Reference

m NBS

PubliAlllOb

IMBSIR 82-2533

Solar Energy Systems - Standards

for Screening Plastic Containment

Materials

June 1982

Prepared for U.S. Department of Energy

Office of Solar Heat Technologies

QC ctive Heating and Cooling Division

i/ashington, DC 20585

. U5G

32-2533

19C2

** flUNAL m.l nij oy BTANDi»ng

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NBSIR 82-2533

SOLAR ENERGY SYSTEMS - STANDARDS

FOR SCREENING PLASTIC CONTAINMENT

MATERIALS

JUL z Z 1982

Oo\ CXX-C . $2.

/<?%

Elizabeth J. Clark

Catherine D. Kelly

Willard E. Roberts

June 1 982

Prepared for U.S. Department of Energy

Office of Solar Heat Technologies

Active Heating and Cooling Division

Washington, DC 20585

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ABSTRACT

Plastic materials are being chosen more frequently in solar energy systems.

Problems with materials in solar systems have indicated a need for standards

to assess the performance and durability of the materials. In this investigation, laboratory studies have been performed to obtain data needed to develop

standards to screen plastic containment materials for the effects of heat

and for compatibility with heat transfer fluids. Five absorbers, three plastic

pipe materials, and three plastics used in storage applications have been

studied. These materials were evaluated to assess their durability when

exposed to heat aging at 100°C and 125°C, and for chemical compatiblity with

six heat transfer fluids at room temperature and at 70°C. After these exposures, the properties measured to evaluate materials durability were hardness,

specific gravity, reflectance, and change in dimension.

The results of the laboratory tests are presented and a draft standard for

screening plastic containment materials is proposed.

iii
ACKNOWLEDGMENT

The authors gratefully acknowledge the contributions of Ms. Anita Sweigert of

NBS for assisting with some of the laboratory tests described in this report.

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

of ASTM Committee E44 on Solar Energy Conversion are gratefully acknowledged.

iv
TABLE OF CONTENTS

Page

ABSTRACT iii

ACKNOWLEDGMENT iv

1. INTRODUCTION . 1

1.1 BACKGROUND 1 1.2 OBJECTIVES AND SCOPE 2

2. PROBLEM ASSESSMENT 3

2.1 PERFORMANCE REQUIREMENTS 3 2 . 2 DEGRADATION FACTORS 4

2.2.1 Elevated Temperature 4

2.2.2 Compatibility with Heat Transfer Fluid 6

3. LABORATORY STUDIES 7

3.1 INTRODUCTION 7 3.2 MATERIALS 7 3.3 PROPERTY TESTS 9

3.4 AGING PROCEDURES TO SIMULATE SERVICE CONDITIONS 10

3.4.1 Heat Stability Aging 10

3.4.2 Chemical Compatibility 10

4. RESULTS AND DISCUSSION 11

4.1 HEAT AGING AT 100°C 11

4.2 HEAT AGING AT 125°C 11

4.3 CHEMICAL COMPATIBILITY AT ROOM TEMPERATURE 13

4.4 CHEMICAL COMPATIBILITY AT 70°

C

14

5. CONCLUSIONS 15

6. PROPOSED STANDARD 16

6.1 STANDARD PRACTICE FOR SCREENING CONTAINMENT MATERIALS FOR THE

EFFECTS OF HEAT AND HEAT TRANSFER FLUIDS IN SOLAR HEATING

AND COOLING SYSTEMS 16

7. REFERENCES 17

APPENDIX A1

v
LIST OF TABLES

Page

Table 1. Potential Uses of Plastic Containment Materials in Solar

Energy Systems 3

Table 2. Service Conditions Potentially Causing Degradation of

Plastic Containment Materials 4

Table 3. Plastic Containment Materials Used in This Study 7

Table 4. Test Methods Used to Measure Material Properties 9

Table 5. Weight Change (Percentage) After Heat Aging at 100°C 18

Table 6. Specific Gravity After Heat Aging at 100°C 19

Table 7. Dimensional Changes (Percentage) After 1000 Hours Heat

Aging 20

Table 8. Hardness Change After Heat Aging at 100°C 21

Table 9. Solar Energy Reflectance (Percentage) After Artificial

Aging 22

Table 10. Weight Change (Percentage) After Heat Aging at 125°C 23

Table 11. Specific Gravity After Heat Aging at 125°C 24

Table 12. Hardness Change After Heat Aging at 125°C 25

Table 13. Weight Change (Percentage) After Immersion at Room

Temperature in Heat Transfer Fluids for 7 Days 26

Table 14. Dimension Changes (Percentage) After Immersion at Room

Temperature in Heat Transfer Fluids for 7 Days 27

Table 15. Hardness After Immersion at Room Temperature in Heat

Transfer Fluids for 7 Days 28

Table 16. Weight Change (Percentage) After Immersion at 70° in Heat

Transfer Fluids for 7 Days 29

Table 17. Dimensional Changes (Percentage) After Immersion at 70°C in

Heat Transfer Fluids for 7 Days 30

Table 18. Hardness After Immersion at 70°C in Heat Transfer Fluids for

7 Days 31

Table A1 . Summary of Property and Exposure Tests A7

Table A2 . Temperatures for Continuous In-Service Screening A9

vi
LIST OF FIGURES

Page

Figure 1. Shape of Extruded Absorbers 8

Figure 2. CPVC Pipe After 1000 Hours Heat Aging 12

Figure Al. Testing Sequence A-ll

vii

1. INTRODUCTION

1.1 BACKGROUND

As manufacturers of solar energy systems seek to improve their products and

lower their costs, innovative materials and designs are being used more often.

Frequently, plastics are being chosen to replace more traditional construction

materials, particularly in many applications where the material is in contact

with the heat transfer fluid. Materials used to contain, transport, or store

fluids in solar energy systems are called containment materials. Such applications include absorbers, transport piping systems, and storage facilities.

Most commonly, containment materials have been made of metal, i.e., copper,

aluminum, or steel. However, recent proposals and manufacturers’ literature

indicate a trend toward the increased use of plastics. For example, solar

collectors for pool heaters are frequently made of plastics, and solar energy

systems with plastic containment materials are now available for domestic hot

water and space heating applications. This trend is expected to continue as attempts are made to reduce the initial cost of systems, reduce weight, and

avoid corrosion.

Plastic materials used in containment applications can be divided into three

groups: thermoplastics, thermosets, and elastomers. Thermoplastics soften

when pressure and heat are applied and exhibit considerable creep under load,

especially at elevated temperatures. The term thermoset is applied to

materials which, once heated, react irreversibly so that subsequent applications of heat and pressure do not cause them to soften and flow. Thermosets

undergo thermally induced reactions to form densely crosslinked materials.

The finished object has a high degree of dimensional stability and is infusible and insoluble. Therraosets normally exhibit higher strength and have less

tendency to creep than thermoplastics. However, they are more brittle than

thermoplastics or elastomers. Elastomers or rubbers are linear polymers of

high molecular weight which generally have been lightly crosslinked to eliminate

flow.

The use of plastics as containment materials introduces a new set of

considerations not previously encountered with metals. The mechanical properties of plastics are time and temperature dependent and their long-term durability is less well known than that of the traditional materials (i.e.,

metals) which they replace. Plastics are readily affected by environmental

factors (such as solar radiation, temperature, moisture, air pollutants, and

contact with liquids) which can have a wide range of effects on their properties by inducing embrittlement, softening, shrinkage, swelling, creep, and

loss of strength and extensibility. Changes in the properties of plastics may occur rapidly or gradual impairment of material properties may occur as a function of time (i.e., stress fatigue).

The consequences of deterioration will vary depending on the particular

containment application since the various applications impose different

requirements on the plastic containment materials. Plastics acceptable for use in one containment application may not be acceptable in another.

1
As with numerous other materials used in solar energy systems, there is an inadequate data base of materials performance to aid in the selection of plastics for containment materials . An urgent need exists for standards to ensure

that plastic materials known to be durable are selected for containment applications.. Established test methods and standards for plastics used in conventional construction are usually unsuitable for plastic containment materials

for solar energy systems as they do not adequately evaluate durability under

the service conditions encountered in solar energy systems. Needed standards

must include methods to evaluate performance properties of the plastics and

aging tests to assess the ability of the material to resist deterioration

caused by environmental exposure tests.

1.2 OBJECTIVES AND SCOPE

This study, which was sponsored by the U.S. Department of Energy (DoE), had

the following objectives:

1) To identify performance requirements for plastic containment materials

to be used in active solar systems,

2) To identify and assess existing test methods as candidates for screening

tests to evaluate the performance of plastic containment materials,

3) To obtain data needed as the technical basis for standards by evaluating

commercially available plastic containment materials^/ according to the

performance requirements, and

4) To prepare draft standards for plastic containment materials for

consideration by the American Society for Testing and Materials (ASTM).

The scope of the laboratory work described in this report was limited to tests

for screening plastic containment materials: 1) for the effects of heat, and

2) for compatibility with heat transfer fluids. The intent was to keep the

tests simple so that obviously unsuitable materials could be identified without

unduly lengthy and expensive testing. Small coupon test specimens were used.

It is recognized that many other factors, (e.g., exposure to sunlight, air

pollutants, ozone, thermal cycling, mechanical stresses) may also affect the

durability of plastic containment materials. However, screening procedures

to assess the effects of these factors are not addressed in this report.

JJ This work does not include rubber hoses which have been previously addressed

in "Solar Energy Systems - Standards for Rubber Hose,” by Stiehler, R. and

Michalak, J., NBSIR 79-1917, National Bureau of Standards, Washington, DC

20234, 1979.

