NBSIR 74-610

investigation of Procedures for

Determination of Thermal Performance

Characteristics of Plastic Piping Used

in Housing

Max Ttyon

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1974

Interim Report for Period

July 1972 through June 1973

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 74-610

INVESTIGATION OF PROCEDURES FOR

DETERMINATION OF THERMAL PERFORMANCE

CHARACTERISTICS OF PLASTIC PIPING USED

IN HOUSING

Max Tryon

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1974

Interim Report for Period

July 1972 through June 1973

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts. Director

Table of Contents

Page

Abstract 1

1. Introduction 1

1 . 1 Background , 1 1.2 Objective , 1 1.3 Materials Background 1

2. Materials 2 2.1 Polyvinyl Chloride (PVC) 2 2.2 Chlorinated Polyvinyl Chloride (CPVC) 3

3- Techniques Used 3 3.1 Thermal Mechanical Analysis (TMA) 3 3.2 Thermogravimetric Analysis (TGA) 3 3.3 Hardness ^ 3.h Method for Chlorine Content ^

3.5 Aging Studies ^

3 •5.1 Weather-Ometer ^ 3-5.2 Indoor Thermal Aging ^ 3.5.3 Outdoor Weathering Study 5

h. Results , 5 k.l TMA 5 h.2 TGA 5

k. 3 Hardness. 6 h.k Aging Effects 6 U.U.I Weather-Ometer Studies 6 U.U.2 Thermal Aging of PVC and CPVC T

5. Summary of Results T

6. Future Needs of This Program 7

List of Tables

Table 1 Glossary of Technical Terms 9 Table 2 Thermoplastic Pipe Materials Studied 10

Table 3 Properties of Thermoplastic Pipe Materials 11

Table U Change in Hardness (Shore D) of PVC and CPVC Piping with Temperature.... 12

Table 5 Weight Loss Study for HCl Content of PVC 13

Table 6 Weight Loss Study for HCl Content of CPVC, lU

Table 7 Dimensional Changes of PVC-DWV Piping on Thermal Aging at 80°C (176°F).. 15

Table 8 Decreases in Length (AL) of Piping on Heating to 90°C (l9U°F) l6

iii
List of Figures

Fig.. 1 Thermomechanical Analyzer (TMA)

Fig., 2 Thermomechanical Analyzer (Detail)

Fig.. 3 TMA Curves on Pipe Samples

Fig., k Thermogravimetric Analysis Apparatus (TGA)

Fig.. 5 Thermogravimetric Analyzer (Detail)

Fig,, 6 TGA Curves on Pipe Samples

Fig.. 7 Hardness Apparatus

Fig., 8 Hardness Apparatus (Detail)

iv
Investigation of Procediires for Determination of Thermal

Performance Characteristics of Plastic Piping Used in Housing

Max Tryon

Abstract

This report is a study to determine the critical factors affecting the performance

of thermoplastic plumbing piping materials. The emphasis in this preliminary study was on thermal properties such as the softening point, relaxation of thermal stress, glass

transition temperature, hardness-temperature relationship, and decomposition temperature. . The techniques used were thermal mechanical analysis (TMA) , thermogravimetric analysis

(TGA), and hardness. Preliminary results obtained on several pipe samples of PVC and CPVC

commercial samples are reported.

Keywords: Chlorinated polyvinyl chloride; hardness; internal stress; plumbing; polyvinyl

chloride; thermogravimetric analysis (TGA); thermal mechanical analysis (TMA); thermoplastic

pipe; thermal properties.

1. Introduction

1.1 Background

The rapid growth of the use of thermoplastic pipe, from its initial production in

the United States in 19^1 to the present annual volume of products valued at hundreds of

millions of dollars, has made these materials an important part of the building construction

industry. The initial plastic used for drain, waste, and vent (DWV) applications was polyvinyl chloride (PVC)(l)» a more recent development is the use of chlorinated polyvinyl

chloride (CPVC) for pressure distribution systems.

While, for the most part, plastic pipe has performed well, there have been some

failures. These appear to be attributable to inadequate quality control, to the use of

materials under conditions beyond their design capabilities, or to improper installation.

To research piping materials the Department of Housing and Urban Development requested the

National Bureau of Standards to perform studies on plumbing criteria and to provide

technical advice concerning the adequacy of performance criteria for plastic pipe for

housing. The work described in this report is part of that carried out in response to this request.

