NBSIR 77-1437

Solar Energy Systems - Standards for Rubber Seals

Stiehler, R. D.., Hockman., A

blasters., L. W.., Existing

for solar collector use.,

35-37 (Aug. 1978)»

New

741

. , Embree,, E. J.,

standards inadequate

Solar Eng. 3^ No -

1^/0

NBSIR 77-1437

Prepared for Department of Energy

Office of the Assistant Secretary

Conservation and Solar Applications

20 Massachusetts Avenue

Washington, DC 20545

NBSIR 77-1437

SOLAR ENERGY SYSTEMS - STANDARDS FOR RUBBER SEALS

Robert D Stiehler

Arthur Hockman

Edward J. Embree

Larry W. Masters

Structures and Materials Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

March 1978

Final Report

Prepared for Department of Energy

Office of the Assistant Secretary

Conservation and Solar Applications

20 Massachusetts Avenue

Washington, DC 20545

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

TABLE OF CONTENTS

Page

ABSTRACT v ACKNOWLEDGMENT vl CONVERSION UNITS vi±

1. INTRODUCTION T 1.1 Background

1.2 Objectives 3

2. PROBLEM ASSESSMENT 2

2.1 Performance Requirements 2 2.2 Key Properties 2 2.3 Key Degradation Factors 2

3. LABORATORY STUDIES 2

3.1 Materials 2 3.2 ASTM Standard Rubber Tests Performed 3

3.2.1 Samples 1 through 15 3 3.2.2 Samples 16 through 31 5

3. 2. 2.1 Loss in Mass (ASTM C792) 6

3. 2. 2. 2 Hardness (ASTM C661) 6 3. 2. 2. 3 Extension-Compression Cyclic Movement (ASTM C719) . ... g 3.2. 2.4 Accelerated Weathering (ASTM C793) g

3.3 Studies to Evaluate the Effect of Out gassing g

3.3.1 Apparatus 7 3.3.2 Procedure 7

4. RESULTS AND DISCUSSION 7

4.1 ASTM Tests of Samples 1 through 15 7 4.2 ASTM Tests of Samples 16 through 31 8

4.2.1 Loss in Mass 9 4.2.2 Hardness 9 4.2.3 Extension-Compression Cycles 9 4.2.4 Accelerated Weathering 9 4.2.5 Conclusions from Samples 16 through 31 10

4.3 Results of Outgassing Test Procedure H

5. PROPOSED STANDARDS H

5.1 Standard Specification for Rubber Seals Used in Flat-Plate Solar

Collectors 11 5.2 Standard Specification for Rubber Seals Contacting Liquids in Solar

Energy Systems 13
TABLE OF CONTENTS, continued

Pa^e

5.3 Standard Specification for Rubber Seals Used in Solar Collectors

(other than Flat-Plate Collectors) 13 5.4 Standard Test Method for Determining the Effect of Outgassing on the

Transmittance of Solar Collector Covers 13

5.5 Recommended Practice for Sealing Joints between Solar Collectors and

Building Components with Rubber Seals 13

6. BIBLIOGRAPHY 13

APPENDICES

Appendix A - Standard Specification for Rubber Seals Used in Flat Solar

Collectors A-l

Appendix B - Standard Specification for Rubber Seals Contacting Liquids in

Solar Energy Systems A-9

Appendix C - Standard Specification for Rubber Seals Used in Solar Collectors

(other than Flat-Plate Collectors) A-14

Appendix D - Standard Test Method for Determining the Effect of Outgassing on the Transmittance of Solar Collector Covers A-22

Appendix E - Recommendations for Sealing Joints between Solar Collectors and

Building Components with Rubber Seals A-27
ABSTRACT

A study was performed to develop standards for rubber seals used in solar

energy systems. Thirty-one preformed and liquid applied seals were evaluated

in the laboratory using modified ASTM standard test methods to obtain data

needed to evaluate those materials and prepare new standards. Also, studies were performed to develop a test method for determining the effects of outgassing on the transmittance of solar collector covers.

The results of the laboratory tests are presented and standards for rubber

seals in solar energy systems are proposed.

v
ACKNOWLEDGMENT

The authors gratefully acknowledge the substantial contributions of Mr. George Bullman

and Mr. Jack Lee of NBS performing the laboratory tests described in this report. The

authors also thank Mr. Willard Roberts of NBS, who obtained the solar transmittance data,

and the U.S. Department of Energy which supported this research.

In addition, the valuable review comments on draft standards provided by members of

ASTM Committees Dll on Rubber and Rubber-like materials and C24 on Building Joint Sealants

and Subcommittee E21.1D on Solar Heating and Cooling Applications are gratefully acknowledged.

The authors also thank the many manufacturers of rubber materials .and heat transport liquids

who supplied samples for testing.
CONVERSION UNITS

In recognition of the position of the United States as a signatory to the General Conference on Weights and Measures, which gave official status to the international system of units

in 1960, SI units of measurement have been used throughout this publication. To assist in

conversion to common U.S. units of measurement, conversion factors have been provided in the

table below. The reader interested in making further use of the coherent system of SI units

is referred to:

NBS SP330, 1977 Edition, "The International System of Units

ASTM E380-76 Standard for Practice (American National Standard Z210.1')

Table of Conversion Factors to Common U.S. Units

Physical

Quantity

To convert

from

to Multiply by

Length meter inch 39. 3701

Area

2 m

. 2 in 1550.0031

Temperature Celsius Fahrenheit t„ = t (1. 8)+32

r c

Mass kg lb 2.2046

Stress MPa lbf /in^ 145

vii
'
1. INTRODUCTION

1.1 Background

Rubber seals are used extensively in solar energy systems to seal or weather-proof -joints

between adjoining materials or to separate dissimilar metallic materials. For example,

rubber seals may be used in solar collectors to seal joints around cover plates and absorber

plates as well as joints in the collector enclosure. They may be used as hydraulic seals

within heat transport or storage subsystems to prevent leakage of fluids. In addition, they

may be used to seal joints between solar system components and the building the system serves.

Numerous standard test methods have been developed for rubber seals for use in building

constructions. However, the performance requirements established for seals used in building

constructions are not entirely adequate for solar energy systems and subsystems. This is

particularly true for seals used in solar collectors, where they may be exposed to high

temperature, and for hydraulic seals which may be degraded by transport or storage liquids

with which they contact. For example, existing standard tests seldom specify temperatures

exceeding 70°C. This temperature limit is based upon the maximum service temperature

encountered by seals in buildings. It has been established that temperatures of materials

in solar energy systems and subsystems will exceed those observed in conventional building

applications. The maximum service temperature of interior cover plates used in flat plate

solar collectors is estimated to be about 150°C while that for absorptive surfaces is

estimated to be 250°C or greater depending on the design of the collector and the materials

used [l]"'”. In addition, hydraulic seals may be exposed to heat transport and storage liquid

temperatures that are not covered by existing standards.

Skoda and Masters [2] reported that rubber seals have failed or exhibited problems in numerous operational solar energy systems. Problems include loss of elasticity, bond failure

to the substrates and thermal decomposition (outgassing) leading to the formation of deposits

on the underside of collector cover plates. These problems with seals can lead to reduced

thermal performance of collectors and to accelerated degradation of other system or building

components

.

There is clearly a need for the development of standard for rubber seals for solar

energy systems and subsystems to ensure that they will perform adequately when initially

installed and when subjected to in-service conditions for extended periods of time.

1.2 Objectives

The study of rubber seals for use in solar energy systems was directed toward the

following objectives:

—^ Numbers in brackets refer to the references in the Bibliography at the end of

this report.

1
1. To identify performance requirements for rubber seals used in solar energy

systems

2. To identify and assess existing test methods for rubber seals and modify

the methods or develop new methods as needed.

3. To evaluate commercially available rubber materials in the laboratory

and obtain data needed to recommend specific test methods.

4. To prepare draft standards for rubber seals for consideration by ASTM as consensus standards.

2. PROBLEM ASSESSMENT

2.1 Performance Requirements

The primary function of rubber seals used in solar energy systems is to seal or weatherproof the joints between materials or components. Rubber seals include both preformed gasket

ing and liquid applied sealants.

In order to perform their primary function, both preformed and liquid applied seals must

possess and maintain sufficient elasticity to permit movement within a joint. In addition,

liquid applied seals must develop and maintain adhesion to the substrates. In general,

rubber seals should be capable of performing their intended functions when initially

installed and after long term exposure to service conditions. In particular, they should be

resistant to deterioration resulting from exposure to elevated and depressed temperature,

temperature cycles, solar radiation, oxygen, ozone and airborne pollutants. They should

also be compatible with adjoining materials. This is particularly important for preformed

hydraulic seals which are in contact with heat transfer or storage liquids.

2.2 Key Properties

Key properties of rubber seals include ultimate elongation, compression set, hardness,

tensile strength, low temperature flexibility, volatile content, condensible volatiles and

adhesion (for liquid applied seals). Table 1 lists ASTM test methods for these properties.

2.3 Key Degradation Factors

Degradation factors that could affect the properties of rubber seals and thereby reduce

their ability to perform are elevated and depressed temperature, ozone, ultraviolet radiation

stresses imposed by cyclic joint movement and contact with liquids. Table 2 lists ASTM test methods for exposure of rubber seals to these degradation factors.

3. LABORATORY STUDIES

3.1 Materials

The rubber seals selected for laboratory testing included the following types:

2
ACM - EAM

CSM

FKM

EPDM

ECO

CO

VMQ

EOT

EU

2 / Acrylate copolymer

Ethylene-vinyl acetate copolymer

Chloro-sulfony1-polyethylene

Fluoro rubber

Terpolymer of ethylene, propylene and a diene

Copolymer of ethylene oxide and chloromethyl oxirane (epichlorohydrin)

Polychloromethyl oxirane

Silicone copolymer containing methyl and vinyl groups

Polysulfide

Polyurethane

Table 3 is a listing of the rubber samples tested and the form in which they were

received for testing from manufacturers, i.e., vulcanized sheet, liquid applied seals, etc.

3.2 ASTM Standard Rubber Tests Performed

3.2.1 Samples 1 through 15

Samples 1 through 15 were tested as vulcanized sheets. Samples 13 and 15, which were

supplied as liquid applied seals, were prepared as sheets before testing. The following

tests were made:

ASTM D395

ASTM D412

ASTM D865

ASTM D1149

ASTM D1229

ASTM D1415

ASTM D2137

Test for Rubber Property-Compression Set

Test for Rubber Properties in Tension

Test for Rubber Deterioration by Heating in a Test Tube

Test for Rubber Deterioration-Surface Ozone Cracking in a Chamber

(Flat Specimen)

Test for Rubber Property-Compression Set at Low Temperature

Test for Rubber Property-International Hardness

Test for Rubber Property-Brittleness Point of Flexible Polymers

and Coated Fabrics

The above tests were selected for the following reasons:

D395 is useful to assess the proper state of vulcanization and the ability to retain

a seal after exposure to high temperatures

.

D412 is generally used to assess the quality of the rubber and, in conjunction with

an aging test, to determine the ability of a rubber to be serviceable for long

periods

.

D865 is a commonly used test for accelerated aging and is convenient for determining

total volatiles at test temperatures and volatiles condensible at room temperature.

— ASTM D1418-76 rubber designations.

