces were not cleaned.

The strengths were also reduced by more than 20 percent when

cured at 158 F° (70 ° C) versus curing at 73 °F (23 °C).

o SEM analysis indicated that some laboratory specimens

cleaned with the proprietary wash solution showed a talclike contamination which was not visible to the unaided eye.

Other laboratory specimens cleaned using the wash solution

did not show such contamination. In both cases, a recommended

cleaning technique was followed. These results provided

evidence that a means for assuring the quality of cleaned

rubber is needed.

23
From the study results, the following recommendation regarding

the Fort Belvoir roof is made:

The roof should receive thorough periodic inspection at 6-

month intervals to assure that it performs as expected.

This recommendation may appear obvious, considering that acceptable

roofing practice emphasizes routine periodic inspection (normally

every 6 months) to maintain satisfactory performance. It is

emphasized herein for the following reasons:

o The Corps of Engineers has indicated that repair of the

existing seams is to be accomplished by adhering a strip of

EPDM rubber over them. Experience has shown that some

rubber patches made over weathered EPDM have not always

provided satisfactory performance, but have prematurely

delaminated. Thus, the periodic inspection should pay

particular attention to the repair strips ovfer the original

seams to assure that they remain intact. On another point,

the evidence obtained in the laboratory indicated that the

talc-like substance on the surface of the rubber in question

was not, in one case, totally removed by normal cleaning

with the recommended wash solution. This suggests that the

surface of the rubber may have been difficult to clean for

the repairs.

o The investigation revealed some poor adhesion of the facer

to the insulation board. Although not discussed in detail,

this observation indicated that, in some areas of the roof,

the attachment of the membrane to its substrate may have

been less than adequate. Thus, the inspectors should check

that the membrane is sufficiently adhered to the substrate,

and not experiencing securement problems due to delamination

of the facer from the insulation board.

In conclusion, this limited field investigation provided evidence

concerning the surface condition of rubber sheets taken from

seams experiencing delamination problems in service. The

evidence raised questions why the wash solution used to clean the

rubber before adhesive application did not totally remove the

talc-like release agent from the rubber surface. The study

suggested that continued research is needed to improve the

understanding of the rubber-adhesive interface.

24
5 . ACKNOWLEDGMENTS

The authors extend their thanks to Mr. Cy Miller, Corps of

Engineers, Baltimore District, for his support in conducting the

field inspections, and for obtaining the materials used for the

laboratory tests. The authors also appreciate the assistance of

their NIST colleagues: Paul Stutzman, Building Materials

Division, for his enthusiastic efforts in providing SEM analysis;

Geoffrey Frohnsdorff, Larry Masters, and Mary McKnight, Building

Materials Division, for their many useful comments on a draft of

this report; Gerald Sleater, Center for Analytical Chemistry, for

his valuable review of a draft; and James Lechner, Center for

Computing and Applied Mathematics, for his assistance with data

reduction and analysis.

25
Table 1. Observations Noted During Sampling of the Seams

Sample^ Observations

No.

Gl, G3 , G5, The seam specimens showed, as viewed along the edge,

B2, B3 , B4, some small voids in the adhesive layer; no water was found

& B5. in the cellular plastic insulation board which appeared dry

to the touch.

Bl. The seam specimens showed, as viewed along the edge, some

small voids in the adhesive layer; no water was found in

the insulation and it appeared dry to the touch.

G2 . The seam specimens showed, as viewed along the edge, some

small voids in the adhesive layer; water was found in the

cellular plastic insulation board, as noted by pressing a

finger on its surface; the adhesion between the membrane

and insulation was poor; the facer on the insulation

appeared to be readily delaminated; in one spot, an

extended tape measure could be inserted 6-7 in. (150-175

mm) under the membrane.

G4 . The seam specimens showed, as viewed along the edge, some

small voids in the adhesive layer; no water was found in

the insulation and it appeared dry to the touch; the

adhesion between the membrane and insulation was described

as poor; the facer on the insulation appeared to be readily

delaminated; in one spot, an extended tape measure could be

inserted about 15 in. (375 mm) under the membrane.

1. G and B refer to "good" and "bad," respectively; see text (p. 7)

for explanation.

26
Table 2. Results of T-Peel Tests of the Field Samples^

Sample^ Sample Strenath, Ibf/in. (W/m) cov Sign^

No. Set Range Average S.D. % Diff

.

G1 1 2.6 — 3.2 2.8 0.27 9.7 Yes

(0.46 — 0.56) (0.49) (0.047)

B1 1.2 — 2.0 1.6 0.42 26

(0.21 — 0.35) (0.28) (0.074)

G2 2 2.5 3.2 2.7 0.34 12 No

(0.44 — 0.56) (0.47) (0.060)

B2 0.9 — 2.4 1.9 0.66 35

(0.16 — 0.42) (0.33) (0.12)

G3"^ 3 1.2 — 2 .