1.2 Objective

The objective of this work is to investigate the sensitivity of plastic pipe materials

to temperature changes and to recommend test proced\ares and performance criteria for these

materials. This report covers the results of initial studies of certain thermal properties

of PVC-DWV piping.

1.3 Materials Background

The plastic materials used in the production of drain, waste, and vent pipe (DWV)

and potable water distribution systems are thermoplastics [l], [2], [8] (2). Thermoplastics

are used because of their relatively low cost, the availability of raw materials

and their ease of fabrication into the finished product with minimal losses due to waste

or scrap. The properties of these materials which allow rapid production, etc. are primarily

related to their thermoplastic characteristics. Thermoplastic materials (e.g. glass, PVC) can be readily shaped or formed under press\ire and elevated temperatures. An essential

(1) Other thermoplastics such as acrylonitrile-butadiene-styrene terpolymer (ABS) and

polybutene (PB) will be considered in a future study.

(2) Numbers in brackets indicate references to the literature.

1
requirement for a useful thermoplastic material is that it should not deform at the

temperatures of end use. Since plastic plumbing piping is subject to a range of temperatures dui'ing normal use, consideration must be given to its thermal response.

Possible thermal responses include: (l) expansion on heating (or contraction on cooling) denoted by the thermal expansion coefficient for the material; (2) stress

relaxation; and (3) decomposition. The coefficient of thermal expansion must be considered

in the design of the system to allow for movements due to temperature changes.

The second possible thermal response, stress relaxation , results from the manufacturing

process. Plastic piping made of thermoplastic materials such as PVC and CPVC is produced

by extrusion [8]. This involves the use of high pressures and elevated temperatures to cause the semi-fluid material to flow through an orifice to give the tubular shape. Sizing

of the outside diameter is achieved by a die using either a positive internal air pressure

or a negative external pressure to cause the hot tube to expand slightly against the inner

wall of the sizing die which is cooler than the pipe. The piping is water-cooled (quenched)

immediately upon leaving the sizing die in order to "freeze" the final dimensions and maintain the desired tolerances in diameter and roundness. The rate of flow of material during

this process varies with the machinery design, the plastic used, the temperature of the

plastic, and the molecular weight of the plastic. However, the rates may be in the range of

10-50 ft /minute. Under these conditions of high shear rate followed by rapid quenching, a high degree of orientation of the plastic results. This orientation is primarily in the

direction of flow or length of the piping and gives a "grain" effect analogous to that in

wood. The large polymer molecules are not only oriented, but stretched lengthwise along the

length of the tubing. As a result, a high degree of internal stress may be present in the

finished product. The amount of this stress is related to the rate of shear, rate of

cooling, and molecular weight of the polymer. Figure 12 shows schematically the effect just

described and indicates the various directions of anisotropy in the internal structure.

The internal stress which remains in the product is a result of two properties of

the material. The first is the property known as the glass transition temperature( 3 ) and

the second, the high viscosity of the material [8]. In order for the stress to be relieved,

the material must be heated above its glass transition temperature for a sufficient length

of time for the molecular stress to relax. The time required depends on the viscosity of

the material.

Finally, at some higher temperature, decomposition will occur. This temperature is

also characteristic of the material but may be altered by the manufacturing process; thus,

it may be raised by certain additives or lowered by improper temperature control during

processing. Again, for the piping to be useful, the decomposition temperature must be well

above the expected use or exposure temperatures of the piping. The nature of the decomposition products must be taken into account in assessing fire hazards, as pointed out in

the fire report [ik] published earlier.

This report contains the results of preliminary studies of these three temperature

effects for the PVC-DWV and CPVC pressure pipe samples described in Table 2. These pipes

were selected as being of immediate interest. Aspects of performance which were not

studied, but which may also be important, include stress-corrosion, slime generation, and

long-term aging effects.

2. Materials

2.1 Polyvinyl chloride (PVC)

Polyvinyl chloride is a resin prepared by the polymerization of vinyl chloride with

or without the addition of small amounts of other monomers [l2]. Some of the properties

of this polymer are given in Table 3. The chlorine content given is the theoretical amount

provided it is formed completely of vinyl chloride with no other monomers added. At this

time, all of the PVC pipe manufactured for pl\imbing use is believed to be made of 100^ vinyl

chloride monomer.

(3) Table 1 is a glossary of technical terms used in this report.