3
P1149 is an important test used to assess the ability of rubber to withstand cracking

by ozone, the component in the atmosphere which causes the greatest deterioration

of rubber.

P1229 is used to determine the tendency of a rubber to crystallize at low temperature

and lose its ability to seal.

P1415 is used to measure hardness (a measure of Young's modulus) that is important for

design purposes, and is useful in conjunction with an accelerated aging test to assess deterioration of rubber.

P2240 gives equivalent results but requires specimens at least 6 mm thick, which may

not be possible to obtain from some seals.

P2137 is used to assure rubbery properties at the low temperatures occurring during

winter in cold climates. This test is not required for seals used in warm climates

(Winter temperatures above - 10°C)

In addition to the above tests, the total volatiles at 150°C and the volatiles condenslbl

at 23°C were determined by a modification of the procedure in ASTM P865. The difference in mass of the specimens before and after heating at 150°C was used to determine total volatiles.

The material collecting on the glass tubes used in ASTM P865 was weighed to determine the

amount of condensible volatiles.

The total and condensible volatiles were measured to determine the amount of material

that could possibly cause fogging of the cover plates and absorption of scattering of solar

energy. Such volatiles may reduce the cover plate transmittance and thereby affect the

efficiency of a solar collector.

Available information [1,3] indicated that the highest temperature for seals around cover plates in flat-plate solar collectors would normally be less than 150°C. Under normal

operating conditions, temperatures would be much lower than under static non-operating

conditions. Therefore, a test temperature of 150°C was used in these studies for assessing

high temperature performance. If a seal were in contact with an absorber plate, the test temperature would depend on the maximum service temperature for a particular design or type.

Hence, tests were not made on materials for this application. Since early studies showed

that liquid applied seals (samples 13 and 15) would be suitable only for external use where

stresses on the seal are very small and temperatures are lower, they were tested at a test temperature of 125°C. To assess performance at low temperature, a test temperature of -10°C was selected to detect crystallization of the rubber by means of compression set. A test temperature of -40°C was selected to assess brittleness of seals in cold winter climates

because this temperature is estimated to be the lowest likely in the continental United States

4
In addition to the above methods, liquid immersion tests were performed to obtain data

regarding the performance of rubbers for use in direct contact with various heat transport

or storage liquids.

Test specimens of samples 1 through 12 were immersed in various liquids for a period of

7 days using a modification of ASTM D471, Test for Rubber Property - Effect of Liquids. The

3/ liquids used were as follows: —

1. Ethylene glycol-water (1:1)

2. Propylene glycol-water (1:1)

3. Polyalkylene glycol ether (U CON 500)

4. Modified ester (Therminol 44)

5. Polyaromatic (Therminol 60)

6. Modified terphenyl (Therminol 66)

7. Silicone A (Dow Q2-1132)

8. Silicone B (Dow X2-1133)

9. Silicone C (GE SF 96-100)

10.

Alkyated aromatic (Dowtherm J)

.

The test temperature for liquids 1 and 2 was 100°C to avoid boiling, while that for other

liquids was 150°C. The changes in mass and hardness as a result of the immersion were

determined. These temperatures were selected to cover most applications. Seals for solar

energy systems operating above 150°C were beyond the scope of this study.

3.2.2 Samples 16 through 31

Four test methods related to performance of sealants and described in ASTM Book of

Standards, Part 18 (1976) were used, with some modifications, in evaluating samples 16

through 31 of table 3. The methods were:

ASTM C792, Test for Effects of Heat Aging on Weight Loss Cracking and Chalking of

Elastomeric Sealants

ASTM C661, Test for Indentation Hardness of Elastomeric-Type Sealants by

Means of Durometer

ASTM C719, Test for Adhesion and Cohesion of Elastomeric Joint Sealants Under

Cyclic Movement

ASTM C793, Test for Effects of Accelerated Weathering on Elastomeric

Joint Sealants

3/ Trade names are included where necessary to describe more clearly the liquids used in the

study. Reference to these liquids does not imply approval of the National Bureau of

Standards for use of the liquids in solar energy systems.

5
3. 2.

2.1

Loss in Mass (ASTM C792)

After vulcanization for 7 days at room temperature duplicate specimens were oven aged at temperatures of 82, 100, 121 and 125°C for 7 days. After the aging, losses in mass were

determined and examinations were made for cracks.

3. 2. 2. 2 Hardness (ASTM C661)

This test was made on the same specimens used for the loss in mass determination.

Instantaneous hardness values were obtained after exposures of the specimens at the respective

temperatures (82, 100, 121, 125°C) . This test is essentially the same as ASTM D2240, and

includes the preparation of the specimen.

3. 2. 2. 3 Extension-Compression Cyclic Movement (ASTM C719)

Four sets of sealant specimens were prepared from each sealant sample for the extensioncompression test. A test specimen consisted of a joint, 50 x 12 x 12 mm, filled with the

sealant sample between two pieces of standard aluminum. Each set was fabricated in triplicate.

After specimen preparation, the following steps were used in the evaluation procedure:

1. Cure for three weeks at room temperature.

2. Immerse in distilled water at room temperature for 7 days.

3. Compress 12.5 percent and oven age at temperatures of 82, 100 and 121°C

for 7 days (triplicate specimens at each temperature)

4. Perform 10 cycles with each cycle consisting of a) oven aging at each of the above

temperatures while specimens are compressed 12.5 percent and b) cooling at -26°C

while specimens are compressed 12.5 percent.

During and after the cycling procedure, the specimens were examined for adhesive, cohesive

and deformation failures.

In addition to the above tests, a number of the samples were tested after bonding to glass substrates (rather than aluminum) . These specimens were tested using steps 1 through

4 with the following exception: the temperature during oven aging in steps 3 and 4 was

125°C

3. 2. 2.4 Accelerated Weathering (ASTM C793)

Eight test specimens, each consisting of 50 x 38 x 30 mm sealant pats on aluminum plates were prepared for each of the 16 samples. After curing for three days at room temperature,

two specimens of each sample were exposed to the respective elevated temperatures in ovens

set at 82, 100, 121, 125°C for seven days. Following the oven exposure, the specimens were

exposed to UV radiation in a carbon arc accelerated weathering machine for 1000 hours. At the end of the UV exposure, the specimens were placed in a freezer at -26°C for 24 hours and

then bent over a 12.7 mm mandrel at -26°C. Examination was made for the presence of cracks.

3.3 Studies to Evaluate the Effect of Outgassing

One problem frequently reported in operational solar systems is called outgassing.

Figure 1 shows the fogging of collector covers by outgassing. It results from the thermal

6
degradation of polymers with the subsequent depositon of degradation products on the underside of collector covers. The volatile condensible measurements, using a modification of

ASTM D865, described in 3.2.1, relate to outgassing. But this method provides no means of

determining the effect of the volatile condensibles on cover plate transmittance. A study was performed to determine the effect of the volatile condensibles and to develop a new

test method for evaluating outgassing.

3.3.1 Apparatus

Figure 2 is a photograph of the apparatus used. The key components are a hot plate,

a specimen holder, a Teflon gasket, a glass plate upon which volatiles are condensed and a filtered air stream to cool the glass plate. The gasket and glass plate are held in place

with two spring clips.

3.3.2 Procedure

Specimens of samples that had been evaluated for volatile condensibles by the modified

ASTM method D865 were heated to 150°C for periods of either 3 or 6 hours. The transmittance

of the glass plate was measured at 50 nanometers (nm) increments in the range from 300 to 2100 nanometers (nm) before and after the test. Also, the masses of the glass plate and the

rubber test specimens were obtained before and after the test.

Test temperature was measured using a copper constantan thermocouple attached to the

hot plate. The hot plate was adjusted to reach a temperature of 150 + 2°C before placing

the rubber test specimen in the chamber, installing the teflon gasket and placing the glass

plate on the apparatus. An air stream was passed over the exterior surface of the glass

plate during the test to cool the glass and allow the condensate to form on its underside.

4. RESULTS AND DISCUSSION

4.1 ASTM Tests of Samples 1 through 15

Table 4 summarizes the results obtained with samples 1 through 15. This table gives the

code number and type of rubber and median values for three specimens in the case of hardness,

tensile strength, ultimate elongation and volatiles, and for two specimens in the case of

compression set, low temperature flexibility, and ozone resistance.

Five materials (samples 5, 8, 9, 10 and 14) which had a high compression set were

retested for compression set after post-vulcanization. The post-vulcanization procedure

consisted of placing uncompressed specimens in an oven at 150°C for 70 and 166 hours. The

specimens were then compressed, as in ASTM D395, and exposed for 70 hours at 150°C prior to measuring compression set. The compression set was reduced in most instances after postvulcanization, as can be seen in table 5. These results indicate that these rubbers were

not properly formulated to give optimum properties for solar collectors. In particular,

the data in tables 4 and 5 for EPDM samples 5, 6, 7 and 8 indicate that only Sample 7 (of

7
the EPDM samples) was properly formulated for solar applications.

A study of the results in tables 4 and 5 indicates that several kinds of rubber, when

properly vulcanized , are suitable for use as seals in flat-plate solar collectors. These

rubbers are EAM, EPDM (when properly formulated and vulcanized), and VMQ, which are suitable

for use in all climates, and ACM and FKM, which are suitable for use in warm climates only.

Rubber types CSM, ECO and CO have higher compression sets than desirable for preformed

gaskets. It may be possible to develop formulations for these rubbers which would be

satisfactory. The compression set values in table 5 were used in drawing conclusions on samples 5, 8, 9, 10 and 14. The 100 percent compression sets of samples 13 and 15 indicated

that sealing compounds should be applied only where there is no mechanical stress

The polysulfide rubber (EOT) tested was not suitable for use in solar collectors since

it melted at 150°C and in subsequent tests at 125°C. A high temperature type of polysulfide

would be required. A test temperature of 125°C was considered the lower limit for seals

exposed to summer sunshine. For vertical solar collectors used for winter heating, con- ventional building sealants should be satisfactory.

Table 6 summarizes the results of the liquid immersion tests. In the aqueous liquids

1 and 2, all of the rubbers performed satisfactorily except the acrylate rubber, ACM, which

softened appreciably more than the others (hardness decrease of 12 and 16 IRHD in the two liquids

The fluoro rubber, FKM, is the only one that performed satisfactorily in all liquids.

The epichlorohydrin rubber, CO, tended to corrode the steel wire support and in one case completely corroded the wire during the tests at 150°C. In the eight organic liquids at 150°C, the following rubbers performed satisfactorily:

Liquid

3

4

5

67,8,9

10

Properly Vulcanized.

These results indicate that rubber seals in contact with heat transfer liquids should be

evaluated in the specific liquid to be used.

4.2 ASTM Tests of Samples 16 through 31

Table 7 summarizes the results obtained on samples 16 through 31.

Rubbers

CSM, FKM, EPDM* , VMQ

FKM

FKM, VMQ

FKM, VMQ

ACM, EAM, FKM, EPDM*

FKM

8
4.2.1 Loss in Mass

The data in table 7 show that the mass losses for silicone sealants ranged from 3.2 to 8.1 percent while mass losses for polysulfides range from 4.0 to 13.6 percent. The two polyurethane sealants, Samples 30 and 31, had mass losses ranging from 11.8 to 21.0 percent.