2
2. PROBLEM ASSESSMENT

2.1 PERFORMANCE REQUIREMENTS

Potential applications of plastic containment materials in active solar energy

systems are listed in table 1. These containment applications are divided

into the three broad categories of absorbers, transport piping, and storage

facilities. The various containment applications impose different requirements on the plastic materials. The functions of absorbers are to absorb the

sunlight and convert it to thermal energy while serving as a conduit for the

heat transfer fluid as it extracts thermal energy from the absorber. The

function of transport piping is to transport the heat transfer fluid between

system components. The purpose of the storage facilities is to hold the heat

transfer fluid when it is not circulating through the solar energy system.

During the life of the system, materials in all of these containment applications are expected to perform these functions while maintaining their original

size and shape. However, the ability of a plastic to retain material properties is dependent upon its ability to resist deterioration resulting from

exposure to service conditions of the solar energy system.

Table 1. Potential Uses of Plastic Containment Materials in Solar Energy

Systems

Absorbers

liquid flows through channels

liquid flows over the surface

air flows through channels

air flows over the surface

Transport Piping

piping for transporting liquids

hoses for connecting collectors

valves

pumps

air ducts

Storage

tanks for liquids

liners for tanks

containers for phase change materials

The service conditions which generally affect plastic containment applications

are summarized in table 2. As can be seen from the table, the absorbers,

piping, and storage tanks should resist deterioration resulting from elevated

temperatures, thermal cycling, moisture, air pollutants, and heat transfer

3
fluids. In addition, absorbers and other system components unprotected by

insulation must be stable to sunlight. All containment materials should be

functional at the internal pressures and the loads encountered by the system

and at both high operating temperatures and low winter night temperatures.

The plastics should not contaminate the heat transfer fluids nor degrade the

adjacent materials.

Table 2. Service Conditions Potentially Causing Degradation of Plastic

Containment Materials

Material Application

Service Condition Absorbers

Transport

Piping

Storage

Tanks

Elevated Temperature / / /

Temperature Cycling / / /

Solar Radiation / Only if exposed

directly to sunlight

Only if exposed

directly to sunlight

Moisture / / /

Air Pollutants / Only if exposed

directly to

atmosphere

Only if exposed

directly to

atmosphere

Internal Pressure / / /

Contact with Heat Transfer Fluids / / /

Contact with Adjacent Materials / / /

2.2 DEGRADATION FACTORS

In a properly designed component, durability of a material is related to its

ability to resist degradation by its environment. To develop screening procedures for potential containment materials, two service conditions (i.e., elevated

temperature and contact with heat transfer fluids) were selected from table 2 for incorporation into initial screening test. Unsuitable performance under

either set of conditions is sufficient reason to reject a material for use as in a specific containment application.

2.2.1 Elevated Temperature

The temperatures that containment materials reach in solar energy systems vary

depending on 1) system operation, 2) specific containment application, 3) system

4
design, and 4) weather conditions. A system usually functions either in normal

operation mode or in stagnation mode. During normal operation of a system the

heat transfer fluid is circulating and continuous in-service temperatures are reached. Stagnation occurs when the sun is shining but the system is not

operating to circulate the heat transfer fluid through the collectors to remove

heat.

Absorbers, transport piping, and storage tanks are exposed to different

temperatures. Higher temperatures cause more serious degradation. Under both

stagnation and operation, the absorber experiences temperatures higher than

those of either transport piping or storage tanks. The temperature of the

transport piping is lower than that of the absorber but higher than that of

the storage tanks (unless the storage tank has auxiliary energy input). In

general, the temperature of the piping is not elevated during stagnation

since the hot fluid is not circulating. An exception to this occurs near the

collectors if therraosyphoning occurs. Storage tanks are exposed to lower

temperatures than transport piping because the hot fluid is usually diluted by

the cooler liquid in the tank. The maximum temperature for the storage tank occurs during operation because during stagnation no heated fluid is added to

the tank, thus the storage tank temperature usually declines.

The design and use conditions of the system will establish the exact temperature

reached by each component. Due to variations in systems, vastly different

temperatures are reached by different solar systems. For example, swimming

pool collectors are frequently not glazed and the temperature of the incoming

are (pool water) is generally below 32°C (90°F). On the other hand, collectors for space heating systems often have double glazing and the heat transfer

fluid may reach 70-80°C (~160 - 180°F) during operation. Stagnation temperatures

are even higher. Clearly, a plastic suitable at temperatures in a swimming

pool application may not be suitable at temperatures in a heating system.

Stagnation temperatures (measured and calculated) for various collectors have

been reported. Solar collector performance data for six commercial black plastic collectors published by the California Energy Commission [1] and Florida

Solar Energy Center [2] indicate that, under weather conditions of 1040 W/m^

(330 Btu/ft^-hr) irradiance and 41°C (105°F) ambient temperature, the stagnation temperatures range between 76-88°C (168-191°F) for unglazed collectors and

90-170°C (194-338°F) for glazed collectors ..2/ In another study [3], under

similar conditions the temperature of single glazed collectors with flat black

rcetal absorbers varied from 134-159°C (273 - 318°F) while double glazed collectors with flat black metal absorbers ranged from 148-194 °C (298 - 381 °F).

Plastic materials exposed to heat may also be subject to many types of physical,

mechanical, and chemical changes. The severity of the exposure in both time

and temperature determines the extent and type of changes that take place. A

plastic material is not necessarily degraded by exposure to elevated temperatures, for example, after short exposures It may be unchanged or improved.

— Clear plastic collectors using a dark heat transfer fluid would have lower

stagnation temperatures.
However, extended periods of exposure of plastics to elevated temperatures

will generally cause some degradation, with progressive change in physical

properties

.

Some plastic materials may become brittle due to loss of plasticizer or decrease in molecular weight after exposure at elevated temperatures. Other

types of plastics become soft and sticky, either due to sorption of volatilized

plasticizer or due to breakdown of the polymer.

2.2.2 Compatibility with Heat Transfer Fluid

The heat transfer fluids most commonly used in solar systems are water,

ethylene glycol, propylene glycol, and silicone oil. (The glycols are generally diluted with water to a 50 percent solution.) Potential compatibility

problems arise from penetration of the fluid into the plastic, extraction of

stabilizers or plasticizers from the plastic, or erosion of the interior walls

of the plastic caused by fluid flow. The plastic may swell, soften, or lose

strength properties.

6
3. LABORATORY STUDIES

3.1 INTRODUCTION

The laboratory studies consisted of measurement of selected properties of

typical containment materials, exposure of materials to aging procedures

which simulate service conditions in solar systems, and subsequent remeasurement of properties. This report addresses the measurement of hardness,

dimensions, weight, and reflectance, and evaluates the effects of heat and

heat transfer fluids on these properties.

3.2 MATERIALS

The containment materials used in this study were typical of those commercially

available. Six materials were from collector absorbers, three were piping

materials, two were tank liners and one was a tank material. The materials

are listed in table 3. All of the absorbers plus the ABS pipe and the

Table 3. Plastic Containment Materials Used in This Study

Materials Description

Collectors - Absorbers

Ethylene propylene diene monomer (EPDM) extrusion with 1.9 nun wall

Silicone coated fiberglass fabric 0.36 mm sheet

Crosslinked polyethylene (XLPE) 17 mm diameter tubing with

1.5 mm wall

Polypropylene extrusion, with 0.5 mm wall

Polypropylene copolymer extrusion, with 0.64 mm wall

Piping

Chlorinated poly(vinyl chloride) (CPVC) 34 mm OD, 4.5 mm wall

Poly(vinyl chloride) (PVC) 34 mm OD, 4.5 mm wall

Acrylonitrile-butadiene-styrene (ABS) 29 mm OD, 2.2 ram wall

Storage

Poly(vinyl chloride) liner 0.8 mm sheet

Chlorosulf onated polyethylene liner - over 0.8 mm sheet

woven fabric

Fiber reinforced plastic tank 1.3 mm sheet

7
chlorosulf onated polyethylene liner were black, due to the addition of carbon

black to the plastic during processing. The PVC and CPVC pipe were different

shades of gray, while the PVC liner was blue, and the fiber reinforced tank

material was transparent.

The shape of the absorbers occasionally interfered with measurement of certain

properties. Figure 1 illustrates their shapes.

ETHYLENE PROPYLENE

DIENE MONOMER

CROSSLINKED

POLYETHYLENE

'v

1.5

POLYPROPYLENE

POLYPROPYLENE

COPOLYMER

Figure 1 . Shape of Extruded Absorbers

8
3.3 PROPERTY TESTS

The property tests which were performed are listed in table 4.

Table 4. Test Methods Used to Measure Material Properties

Property ASTM Method

Appearance Visual observations

Dimensions D471 - Method for Rubber Property - Effect of Liquids [4]

Hardness D785 - Method for Rockwell Hardness of Plastics and

Electrical Insulating Materials [5]

D2240 - Method for Rubber Property - Durometer

Hardness [6]

Reflectance E424 - Methods for Solar Energy Transmittance and

Reflectance (Terrestrial) of Sheet Materials [7]

Specific Gravity

and Weight

D792 - Methods for Specific Gravity and Density of

Plastics by Displacement [8]

The appearance of the test specimens was checked by visual observation after

heat stability and chemical compatibility exposures were completed. Obvious

changes in color, size or shape were noted.

Dimensional changes were determined according to the procedures in ASTM D 471,

Method for Rubber Property Effect of Liquids [4], For the piping and tubular

samples, the wall thickness was measured, while for the other samples the

length and width were measured.

Hardness was evaluated using ASTM D785, Method for Rockwell Hardness of

Plastics and Electrical Insulating Materials [5], and D2240, Method for Rubber

Property - Durometer Hardness [6]

.