2
2.2 Chlorinated Polyvinyl Chloride (CPVC)

This is a resin prepared "by the addition of chlorine to polyvinyl chloride to approximate the amount of one chlorine atom for each carbon atom in the polyvinyl chloride. The

actual chlorine content is usually less than the theoretical amount. This resin is a newcomer to the plastics industry and its properties have not been as extensively studied as those of PVC. Also, the composition of CPVC is' not as veil defined as it is for PVC and so variations in the properties fo CPVC may be expected from batch to batch. The extent of

these variations is not known so that the important properties need to be determined for each

batch. Typical known property ranges are listed in Table 3.

3. Techniques Used

3.1 Thermal Mechanical Analysis (TMA)

The thermal mechanical analyzer used allowed the investigation and measurement of such

properties of materials as: coefficient of linear expansion, melting point, softening point,

internal stresses, and flow properties [3].

The apparatus consists of a mechanical section, shown in figure 1, and a control

section. The mechanical section is made up of a sample area and probe with a probe positionining sensor, a means for applying different loads on the probe, and a heater for controlling the sample temperature. The control section contains the electronic controls for

programming of the sample temperature and a recorder for recording of the probe position

(sample height) as a function of temperature or time.'

In the procedure used in this study, ring-shaped samples about l/i+" long, were cut from the pipes with a saw, care being exercised to keep from overheating the sample.

Smaller, roughly cubic, sections (see figure 12) were cut from the ring by cleaving with a sharp knife blade and a hammer; the final sample size was the wall thickness of the piping

and the various orientation directions were marked on the sides of the cube with a felt-tip

pen. The cut sides had to be relatively parallel to one another to prevent the sample from

tilting, and the probe from slipping, during the test. The sample was measured with a micrometer and it was placed in the apparatus with the orientation of interest between the

base and the probe (figure 2). The probe was lowered into contact with the sample and a selected weight applied to the pan atop the probe. The probe sensor was adjusted to give

the proper pen position on the chart, the heater placed aroimd the sample, the insulating

flask placed around the heater, and the temperature program initiated by turning on the

recorder. The choice of parameters such as probe type (ball tip or flat end), size of

loading weight, heating rate, starting temperature, recorder sensitivity and range, were all

based on previous investigations and were recorded on the chart. The probe displacement was recorded as a function of temperature

Typical results are shown in figure 3.

3.2 Thermogravimetric Analysis (TGA)

The thermobalance [h] used for thermogravimetric analysis was as shown in figure h. It consisted of a sensitive recording balance (microbalance ) combined with a means for

programmed control of the sample temperature and for control of the atmosphere surrounding

the sample, i.e. vacuum, air, or other gases. A close-up of the sample crucible and furnace

is shown in figure 5.

In the procedure used in this study, a sample of about 10 mg weight, which had been

cleaved from the pipe, was heated from room temperature, at a rate of 2°C/minute to a temperature of 600°C; the measurements were made in both vacuum and in air. The weight of

the sample was recorded as a function of the temperature.

Typical results are shown in figure 6.

3
3.3 Hardness

A property of a material related to its resistance to deformation is its hardness.

Hardness, however, is an empirical measiireraent and values ohtained depend on the apparatus

and technique used as well as the material. The standard hardness apparatus for hard

plastics is the Diirometer, type D. This apparatus, as normally used and described in

ASTM D22U0-68 [2], requires flat specimens with measurements being made at room temperature

only. There is no standard test for hardness of plastic pipe [6]. Hence, an apparatus

based on the standard hardness meter was developed. Figure T shows the basic apparatus with

its V-block to support the pipe and a lever arrangement and bearing support for the gauge.

Additionally, provision for circulating water at a constant temperature through the pipe

allows the determination of a hardness/temperature relationship for the piping. A close-up

of the hardness indentor in contact with a pipe sample is shown in figure 8.

Typical resvilts obtained using the apparatus are summarized in Table k. They appear

to be in the range of values (85 to 95 Shore D at room temperature) reported for rigid PVC

and CPVC in Modern Plastics Encyclopedia.

3.^ Method for Chlorine Content

The results obtained with the TGA in air, indicating the same weight loss was obtained

as in a vacuum, suggested the possibility of a new quick procedure for determining the

chlorine content of PVC and CPVC plastics. This is particularly important for CPVC since

the chlorine content of the raw material is variable and the physical properties depend

on the chlorine content. Also, overheating of either material during processing or pipe

manufacture causes loss of chlorine as HCl. Hence, low chlorine values might indicate

overheated material [5].