4.2.2 Hardness

The hardness data in table 7 show that silicone sealants had hardness values of from

27 to 44 after exposure at the four temperatures. The values for silicones were relatively

independent of the test temperature. The hardness range for polysulfides was from 0 to 65

units. Two polysulfides. Samples 25 and 26, became harder with increasing temperature while

others, Samples 22 and 27, became softer. The hardness values of the two polyurethane

samples ranged from 45 to 69.

4.2.3 Extension-Compression Cycles

Bond loss in the extension-compression test was rated as being greater than or less

than 25 percent. The value represents bond to the substrate and cohesive bond within the

sealant

.

The test results in table 7 show that four of the six silicone samples with aluminum

substrate had less than 25% bond loss after exposure to the four temperatures. Of the five

silicone samples tested with glass at 125°C, two had less than 25% bond loss.

Seven of the eight polysulfides that were tested after exposure to 82, 100 and 121°C

test conditions exhibited more than 25% bond loss in eleven instances and less than 25%

bond loss in ten instances.

One polyurethane sample (Number 30) , had more than 25% bond loss at the four test temperatures and the other polyurethane sample (Number 31) had less than 25% bond loss at all test temperatures.

4.2.4 Accelerated Weathering

The accelerated weathering results in table 7 indicate that none of the silicone sealants developed cracks after 1000 hours UV exposure nor did any cracks develop after the

180° bend test at -26°C.

Seven of the eight polysulfide sealants tested developed no cracks after exposure at each of four temperatures followed by 1000 hours in the weatherometer . The specimens of

9
sample 23 that were exposed to 100, 121 and 125°C showed cracks after UV treatment. Samples

23, 24, 26, 27 and 29 developed cracks after the bend test following exposure to one or more of the temperature treatments.

Of the two polyurethane samples tested, one (Sample 31) developed cracks after UV exposure. The cracks deepened after the bend test at -26°C. The other, sample 30, did not crack after UV exposure but developed cracks after one bend test.

4.2.5 Conclusions from Samples 16 through 31

The test results Indicate that silicone sealants might be the best choice for sealing

joints around solar collectors where the sealant temperatures may reach 125°C. Polysulfide

and polyurethane sealants tend to be adversely affected by these elevated temperatures.

However, the test results also indicate that bonding properties of some of the silicone

sealants to certain substrates are unsatisfactory.

It is probable that in addition to silicones, polysulfide and perhaps certain polyurethane sealants may be suitable for the installation of solar collector units where substrate

and sealant temperatures do not exceed 80°C. These polymers have been used sucessfully in

building joints for the past several years.

4.3 Results of Outgassing Test Procedure

Table 8 summarizes the results obtained with the outgassing test apparatus and procedure

described in 3.3. The table also compares the results of the outgassing test with the

results obtained with modified ASTM D865 (table 4)

Since both tests were run at 150°C, the percent volatiles would be expected to be

comparable in the two tests. For example, the three and six hour exposures using the outgassing procedure would be expected to yield lower volatile contents than the 70 and 166 hour

exposures using modified ASTM D865. Only sample 5 results are approximately comparable to the expected results. The apparent discrepancies cannot be explained at this point.

The percent condensibles obtained by the two tests are reasonably comparable except

for samples 7 and 8. The condensibles obtained for sample 7 by modified ASTM D865 were 0.04

and 0.05 percent at 70 and 166 hours, respectively, while the outgassing test yielded results

of 0.15 and 0.25 percent at 3 and 6 hours, respectively. For sample 8, the outgassing test yielded lower condensibles than the modified ASTM D865. The change in transmittance does

not appear to be directly related to the gross weight of condensibles collected on the glass.

It is probable that the chemical composition of the condensibles is more important than the

amount of condensibles in evaluating their effect on transmittance.

10
These preliminary results of studies to develop a new outgassing test are inconclusive

and additional work is needed. We believe, however, that the test procedure is sound since

it closely simulated collector outgassing. A test procedure, based on the studies performed,

is proposed in Appendix D to this report. Additional work will be done to obtain answers to the questions raised by this preliminary work. Also additional materials, such as absorptive

coatings and insulation, will be studied with the outgassing apparatus and attempts will be

made to correlate the test results with changes observed in solar collectors in the field.

5 . PROPOSED STANDARDS

Based upon the results of the laboratory tests described in Chapters 3 and 4, standards

have been prepared for rubber seals in solar systems. The proposed standards are included

in the following Appendices to this report:

Appendix A - Standard Specification for Rubber Seals Used in Flat-Solar Collectors

Appendix B - Standard Specification for Rubber Seals Contacting Liquids in Solar

Energy Systems

Appendix C - Standard Specification for Rubber Seals Used in Solar Collectors

(other than Flat-Plate Collectors)

Appendix D - Standard Test Method for Determining the Effect of Outgassing on the

Transmittance of Solar Collector Covers

Appendix E - Recommendations for Sealing Joints between Solar Collectors and

Building Components with Rubber Seals

5.1 Standard Specification for Rubber Seals Used in Flat-Plate Solar Collectors

Appendix A is a proposed specification for rubber seals used in flat-plate solar

collectors except vertically mounted passive collectors. The document is based upon the

laboratory test results of the samples in table 3 (except the liquid immersion tests) and is

being considered for acceptance as a consensus standard by ASTM Committee Dll on Rubbers,

Subcommittee Dll. 36 on Seals.

The proposed standard defines two types of seals; one for use in all climates (Type C)

and the other for use only in regions where minimum temperatures are above -10 °C (Type W) . The requirements for the two types are the same with the exception of resistance to low

temperature.

The proposed standard establishes six grades of preformed rubber seals and three grades

of sealing compounds. The grade to be used depends on the design of the seal or solar

collector, particularly on the stresses likely to be placed on the seal during the life of

the solar collector.

11
i A requirement is included to minimize the possibility of deterioration by ultraviolet

light. Physical requirements include (1) minimum elongation values for each grade, (2)

compression set after heating at 150°C for 70 hours to assure that the seal will be effective

in service for extended periods of time, (3) compression set after exposure at -10°C for

166 hours to assure that crystallization of the rubber polymer will not cause an air leak,

(4) resistance to heating and ozone to assure that deterioration of the seal will be slow

and not adversely affect the performance of the collector during its expected life, (5)

resistance to low temperatures for seals likely to be at low temperatures (below -10°C)

during winters and (6) total and condensible volatile matter.

The requirements for compression set are not applicable to sealing compounds and the

test for resistance to heating of sealing compounds is conducted at 125°C instead of 150°C

or more used for preformed rubber seals. An adhesion requirement is included for sealing

compounds to assure maintenance of the seal during repeated thermal expansion and contractions

of the members of the solar collector. ASTM C792 is not used for loss in mass since it is

not easy to modify for determining condensible volatile matter.

The design of the seal is not specified except for a limitation on the amount of thermal

expansion and contraction which could cause failure of the seal or a loss in its sealing

ability. Commercial tolerances are specified for design dimensions of preformed seals. The

proposed standard also includes requirements on workmanship, marking, and packaging, and

gives instructions on procedures for sampling, inspection and testing.

5.2 Standard Specification for a Rubber Seals Contacting Liquids in Solar Energy Systems

Appendix B is a proposed specification for rubber seals for use in direct contact with

heat transport or storage liquids. The document is based upon the laboratory test results

of samples 1 through 15, including liquid immersion, as described in Chapters 3 and 4. The

standard is being considered for acceptance as a consensus standard by ASTM Committee Dll

on Rubbers, Subcommittee Dll. 36 on Seals.

The proposed standard defines two types of seals; one for use in all climates (Type C)

and the other for use only in regions where minimum temperatures are above -10°C (Type W)

The requirements for the two types are the same with the exception of resistance to low

temperature

The proposed standard establishes six grades of preformed rubber seals and two classes:

A, for use with aqueous liquids, and N, for use with non-aqueous liquids. The grade to be

used depends on the design of the seal and solar collector, particularly on the stresses

likely to be placed on the seal during the life of the solar collector.

Physical requirements include (1) minimum elongation values for each grade, (2)

compression set after exposure to elevated temperature for 70 hours to assure that the seal

will be effective in service, (3) compression set after exposure at -10°C for 166 hours to 12

L
assure that crystallization of the rubber polymer will not cause leakage, (4) resistance to heating and ozone to assure that deterioration of the seal will be slow and not adversely

affect the performance of the system during its expected life, (5) resistance to low temperatures for seals likely to be at low temperatures (below -10°C) during winters and (6)

resistance to liquid immersion.

The design of the seal is not specified except for a limitation on the amount of thermal

expansion and contraction which could cause failure of the seal or a loss in its sealing

ability. Commercial tolerances are specified for design dimensions of preformed seals. The

proposed standard also includes requirements on workmanship, marking and packaging, and

gives instructions on procedures for sampling, inspection and testing.

5.3 Standard Specification for Rubber Seals Used in Solar Collectors (other than FlatPlate Collectors)

Appendix C is a proposed specification for rubber seals used in solar collectors other

than flat-plate collectors. This standard is intended for use with vertically mounted passive

systems as well as curved concentrating collectors. The document is identical to the standard

in Appendix A, except that elevated test temperatures are related to the maximum in-service

temperatures. Specifying the test temperature in this manner is necessary because of the

broad range of temperatures which can be reached with various collector designs. The maximum

temperature will normally be attained under stagnation conditions when the collector is

receiving the maximum radiation flux to which it will be exposed.

5.4 Standard Test Method for Determining the Effect of Outgassing on the Transmittance

of Solar Collector Covers

Appendix D is a proposed test method for determining the effect of outgassing on the

transmittance of solar collector covers. The document is based upon the apparatus and

procedure described in 3.3 and upon the test results described in 4.3.

5.5 Recommendations for Sealing Joints between Solar Collectors and Building

Components with Rubber Seals

Appendix E includes recommendations for sealing the joints between solar collectors and

building components with rubber seals. The document applies to 1) joints between collectors

integral with building components and those building components and 2) joints between

collector standoffs and the roof or other building components.

6. BIBLIOGRAPHY

[1] Interim Performance Criteria for Solar Heating and Cooling Systems in Commercial

Buildings

,

NBSIR 76-1187, National Bureau of Standards Report (November 1976).

[2] Skoda, Leopold F. and Masters, Larry W. , Solar Energy Systems - Survey of Materials

Performance, NBSIR 77-1314, National Bureau of Stnadards Report (October 1977).

[3] Unpublished NBS temperature data obtained on the materials of two types of collectors

under stagnation conditions (1977)

.