1

1.6 0.44 27 No

(0.21 — 0.37) (0.28) (0.077)

B3 1.7 — 2.1 2.0 0.18 9.4

(0.30 — 0.37) (0.35) (0.032)

G44 4 2.1 — 2.7 2.5 0.31 12 No

(0.37 — 0.47) (0.44) (0.054)

B4 1.2 — 2.2 1.8 •0.46 25

(0.21 — 0.39) (0.32) (0.081)

G5 5 1.9 — 2.8 2 .

3

0.38 17 No

(0.33 — 0.49) (0.40) (0.067)

B5 2.3 — 2.8 2.5 0.26 11

(0.40 0.49) (0.44) (0.046)

All 1.2 — 3.2 2.4 0.51 21 Yes

Good (0.21 — 0.56) (0.42) (0.089)

All 0.9 — 2.8 1,9 0.48 25

Bad (0.16 0.49) (0.33) (0.084)

All 0.9 — 3.2 2.2 0.54 25

Specimens (0.16 0.56) (0.39) (0.095)

1. Average of four measurements, unless otherwise indicated.

2. G and B refer to ’’good" and "bad,” respectively; see text (p. 7)

for explanation.

3. The column indicates whether a difference was found at the 0.05

percent significance level between pairs of good and bad

specimens

.

4. Average of three measurements.

27
Table 3. Observations on the Condition of the Field Seam Specimens^

Sample^ Specimen Failure Observations

No. No. Mode^

G1 1 A - 95% no visible signs of contamination; small

pockets in the adhesive layer"^ ; not shiny^

G1 2 A - 95% as for G1 - 1

G1 3 A - 95% as for G1 - 1

G1 4 A - 95% as for G1 - 1

B1 1 A - 50% significant contamination; brownishL oil-like

B1 2 A - 50%

film on bottom of top sheet and on

of adhesive of bottom sheet; small

in the adhesive layer^; shiny^

as for B1 - 1

the top

pockets

B1 3 A - 90% as for B1 - 1

B1 4 A - 90% as for B1 - 1

G2 1 A - 95% no visible signs of contamination; small

pockets in the adhesive layer^; shiny^

G2 2 A - 95% as for G2 - 1

G2 3 A - 75% as for G2 - 1

G2 4 A - 75% as for G2 - 1

B2 1 A - 80% as for G2 - 1

B2 2 A - 90% as for B1 - 1

B2 3 A - 90% as for G2 - 1

B2 4 A - 60% as for B1 - 1

1. These observations were made by eye on the delaminated field

specimens

.

2. G and B refer to "good" and "bad," respectively; see text (p. 7)

for explanation.

3 . This column represents the percent area of the specimen estimated

to fail adhesively (A)

;

the remainder is cohesive failure.

4. This note refers to pockmark-like depressions in the adhesive in

areas where the failure was "cohesive" in nature.

5. This note refers to the appearance of the surface of the adhesive

in the pockmark areas.

28
Table 3. Observations on the Condition of the Field Seam Specimens^

Sample^ Specimen Failure Observations

No. No. Mode^

G3 1 A — 90% as for G2 - 1

G3 2 specimen not examined

G3 3 A - 90% small spot (3-4 mm) of brownish oil-like

film on bottom of top sheet; small pockets

in the adhesive layer^; shiny^

G3 4 A * 95% as for G3 - 3

B3 1 A 95% as for G2 - 1

B3 2 A - 95% as for G2 - 1

B3 3 A 90% a couple of small white spots (3-4 mm) on

top sheet; small pockets in the adhesive

layer^ ; shiny^

B3 4 A 95% as for B3 - 3

G4 1 A 80% as for G2 - 1

G4 2 A — 80% as for G2 - 1

G4 3 specimen not examined

G4 4 A 75% as for G2 - 1

B4 1 A * 75% white streaks (talc-like) , apparently at

juncture of factory sheet welds; small

pockets in the adhesive layer"^; not shiny^

B4 2 A 95% small spot (5-6 mm) of brownish oil-like

film on top of bottom sheet; small pockets

in the adhesive layer^ ; not shiny^

B4 3 A — 90% as for G2 - 1

B4 4 A — 90% as for G2 - 1

1. These observations were made by eye on the delaminated field

specimens

.

2. G and B refer to "good” and "bad," respectively; see text (p. 7)

for explanation.

3 . This column represents the percent area of the specimen estimated

to fail adhesively (A)

;

the remainder is percent cohesive failure.