Hardness is the resistance of a material to

indentation. Hardness measurement of plastics and rubber takes the form of

forcing a standard indentor under a known load into a flat surface of the

materials and measuring the resulting degree of penetration. Method D785 makes

use of the Rockwell hardness tester. It has five scales which overlap to a degree. Method D 2240 uses the Shore durometer and has two scales. Type A

Shore hardness is for soft materials and Type D is for hard materials. Since

indentation is a complex function of properties including modulus, force, and

indentor profile, hardness values measured using one method cannot generally

be compared with those derived from another.

Solar energy reflectance is an important factor in the capture of solar energy

by a solar collector absorber. Any energy which is reflected cannot be absorbed

to heat the collector. Spectral reflectance was measured over the solar energy

9
range from 300 to 2150 nm using ASTM E424, Methods for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials [7], Solar reflectance

was calculated using air mass 2.

The specific gravity and weight of the test specimens were measured using ASTM

D792, Methods for Specific Gravity and Density of Plastics by Displacement [8],

Specific gravity is the ratio of the weight of a material in air to the weight

of an equal volume of distilled water in air. Specific gravity can be used to

follow physical changes in a sample, to indicate degree of uniformity among

different test specimens, and to indicate average density of a large item.

Changes in density of a specimen may be due to changes in crystallinity, loss

of plasticizer, absorption of solvent or to other causes. Parts of a sample

may differ in density because of difference in crystallinity, porosity, and

composition (proportion of resin, plasticizer, pigment or filler).

3.4 AGING PROCEDURES TO SIMULATE SERVICE CONDITIONS

3.4.1 Heat Stability Aging

Temperatures of 100°C (212°F) and 125°C (257°F) were selected for the heat

aging. Separate sets of test specimens were used for each temperature. Each

set consisted of three test specimens, approximately four inches square. The

specimens were placed in a horizontal, completely supported position in a mechanical convection oven during the heat aging. The materials were evaluated

for linear dimensions, hardness, weight change, appearance, and reflectance

(absorbers only) after 100, 250, 500, and 1,000 hours exposure.

3.4.2 Chemical Compatibility

Compatibility of the materials with the heat transfer fluids was evaluated

using the procedure described in ASTM D543, Test for Resistance of Plastics to

Chemical Reagents [9]. The test specimens were immersed in the heat transfer

fluids. Each test specimen was placed in a wide mouth glass jar containing

about 400 ml of heat transfer fluid. When necessary, weights were attached to assure that the test specimen was immersed. The heat transfer fluids were:

water; 100 percent ethylene glycol; 50 percent ethylene glycol in water; 100

percent propylene glycol; 50 percent propylene glycol in water; 100 percent

silicone oil. Tops with inert liners were placed on all jars. One set of

test specimens was exposed at room temperature, while a second set was placed

in an oven at 70°C (158°F). After one week as specified in ASTM D543 the

materials were evaluated for linear dimensions, hardness, weight change,

appearance and reflectance (absorbers only).

10
4. RESULTS AND DISCUSSION

The primary purpose of the research described in this report was to obtain

laboratory data needed to develop the technical basis for standards to screen plastic containment materials, and not to evaluate commercially available plastic containment materials. However, in order to develop the needed data, it was essential that a variety of plastic containment materials be tested. No attempt

was made to test every type of plastic containment material on the market. The

materials selected were typical of those commercially available. Many plastic

containment materials are marketed and, in order to improve their performance,

manufacturers sometimes modify the materials. The properties of a material can

be changed by alterations in minor constituents (i.e. stabilizers, plasticizers,

antioxidants), in processing techniques, and in chemical composition. The

properties of materials currently on the market may differ from those described

in this report. The reader is cautioned against direct application of these

data to materials currently on the market.

4.1 HEAT AGING AT 100°

C

The weight changes resulting from the 100°C exposures are shown in table 5.

The greatest weight loss (8.0 percent) occurred with the storage PVC tank

liner. The EPDM lost 2.5 percent weight and the chlorosulfonated polyethylene

liner lost 1.5 percent weight. At first, the ABS pipe lost weight, but then

regained it. The initial loss is probably due to plasticizer loss while the

gain could be accounted for by oxidation. The other materials lost less than

one percent. The specific gravity values after heat aging at 100°C are given

in table 6. In general, the changes are small, although PVC tank liner

increased 2.4 percent after 1,000 hours.

Dimensional changes are given in table 7. The anisotropic nature of the

materials is illustrated by the unequal changes in the length and width and

wall thickness. The extruded shapes of most of the materials made it difficult

to accurately measure dimensional changes. Consequently, the values reported

are approximate. Hardness data are reported in table 8. In general the

hardness increased slightly, although it rose significantly for the PVC tank

liner. Reflectance values are given in table 9. The changes in reflectance

after 1,000 hours were minimal with the largest occurring with EPDM which went

from 4.5 percent to 3.6 percent.

4.2 HEAT AGING AT 125 °C

Only absorber and piping materials were exposed to heat aging at 125°C. Weight

changes after this exposure are given in table 10. Three materials (EPDM, CPVC

pipe, and PVC pipe) had significant weight losses after 1,000 hours. The EPDM

had a gradual weight loss over time, whereas the CPVC and PVC pipe had significant losses between 500 and 1,000 hours. During this time, the CPVC pipe

developed bubble-looking bumps on the interior and exterior surfaces, as shown

in figure 2.

11
Figure 2. CPVC Pipe After 1000 Hours Heat Aging

12
The specific gravities of the exposed materials are shown in table 11. The

greatest change (loss) occurred with the CPVC pipe. The silicone coated

fiberglass fabric had smaller losses. The EPDM and the ABS pipe showed

gradual increases amounting to 2.6 and 1.5 percent, respectively.

Dimensional changes are given in table 7. The crosslinked polyethylene

absorber softened and deformed to the extent that meaningful measurements

could not be made. The ABS pipe softened during the heat aging and it adopted

an oval shape. The ABS pipe shortened about 17 percent and the ends flared

making it impossible to measure wall thickness. Bubbles in the CPVC pipe also

prevented meaningful measurement of wall thickness. Hardness changes are given in table 12.

4.3 CHEMICAL COMPATIBILITY AT ROOM TEMPERATURE

The weight changes resulting from the immersion in heat transfer fluids at room

temperature are shown in table 13. In general, the changes are small. Silicone

oil had the greatest effect on the materials, generally causing them to swell,

(e.g., ABS pipe gained 21.5 percent and the chlorosulfonated polyethylene liner

gained 34 percent). In comparing the materials immersed in the concentrated

ethylene and propylene glycols with the corresponding solutions diluted 50 percent with water, it appears that the only significant differences were for the

polypropylene absorber and the PVC liner. The polypropylene absorber gained

about 0.1 percent weight in the concentrated propylene glycol but lost 23 percent in the dilute solution while the PVC liner lost 3.5 percent weight in the

concentrated propylene glycol but only 0.2 percent in the 50:50 solution.

Dimensional changes after immersion in the heat transfer fluid are given in

table 14. Changes less than one percent are not listed in the table. In

general, silicone oil again had the largest effect on the materials although the

ABS pipe swelled 10 percent in the propylene glycol/water solution.

Hardness after immersion in the room temperature fluids is shown in table 15.

The EPDM became slightly harder in all fluids except the ethylene glycol. The

PVC pipe softened somewhat in all fluids. The ABS pipe and chlorosulf onated

polyethylene liner softened in silicone oil.

Reflectance of the materials after immersion is shown in table 9. The EPDM

decreased from 4.5 percent to 3.6 percent after the distilled water immersion,

with smaller losses caused by the other fluids. The silicone coated fiberglass

fabric changed very little. The propylene absorber remained essentially

unchanged except in the silicone oil, which caused the reflectance to decline

from 4.4 percent to 3.3 percent. The reflectance of the propylene copolymer

absorber decreased from 3.5 percent to 2.2 percent and 2.1 percent from the

ethylene glycol and propylene glycol/water solutions, respectively. The

reflectance of the chlorosulf onated polyethylene liner was most affected by

the concentrated ethylene and propylene glycols.

13
4.4 CHEMICAL COMPATIBILITY AT 70°C

The weight changes caused by immersion in the heat transfer fluids at 70°C are shown in table 16. Silicone oil caused significant weight gains in all materials

which were exposed at this temperature. The crosslinked polyethylene absorber,

CPVC pipe, and PVC pipe were essentially unchanged by the other fluids and only

the distilled water caused much other change in the ABS.

Dimensional changes measured after immersion in the hot fluids are shown in

table 17. They indicate that silicone oil causes the greatest changes. Small

changes of less than one percent are not shown.

Hardness values measured after immersion in the heat transfer fluids at 70°C

are given in table 18. Silicone oil generally caused the materials to soften

appreciably while other hot fluids had much less effect.

14
5 CONCLUSIONS

1. The data obtained in this study show that the environment experienced by

materials in solar energy systems, (i.e., elevated temperature and contact

with heat transfer fluids) can degrade some plastic materials typically

used as absorber, piping, and storage materials.

2. Accelerated laboratory screening tests can be used as an effective means of

determining if plastic materials are likely to be affected by specific

degradation factors, such as elevated temperature or contact with heat

transfer fluids. Thus, these test methods can provide a basis for

evaluation standards which aid in screening materials.

3. Exposure to elevated temperature is an important test in evaluating plastic

materials for application in active solar systems. Many polymeric materials are susceptible to thermal degradation in the range of in-service

temperatures of solar systems. Oven aging at 100°C and 125°C showed that some candidate plastic materials are dimensionally unstable, lose weight,

become harder, or change reflectance.