13
Table 1. ASTM Test Method for Measuring Key Properties

of Rubber Seals

Property ASTM Designation

Ultimate Elongation D412

Compression Set D395 (Method B) , D1229

Hardness D1415 , D2240

Tensile Strength D412

Low Temperature Flexibility C711, C734, C765 , D2137

Volatile Content and

Condensible Volatiles D865

Adhesion C719

Table 2. ASTM Test Methods for Exposure of

Rubber Seals to Key Degradation Factors

Degradation ASTM Designation

Elevated Temperature C771 , C792 , D865

Depressed Temperature D1229 , D2137

Ozone D1149

Ultraviolet Radiation C732 , C793

Stresses via Joint Movement C719

Liquid Immersion D471

14
Table 3. Rubbers Used in Laboratory Testing

Sample

Number

ASTM

Designation Type

Form in Which

Received

1 ACM Acrylate Copolymer Vulcanized Sheet

2 EAM Ethylene-Vinyl Acetate Copolymer Vulcanized Sheet

3 CSM Chloro-Sulfony 1-Polyethylene Vulcanized Sheet

4 FKM Fluoro Rubber Vulcanized Sheet

5 EPDM Terpolymer of

and a Diene

Ethylene, Propylene

Vulcanized Sheet

6 EPDM Terpolymer of

and a Diene

Ethylene, Propylene

Vulcanized Sheet

7 EPDM Terpolymer of

and a Diene

Ethylene, Propylene

Vulcanized Sheet

8 EPDM Terpolymer of

and a Diene

Ethylene, Propylene

Vulcanized Sheet

9 ECO Copolymer of Ethylene Oxide and

Chloromethyl Oxirane

(Epichlorohydrin) Vulcanized Sheet

10 CO Polychloromethyl Oxirane Vulcanized Sheet

11 VMQ Silicone Copolymer Vulcanized Sheet

12 VMQ Silicone Copolymer Vulcanized Sheet

13 VMQ Silicone Copolymer Liquid Applied Seal

14 VMQ Silicone Copolymer Cellular Rubber

15 EOT Polysulfide Liquid Applied Seal

16 VMQ Silicone 1-part Liquid Applied Seal

17 VMQ Silicone 1-part Liquid Applied Seal

18 VMQ Silicone 1-part Liquid Applied Seal

19 VMQ Silicone 1-part Liquid Applied Seal

20 VMQ Silicone 1-part Liquid Applied Seal

21 VMQ Silicone 1-part Liquid Applied Seal

22 EOT Polysulfide 1-part Liquid Applied Seal

23 EOT Polysulfide 2-part Liquid Applied Seal

24 EOT Polysulfide 1-part Liquid Applied Seal

25 EOT Polysulfide 1-part Liquid Applied Seal

26 EOT Polysulfide 1-part Liquid Applied Seal

27 EOT Polysulfide 2-part Liquid Applied Seal

28 EOT Polysulfide 2-part Liquid Applied Seal

29 EOT Polysulfide 1-part Liquid Applied Seal

30 EU Polyurethane 1-part Liquid Applied Seal

31 EU Polyurethane 1-part Liquid Applied Seal

1 ASTM D1418-76

15
Table

4.

Results

of

Tests

of

Samples 1

through

15—

<r ”0 2 rH 2 X

m

XX on o 1 1 1 1 o 2

<r QJ QJ • <D a) < QJ QJ o 1 1 1 1 X QJ

H

X 4-J rH 4J 4-> rH 4-J 4-J

X 1 X

X

O i—

X rH rH rH

X

X

Pd qj QJ a) QJ a> QJ QJ B e e B B B Xi 1 O’ ON o

r*. rH vO NO

m

m inX

X o CNX 1 1 O’

<r O' rH • • • oo o vO

X o • • 1 1 1 i—

O O o CN CN X X O o X X 00 CN o

CO O' nO o o oo o CN

mm

X o o r** ON CN CN O’

X CN co CO • • 00 CO NO CN

O • • • • 1 rH CN CN in m X X o o o o

on iH On <r NO

O o o o CN

X o O’

X O’ o

CN O' in •- • NO NO

X

X

X o o o O’

rH ON

O rH NO NO NO • • • • 1 rH rH o o o o

r>. nO 00 NO NO CN

mm o ON

X CN o NO

X o

rH O' ^o- <t • • • <r NO

X NO oo o X O’ i—

00 <r o o o o 1

rH

m CN <r o m o 00 ON

XX n- O’ o c o o 00 C7n - • • 00 NO X X O’ NO r— o o X o

rH o <T 00

m CNX

X • • • • 1 X

X rH o o o o 4-J coN # •H o CN CN i—

CO rH on

mmX

O O’

XX NO

X o p

ON o r-* 00 00 * •- • m CN O’

XX CN O’ o X O’ cO

w CN rH I-"- co CN CN • • • • 1 u

rH rH

XX o o X0>

on 1 a no m rH m o m o X CN ON X X NO o X n i nO • m • <r O ON 00 NO NO X O’ 03 00 Cd m o rH o m <r CN • • • • 1 o

Pd nO rH »H rH o o o o aX

QJ

a CN <r o m o X nx O’ 00 O’

X o X o nO NO NO * • • ON o 00 X X 00 ON o o O’ X

Ph NT CN CO CN • • • • 1 Q CO Pd rH rH rH o o o o w

CO

X

CO< QJ

a

O CO NO 00 NO rH o in

X

XX CN

X CN

X o pH

X o nO NO NO * • • ON CN X o- NO rH CN O’ 2 nO Ph CN rH ON CO CN X • • • • 1 co Pd rH rH o o o o XpX a CO oo O CN nO NO m o o On o ON X X 00 o LO p nO nO • • ON NO o CN o X O’ o o O’ O’

Ph 00 nO CO

X

X • • • 1 X

Pd o o o o

TOc

CO V! NT <r <r ON rH CN m m X x oo X NO O’ CN X • • o 00 X X NO o o X o

Id CN CN CO CN

XX • • • 1 X

rH rH rH CN CN o o

ON

a o 00 ON on CN r^*

O

mX co O’ CN NO o CO CP NO NO • • CO X no O’ 00 X X O’ oo o 00 CN NO CN X • • • 1 rH rH X CN o o r X

C/J NO NO 00 00 CN o o o X ON r-- ON O’ o QJ

TT*

m

mm • • 00 ooXX

X O’ o o O’

X

CN <£

m NO CO

X

X • • • • 1 a

Pd rH rH rH o o o o B

CO

C/3 nO NO NO ON 00 m X o NO O o NO NO O’ o X

a n* P"- • • • rH rH ON O’ CN

XX o o X o

rH o 00 00 oo rHX • • 1 < o o o o 1 X

QJ03

25 0 W >* X *H U X O C/3 X X p X 03 w 2 < X cO QJ Ph W H JH X

p co CJ

O PQ

B

a o Ph 1 QC H X S d •H g W X o 0

a)X 2 PH

H CJ

w o CJ x> co 1 O 2 o X rH 6 p X | Pd X X X a 00 X X Cd CN X 0 a X p o EH CJ < CJ X CJ Pi CJ CJ w CJ

C/3 s CJ o o U o o U o w o CJ Pd CJ

O

X CJ

O P5 2 CJ 4J

01 QJ pz o o 25 o O 2 o O CO o o Ph o O <s o O 2 < o 03 rH c X o X X O X O O X X O O X O X X X O QJ CL X rH X X X rJ X X 2 1 X 1 X X w X X < X <r X B 1 1—

1—

H X x w X X O X X X X 2 u f—

QJ cd x CO <EJ CO CO C2J CO <SJ X (£J CP CEJ CQ CEJ w o X CEJ H

CO CO CO

p CEJ

p csj wa ce> CO CEJ Pd CEJ

X <SJ

X

X < CO •H X W •H X X X rP CO X P rP CO rP y X rP QJ w 00 Jp rJ 00 X 00 rP w rP i—

rP 2 rPX o X

25

X nO

X

X NO 2 •H NO

X NO

H NO

X NO

X rH

X NOO

Q

u o nD CO

HO NO

M

H

O NO Ph NO o < O NOQ

O NO QJ 2 NO 2 & o p". X 2: O X X O X 2 X n- P x § r>. x 2 CQ o X w X O O o O CN X H 2 o > o X O x|

16
Table 5. Repeat of Compression Set Measurements

after Post Vulcanization

Sample

Number

ASTM

Designation

Post Cure in Air of Uncompressed Specimens

None 7 Oh at 150°C 166h at 1 50°C

5 EPDM ]00 53 38

8 EPDM 82 55 60

9 ECO 54 71 80

10 CO 49 51 48

14 VMQ 100 82 32

— Percent set after compression for 70 hours at 150°C.

17
Sample

ASTM

Ethylene

Glycol-Water (1;)1

Propylene

Glycol-Water

(1:1)

18

NOTE:

Rubber

immersed 7

days

in

liquid

at

100°C.
Table

6.

(continued)

Effect

of

Heat

Transfer

Liquids

at

150°C

on

Rubbers

for

Solar

Collectors

M

<D 4JW

<D

<D

<U. 60G

cd CJ

co

co

<Dg

Cd sa

00

COI

on

CNJl

00

>3-I

<rm

m

<ri

onI

00

COI

00i

T)OS 60c

cd x

cj

(0co

nO <ro

nOm co

iH+

r^- <rOn

mvO on< m+ I <r

co <1- o CNJ «H I + oCO+

CO

COI oa

>>

60

<Ds&iH

ctf >>

r—I o

a)60G

cd rC

CJ

CO

co

cd £

CNmCNJ +rH

r** 00 00 NO VO 00

ON co o

On r*- o m l—)r—tCO rH o + 1 + 1 i—i 1

CNJ1 + + 1 + GO

•H

4J

cdc

60

•H

CO

(U o s s 2 2 s X o o o Q o o in 2 Ol (X Oh o o < w CJ w w w w w CJ

O'

CU V4 i—I CD CL rO a a

Cd 3 W 2

19

NOTE:

Rubber

immersed 7

days

in

liquid

at

150°C.
Table

6.

(continued)

Effect

of

Heat

Transfer

Liquids

at

150°C

on

Rubbers

for

Solar

Collectors

&0G

<D 42au

<u

a»00G

cd cj

CO

CO

CDc

x)

co

CNI coI

oo

CN vrml

ON<rl

<rmi

"O

<D

noO

a;ooc

cd 42

CJ

COCO

Os 00 Os CNJ *co Os rH o ON ON

O Os < O OS o CO CO v£> iH CNJ 1—

r—

CNJ CNJ rH CNI + + + + + + + 4- + + + +

<D

H i—I Q) (X _G B B

cd o

oo 2

CNI

in

CNJl

-d"

CNJ ONCOI

co<rI COI

on

CNII ou

cd I—

o

P-»

V

00c

cd 42

CJ

co

CO

cd

CO <r r- vO 00 O

t-H + + +

tH+

OsOS <r

cdG

oo

•H

CO

d) Q

a

aaa

a su

X 25 QQQn o u <r CO ^2 cm PM PM CM u o

<£U

J CJ PM

WWW

w

w CJ

20

NOTE:

Rubber

immersed 7

days

in

liquid

at

150°C.
Table

6.

(continued)

Effect

of

Heat

Transfer

Fluid

at

150°C

on

Rubbers

for

Solar

Collectors

CM

I

CM

CM

I + om

+

CD00e

cO CJ

co

co

<r

»—

i

i

o\

•—

i

i

in

i

tn

i

r—I O

r—I O'* + +

*H rH •<r rH rH o vO rH vO 00 CM r^

CM rH CM CO iH iH CM rH + + + + + + + + + + + 1

o

m

CD00G

CO

CJ>

CO

CO

CO X

m

0

1 o

rH

I o

+

LO

rH

I o

CM

I

vO

I

oo

rH CO

i—I CTn + +

•Ho

c

r

COPo

cO X)

C

O

•HU

cOa

oo

•H

CO

CD Q

(D U

rH CD a- ,0 B § CO G

CO

s s s s X X Q o o O o

CJ CO 2 P p p Pi u o

< w CJ Ph w w w W w CJ

O'

CD

COU

CD

U

0) rDrOG

pci

w

HO

2;

21
Table

6.