The procedure is a simple one in which a finely cut up sample is weighed in a porcelain crucible and heated to constant weight (approximately two hours) in a furnace

carefully controlled to 250°C + 0° - 10°C. The weight loss is calculated as ^HCl and

compared to the theoretical values of 58.1^ and 75.0^ for PVC and CPVC respectively.

Some typical results are given in Tables 5 and 6.

3.5 Aging Studies

3.5.1 Weather-Ometer*

Laboratory aging studies were carried out in a commercial apparatus called a Weather-Ometer [T]. Its interior is shown in figure 9- This apparatus is capable of

cycles of simulated rain, of simulated sunlight and darkness, and limited cycles 'of temperature. The studies carried out on the plastic pipe used the rain cycle and con- tinuous sunlight only. The cycles were set for 9 min. rain per hour to give a total of

805 hrs light and 120 hrs of rain during the test period. At 5 intervals, the pipe was removed and tested for change in hardness and in TMA characteristics. TGA curves were run

on selected samples after the weathering was completed. Figure 10 shows samples before

and after weathering.

3.5.2 Indoor Thermal Aging

Although the majority of the plastic piping would not normally be exposed to exterior

weathering conditions, it might well be subjected to thermal aging in the walls of a building. Hence, a thermal aging procedure was developed. Samples were measured, placed

in a closely controlled oven (80 ± 0.1°C or 1T6 ± 0.2°F) and held at this temperature for

prolonged periods of time. Measurements of hardness, TMA, and TGA studies were made

after oven aging. Figure 11 shows the samples before and after aging. Table 7 lists the

observed changes in dimensions wi th heating.

* Certain commercial instruments are identified in this paper in order to adequately specify

the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that equipment

identified is necessarily the best available for the purpose.

1;
3.5-3 Outdoor Weathering Study

The Weather-Ometer results discussed in section k.k.l indicate that outdoor weathering

studies are desirahle. However, since they will require long periods (over one year), they

have been deferred for future work.

h. Results

h.l TMA

The thermomechanical analyzer results indicate the various movements of the sample

resulting from stress relaxation and flow \inder the thermal environment and external

loading applied.

Figure 3, A and B, show the effects observed with the TMA and may be interpreted in the

following manner. In figure 3A, for the transverse section of a 1 1/2" PVC DWV pipe, the

pipe material expands slightly with temperature in the range from room temperatiire to about

T9.5°C (1T5°F) at which point the material shows a small, but rapid, expansion as it \mdergoes its glass transition. Above 85°C (i85°F), following completion of the glass transition,

the material continues to expand in the transverse direction, at an ever increasing rate,

until a temperature of about 193°C (380°F) is reached. In this temperature region, the

material begins to flow rapidly under the weight of the probe which penetrates into it

causing an apparent shrinkage. Comparing these results with the other curves in figiire 3A,

it can be seen that the material behaves quite differently in the longitudinal and circumferential directions (see figure 12). Again, normal expansion occurs up to about T5.5-82°C

(1T5-180°F), but then rapid contraction takes place between 82 and 88°C (l80 and 190°F),

with a slower contraction changing to flow as the temperature is increased further. These

behaviors can be explained on the basis of the previous description of the extrusion process

and the properties of thermoplastic materials. PVC exhibits its glass transition at about

80°C (1T6°F) [5]. There is a little variation in this temperature with the molecular

weight of the polymer. Hence, the first change in the expansion curve at 82°C (l80°F)

appears to be associated with the glass transition.

The rapid expansion above this temperature for the transverse sample may be accounted

for by the spontaneous deformation of the sample as the internal molding stresses are relieved at the higher temperature. As expected, such swelling in wall thickness is

accompanied by shrinkages in the longitudinal and circumferential directions. The viscosity

woTild fall with increasing temperature allowing the stress relaxation to occur more and more rapidly until complete and/or until the viscosity is too low for the material to

support the probe. The temperature at which the probe begins to sink into the transverse

sample (l93°C or 380°F) is near the temperature used in the original extrusion process.