4. This note refers to pockmark-like depressions in the adhesive in

areas where the failure was cohesive.

5. This note refers to the appearance of the surface of the adhesive

in the pockmark areas.

29
Table 3. Observations on the Condition of the Field Seam Specimens^

Sample^

No.

Specimen

No.

Failure

Mode^

Observations

G5 1 A - 90% white streaks (talc-like) , apparently at

juncture of factory sheet welds; small

pockets in the adhesive layer^ ? shiny^

G5 2 A - 75% as for G5 - 1

G5 3 A - 60% as for G2 - 1

G5 4 A - 60% as for G2 - 1

B5 1 A - 60% a few small areas (2-3 mm) of white deposit;

small pockets in the adhesive layer^ ; shiny^

B5 2 A - 60% as for G2 - 1

B5 3 A - 90% as for G2 - 1

B5 4 A - 50% as for G2 - 1

1. These observations were made by eye on the delaminated field

specimens.

2. G and B refer to "good" and "bad," respectively*; see text (p. 7)

for explanation.

3 . This column represents the percent area of the specimen estimated

to fail adhesively (A)

;

the remainder is percent cohesive failure.

4. This note refers to pockmark- like depressions in the adhesive in

areas where the failure was cohesive.

5. This note refers to the appearance of the surface of the adhesive

in the pockmark areas.

30
Table 4. Variables Studied for Their Effect on the Bond Strength

of the Laboratory Specimens

Variable

Cure Temperature

Cure Time

Surface Condition

of the Rubber

Conditions

73 “F (23 “C) and 158 “F (70 *C); the high

temperature cure included holding the specimens

at room temperature for one day to minimize a

risk of damaging the specimens due to rapid

adhesive solvent release.

7 and 14 days

cleaned and uncleaned; cleaning was done by

washing with the proprietary solvent solution.

31
Table 5. Results of T-Peel Tests of the Laboratory Specimens^

Sample^ Cure Time Cure Temp Strer. Pth, Ibf/in. ( > O ^ T T No. days op (»C) Range Average S.D. %

Cl 7 73 3.3 6.0 4.7 1.1 23

(23) (0.58 — 1.1) (0.82) (0.19)

UCl 7 73 2.8 — 3.2 2.9 0.34 12

(23) (0.49 — 0.56) (0.51) (0.06)

C2 14 73 4.2 — 6.6 5.7 0.95 17

(23) (0.74 — 1.2) (1.0) (0.17)

UC2 14 73 2.5 — 4.8 3.6 0.94 27

(23) (0.44 — 0.84) (0.63) (0.16)

C3 7 158 3.3 — 4.6 3.7 0.49 13

(70) (0.58 — 0.81) (0.65) (0.09)

UC3 7 158 2.1 — 2.8 2.3 0.27 12

(70) (0.37 0.49) (0.40) (0.05)

C4 14 158 3.9 5.8 4.4 0.72 17

(70) (0.68 — 1.0) (0.77) (0.13)

UC4. 14 158 1.9 — 2.1 2.1 0.085 4.2

(70) (0.33 — 0.37) (0.37) (0.015)

1. Average of six measurements.

2. The C and UC refer to "cleaned" and "uncleaned" specimens,

respectively.

32
Table 6. Modes of Failure of Laboratory Specimens During T-Peel

Specimen

No.

Mode of Failure^ Specimen

No.

Mode of Failu:re^

Cl 1 Coh. — 100% UCl — 1 Coh. — 100%

Cl — 2 Coh

.

- 100% UCl — 2 Coh. — 100%

Cl — 3 Coh. - 100% UCl - 3 Coh. - 70% & adh

.

- 30%

Cl — 4 Adh. — 100% UCl - 4 Adh. - 100%

Cl — 5 Coh. — 20% & adh. - 20% UCl - 5 Adh. - 90% & coh. - 10%

Cl — 6 Adh

.

— 100% UCl — 6 Adh. — 60% & coh. - 40%

C2 • 1 Adh. — 100% UC2 — 1 Adh. — 100%

C2 - 2 Adh. - 15% & coh. - 85% UC2 - 2 Adh. - 100%

C2 - 3 Coh. — 100% UC2 - 3 Adh. — 50% & coh. - 50%

C2 — 4 Adh. - 40% & coh. - 60% UC2 - 4 Adh. — 50% & coh. - 50%

C2 - 5 Adh. - 90% & coh. - 10% UC2 - 5 Adh. - 100%

C2 — 6 Adh. — 100% UC2 — 6 Adh. — 100%

C3 — 1 Adh. — 100% UC3 — 1 Adh. — 100%

C3 — 2 Adh. — 100% UC3 - 2 Adh. - 100%

C3 - 3 Adh. — 100% UC3 - 3 Adh. - 100%

C3 — 4 Adh. - 100% *' UC3 — 4 Adh. — 100%

C3 - 5 Adh

.