(continued)

Effect

of

Heat

Transfer

Fluid

at

150°C

on

Rubbers

for

Solar

Collectors I

cdao

cO X)

0) U

cO

CDcoa

•H

<DGOa

cO XO

coCO

a;c

x»

>-< cO Pd

CDGOe

cO xu

COCO I

CDGOc

cO Xo

co

co

cuc

X>

CO PC

<dGOc

cO Xo

CO

CO

CO X

co

H §)

CO -H < CO

Q> Q

CD

r-H CD O. X g B

cO P3 CO z m

co <r

co oiCsJI oco

<r

-O’ a>oco+ mON

CN+

00

roi X

CN+

coI

co+

CO+ o

rH+

vO 00

i-H CN CN + I I O+

00

CMI mvOIvOI 00+

oo

sO s X X s S 53 s x o a o Q o U <C CO 52 (x, K eu e c_> o < uJ o fc w w w u w u om

CO X

22

A

NOTE:

Rubber

immersed
cd

0)

C/)

CO 44

(0

<D H

*4o

4J

cduo

£>

cd hJ3

0)

a)

00c

•H

0) X44 “N

cd co

(L) ON 3 r-I cj co

*H

(0CO /-s

<U /-N M On ^

Q- rH g ^ O I a cj ico

•H

COc

CJ -u 3

CO

cooXco

PQ

)-> CJ

X

44

C

4-1 (1) < PQ

0)M X) o c

44 0) CD PQ

PQ

"A,

CO

cd

t-H o

v£> vO

CO

<d

ON

(0 ^

CO 0 a&

cd co

O)p3

COoaxw

(0 CO CO CO ^ ^ a cj cj cj

cd cd cd cd u u Pa u

co co co co ^ ^ ^ ^ a o u o

cd cd cd cd U >4 U >4 o o a a o o c c m

cm

in

mmm

CM CM CM CM v v v v

sj CM CM OO

<r <r <r co M On H

vO oo

CM

O rH CO O cm

CO co CO CO co CO CO

cj

u o u o o o

cd cd cd cd cd cd cd g >4 >- p u p

cj

u

u

U CJ

uu o o o o o o o c c c c c c c

CO CO CO CO CO (0 (0 u u o a O cj o

cd cd cd cd cd cd cd g p u >4 u >4 p u a u CJ u u u o o o o o o o c c c g c c c

in • CMv

in

mmm

CM CM CM CM v v v v

cm o co o

<f <f <f

ON CO CM CM co m <r vO O rH m

CM CM

mm inm

CM CM CM CM A A A A m m m

CM CM CM I V V V m vo in cm CO CO CO CO O CO CM CO

oom co co o h m o CM CM

(O CO CO (0 M ^ o a o o

cd cd cd cd

CO CO CO CO ^ ^ M o u u u

cd cd cd cd P U u u m m m m

CM CM CM CM

in

m

mm

CM CM CM CM O rH in

CM CM

(0 CO CO CO CO co CO CO CO r* a; rX

CJ o CJ o u

auua

cd cd cd cd cd cd cd cd cd G g p u u G G u a u u u u u a o o o o o o o o o o G c G c G c c c c

co CO CO CO u u a u

cd cd cd cd

>4 >4

u o u CJ o o o o o c C G GmI CM m m <n m

CM CM CM CM A A A A

CM CO iH

O CO CO CO CO

vD fN CTN ID ^ <f

CM

O rH

m

00 CM CM oCM

mm

mm

CM CM CM CM A A A A

rH

O rH CO CO CO CM

CO CO CO CO C0 u CJ CJ u o

Cd cd cd cd cd J4 u p H O CJ u o U o o o o o c c c G c

lilt m m m

CM CM CM

vO vO i—I <t CO CO rH t—I G

cd x:\

oj

cd • u p>. •H >—I X 0) c > ^ u r 0) ^ a

co X) 0)

0)

X

rC

C E-4 cd

<N|

•H 44 XJ

j= >-

r-- 00 rH <r o CM r—\ ON •U (J cd

>4 XI

m

m NO v£> co ON •—1 o G 3 e

rH f-4 •H CO

G

O 44 X3 a (0

a;X

CO 0) s 3 H

OJ CO

CO x: <

a> 44

>4 CJ 3 c x:

•U cd 44 -C

44 c

CD •H

O LJ

a Ui o o e CJ

X

CM o r—

H

m CM

O r-4 «n CD -C CJ 00 O CM CM oo o CM CM 44 00 •r4 r—H

f-4 i—i

r-4 i-4 f-4 •H U—i

a» j= •H H (J 3 CJ (J

CO V-.

a o CJ CO aX

0) CJ

X) 0

CJ 3 o

,c 44 rH CM H CO

cd

•H

,g

23
d

d)o

c

co u

c

CO rH

cd

CD COu

•rHH

0)0ou

coco

co

0) H

PnU

o

+J

cOo

rd

CO hJ

3

co

<u PS

rD

CO H

00CH

d) rC

4-1 /—

CO co

d) ON

I d u

<u

<1) u

uC

c

o

•H

CO

CO

(1) ^M o>

O- rH 6 r- 0 I U CJ

1c s

O H

•H CO

CO <J C w

(1) 4-J Xw

co

co

0)ad

u

co PC

0

ae

*Hx

cO s

cx0

CO CO

<D d 4J cs

<4-4 d) < CQ

"A,

CO

co rHa

vO

VD

CO<

w CM

r. r^. co

co cj O w hJ S

a

u

o

COoa

xw

CO CO CO CO Hi Hi ^ Hi u u u o

cO cO cO cO

J-I u u

a u u a

co co co co ^ Hi Hi M

a a a u

cO co CO H U H

o a

oc

m m m

CM CN CN

co m co

co co co

m o h m

00 O CM CM

CO

CM

CO CO CO CO Hi Hi Hi Hi a a u u

cO CO cO co H H M H o a a o

co co co co Hi Hi Hi Hi a a o

CO CO

m m m

cm cm CM v A A

O vo o

CM CM O vD <f vO rH o

CM o rH in

00 O CM CM

CM

CO (0 CO CO Hi Hi Hi Hi a o a u

cO cO cO cO

CO CO CO CO Hi Hi Hi Hi o a a a

cO cO cO u u u o

m m m in

CM CM CM CM V V V A

co vc m o co <r

ON vO vD m co co

CM O rH in

00 O CM CM

m

CM

CO CO CO CO Hi Hi Hi Hi a o u u

cO co co cO

CO CO CO CO Hi Hi Hi Hi a a u a

cO co cO co U H u u

o u o u

o o

c c

m m m

CM CM CM V V A

m m cm

rH CM

VO ^ N Q\

m vo o o

cn o h m

00 O CM CM

vO

CM

CO CO CO CO Hi Hi Hi Hi u u a o

co CO CO CO

J-i a a

co co co co Hi Hi Hi Hi a o u a

cO cO cO u u u u u u

m «n m

CM CM CM

•<r m <r

CM CM rH

O (Js <T <t

<T <T vd 00

CM O rH m

00 CM CM

CO CO CO CO Hi Hi Hi Hi U U CJ CJ

cO co cO co

m m m

CM CM CM

CO CO CO CO Hi ^ Hi Hi u u u u

cO cO co cO U u H H o cj cj

CO CO CO CO Hi Hi Hi Hi a a a cj

cO co CO CO u u u u

CO CO CO CO Hi Hi Hi Hi

CJ CJ CJ CJ

co CO CO CO

cj a u

j-i cj o

o o

c c

m m m

CM CM CM v v A

m <r n o vo vo vo in m m vO

4 N vO O O m in ^ m n m in oo r^

CM O rH m

00 O CM CM

CM O rH m

00 O CM CM

00

CM CM

24
Table

7.

Results

of

Laboratory

Tests

of

Elastomeric

Sealants

(continued)

00 CO CO CO CO CO CO CO CO d M M J* J*

•H (1) T) o a cj CJ cj CJ O CJ U n c (0 CO CO CO cO CO CO CO

0) CM CU M M M U H M U

Jd <J PQ a a cj CJ a a U CJ 4J /—v

CO CO o o o

0) ON c c c o

<D M s co CO (0 CO co co CO CO

CO H M

M CO <u cj o o o o a CJ CJ

a) < M •a co cO CO co CO co CO CO •H O c M u M M M H M u

0) CM 0) CJ u CJ a O a CJ CJ a 0) PQ

cj « O o O o < c c c d

d CNl o CO •H CO

CO cO 1 1 1 i | i | 1 CO rH

0) o

M On v_x CL rH B CO O 1 CO u u o

1c s

o f—

(

TJ 0

•H CO c 0

W < o c c 'w' PQ *H m in in m m m m m

<u 0 CN| CN CN CN CN CN CN CN

JJX

3

rH A A A A V V V V w <

rH

CO NO

CO VO

a)d CJ

X> ON CO O' m m 00 <r co s m v£> VO m 'd- <r m m

CO H

ff2 CO

s*/ <

—s

CNJ 'w' ON

CO r^ 00 o >0- 00 00 00 rH

CJ • • • • • • • • CO CN m rH nO rH <r nO NO o

fj

33H

rH rH CN rH rH rH rH rH

CO

CO

CO s <v-/

*“•1

CO

CL) B HI H

3 d

s 3 u CJ CJ

•H CO cO o o X O M CN O rH m CN O rH m

cfl a (1) 00 o CN CN 00 o CN CN s X cu rH rH —1 rH rH rH w 0

<D H

<D iH • a o o rH B z co CO

(0 CO

25
<uu3ooonw

<u H

603

•H

cocn

cd60U3O

0-CO

CO3wa

osJ

00

<u rH

cd H ooouoom6ow

0-4

a)a3

cd

cd • u

4J

a) •a

rH a) •O 4J

cd cd •U u

60 e a) o 4J u 3

P-<

M

*^l CN|

26
1

Figure 1. Fogging of Collector Cover Plates by Outgassing Products.

Figure 2. Components of the Outgassing Test Apparatus.

27

APPENDIX A

Proposed Standard Specification for Rubber

Seals Used in Flat-Plate Solar Collectors

1. Scope

1.1 This specification gives the general requirements for materials used in rubber seals

of flat-plate solar collectors except vertically mounted passive collectors. Particular

applications may necessitate other requirements which would take precedence over these

requirements when specified.

1.2 Design requirement pertains only to permissible deflections of the rubber during

thermal expansion or contraction of the seal in use and the tolerances in dimensions of

molded and extruded seals.

1.3 This specification does not include requirements pertaining to the fabrication or installation of the seals.

2. Applicable Documents

2.1 ASTM Standards

C661 Test for Indentation Hardness of Elastomeric Type Sealants by means

of a Durometer.