4. Exposure to heat transfer fluids is also an important test in evaluating

the chemical compatibility of the plastic and the fluid. Exposure of the

plastics to six heat transfer fluids at both room temperature and 70°C

illustrated that there are interactions between the plastic and fluid.

Silicone oil generally caused the plastics to swell, soften, and gain

weight. The effects of the other fluids ranged from essentially no change

to increases in hardness or softness, weight gains, or dimensional

changes

.

5. The procedures described in this report are intended to provide data to screen out unsuitable materials and to provide a basis for establishing an initial relative ranking of the resistance of candidate materials to heat

and to heat transfer fluids. Components in solar heating and cooling systems experience different levels of environmental exposure and mechanical

stresses. Additional exposure and property measurement tests are recom- mended to evaluate candidate materials, especially when such tests more closely simulate field service conditions and when candidate materials are fabricated as components of actual solar systems.

15
6 . PROPOSED STANDARD

Based upon the laboratory work reported in this report, a standard for use

in evaluation of plastic containment materials in solar heating and cooling

systems was drafted and submitted for consideration for acceptance as a consensus standard by ASTM Committee E44 on Solar Energy Conversion,

Subcommittee E44.04 on Materials Performance. The proposed standard is

included as Appendix A of this report.

6.1 STANDARD PRACTICE FOR SCREENING POLYMERIC CONTAINMENT MATERIALS FOR THE

EFFECTS OF HEAT AND HEAT TRANSFER FLUIDS IN SOLAR HEATING AND COOLING

SYSTEMS

This is a proposed practice for screening polymeric materials for containment

applications in solar heating and cooling systems by determining the effects

of heat and heat transfer fluids on selected properties. It provides both

exposure procedures and property measurement tests. The exposure procedures

are relatively short-term exposures intended to screen out unsuitable materials.

Procedures are included for exposure to heat representative of potential

application temperatures and to heat transfer fluids. The property measurement

tests included are appearance, dimensions, hardness, mass, flexural and

tensile properties.

16
REFERENCES

[1] Testing Results from Testing and Inspection Program for Solar Equipment,

P500-80-056, California Energy Commission, October 1980.

[2] Summary Information Sheets, FSEC #78093D, #79014D, #80041D, #80118W,

#80145D, dated April 1979 through January 1981. Available from Florida

Solar Energy Center, 300 State Road, Cape Canaveral, FL 32920.

[3] Clark, E. J. , Roberts, W. E., Grimes, J. W., and Embree, E. J., "Solar

Energy Systems - Standards for Cover Plates for Flat Plate Solar

Collectors", National Bureau of Standards Technical Note 1132 (1980).

Available from U. S. Superintendent of Documents, U. S. Government

Printing Office, Washington, DC 20402.

[4] ASTM D471, Standard Test Method for Rubber Property - Effect of Liquids,

Annual Book of ASTM Standards, Part 37, American Society for Testing and

Materials, 1916 Race Street, Philadelphia, PA 19103.

[5] ASTM D785, Standard Test Method for Rockwell Hardness of Plastics and

Electrical Insulating Materials, Annual Book of ASTM Standards, Part 35,

American Society for Testing and Materials, 1916 Race Street,

Philadelphia, PA 19103.

[6] ASTM D2240, Standard Test Method for Rubber Property - Durometer

Hardness, Annual Book of Standards, Part 35, American Society for

Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.

[7] ASTM E424, Standard Test Methods for Solar Energy Transmittance and

Reflectance (Terrestrial) of Sheet Materials, Annual Book of Standards,

Part 46, American Society for Testing and Materials, 1916 Race Street,

Philadelphia, PA 19103.

[8] ASTM D792, Standard Test Methods for Specific Gravity and Density of

Plastics by Displacement, Annual Book of Standards, Part 35, American

Society for Testing and Materials, 1916 Race Street, Philadelphia, PA

19103.

[9] ASTM D543, Standard Test for Resistance of Plastics to Chemical Reagents,

Annual Book of Standards, Part 35, American Society for Testing and

Materials, 1916 Race Street, Philadelphia, PA 19103.

17
Table 5. Weight Change (Percentage) After Heat Aging At 100°C

Plastic Hours Exposure

Containment

Material 100 250 500 1000

Absorbers

Ethylene propylene

diene monomer -1.9 -2.0 -2.5 -2.5

Silicone coated

fiberglass fabric -0.34 -0.43 -0.55 -0.65

Crosslinked

polyethylene

-0.18 -0.17 -0.16 +0.33

Polypropylene -0.14 -0.17 -0.16 -0.19

Polypropylene

copolymer

-0.18 -0.24 -0.26 -0.31

Piping

Chlorinated

poly (vinyl chloride) -0.07 -0.07 -0.10 -0.10

Poly(vinyl chloride) -0.12 -0.15 -0.20 -0.21

Acrylonitrile-butadienestyrene -0.32 *— o

H

o • -0.24 + .03

Storage

Poly(vinyl chloride)

liner -1.5 -2.7 -5.2 -8.0

Chlorosulfonated

polyethylene liner -1.3 -1.2 -1.7 -1.5

Fiber reinforced

plastic tank -0.55 -0.49 -0.79 -0.68

NOTE: These values are the average of three test specimens.

18
Table 6, Specific Gravity After Heat Aging At 100°C

Plastic Initial Hours Exposure

Containment Specific

Material Gravity 100 250 500 1000

Absorbers

Ethylene propylene 1.167 1.160 1.165 1.164 1.169

diene monomer

Silicone coated 1.508 1.524 1.507 1.502 1.488

fiberglass fabric 1.511 1.510 1.495 1.493 1.502

1.512 1.513 1.499 1.499 1.492

Crosslinked 0.930 0.933 0.933 0.934 0.941

polyethylene

Polypropylene 0.909 0.910 0.912 0.912 0.912

Polypropylene 0.917 0.917 0.918 0.917 0.918

copolymer

Piping

Chlorinated 1.574 1.573 1.574 1.573 1.574

poly(vinyl chloride)

Poly(vinyl chloride) 1.387 1.390 1.391 1.391 1.391

Acrylonitrile-butadiene 1.031 1.029 1.031 1.031 1.034

styrene

Storage

Poly(vinyl chloride) 1.240 1.243 1.250 1.254 1 .270

liner

Chlorosulfonated 1.305 1.301 1.309 1.309 1.311

polyethylene liner

Fiber reinforced 1.315 1.310 1.312 1.310 1.312

plastic tank 1.313 1.307 1.308 1.308 1.309

1.311 1.309 1.309 1.308 1.310

NOTE: These values are the average of three test specimens for all

materials except the silicone coated fiberglass fabric and

the fiber reinforced plastic tank.

19
Table 7. Dimensional Changes (Percentage) After 1000 Hours Heat Aging

100°C 125°C

Plastic Containment

Material Length Width

Wall

Thickness Length Width

Wall

Thickness

Absorbers

Ethylene propylene

diene monomer ~ -1.5 ~ -3.3

Silicone coated

fiberglass fabric

<1 0 0 0

Crosslinked

polyethylene ~ -4 ~ -3 test si me!

jecimens

.ted

Polypropylene <-l <-l ~ 0 ~ 0

Polypropylene

copolymer

<+l <-l <+l ~ -1.2

Piping

Chlorinated

poly(vinyl chloride)

1 ~ -2 >-3

Poly(vinyl chloride) ~ -2 0 ~ -6 ~ -1.3

Acrylonitrilebutadiene-styrene ~ -5 ~ +3 ~ -17 wall

flared

at ends

Storage

Poly(vinyl chloride)

liner ~ —8 ~ -2

Chlorosulf onated

polyethylene

liner

~ -3 <+l

Fiber reinforced

plastic tank

0 0

Note: These values are the average of three test specimens.

20
Table 8. Hardness Change After Heat Aging at 100°C

Plastic Hours Exposed

Containment

Material

Initial

Hardness 100 250 500 1000

Absorbers

Ethylene propylene

diene monomer 26 0 +1 +3 +6

Silicone coated

fiberglass fabric

31 +2 +2 +2 +4

Crosslinked

polyethylene

50 +2 +2 +4 +7

Polypropylene 57 +5 +3 +4 +3

Polypropylene

copolymer

58 +1 +3 +4 +5

Piping

Chlorinated

poly(vinyl chloride)

84 0 +2 +4 +3

Poly (vinyl chloride) 82 +1 +1 +3 +2

Acrylonitrile-butadiene- 76 +2 +2 0 +7

styrene

Storage

Poly(vinyl chloride)

liner

40 +2 +5 +8 +12

Chlorosulfonated

polyethylene liner

42 +3 +1 +3 +4

Fiber reinforced

plastic tank

87 +3 +1 +2 +3

Hardness measured with D2240 Shore Durometer Type D2. A reading of + 3 graduations is significant. Reproducibility is + 2 graduations.

21
Table

9.