— 100% UC3 - 5 Adh

.

100%

C3 — 6 Adh. — 100% UC3 — 6 Adh. — 100%

C4 — 1 Adh. — 100% UC4 — 1 Adh

.

— 100%

C4 - 2 Adh. — 100% UC4 — 2 Adh

.

— 100%

C4 — 3 Adh. - 100% UC4 — 3 Adh

.

- 100%

C4 - 4 Adh. — 100% UC4 — 4 Adh. - 100%

C4 - 5 Adh. — 100% UC4 — 5 Adh. - 100%

C4 — 6 Adh

.

— 100% UC4 — 6 Adh. — 100%

1. Adh. and coh. indicate adhesive and cohesive failure, respectively;

the percent is the estimated area of the bond which failed in the

stated mode.

33
Lap sealant with crack Contact adhesive

EPDM rubber

EPDM membrane

Contact adhesive bond of

membrane to insulation

Insulation board

Asphalt adhesive bond

Monolithic-plate steel deck

Figure 1. Cross Section of the Roof Construction Including a Seam

and the Lap Sealant at the Seam Edge (Not to Scale)

.

34
235.4 ft (71 .7 m)

146.4 ft (44.6 m) 158

( 48.

Figure 2

.

Plan Indicating Approximate Dimensions of the

Roof and Locations of the Test Cuts.

35

ro>
•E

B

i:

f“

CD

z

LU

DC

h“

C/D

-J

LU

LU

Dl

CURE TEMPERATURE, °C

23 70 23 70 23 70 23 70

1—

r

Field

Specimens

6 -

5

-

4 -

0

o

D)C

CO

CD

s

c5 Q

2

-

1 -

o

o

o

o

o

o

o 00

1 r

g Laboratory Specimens - 1.2

- 1.0

8

o

"oo o

o

8

Note: Bold lines

represent averages

oo

o

1 L

0.8

0.6

0.4

0.2

0

I

h“

CD

Z

LU

DC

H”

C/D

-J

LU

LU

CL

Good Bad: 73158 73158 73 158 73158 CURE TEMP, "F

14

Cleaned Uncleaned

14 CURE TIME, days

SURFACE

Figure 3 . Results of the T-peel Tests for the Laboratory Samples

in Comparison With Those of the Field Samples.

36
NBS»n4A (REV. 2«6C) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

4. TITLE AND SU BT

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. NISTIR 88-3893Publication Date

NOVEMBER 1988

Report of Roof Inspection: Delamination of '.dhesive - Bonded Seams at an

Army Facility

5. AUTHOR(S)

Walter J. Rossiter Jr. and James F. Seiler Jr.

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No.

I

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

S. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

US Army Engineer District, Baltimore

PO Box 1715

Baltimore, MD 2121 '-1715

10.

supplementary notes

I I Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

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

bi bliography or literature survey, mention it here)

This document was prepared at the request o-f U.S. Army Engineer District, Baltimore, to provide assistance in obtaining data on the delamination o-f seams o-f an EPDM roo-fing system at Fort Belvoir, Virginia. The

investigation was bene-ficial to NIST, because it provided an opportunity to

characterize adhesive-bonded seams in service and to obtain data relative

to NIST laboratory research on the e-f-fect o-f sur-face contamination on seam

per -f ormance.

Seam specimens were taken from the roof and analyzed for peel strength and

. surface condition of the rubber . In addition, seams were prepared in the

laboratory using the same brand name rubber /adhesi ve system to obtain peel- strength values for comparison with those measured for the field specimens.

The results of the study indicated that the field specimens had low T-peel bond strengths in comparison to the strengths achieved by the laboratoryprepared seams. Small voids in the adhesive layer of the seams of the

field seams may have contributed, in part, to the low bond strength. SEM

analysis of the field-formed seams indicated the presence of a talc-like

contamination on the rubber surface which may have also contributed to the

1 strength. In addition, SEM analysis of some laboratory specimens

cleaned with the proprietary wash solution showed a talc-like contamination

which was not visible to the unaided eye. Other laboratory specimens

cleaned using the wash solution did not show such contamination.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons;

adhesive-bonding; bond strength; contamination; EPDM; field inspection; low-sloped

roofing; membranes; roofs, seams, SEM analysis, surface condition

13. availability 14. NO. OF

PRINTED PAGES

[X i Uni imited

1 For Official Distribution. Do Not Release to NTIS

42

I" ; Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402. 15. Price

1 Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $11.95

USCOMM-DC 6043-P80
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