C717 Definition of Terms Relating to Building Seals

C719 Test for Adhesion and Cohesion of Elastomeric Joint Sealants

under Cyclic Movement

D395 Test for Rubber Property - Compression Set

D412 Test for Rubber Properties in Tension

D865 Test for Rubber Deterioration by Heating in a Test Tube

D1149 Test for Rubber Deterioration - Surface Ozone Cracking in a Chamber (Flat Specimen)

D1229 Test for Rubber Property - Compression Set at Low Temperature

A-l
D1415 Test for Rubber Property - International Hardness

D1566 Definition of Terms Relating to Rubber

D2137 Test for Rubber Property - Brittleness Point of Flexible

Polymers and Coated Fabrics

D2240 Test for Rubber Property - Durometer Hardness

D3182 Rubber - Materials, Equipment and Procedures for Mixing

Standard Compounds and Preparing Standard Vulcanized Sheets

D3183 Rubber - Preparation of Pieces for Test from Other Than

Standard Vulcanized Sheets

2.2 Other Standards

RMA Handbook - Rubber Products, Molded-Extruded-Lathe Cut-Cellular

3. Classification

3.1 Types

Type C, intended for use in cold climates (below - 10°C in winter)

Type W, intended for use in warm climates (above - 10°C in winter)

3.2 Grades

Grade designations represent differing degrees of hardness as follows:

Grade 2, Hardness of 20+5

Grade 3, Hardness of 30 ± 5

Grade 4, Hardness of 40 ± 5

Grade 5, Hardness of 50 ± 5

Grade 6, Hardness of 60 ± 5

Grade 7, Hardness of 70 ± 5

Grade 8, Hardness of 80 ± 5

Note 1 - The grade to be used in a particular application depends on

the design of the seal and must be specified by the designer.

A-2
3.3 Classes

Seals shall be classified as follows:

Class PS, Preformed rubber seal

Class SC, Sealing compound

Note 2 - Class SC material should not be used in designs where the

seal is under mechanical stress.

4. Terminology

4.1 Definitions of terms are given in ASTM C717 and D1566

5. Materials

5.1 Seals shall be made from rubber formulations that are impervious

to ultraviolet light and when vulcanized conform to the requirements in

Section 6.

6. Requirements

6.1 Class PS material shall conform to the requirements given in

Table 1.

6.2 Class SC material shall conform to the requirements given in

Table 2.

7. Dimensions

7.1 The design of the seal shall not permit the rubber to deflect more

than 25% in anv direction durine thermal expansion and contraction of

the solar collector.

Note 3 - If the thermal coefficient of linear expansion for the

rubber is not known, a value of 0.0003/K may be assumed for design purposes.

7.2 The tolerances in dimensions of molded seals shall conform to RMA

A3
A3-F3-T.032 as given for molded products in the RMA Handbook. Tolerances

on any critical dimension shall conform to RMA A2-F3-T.032 in that

handbook.

7.3 The tolerances in dimensions of extruded seals shall conform to

RMA A2-F3 given for extruded products in the RMA Handbook.

8. Workmanship

8.1 Class PS seals shall be free of blisters, checks, cracks, and

other imperfections that can affect their ability to make or maintain

a water-tight seal.

8.2 Class SC material shall be uniform in composition and be free of

defects that may affect serviceability.

9. Sampling and Inspection

9.1 Class PS material. Manufacturers of preformed seals may use their

quality control systems for production inspection to assure the seals

conform with this specification, provided appropriate records are kept.

In case of dispute regarding the quality of a delivered product, a

sample of five seals shall be taken from the lot and tested for compliance

with this specification. If one of the five seals does not conform, a

second sample of five seals may be taken and tested. If two or more of

the ten seals do not conform, the lot may be rejected.

9.2 Class SC material. Manufacturers may use their quality control

systems to assure production conforms with this specification. In case

of dispute regarding the quality of a delivered product, five test

sheets and five adhesion specimens shall be prepared, preferably from

five different packages, in accordance with the instructions supplied

with the sealing material. If one of the five sheets 'or adhesion
specimens does not conform, an additional five sheets or adhesion

specimens may be prepared and tested. If two or more of the ten

sheets or adhesion specimens do not conform, the lot may be rejected.

10. Testing

10.1 Class PS material. Specimens shall be prepared as prescribed in

ASTM D3183 and tested in accordance with the methods of test given in

Table 1. For control of production, specimens may be taken from standard

test sheets prepared in accordance with ASTM D3182, using the same

unvulcanized material used to prepare the seals and vulcanizing the

material at the same temperature used for the seals to an equivalent

state of vulcanization.

10.2 Class SC material. Five sheets approximately 150 by 150 by 2 mm

(6 by 6 by 0.08 in) shall be prepared in accordance with instructions supplied

with the sealing material. Also, five adhesion specimens shall be prepared

in accordance with ASTM C719. Preferably, each sheet and adhesion specimen

should be prepared from material in a different container. Condition the

sheets and adhesion specimens for 1A days at a temperature of 23°C and

relative humidity of 50 percent. Test the material in accordance with

the methods of test given in Table 2.

10.3 Volatiles lost shall be determined from the difference in mass of

the specimens before and after heating for 166 h at the temperature

given in Table 1 or 2 and as prescribed in ASTM D865.

10. A Volatiles condensible at 23°C shall be determined from the difference

in mass of the outlet tubes (ASTM D865) before and after heating the

specimens for 166 h at the temperature given in Table 1 or 2. The exposed

portion of the outlet tube shall be cooled, if necessary, with a stream
of air to maintain a temperature of 23 ± 2°C. If any volatiles condense

on the inlet tube or other parts of the apparatus, the mass of this

condensed material shall be added to the mass of the material on the

outlet tube.

11. Marking

11.1 Name, brand or trademark of the manufacturer.

11.2 Type and Grade.

11.3 Compliance with this standard, ASTM DXXXX.

11.4 Other information required by manufacturer or purchaser.

11.5 Marking may be on either seal, packaging, label, or tag.

12. Packaging

12.1 Material shall be protected by suitable packaging to prevent

damage during shipment or storage prior to installation in solar collector.
Table 1. Requirements for Class PS Material

Used to Seal Flat-Plate Solar Collectors

Property Grade Method

3 4 5 6 l 8

Ultimate Elongation-% min 350 300 250 200 150 100 D412

Compression Set-% max

after 70 h at 150°C 30 30 30 30 30 30 D395

a

after 166 h at -10°C 60 60 60 60 60 60 D1229

b

Resistance to Heating (166 h at 150°C)

C D865

Hardness change, max

Ultimate Elongation

10 10 10 10 10 10 D1415 or D2240

Change-% max

Tensile Strength

30 30 30 30 30 30 D412

Change-% max 20 20 20 20 20 20 D412

Volatiles lost-% max 1 1 1 1 1 1 See 10.3

Volatiles condensible

-X max 0.1 0.1 0.1 0.1 0.1 0.1 See 10.4

Resistance to Ozone D1149

100 mPa, 166 h at 40°C No Cracking

Resistance to Low Temperature D2137

Type C only, °C max -40 -40 -40 -40 -40 -40

3 Method B

b

Set to be measured at 10 seconds after release. Lubricated plates or polytetrafluoroethylene film is recommended if the rubber adheres to the

metal compression plates during test.

C The test temperature of 150°C is used to test seals for cover plates. A seal in

contact with an absorber plate should be tested at a standard test temperature

listed in ASTM D1349 next above the maximum temperature of the absorber plate in

service (which generally occurs under stagnation conditions and maximum radiation

flux) but not less than 150°C. The higher test temperatures are: 175, 200, 225

and 250°C.
Table 2. Requirements for Class SC Material

Used to Seal Flat-Plate Solar Collectors

Property Grade Method

2 3 4

Ultimate Elongation-% min 200 150 100 D412

Resistance to Heating

(166 h at 125°C) D865

Hardness Change, max Ultimate Elongation

10 10 10 C661

Change, % max

Tensile Strength

30 30 30 D412

Change, % max 20 20 20 D412

See 10.3

a; Volatiles Lost, % max

Volatiles Condensible,

1 1 1

See 10.4

a) % max 0.1 0.1 0.1

Resistance to Ozone D1149

100 mPa , 166 h at 40°C No Cracking

Resistance to Low

Temperature D2137

Type C only, °C max -40 -40 -40

Adhesion loss (-cm^ max)^ 9 9 9 C719 c)

a) This test is not required if the design precludes condensing of

the volatiles on the cover plate(s) of the solar collector.

b) The combined loss in bond and cohesion^areas for the three

specimens tested shall not exceed 9 cm . c) The temperature in 6.3 of ASTM C719 shall be modified to 125°C.

A-8
APPENDIX B

1. Scope

Proposed Standard Specification for Rubber

Seals Contacting Liquids in Solar Energy Systems

1.1 This specification gives the general requirements for materials used in

preformed rubber seals that contact the circulating liquid in solar energy

systems. Particular applications may necessitate other requirements which

would take precedence over these requirements when specified.

1.2 This specification does not include requirements pertaining to the design,

fabrication or installation of ^he seals.

2. Applicable Documents

2.1 ASTM Standards

D395 Test for Rubber Property - Compression Set

DA 12 Test for Rubber Properties in Tension

D471 Test for Rubber Property - Effect of Liquids

D865 Test for Rubber Deterioration by Heating in a Test Tube

D1149 Test for Rubber Deterioration - Surface Ozone Cracking in

a Chamber (Flat Specimen)

D1229 Test for Rubber Property - Compression Set at Low Temperature

D13A9 Rubber - Standard Temperatures and Atmospheres for Testing

and Conditioning

D1415 Test for Rubber Property - International Hardness

D1566 Definition of Terms Relating to Rubber

D2137 Test for Rubber Property - Brittleness Point of Flexible

Polymers and Coated Fabrics

A9
D3182 Rubber - Materials, Equipment and Procedures for Mixing

Standard Compounds and Preparing Standard Vulcanized*

Sheets

D3183 Rubber - Preparation of Pieces for Test from Other Than

Standard Vulcanized Sheets

2.2

Other Standards

RMA Handbook - Rubber Products, Molded-Extruded-Lathe Cut-Cellular

3. Classification

3.1 Types

Type C, intended for use in cold climates (below -10°C in winter)

Type W, intended for use in warm climates (above -10°C in winter)

3.2 Grades

Grade designations represent differing degrees of hardness as follows:

Grade 3, Hardness of 30 ± 5

Grade A, Hardness of AO ± 5

Grade 5, Hardness of 50 ± 5

Grade 6* Hardness of 60 ± 5

Grade 7, Hardness of 70 ± 5

Grade 8, Hardness of 80 '± 5

Note 1 - The grade to be used in a particular application depends on the

design of the seal and must be specified by the designer.

3.3 Classes

Seals shall be classified as follows:

Class A, Seals for use with aqueous liquids

Class N, Seals for use with non-aqueous liquids

Note 2 - Aqueous liquids include water and antifreeze solutions.

A-10
4. Terminology

4.1 Definitions of terms are given in ASTM D1566

5. Ordering Information

5.1 Orders for seals under this specification shall include the following information

5.1.1 Reference to this Standard: ASTM Dxxxx

5.1.2 Type, Grade and Class

5.1.3 Design and dimensions of seal

5.1.4 Contacting liquid

5.1.5 Maximum service temperature

6 . Requirements

6.1 Seals shall be vulcanized from suitable rubber formulations and conform

to the requirements given in Tables 1 and 2.