Solar

Energy

Reflectance

(Percentage)

After

Artificial

Aging

a;M3C/5 O

o.xw3a

<u

Is3

4-1 3M

CDa.BoHBo

(§

a)Co3 iH

i-l vS

r—I O

•H

C/5

i—I

a, o o o

is 04 rSo

a)c3 <H

rS

O

>1

O

a >o o I-1 Is o

Pi

>1 r-l J= O ' 4-1 3 I W to

rH

CJ

a;c t—I

a> o

i—I CJ >i >i

Xi r-l 4J cj w

35

a) iH is rS 3

•H 4J 4-) 3

CO £3 iSQ

co

co

co

st

CM co

CM

rs

co

co

st

00CM

00CO

CM CO-t

sO

co

00COCMst

St

-t

CMCM

NOCOCM CO ON

00 CO 3 l-l •H - 3

bO CJO c 0 jd vO <r St ON o • • • • •

4-J

O o CO sf co St

CO «—4 o

05 o

Pd *—l3O

rH 3 3 Is cd

m co It

m CM

•H 03 4-J • • • • • 4J r-| 3 st CO m

•H

O 3 3 CO rH M <4-1 3

oi

4J 3 3 3 •H 3 3 Is e 3 -O -3 3 ' 1 is -3 3 3

•H r-l to 3 3 <4S 4J 3 3 3 a. a 4-J 3 3 3 3

4-J -H o o 3 CO 3 3 3 3 3 3 Is 3 O CO 3 3 3 O rH O 3 Or O 3 3 rH rH 3 Ms to

CJ 4J

a rH to to

a rH Jd

•iS 3 3 b0 Or Or >N 3 4-1 cj S 3 3 3 Is o O rH co 3 Is •H 3 3 O 3 Is Is o o to 3

4-J co < 1 3 3 Or Or Or 3 rS 3

CO Is to •H iS •H to to

OOO iS 3 3 -3 31 rH *4S rH rH 3 3 r—1

Or rH ' 1 J3 4J •H o o b0 Jd

a, Is

w CO Or Or 3 CJ

Onm

vO

SION

COst

NOst

CM

COCO

coBu

•H

CObO3

•H

CO3

3)

0)

a/o33

4-) CJ

cu iH

MS

05

istobO3

053

05

l-l 3

r-lo

CO o

CO -O< CO

22
Table 10. Weight Change (Percentage) After Heat Aging at 125°C

Plastic Hours Exposure

Containment

Material 100 250 500 1000

Absorbers

Ethylene propylene

diene monomer -3.9 -5.1 -6.0 -7.0

Silicone coated

fiberglass fabric -0.54 -0.64 -0.79 -0.87

Crosslinked tes>t specisaens meltzed

polyethylene

Polypropylene +0.05 +0.09 +0.15 +0.13

Piping

Chlorinated

poly(vinyl chloride) -0.13 -0.18 -1.2 -13.7

Poly(vinyl chloride) -3.3 -0.64 -1.7 -4.9

Acrylonitrile-butadienestyrene -0.25 -0.42 -0.13 +0.23

Note: These values are the average of three test specimens.

23
Table 11. Specific Gravity After Heat Aging at 125°C

Plastic Initial Hours Exposure

Containment Specific

Material Gravity 100 250 500 1000

Absorbers

Ethylene propylene 1.167 1.168 1.176 1.185 1.197

diene monomer

Silicone coated 1.514 1.512 1.505 1.500 1.482

fiberglass fabric 1.510 1.492 1.485 1.489 1.458

1.510 1.501 1.482 1.480 1.435

Crosslinked 0.932 tes t specinlen raelt<=:d polyethylene

Polypropylene 0.907 0.912 0.912 0.913 0.910

Polypropylene copolymer 0.917 0.917 0.918 0.918 0.919

Piping

Chlorinated 1.574 1.574 1.575 1.573 1.273

poly(vinyl chloride) 1.387

1.473

Poly(vinyl chloride) 1.387 1.388 1.390 1.392 1.390

Acrylonitrile-butadiene- 1.032 1.032 1.034 1.039 1.047

styrene

NOTE: These values are the average of three test specimens for

all materials except silicone coated fiberglass and CPVC

pipe at 1000 hours.

24
Table 12. Hardness Change After Heat Aging at 125°C

Plastic Hours Exposure

Containment

Material

Initial

Hardness 100 250 500 1000

Absorbers

Ethylene propylene

diene monomer 26 +5 +7 +10 +18

Silicone coated

fiberglass fabric 31 +2 +1 +2 +3

Crosslinked

polyethylene

50 +9 +3 +4 test specimen too

distorted to get

a reading

Polypropylene 57 +3 0 +3 +4

Polypropylene

copolymer

58 +4 +6 +7 +6

Piping

Chlorinated

poly(vinyl chloride)

84 +1 +1 +3 Sample to

distorted to get

a reading

Poly(vinyl chloride) 82 0 -2 +2 +4

Acrylonitrile-butadienestyrene 76 +1 0 -1 +3

Hardness measured with D2240

graduations is significant.

Shore Durometer Type D2. A reading of +3

Reproducibility is +2 graduations.

25
Table 13. Weight Change (Percentage) After Immersion at Room Temperature

in Heat Transfer Fluids for 7 Days

Heat Transfer Fluid

Plastic

Containment

Material

Distilled

Water

Ethylene

Glycol

Ethylene

Glycol/

Water 50:50

Propylene

Glycol

Propylene

Glycol/

Water

50:50

Silicone

Oil

Absorbers

Ethylene propylene

diene monomer +0.7 +2.7 +1.1 +0.7 +1.4 +5.7

Silicone coated

fiberglass fabric +0.2 +1 .4 +1.0 +0.7 +1.8 +3.4

Crosslinked

polyethylene

+0.06 +0.08 +0.04 -0.02 +0.04 +2.7

Polypropylene +0.34 0 +0.02 +0.11 -23 +2.1

Polypropylene

copolymer

-0 -0.02 0 -0.01 -0.02 +3.0

Piping

Chlorinated

poly (vinyl chloride) +0.08 +0.02 +0.07 +0.04 +0.04 +0.04

Poly(vinyl chloride) +0.07 0 +0.02 0 +0.03 +0.03

Acrylonitrilebutadiene-styrene+0.9 -0.1 +0.4 -0.07 +0.4 +21.5

Storage

Poly(vinyl chloride)

liner

0 -0.4 -0.2 -3.5 -0.2 -2.9

Chlorosulfonated

polyethylene liner

+1.67 +0.3 +0.7 +0.02 +0.9 +34.0

Fiber reinforced

plastic tank

+0.4 -0.07 +0.2 -0.02 +0.3 +0.2

26
Table 14. Dimension Changes (Percentage) After Immersion at Room Temperature in Heat Transfer

Fluids for 7 Days

Heat Transfer Fluid

Plastic

Containment

Material

Distilled

Water

Ethylene

Glycol

Ethylene

Glycol/

Water 50:50

Propylene

Glycol

Propylene

Glycol/

Water

50:50

Silicone

Oil

Absorbers

Ethylene propylene

diene monomer Length ~ -1.5 ~ -1.5 ~ -1.5

Silicone coated

fiberglass fabric

Length ~ -3 ~ -1

Crosslinked

polyethylene

Length ~ +1

Polypropylene Width ~ +1.7

Length -1.4

Polypropylene copolymer Width ~ +1 ~ +1 ~ +1 +1

Piping

Chlorinated

poly(vinyl chloride)

Width ~ -1 ~ +1

Poly (vinyl chloride) Length ~ +2 ~ -2

Acrylonitrile-butadienestyrene Width ~ +2 ~ +10 ~ +4

Storage

Poly(vinyl chloride)

liner

Length

Width ~ -1.5 ~ -1.5 ~ -4 ~ -1.5

Chlorosulf onated

polyethylene liner

Length

Width ~ +6.5 ~ +11

Fiber reinforced

plastic tank Width ~ +1 1 ~ -1

Note: Changes less than one percent are not listed.

27
Table 15. Hardness After Immersion at Room Temperature in Heat Transfer Fluids for 7 Days

Heat Transfer Fluid

Plastic

Containment

Material

Initial

Hardness

Distilled

Water

Ethylene

Glycol

Ethylene

Glycol/

Water 50:50

Propylene

Glycol

Propylene

Glycol/

Water

50:50

Silicc

Oil

Absorbers

Ethylene propylene

diene monomer

66 74 66 75 76 74 75

Silicone coated

fiberglass fabric*

81 84 85 85 85 84 87

Crosslinked polyethylene^ 50 50 51 51 50 50 46

Polypropylene^ 59 60 60 59 55 54 58

Polypropylene

copolymer^

49 45 46 50 51 45 54

Piping

Chlorinated

poly(vinyl chloride)-*

71 71 71 70 69 63 69

Poly(vinyl

chloride)^ 65 53 54 54 52 53 56

Acrylonitrile-butadienestyrene^

78 74 75 74 75 75 63

Storage

Poly(vinyl chloride)

liner^

35 34 30 31 30 31 34

Chlorosulfonated

polyethylene liner*

81 87 90 90 90 90 67

Fiber reinforced

plastic tank^

69 73 71 70 72 72 70

* Hardness measured with D2240 Shore Durometer Type A2.

2 Hardness measured with D2240 Shore Durometer Type D2

3 Hardness measured with D785 Rockwell 15W.

^ Hardness measured with D785 Rockwell 30W.

28
4 Table 16. Weight Change (Percentage) After Immersion at 70°C in Heat Transfer

Fluids for 7 Days

Heat Transfer Fluid

Plastic

Containment

Material

Distilled

Water

Ethylene

Glycol

Ethylene

Glycol/

Water 50:50

Propylene

Glycol

Propylene

Glycol/

Water

50:50

Silicone

Oil

Absorbers

Ethylene propylene

diene monomer

+3.2 +4 .

3

+2.1 -0.5 +2.3 + 19.5

Crosslinked polyethylene +0.1 -0.03 +0.04 -0.1 +0.04 + 12.6

Polypropylene +0.4 +1.1 +1.6 +1.4 +1.5 + 12.1

Polypropylene copolymer +0.2 +1.5 +1.1 +1.6 +0 .

7

+ 13.4

Piping

Chlorinated

poly(vinyl chloride)

+0 .

3

-0.06 +0.1 -0.1 +0.2 + 24.6

Poly(vinyl chloride) +0.2 -0.05 +0.1 -oa +0.2 + 2.5

Acrylonitrile-butadienestyrene

+2.0 -0.02 +0.3 +0.02 +0.5 +197.

29
Table 17. Dimensional Changes (Percentage) After Immersion at 70°C in Heat Transfer

Fluids for 7 Days

Heat Transfer Fluid

Plastic

Containment

Material

Distilled

Water

Ethylene

Glycol

Ethylene

Glycol/

Water

50:50

Propylene

Glycol

Propylene

Glycol/

Water

50:50

Silicone

Oil

Absorbers

Ethylene propylene

diene monomer

Length

Width ~ +1 ~ +1 ~ +2.3

<-l ~ +1 .3 ~ +2.9 ~ +4.7

Crosslinked polyethylene Length

Width ~ +1.3 ~ -1 <-l

• <-l~ +2 ~ +4 ~ +7

Polypropylene Length

Width

~ +2.5 ~ +3

Polypropylene copolymer Length

Width

~ +2.3 ~ +2.2

Piping

Chlorinated

poly (vinyl chloride)

Length

Width ~ +2 ~ +4.5

Poly(vinyl chloride) Length <-l <-l

Acrylonitrile-butadienestyrene

Length

Width

~ +7 ~ +19

NOTE: Changes of less than one percent are not shown.

30
Table

18.

Hardness

After

Immersion

at

70°C

in

Heat

Transfer

Fluids

for 7

Days

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31

APPENDIX A

PROPOSED STANDARD PRACTICE FOR SCREENING POLYMERIC CONTAINMENT MATERIALS FOR

THE EFFECTS OF HEAT AND HEAT TRANSFER FLUIDS IN SOLAR HEATING AND COOLING

SYSTEMS

1 . SCOPE

1.1 This practice is intended for evaluation of candidate polymeric materials

for containment applications in solar heating and cooling systems by determining the effects of heat and heat transfer fluids on selected mechanical and

dimensional properties.

1.2 This practice contains both environmental exposure procedures and

property measurement tests. The exposure procedures are relatively short-term

exposures intended to screen out unsuitable materials. Procedures are included

for exposure (1) to heat representative of potential application temperatures

and (2) to heat transfer liquids. The property measurement tests included are appearance, dimensions, hardness, mass, flexural and tensile properties.

1.3 The effects of the exposure procedures are evaluated by comparison of the

initial material property values with those obtained after the exposure

procedures

.

1.4 This practice applies to, but is not limited to, the evaluation of

polymeric materials intended for the following containment applications:

transport piping, solar collector absorbers, storage tanks, storage tank liners,

pumps and valves. The practice shall not apply to the testing of organic

coatings or glazing materials. This practice also does not apply to evaluation

of components, subassemblies, and assemblies except where such fabricated articles may provide the specimens for materials screening. For example, rubber

hose should be evaluated using specification D3952, and rubber seals should be

evaluated using specification D 3832.

1.5 This standard may include the use of hazardous materials, operations, and

equipment. It is the responsibility of whoever uses this standard to establish

appropriate safety practices and to determine the applicability of regulating

limitations prior to use.

2 . APPLICABLE DOCUMENTS

2.1 ASTM STANDARDS

D 412 Tests for Rubber Properties in Tension^

D 543 Test for Resistance of Plastics to Chemical Reagents^

D 573 Test for Rubber-Deterioration in an Air Oven^

1 Annual Book of ASTM Standards, Part 37.

2 Annual Book of ASTM Standards, Part 35.

A-l
D 618 Conditioning Plastics and Electrical Insulating Materials

for Testing^

D 638 Test for Tensile Properties of Plastics^

D 790 Tests for Flexural Properties of Plastics and Electrical

Insulating Materials^

D 882 Tests for Tensile Properties of Thin Plastic Sheeting^

D 883 Definitions of Terras Relating to Plastics^

D 1042 Tests for Linear Dimensional Changes of Plastics Under

Accelerated Service Conditions^

D 1181 Test for Warpage of Sheet Plastics^

D 1204 Test for Linear Dimensional Changes of Nonrigid Thermoplastic

Sheeting or Film at Elevated Temperatures^

D 1415 Test for Rubber Property - International Hardness^

D 1556 Definitions of Terms Relating to Rubber^

D 2240 Test for Rubber Property - Durometer Hardness^-

D 3832 Specification for Rubber Seals Contacting Liquids in Solar

Energy Systems

D 3952 Specification for Rubber Hose Used in Solar Energy Systems

E 632 Practice for Developing Short-Term Accelerated Tests for

Prediction of the Service Life of Building Components and

Materials^

E 772 Definitions of Terms Relating to Solar Energy Conversion^

F 412 Definitions of Terms Relating to Plastic Piping^

3. SIGNIFICANCE AND USE

3.1 Containment materials in solar heating and cooling systems are exposed for

long periods to heat and to heated fluids. Such long-term exposures may alter

the key properties of polymeric containment materials sufficiently to jeopardize the performance and durability of components made using the materials.

This practice is to be used to provide the data to screen out materials

unsuitable for use at the test temperatures or with the heat transfer fluids,

and to provide a basis for establishing a relative ranking of the resistance

of candidate materials to heat and to heat transfer fluids.

3.2 ELEVATED TEMPERATURES

3.2.1 In solar energy systems the various containment materials are exposed to

elevated temperatures. The actual temperatures vary depending on (1) the

specific containment application, (2) type of system, (3) solar system operation,

1 Annual Book of ASTM

2 Annual Book of ASTM

3 Annual Book of ASTM

^ Annual Book of ASTM

3 Annual Book of ASTM

Standards

,

Part 37

Standards Part 35

Standards

,

Part 18

Standards

,

Part 41

Standards Part 34

A2
and (4) weather. Continuous in-service temperatures occur during typical

operation of the system. Stagnation temperatures occur when the sun is shining

but the system is not operating to remove heat from the collectors. Certain

components, such as absorbers, are subject to maximum temperature elevation

during stagnation. For other components, such as storage tanks, stagnation

conditions would not cause their temperatures to rise significantly above the

continuous in-service temperatures.

3.2.2 Polymeric materials exposed to heat undergo many types of physical,

mechanical, and chemical changes. The severity of the exposures in both time

and temperature determines the extent and type of change. A polymeric material

is not necessarily degraded by exposure to elevated temperatures, but may be

unchanged or improved if the exposure is short-term. However, extended periods

of exposure of polymers to elevated temperatures will generally cause some degradation, with progressive change in physical properties.

3.2.3 Generally, short exposures at elevated temperatures may drive out

volatiles such as moisture, solvents, or plasticizers, relieve molding stresses,

advance the cure of thermosets, and cause some change in the color of the polymer or coloring agent or both. Normally, additional shrinkage should be

expected with loss of volatiles, advance in polymerization, or relief of molding

stresses

.

3.2.4 Some polymeric materials may become brittle after exposure at elevated

temperatures due to loss of plasticizers or to thermal degradation. Other

types of polymers become soft and sticky, either due to absorption of volatilized

plasticizer or due to breakdown of the polymer.

3.2.5 Effects of exposure may be quite variable, especially when specimens are exposed for long intervals of time. Moreover they are cumulative with time.

Factors that affect the reproducibility of data are the degree of temperature

control of the enclosure, the type of molding, type of cure, humidity of the

oven room, air velocity over the specimen, and period of exposures.

3.2.6 The changes in the mechanical and dimensional properties of polymeric

containment materials caused by elevated temperatures may be sufficient to

discourage the use of a particular material for one application, but not for

others. Since this practice may be used to evaluate materials for components

and applications having widely different in-service temperatures, both the

test temperatures chosen and the results of testing need to be examined

critically and with respect to application, exposure temperatures and times

expected. Different heat stability test temperatures are recommended for

materials intended for different applications in solar heating and cooling

systems

.

3.3 CHEMICAL COMPATIBILITY

3.3.1 Inertness of polymeric containment materials in contact with heat

transfer fluids is essential. This practice may be used to evaluate the shortterm chemical compatibility of polymeric containment materials with aqueous or organic based heat transfer fluids. Care must be taken to select appropriate
test conditions for a given containment material, i.e., the different heat

transfer fluids to which the material may realistically be exposed; the maximum

continuous temperature to which the fluid will be raised; and the duration of

exposure,, Test results are indicative of the performance of the containment

material only as part of a polymeric material/fluid pair. 3.3.2

Taken by itself, performance in these laboratory test procedures does

not necessarily provide an adequate basis for acceptance or rejection of a particular polymeric material/fluid pair in solar heating and cooling systems.

For containment applications involving continuous immersion, the data obtained

in short time tests are of interest only in eliminating the most unsuitable

materials or indicating a probable relative order of resistance to chemical

reagents

.

3.4 Material property changes may be used to evaluate the effect of heat and

heat transfer fluids on polymeric containment materials. The degree of change

observed will depend on the property measured. Different properties do not

necessarily change at the same rate. Ultimate properties such as strength or elongation at break are generally more sensitive to degradation than are bulk

properties such as modulus.

3.4.1 Permanent changes in the size, shape, mass, and appearance of a polymeric material may result from exposure to heat and to aqueous- and

organic-based liquids. A molded or extruded material may discolor, expand,

shrink, or warp. Changes in shape or dimensions may induce additional stresses

in the components in a system or they may make a component unsuitable for use.

3.4.2 Tensile properties are the most important indication of strength in a material when it is subjected to forces which tend to pull it apart. Tensile

properties include tensile strength, percent elongation at yield and rupture,

and the modulus of elasticity.