7. Dimensions

7.1 The tolerances in dimensions of molded seals shall conform to ‘RMA

A3-F3-T.032 as given for molded products in the RMA Handbook. Tolerances on

any critical dimension shall conform to RMA A2-F3-T.032 in that Handbook.

7-2 The tolerances in dimensions of extruded seals shall conform to RMA

A2-F3 given for extruded products in the RMA Handbook.

8. Workmanship

8.1 Seals shall be free of blisters, checks, cracks, and other imperfections

that can affect their ability to make or maintain a liquid-tight seal.

9. Sampling and Inspection

9.1 Manufacturers of seals may use their quality control systems for production

inspection to assure the seals conform with this specification, provided

appropriate records are kept. In case of dispute regarding the quality of a

delivered product, a sample of five seals shall be taken from the lot and tested

for compliance with this specification. If one of the five seals does not

conform, a second sample of five seals may be taken and tested. If two or more

of the ten seals do not conform, the lot may be rejected.

A- 11
10.

Testing

.t:v «*• 10.1 Specimens shall be prepared as prescribed in ASTM D3183 and tested in

accordance with the methods of test given in 10.2. For control of production,

specimens may be taken from standard test sheets prepared in accordance with

ASTM D3182, using the same unvulcanized material used to prepare the seals

and vulcanizing the material at the same temperature used for the seals to

an equivalent state of vulcanization.

10.2 Ultimate elongation shall be determined in accordance with ASTM D412.

Other requirements

# shall be determined in accordance with the ASTM methods

specified in Table 2.

10.3 Class A seals shall be tested for heat resistance and compression set at

a temperature of 125°C and for resistance to liquids at a temperature of 100°C.

10.

A Class N seals shall be tested for heat resistance and compression set

at the standard test temperature in ASTM D1349 that is between 25°C and 49°C

above the maximum service temperature, and for resistance to liquids at the

standard test temperature that is between 1°C and 25°C above the maximum service

temperature. The standard test temperatures shall not be less than those for

Class A seals. Above 125°C, the standard test temperatures are: 150, 175, 200, 225 and 250°C.

10.5 The liquid used for tests in accordance with ASTM D471 shall be the one

used in service for the particular heat transport system.

11. Marking

11.1 Name, brand or trademark of the manufacturer.

11.2 Type and Grade.

11.3 Compliance with this standard, ASTM DXXXX.

11.4 Other information required by manufacturer or purchaser.

11.5 Marking may be on either seal, packaging, label, or tag.

12. Packaging

12.1 Material shall be protected by suitable packaging to prevent damage

during shipment or storage prior to installation in solar collector'.

A-12
Table 1. Elongation Requirements for Rubber Seals in Liquid Heat-Transport Systems

Grade

Ultimate Elongation

percent, minimum

3

4

5

6.

7

8

350

300

250

200

150

100

Table 2. Other Requirements for Rubber Seals in Liquid Heat-Transport Systems

Property Unit Requirement ASTM Method

Compression Set

2 High temperature % 30 maximum D395,* Method B Low temperature*3 % 60 maximum D1229

c Resistance to Heating

Hardness change IRHD 10 maximum D1415

Ultimate elongation

change

% of

original 30 maximum D412

Resistance to Ozone5* - - no cracking D1149

Resistance to Low

Temperaturee °C -40 maximum D2137

Resistance to Liquid^

Volume change % +40 to -10 D471

Hardness change IRHD ±10 D1415

Q

After, compression for 70 hrs. at temperature specified in 10.3 or 10.4.

^After compression for 166 hrs. at -10°C. Set shall be measured at 10 sec. after

force is release. Lubricated plates or polytetraf luoroethylene film is recommended

if the rubber adheres to the metal plates during test.

QCondition for 166 hrs. at temperature specified in 10.3 or 10.4.

^This requirement does not apply to seals that are not exposed to outside

atmospheres

.

^his requirement applies to Type C seals only.

^Rubber shall be immersed in liquid used in service for 166 hrs. at temperature

specified in 10.3 or 10.4.

A- 13
APPENDIX C Proposed Standard Specification for Rubber

Seals Used in Solar Collectors

(other than Flat-Plate Collectors)

1. Scope

1.1 This specification gives the general requirements for materials used in rubber

seals of vertically mounted passive solar collectors and curved concentrating collectors.

Particular applications may necessitate other requirements which would take precedence

over these requirements when specified.

1.2 Design requirement pertains only to permissible deflections of the

rubber during thermal expansion or contraction of the seal in use and the tolerances

in dimensions of molded and extended seals.

1.3 This specification does not include requirements pertaining to the fabrication

or installation of the seals.

2. Applicable Documents

2.1 ASTM Standards

C661 Test for Indentation Hardness of elastomeric Type Sealants by means of a Durometer.

C717 Definition of Terms Relating to Building Seals

C719 Test for Adhesion and Cohesion of Elastomeric Joint Sealants

under Cyclic Movement

D395 Test for Rubber Property - Compression Set

D412 Test for Rubber Deterioration by Heating in a Test Tube

D1149 Test for Rubber Deterioration - Surface Ozone Cracking in a Chamber (Flat Specimen)

D1229 Test for Rubber Property - Compression Set at Low Temperature

A-14
D1415 Test for Rubber Property - International Hardness

D1566 Definition of Terms Relating to Rubber

D2137 Test for Rubber Property - Brittleness Point of Flexible

Polymers and Coated Fabrics

D2240 Test for Rubber Property - Durometer Hardness

D3182 Rubber - Materials, Equipment and Procedures for Mixing

Standard Compounds and Preparing Standard Vulcanized Sheets

D3183 Rubber - Preparation of Pieces for Test from Other Than

Standard Vulcanized Sheets

2.2 Other Standards

RMA Handbook - Rubber Products, Molded-Extruded-Lathe Cut-Cellular

3. Classification

3.1 Types

Type C, intended for use in cold climates (below - 10°C in winter)

Type W, intended for use in warm climates (above - 10°C in winter)

3.2 Grades

Grade designations represent differing degrees of hardness as follows

Grade 2

,

Hardness of 20 + 5

Grade 3, Hardness of 30 ± 5

Grade 4, Hardness of 40 ± 5

Grade 5, Hardness of 50 ± 5

Grade 6, Hardness of 60 ± 5

Grade 7, Hardness of 70 ± 5

Grade 8, Hardness of 80 ± 5

Note 1 - The grade to be used in a particular application depends on

the design of the seal and must be specified by the designer.

A-15
3.3

Classes

Seals shall be classified as follows:

Class PS, Preformed rubber seal

Class SC, Sealing compound

Note 2 - Class SC material should not be used in designs where the

seal is under mechanical stress.

4. Terminology

4.1 Definitions of terms are given in ASTM C717 and D1566

5. Ordering Information

5.1 Orders for seals under this specification shall include the following information

5.1.1 Reference to this Standard: ASTM Dxxxx

5.1.2 Type, Grade and Class

5.1.3 Design and dimensions of seal

5.1.4 Maximum service temperature

5.1.5 Quantity

6. Materials

6.1 Seals shall be made from rubber formulations that are impervious

to ultraviolet light and when vulcanized conform to the requirements in

Section 6.

7. Requirements

7.1 Class PS material shall conform to the requirements given in

Table 1.

7.2 Class SC material shall conform to the requirements given in

Table 2.

8. Dimensions

8-1 The design of the seal shall not permit the rubber to deflect more

than 25% in anv direction during thermal expansion and contraction of

the solar collector.

A-16
4

Note 3 - If the thermal coefficient of linear expansion for the

rubber is not known, a value of 0.0003/K may be assumed for design purposes

8.2 The tolerances in dimensions of molded seals shall conform to RMA

A3-F3-T.032 as given for molded products in the RMA Handbook. Tolerances

on any critical dimension shall conform to RMA A2-F3-T.032 in that

handbook.

8.3 The tolerances in dimensions of extruded seals shall conform to

RMA A2-F3 given for extruded products in the RMA Handbook.

9 . Workmanship

9.1 Class PS seals shall be free of blisters, checks, cracks, and

other imperfections that can affect their ability to make or maintain

a water-tight seal.

9.2 Class SC material shall be uniform in composition and be free of

defects that may affect serviceability.

10. Sampling and Inspection

10.1 Class PS material. Manufacturers of preformed seals may use their

quality control systems for production inspection to assure the seals

conform with this specification, provided appropriate records are kept.

In case of dispute regarding the quality of a delivered product, a

sample of five seals shall be taken from the lot and tested for compliance

with this specification. If one of the five seals does not conform, a

second sample of five seals may be taken and tested. If two or more of

the ten seals do not conform, the lot may be rejected.

10.2 Class SC material. Manufacturers may use their quality control

systems to assure production conforms with this specification. In case

of dispute regarding the quality of a delivered product, five test

sheets and five adhesion specimens shall be prepared, preferably from

five different packages, in accordance with the instructions supplied

with the sealing material. If one of the five sheets ‘or adhesion

A-17
specimens does not conform, an additional five sheets or adhesion

specimens may be prepared and tested. If two or more of the ten

sheets or adhesion specimens do not conform, the lot may be rejected.

11. Testing

11.1 Class PS material. Specimens shall be prepared as prescribed in

ASTM D3183 and tested in accordance with the methods of test given in

Table 1. For control of production, specimens may be taken from standard

test sheets prepared in accordance with ASTM D3182, using the same

unvulcanized material used to prepare the seals and vulcanizing the

material at the same temperature used for the seals to an equivalent

state of vulcanization.

11.2 Class SC material. Five sheets approximately 150 by 150 by 2 mm

(6 by 6 by 0.08 in) shall be prepared in accordance with instructions supplied

with the sealing material. Also, five adhesion specimens shall be prepared

in accordance with ASTM C719. Preferably, each sheet and adhesion specimen

should be prepared from material in a different container. Condition the

sheets and adhesion specimens for 14 days at a temperature of 23°C and

relative humidity of 50 percent. Test the material in accordance with

the methods of test given in Table 2.

11.3 Volatiles lost shall be determined from the difference in mass of

the specimens before and after heating for 166 h at the temperature

given in Table 1 or 2 and as prescribed in ASTM D865.

11.4 Volatiles condensible at 23°C shall be determined from the difference

in mass of the outlet tubes (ASTM D865) before and after heating the

specimens for 166 h at the temperature given in Table 1 or 2. The exposed

portion of the outlet tube shall be cooled, if necessary, with a stream

A-18
of air to maintain a temperature of 23 ± 2°C. If any volatiles condense

on the inlet tube or other parts of the apparatus, the mass of this

condensed material shall be added to the mass of the material on the

outlet tube.

12 . Marking

12.1 Name, brand or trademark of the manufacturer.

12.2 Type and Grade.

12.3 Compliance with this standard, ASTM DXXXX.

12.4 Other information required by manufacturer or purchaser.

12.5 Marking may be on either seal, packaging, label, or tag.

13 . Packaging

13.1 Material shall be protected by suitable packaging to prevent

damage during shipment or storage prior to installation in solar collector.