3.4.3 Flexural properties reflect the ability of a material to withstand

rupture when a bending stress is applied at the center of a beamlike specimen

supported at both ends. Flexural properties include flexural strength, tangent

or secant modulus of elasticity and flexural yield strength. Flexural properties are especially sensitive to changes that occur in specimen surfaces.

3.4.4 Indentation hardness as determined by a durometer is a measure of the

ability of a material to resist penetration and scratching when an indentor of

specified geometry is forced into the material under specific conditions. The

indentation hardness of elastomeric materials, in particular, is especially

sensitive to changes that occur in specimen surfaces.

3.5 This practice is designed to facilitate the rejection of unsuitable

materials from the list of candidate materials. This practice is an expedient

screening procedure to rapidly identify those candidate polymeric materials

which are adversely affected by heat or are incompatible with a particular heat

exchange fluid in question at particular temperatures of operation. Numerous

other aspects of performance and durability may also affect the choice of

A4
suitable materials (for example, creep resistance, low temperature imbrittlement, impact strength, and ultraviolet light stability), depending upon the

end-use service.

3.6 This practice is not a comprehensive methodology for determining the most

suitable materials for specific components and applications. Additional exposure and property measurement tests are recommended to complete the process of

selecting a candidate material, especially when such tests more closely simulate field service conditions and when candidate polymeric materials are fabricated as components of actual solar heating and cooling systems. Other tests

for screening and evaluative purposes that may be performed are listed in the

Appendix (Note 1).

Note 1 : Components in solar heating and cooling systems experience different

levels of environmental exposure and mechanical stresses. Therefore, candidate

materials for each application should be evaluated with the severity and com- pleteness demanded by the ultimate application. Key properties of a containment material should be determined following exposure to maximum levels or ranges of sunlight, temperature, and moisture that are typical of actual ser- vice conditions. Table 1 of Practice E632 contains a comprehensive outline of

factors that are expected to affect the durability of materials and components

when subjected to outdoor weathering conditions.

3.7 Insufficient data exist at this time to demonstrate correlations between

the results of short-term laboratory evaluations and field performance.

4 . TERMINOLOGY

4.1 DEFINITIONS HAVING GENERAL APPLICATION :

4.1.1 Plastics - Definition D883, Definitions of Terms Relating to Plastics

4.1.2 Rubber - Definition D1566, Definitions of Terms Relating to Rubber and

Rubber-Like Materials

4.1.3 Solar Energy - Definition E772, Definitions of Terms Relating to Solar

Energy Conversion

4.1.4 Plastic Pipe - Definition F412, Definitions of Terms Relating to Plastic

Piping Systems

4.2 DESCRIPTION OF TERMS:

4.2.1 Heat Transfer Fluid - This terra as used in this practice pertains to

both circulating heat exchange liquids and heat storage liquids.

4.2.2 Polymeric Materials - Includes rigid and nonrigid plastics and elastomer

as single components, laminates, foams, and other polymer-matrix composites.
4.2.3 Containment Material - Any material comprising a component within a solar energy system intended to hold, store, convey, or otherwise come into

direct contact with a heat transfer fluid.

5 . MATERIALS

5.1 Any polymeric material may be selected for evaluation. The material must

be capable of being described adequately to permit duplication of the test.

5.2 Any heat transfer fluid may be selected for assessing its compatibility

with the polymer. The heat transfer fluid should be capable of being described

chemically as to its basic components and their concentrations. The presence

or absence of minor components which may affect the interactions with the

polymer shall be noted. Commercially available fluids may be described by

proprietary designation.

6 . CONDITIONING

6.1 CONDITIONING

Condition all test specimens at 23° + 2°C (73° + 4°F) and 50 + 5 percent

relative humidity for not less than 40 hours prior to test or measurement in

accordance with Procedure A of Method D618.

6.2

TEST CONDITIONS

Conduct all tests in the standard laboratory atmosphere of 23° + 2°C (73° +

4°F) and 50+5 percent relative humidity (Note 2) unless otherwise specified

in the methods.

Note 2 : In actual practice, plastic and elastomeric containment materials

must have acceptable physical properties over a wide range of temperature and

humidity conditions. Where it is possible to conduct tensile tests above and

below ambient conditions, investigators are encouraged to do so.

7.

TEST SPECIMENS

7.1 The minimum number of specimens needed for each of the property tests

(Note 3) is specified in Table Al. The type of test specimens shall be in

accordance with the ASTM test method for the specific property to be determined.

Note 3 : Tensile and flexural property tests are critically dependent on specimen anisotropy. Where anisotropy is known to be present (injection moldings and composite materials such as laminates) or suspected (thin wall extrusions), tensile and flexural properties need to be measured for two of the

three principle axes of the specimen.

7.2 Specimens may be cut from sheets, plates, or molded shapes (Note 4) or may be molded to the desired finished dimensions.
TABLE A1 Summary of Property and Exposure Tests

Numbers in Columns Refer to the Minimum Number of Specimens Required for Each of the Tests

Property

TensileA Properties

(8.1.3)

Flexural^

Properties

(8.1.4)

Dimensional Stability

Test Exposure (Section)

Procedure

(Section)

Hardness®

(8.1.5)

Linear

Dimensions

(8.1.1)

Mass and

Appearance*-'

(8.1.2)

No Exposure - Establish

Initial Properties and

Dimensions

3 5 1 3 (5)

Heat Stability - 300 hours at stagnation

temperature (8.2.2)

5 5 1 3 (5)

1000 hours at in-service

temperature (8.2.1)

Chemical Compatibility

(8.2.3)

5 5 1 3 (5)

Fluid A, Concentrated

7 days at in-service

temperature

Fluid A, Aqueous

7 days at in-service

temperature

5 5 1 3 (5)

Fluid B, Concentrated

Etc.

5 5 1 3 (5)

A Five specimens are sufficient for testing isotropic specimens. Anisotropic moldings require a minimum

of ten specimens per set, five specimens for each axis of anisotropy.

® Three measurements required per specimen.

C Undeformed tensile specimens may be used.
Note 4 : Although fabricated articles may be used as a source of specimens, it

may be impracticable to determine their tensile and flexural properties if the

articles present complex profiles of varying thicknesses.

The tensile and flexural properties tests demand that specimens possess uniform

cross-sectional areas to insure good precision and repeatability of results.

7.3 The geometry of the test specimens used to evaluate the properties of

polymeric containment materials shall be in accordance with the ASTM method for

the specific property to be determined. The thickness of the specimens may be

either as specified in the appropriate test method, or equivalent to the thickness of material in an intended component or assembly. The latter is preferred.

7.4 Certain materials are susceptible to edge effects when exposed to a variety of chemical reagents. Since edges are not normally exposed to the

environment in the intended field application, specimens to be immersed in heat

transfer fluids may have the edges sealed prior to testing. The sealing method

and sealant must not distort the test results.

7.5 Separate test specimens shall be used for the physical property tests.

8. METHODS OF TEST

8.1

PROPERTY MEASUREMENT TESTS

8.1.1 Dimensional Stability - Determine the dimensional stability of rigid

and semirigid materials according to Method D1042 and for nonrigid materials

according to Method D1204.

8.1.2 Mass and Appearance - Determine changes in mass and appearance according

to Method D543.

8.1.3 Tensile Properties - Determine the tensile properties of rigid and

semirigid plastic materials according to Method D638 using speed B and Type IV

specimens^. Use Method D882 for flexible sheet plastic materials or Method

D412 for elastomeric materials.

8.1.4 Flexural Properties - Determine the flexural properties of rigid and

semirigid plastic materials according to Method D790.

8.1.5 Hardness - Determine hardness of elastomers according to either Method

D1415 or Method D2240 using Type A duroraeter^. Determine hardness of rigid and

semirigid plastic materials according to Method D2240 using a Type D durometer.

6 Type C die may be used to produce specimens from both plastic and elastomeric

materials

.

7 Method D1415 (International Hardness) is the more commonly employed method

for purposes of specification.

A8
8.2 EXPOSURE PROCEDURES

8.2.1 Continuous In-Service Temperatures - Using an air-circulating oven and

the procedure described in Method B573, expose one set of test specimens for

1000 hours to the appropriate test temperature in Table A2. The recommended

temperatures in Table A2 approximate in-service temperatures in a variety of

typical solar systems incorporating flat-plate collectors

Table A2. Temperatures for Continuous In-Service Screening

Polymeric Material Application Recommended Test Temperature

Flat-plate Absorber Panels - glazed 70° + 2°C (158° + 4°F)

unglazed 43° + 2°C (110° + 4°F)

Transport piping, valves, fittings,

pumps - within collector 70° + 2°C (158° + 4°F)

- outside collector 43° + 2°C (110° + 4°F)

Storage tanks, liners 70° + 2°C (158° + 4°F)

For materials intended for systems incorporating collectors other than

flat-plate, the maximum anticipated temperature shall be used.

8.2.2 Stagnation Temperatures - Polymeric materials to be used to fabricate

components, such as absorbers, headers, valves, and fittings, will be subject to

the maximum temperature elevation during stagnation.

Expose these materials to heat for 300 hours at the maximum expected stagnation

tion temperature (Note 5). The stagnation temperature shall be no lower than

45°C (81°F) above the maximum in-service temperature (Note 6).

Note 5 : No single temperature or procedure can duplicate the range of

temperatures and environmental conditions to which absorbers may be exposed

during stagnation conditions. Moreover, maximum stagnation temperatures,

whether determined experimentally or calculated from theoretical models, will

depend upon a number of collector design factors, which include whether or not

the collector is glazed and whether or not the design incorporates mechanical

or other means for limiting temperature during non-operational conditions.

Therefore, the temperature approximating the stagnation mode must be selected

rationally on the basis of intended application and field or simulated

temperature and solar irradiance measurements.

Note 6 : Solar collector performance data published by such collector testing

and certifying agencies as California Energy Commission and Florida Solar

Energy Center can provide guidance for selecting stagnation temperatures. The

A-9
performance curves and data listed by the above for six commercial collectors

indicate that under such conditions as 330 Btu/ft^ hr irradiance and 4l°C

(105°F) ambient temperature the stagnation temperature for unglazed and glazed

collectors range between 75-88°C (168-191°F) and 90-169°C (194-336°F), respectively. 8.2.3

Chemical Compatibility

8. 2. 3.1 Evaluate the chemical compatibility according to Method D543 using a seven day exposure. Substitute the applicable heat transfer fluids, including

distilled or deionized water , for the standard reagents listed in Method D543.

For heat transfer fluids commonly used as aqueous solutions, the test reagents

shall include both an undiluted fluid and the fluid diluted for in-service use. Select the test temperature from the list of test temperatures given in Table

A2 of Sec. 8.2.1. Use higher test temperatures in evaluating the compatibility

of polymer/fluid pairs for systems having concentrating collectors.

8. 3. 3. 2 Particular attention should be exercised in handling materials, fluids,

or polymer/fluid pairs that can be hazardous to laboratory personnel. The

flammability, vapor pressures, and toxicity of the heat transfer fluid shall be

known prior to initiation of testing and appropriate precautionary measures

shall be taken to insure the safety of all personnel.

9 . PROCEDURE

9.1 Prepare an adequate number of test specimens for the property tests and

exposure procedures to be performed. As a minimum, this shall consist of the

number shown in Table A1 . The preferred testing sequence is shown in Figure A1

.

9.2 Condition the test specimens according to Sec. 6.1.

9.3 Measure linear dimensions (Sec. 8.1.1), mass and appearance (Sec. 8.1.2),

tensile properties (Sec. 8.1.3), flexural properties (Sec. 8.1.4), and hardness

(Sec. 8.1.5) of one set of test specimens to establish properties of the polymeric containment material. Record visual surface appearance characteristics,

including color, gloss, texture, etc.

9.4 Expose one set of test specimens to the heat stability procedure for

continuous in-service temperatures (Sec. 8.2.1).

9.5 Measure linear dimensions, mass and appearance, tensile properties,

flexural properties, and hardness of the test specimens from 9.4. Record

visible surface changes, including discoloration, tackiness, loss of apparent

gloss, pitting, cracking, swelling, and shrinkage.

9.6 Expose another set of test specimens to the heat stability procedure for

stagnation temperatures (Sec. 8.2.2).

9.7 Make measurements and observations as in 9.5 on test specimens from 9.6.

A- 10
A.-1

1
9.8 Expose a separate set of test specimens to each heat transfer

fluid included in the chemical compatibility procedure (Sec. 8.2.3).

9.9 Make measurements and observations as in 9.5 on test specimens

from 9.8. Also record any visible changes in the heat transfer fluid.

9.10 Express the deterioration of each property by the difference between

the measurements made before and after each exposure as a percentage of the

original property.

10. INTERPRETATION OF RESULTS

10.1 No acceptance or failure criteria are proposed, as the intention

of this practice is to standardize testing and screening procedures for polymeric

containment materials. It may be helpful with regard to materials selection

and development efforts to adopt a general definition of failure as it appears

elsewhere in these standards. Failure due to heat or due to contact with chemical reagents is defined as a change in mechanical property, dimension, weight,

appearance, or other property that alters the containment material to a degree

that is no longer acceptable for the service in question. Failure may result

from blistering, cracking, loss of plasticizer or other soluble or volatile

material that may cause embrittlement, warpage, shrinkage, or change in

necessary mechanical properties.

10.2 It is recommended that, whenever practicable, candidate plastic

and elastomeric containment materials should undergo no more than 25 percent

reduction in tensile strength or hardness and change permanently by no more

than 3 percent in linear dimensions.

10.3 Polymeric materials differ widely in their responses to environments

which cause chemical degradation and reduction in molecular orientation. The

rate of change with time (or temperature) of a key property may be of far

greater significance than a single value determined at an arbitrarily selected

condition. A graphical plot of test results for specimens exposed to the same elevated temperature but for different times will indicate whether a particular

material will approach constant tensile strength, hardness modulus, etc., with

time or will continue to deteriorate as the test progresses.

1 1 . REPORT

11.1 The test report shall include the following;

11.1.1 Identification of the plastic or elastomeric containment material by

standard specification (where applicable), by proprietary designation or by

chemical analysis.

11.1.2 Details of specimen preparation.

11.1.3 For linear dimensional stability, the test specimen size and the average

percentage change in linear dimensions following exposure to heat and to heat

transfer fluids.

A- 12
11.1.4 For tensile properties prior to and following exposure to heat and to

heat transfer fluids, the information necessary to complete the report in

Methods D638, D882, or D412.

11.1.5 For flexural properties prior to and following exposure to heat and to

heat transfer fluids, the information necessary to complete the report in

Method D790.

11.1.6 For durometer hardness prior to and following exposure to heat and to

heat transfer fluids, the information necessary to complete the report in

Methods D2240 or D1415.

11.1.7 For the heat stability test, the temperature and duration of the test

for continuous in-service conditions and for stagnation conditions.

11.1.7.1 The procedure for selecting the stagnation test temperature should

be described and should include a record of temperature, solar irradiance, and

other pertinent measures.

11.1.8 For the chemical compatibility test Method D543, the temperature and

duration of each test, if longer than seven days.

11.1.8.1 The heat transfer fluids selected should be identified by standard

specification (where applicable), by proprietary designation, or by chemical

analysis

.

11.1.9 Description of visible and mass changes in test specimens following

exposure to heat and to heat transfer fluids.

11.1.9.1 Description of visible changes (color, turbidity, residue, etc.) in

heat exchange fluid at the end of each test.

A- 13
APPENDIX

XI. 1

XI. 1.1

XI. 1.2

XI. 1.3

XI. 1.4

XI. 1.5

XI. 1 .6

XI. 1.7

XI. 1.8

XI. 1 .9

XI Supplementary Tests

Property Measurement Tests — General

Brittleness Temperature

D746 Brittleness Temperature of Plastics and Elastomers by Impact

D1790 Brittleness Temperature of Plastic Film by Impact

Chemical Resistance

C581 Chemical Resistance of Thermosetting Resins Used in Glass

Fiber Reinforced Structures

Coefficient of Expansion

D696 Coefficient of Linear Thermal Expansion of Plastics Creep

Creep

D2990 Tensile, Compressive and Flexural Creep and Creep-Rupture

of Plastics

Density

D792 Specific Gravity and Density of Plastics by Displacement

Heat Distortion Temperature

D1637 Heat Distortion Temperature of Plastic Sheeting and Film

Under Tensile Load

Impact Resistance

D256 Methods of Test for Impact Resistance of Plastics and

Electrical Insulating Materials

D3029 Impact Resistance of Rigid Plastic Sheeting or Parts by Means

of a Tup (Falling Weight)

D785 Test for Rockwell Hardness of Plastics and Electrical

Insulating Materials

Stiffness

D747 Method of Test for Stiffness of Plastics by Means of a Cantilever Beam

D790 Flexural Properties of Plastics and Electrical Insulating

Materials

A- 14
XI. 1.10 Tensile and Elongation Properties

XI.

2

D1708 Method of Test for Tensile Properties of Plastics by Use of

Microtensile Specimens

D2289 Method of Test for Tensile Properties of Plastics at High

Speeds

Property Measurement Tests — Specific Plastics and Plastic Types

D1939 Residual Stresses in Extruded and Molded ABS

D3296 Dimensional Stability of FEP Plastic Tubing

D1547 Dimensional Stability of Extruded Methacrylate Sheet

D1693 Environmental Stress Cracking of Ethylene Plastics

D2115 Thermal Stability of PVC by Discoloration from Oven Heat

Exposure

D3012 Thermal Oxidative Stability of Polypropylene to Heat and Air

D2445 Thermal Oxidative Stability of Polypropylene Heat and Oxygen

A- 15
NBS-114A (rev. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instruction s)

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

4. TITLE AND SUBTITLE

Solar Energy Systems - Standards for Screening Plastic Containment Materials

5. AUTHOR(S)

Elizabeth J. Clark, Catherine D. Kelly and Willard E. Roberts

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7 . Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

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

U.S. Department of Energy

Office of Solar Heat Technologies

Active Heating and Cooling Division

Washington, DC 20585

10. SUPPLEMENTARY NOTES

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

11.

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

bi bl iography or literature survey, mention it here) Plastic materials are being chosen more frequently for various applications in

solar energy systems. Problems with materials in solar systems have indicated

a need for standards to assess the performance and durability of the materials.

In this investigation laboratory studies have been performed to obtain data

needed to develop standards to screen plastic containment materials for the

effects of heat and for compatibility with heat transfer fluids. Five

absorbers, three plastic pipe materials, and three plastics used in storage

applications were included. They were evaluated to assess their durability

after exposure to heat aging at 100°C and 125°C and to chemical compatibility

with six heat transfer fluids at room temperature and at 70°C.

The results of the laboratory tests are presented and a draft standard to

screen plastic containment materials is proposed.

12.

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

durability; plastic containment materials; solar energy systems; standards

13. AVAILABILITY 14. NO. OF

Unlimited

| 1 For Official Distribution. Do Not Release to NTIS

] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

PRINTED PAGES

15. Price 20402.

jXX] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

U SCOMM-DC 6043-P80