A-19
Table 1. Requirements for Class PS Material

Used to Seal Solar Collectors

Grade

Property 3 4 5 6 7 8 Method

Ultimate Elongation-% min 350 300 250 200 150 100 D412

Compression Set-% max

after 70 h at MST

c) 30 30 30 30 30 30 D395a

after 166 h at -10°C 60 60 60 60 60 60 D1229b

Resistance to Heating (166 h at MSTC

) Hardness change , mas Ultimate Elongation

10 10 10 10 10 10 D1415 or D2240

Change-% max

Tensile Strength

30 30 30 30 30 30 D412

Change-% max 20 20 20 20 20 20 D412

Volatiles lost-% max Volatiles condensible

1 1 1 1 1 1 See 10.3

-% max 0.1 0.1 0.1 0.1 0.1 T—

j

o See 10.4

Resistance to Ozone D1149

100 mPa, 166 h at 40°C No Cracking

Resistance to Low Temperature D2137

Type C only, °C max -40 -40 -40 -40 -40 -40

-

Method B

k"* Set to be measured at 10 seconds after release. Lubricated plates or polytetraf luoroethylene

film is recommended if the rubber adheres to the metal compression plates during test.

c ) The test temperature is based on the maximum service temperature (MST) which normally

occurs when the collector is under stagnation conditions and receiving the maximum radiation

flux. The test temperature listed in ASTM D1349 that is between 25°C and 49°C above the

maximum service temperature is used. These temperatures are: 100, 125, 150, 175, 200,

225 and 250°C.

A-20
Table 2. Requirements for Class SC Material

Used to Seal Solar Collectors

Grade

Property 2 3 4 Method

Ultimate Elongation-% min 200 150 100 D412

Resistance to Heating

(166 h at MST a)

Hardness Change, max Ultimate Elongation

10 10 10 C661

Change , % max Tensile Strength Change,

30 30 30 D412

% max 20 20 20 D412 M

See 10.3 ; Volatiles Lost, % max Volatiles Condensible,

1 1 1

See 10.4

b)

% max 0.1 0.1 0.1

Resistance to Ozone

100 mPa , 166 h at 40°C No Cracking

Resistance to Low Temperature D2137

Type C only, °C max -40 -40 -40

C719 2 c d)

)

Adhesion loss (-cm max) 9 9 9

The test temperature is based on the maximum service temperature (MST) which

normally occurs when the collector is under stagnation conditions and receiving

the maximum radiation flux. The test temperature listed in ASTM D1349 that is

between 25°C and 49°C above the maximum service temperature is used. These

temperatures are: 100, 125, 150, 175, 200, 225 and 250°C.

^This test is not required if the design precludes condensing of the volatiles

on the cover plate(s) of the solar collector.

c) The combined loss in bond and cohesion areas for the three specimens tested

shall not exceed 9 cm^

.

d) The temperature in 6.3 of ASTM C719 shall be modified to the MST (see

footnote a) above.

A-21
APPENDIX D

PROPOSED STANDARD TEST METHOD FOR DETERMINING

THE EFFECT OF OUTGASSING ON THE TRANSMITTANCE

OF SOLAR COLLECTOR COVERS

1

Scope

1.1 This method covers the determination of the effect of outgassing

on the transmittance of cover plates in solar energy collectors. It

is applicable to polymeric materials such as rubber seals, insulation

and absorptive coatings.

2 . Summary of Method

2.1 The material to be evaluated is heated in a test apparatus as described

in Section 5.1. The condensible decomposition products are collected on a

glass plate. The transmittance of the glass plate is measured from 300 to

2100 nm (in increments of 50 nm) before and after testing to determine any

change in transmittance resulting from the deposited products. The mass

loss of the polymeric test specimen and the weight gain of the glass plate

are also determined.

3 . Significance

3.1 This method can be used to determine the effect of outgassing products

on the transmittance of solar collector cover plates and to determine and

compare the relative effect of volatile condensible degradation products

of specific polymeric materials on cover plate transmittance.

4 . Description of Terms

4.1 Outgassing - The emission of gases by materials and components, usually

during exposure to elevated temperature or reduced pressure.

Ar-22
5. Apparatus

5.1

Outgassing apparatus - a test apparatus containing a controlled temperature

heatipg device, a temperature monitor, an enclosed specimen chamber, a test

specimen holder, a glass plate upon which volatiles are condensed and a filtered

air stream directed toward the external surface of the glass plate. Figure 1

is a diagram of the individual components of the apparatus and Figure 2 shows

the assembled apparatus.

5.2

Spectrophotometer - a spectrophometer as described in ASTM E424-71.

6. Test Specimen

6.1 The test specimen shall consist of a sample of the material.—^

6.2 Specimens of absorptive coatings, which are applied to metallic substrates,

shall consist of both the coating and the substrate.

6.3 Specimens of absorptive coatings, which are normally applied to polymers

for use in solar collectors, should be applied on a metallic substrate as in 6.2.

6*4 The size of specimen should be approximately proportional to the ratio of apparatus

glass plate area to cover plate areas of solar collector.

7 . Conditioning

7.1

Test specimens shall be conditioned at room temperature prior to testing.

8. Procedure

8.1

Measure the transmittance of the glass plate from 300 to 2100 nm according

to ASTM E424-71

.

1 / Optimum specimen size as yet to be determined.

A-23
8.2 Weigh the test specimen and the glass plate of the test apparatus to the

nearest 0.01 gm.

8.3 Adjust the temperature of the test apparatus to the desired test temperature

prior to inserting the test specimen and installing the glass plate.

8.4 Place the test specimen in the specimen holder and install the glass plate

over the teflon gasket using the spring clips.

8.5 Turn on the air stream and direct the flow to the center of the exterior surface

of the glass plate.

8.6 Allow the test to proceed for 3 hours or the time mutually agreed upon by

the purchaser and the seller.

8.7 Stop the flow of the air stream, turn off the hot plate and remove the glass

plate and the test specimen.

8.8 Allow the test specimen and the glass plate to reach room

temperature and weigh both.

8.9 Measure the transmittance of the glass plate from 300 to 2100 nm

according to ASTM E424-71.

8.10

Clean the glass plate with ethyl alcohol for repeat usage.

Measure the transmittance of the cleaned plate using the procedure in

8.1 prior to reusing.

A-24
9. Calculations

9.1 Integrate the area under the transmittance curves obtained in

8.1 and 8.9 and calculate the difference between the integrated values.

9.2 Calculate the weight gain of the glass plate and the mass loss

of the test specimen.

10 . Report

10.1 The report shall include the following:

10.1.1. Identification of the test specimen, including type of

material, source or manufacturer, product identification, batch

or lot serial number.

10.1.2. Identification of metal used if the test specimen is an

absorptive coating applied to a substrate.

10.1.3. Conditioning procedure prior to testing.

10.1.4. Identification of type of glass used as the glass plate,

test temperature and test duration.

10.1.5. Test specimen mass before and after test and mass loss.

10.1.6. Glass plate mass before and after test and mass gain.

10.1.7. Integrated transmittance from 300 to 2100 nm of the glass

plate before and after testing and the difference between the two

values

.

A-25
Figure 1. Components of the Outgassing Test Apparatus,

Figure 2. Assembled Outgassing Test Apparatus.

A-26
APPENDIX E

RECOMMENDATIONS FOR SEALING JOINTS

BETWEEN SOLAR COLLECTORS AND

BUILDING COMPONENTS WITH RUBBER SEALS

1. Scope

1.1 These recommendations apply to the sealing of 1) joints between

solar collectors integral with building components and those building

components and 2) joints between collector standoffs and the roof or

other building components.

1.2 These recommendations apply to rubber seals used to seal the

joints described in 1.1.

1.3 The joint sealing compounds covered by specifications listed in

2.0 are intended, among other uses, to seal joints against dust, dirt,

wind and water.

2 . Compliance with Specifications

Sealants that are selected for use in the installation of solar collectors

should meet all the requirements of one of the appropriate following

Federal Specifications:

TT-S-00230C (COM-NBS), February 2, 1970, Ammend 2; Sealing Compound:

Elastomeric Type, Single Component (For Caulking, Sealing, and Glazing in Buildings and Other Structures).

A-27
TS-S-00227E (COM-NBS), November 4, 1969, Ammend 3; Sealing Compound:

Elastomeric Type, Multi-Component (For Caulking, Sealing, and Glazing in Buildings and Other Structures).

TS-S-001543A (COM-NBS), June 9, 1971, Sealing Compound: Sili- cone Rubber Base (For Caulking, Sealing, and Glazing in Buildings and Other Structures).

3 . Suggested Installation Practices

3.1 Liquid applied seals are supplied in two types as follows:

(a) one component material in metal, cardboard or plastic cartridges

as well as in bulk containers of various capacities; (b) two or

more components, usually referred to as base and curing agents or

accelerators. Small quantities may be mixed on a board or plate

instead of using the base container.

3.2 The compound supplied in cartridges should be installed with

either a hand or power gun. Bulk compound should be installed with

a caulking gun or with a hand tool.

3.3 It is of prime importance that the joint be dry, free of dust,

dirt, oil or grease before the sealant is placed in the joint.

3.4 Sealant producers often recommend the use of a specific primer

(or surface conditioner) for specific surfaces. The primer is designed

to assure adhesion of the compound to a specific surface. Substituted

primers or conditioners other than those recommended by the producer

should not be used.

A-28
3.5 Whenever possible, the compound should not be applied to a joint at temperatures

below 40°F. At such temperatures, a film of moisture is likely to form on the

surfaces of the joint as a result of condensation that is not readily visible.

This invisible moisture film may prevent the formation of a strong bond between

the compound and the substrate.

3.6 A sealant should be tooled as soon as possible after application. This is

done to force the sealant into the joint and eliminate air pockets. Tooling

also insures contact of the sealant to the sides of the joint.

3.7 A sealant should not be placed in a joint if there is evidence that it

has begun to cure.

A-29
N0S-1 14A (REV 7 7-=»l

U.S DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 77-1437

2. Gov’t Accession

No.

3. Recipient's At u-ssion N«>

4. TITLE AND SUBTITLE- SOLAR ENERGY SYSTEMS - STANDARDS FOR RUBBER SEALS

5. Publ it at ion 1 Jate March 1978

6. Performing Organization ( ode

7. A UTHOR(S)

R.D. Stiehler, A. Hockman, E. Embree, § L. W. Masters

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON. D.C. 20234

10. Proiet t/Task/Work Umi No

11. Contrail /Gram No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Division of Solar Energy

Department of Energy

20 Massachusetts Avenue

Washington, D.C. 20545

13. Type of Report & Period

( - overed Final Report

14. Sponsoring Agent y

C ode

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. ) A study was performed to develop standards for rubber seals used in solar energy

systems. Thirty preformed and liquid applied seals were evaluated in the

laboratory using modified ASTM standard test methods to obtain data needed to

prepare the standards. Also, studies were performed to develop a test method

for determining the effects of outgassing on the transmittance of solar

collector covers.

The results of the laboratory tests are presented and standards for rubber

seals in solar energy systems are proposed.

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

)

Rubber seals; solar collectors; solar energy systems; standards; test methods.

18. AVAILABILITY [X Uni imited

Eor Official Distribution. Do Not Release to NTIS

! Order I* rum Sup. of Doc., U.S. Ciovernment Printing Office Washington, D.( . 20402, SD ( at. No. ( 13

[X! Ordei 1 rom National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS 21. NO. OF P AG ES

(THIS REPORT)

UNCLASSIFIED

63

20. SECURITY CLASS 22. Price (THIS PAGE)

UNCLASSIFIED $ 5.25