The results of similar experiments on CPVC piping are shown in figure 3B. The

figures suggest that the glass transition for this CPVC material is in the temperature

region of 110-120°C (230-2l+0°F)

.

h.2 TGA

The thermal stability of a polymeric material, including a thermoplastic, is the

ability of the material to withstand heating without irreversible changes in its chemical

and physical properties. In this study, TGA was used to determine the ranges of thermal

stability of PVC and CPVC piping. Weight loss curves were obtained both in vacuum and

in air for both materials [6]. Typical results sxe shown for each material in figures 6a

and B.

The resulting weight losses are explained in the following manner. The weight loss

behavior for both PVC and CPVC, with increasing temperature, is the same both in air and vacuum for room temperature to about 220°C (U30°F). Both materials begin to break down

thermally at about 20U°C (UOO°F) liberating HCl [9]. The HCl comes off quantitatively

\mtil all chlorine is stripped from the molecules. This point was reached at about 315°C

(600°F) in this experiment. The remaining unsaturated hydrocarbon chains are thermally

stable in vacuum to about 388°C (730°F) at which point they break down and boil off

5
leaving a carbon residue. The carbon residue can then be burned off by introducing air

to the hot sample and the final residue is mineral ash. In air, combustion takes place

at temperatures above U00°C burning the carbonaceous residue directly to leave mineral

ash [10].

This test shows that both PVC and CPVC lose HCl under heating to 315°C (600°F) and

that, for PVC, this loss agrees with the theoretical complete loss of HCl, Also, the HCl

is evolved at temperatures well below combustion and there is little difference in the

temperature dependence of the evolution of HCl in air or vacuum.

It .is possible that this test may also be used as a test for adulteration with other

materials as the shape and magnitude of the weight loss curve wovild be affected by the

presence of other materials. The degree of chlorination of the CPVC can also be estimated

by this test as described in section 3.^.

h.3 Hardness

Impact resistance is an important property of pipe materials. A related property, and

one which is easier to measure and may be useful in the establishment of performance

criteria is hardness. The temperature dependence of hardness may reflect the sensitivity

of the material to temperature changes.

The usual hardness range for rigid PVC is 85-95 on the Shore D scale. This

measurement is normally made on flat specimens prepared according to the ASTM D-22^0-68

procedure. The ASTM procedure is concerned with the- hardness at only one temperature,

23°C (T3.5°F). Since the PVC and CPVC piping is likely to be subjected to hot water as well as water at room temperatures, it is important that hardness testing should include

temperature as a variable. By using the apparatus described in Section 3.3 and carefully

controlling the rate of contact of the hardness gage and time of readings, good

reproducibility of results may be obtained. Table h summarizes some typical data along

with the average values and standard deviations of the sets of meas\irements . The

apparatus designed for this work gives: a 2 to 5 fold improvement over the usual precision

of such measurements.

The effects of temperature on the hardness of PVC and CPVC samples are shown in

figure 13. These results cover the range from room temperature to 90°C (19'+°F). The

hot water was circulated through the pipe samples until the outer wall temperature of the

pipe sample stabilized. The coefficient of the temperatiire, T, in the equations given

in figure 13, represent the rate of change of hardness as the temperature is changed. This

coefficient for different materials may be a good measure of the sensitivity to temperature

of the mechanical properties of the materials. If so, the hardness test apparatus could

be readily modified to be used in the field for direct hardness measurements without

interrupting service.

k.k Aging Effects

i+.i+.l Weather-Ometer Studies

The PVC and CPVC piping samples exposed in the xenon arc Weather-Ometer were not

^Iniformly irradiated by the arc. As a result, in the case of PVC, the more exposed

portion (front) showed a marked change as compared to the more sheltered portion (back)

of the same specimen. Hardness measurements, at two different temperatures, were made

on front and back after various exposure times. The PVC showed little difference between

front and back versus exposure time when measured at room temperature but, at higher

temperatures, it did show a tendency for the front to decrease in hardness with exposure

time. The CPVC showed a slight decrease in hardness with exposure, but there was little

difference between the front and back.

Even with the short exposures given in this test, some changes in the properties of

the PVC occurred. For this reason, this work should be extended to evaluate the importance

of weathering on these products.

6
k.k.2 Thermal Aging of PVC and CPVC

Heating a specimen of PVC DWV in an oven at 80°C (l76°F) for about 6 days produced

remarkable changes in the appearance of the piping and in its dimensions. Table T shows

the dimensional changes of the samples shown in figure 11. Table 8 showed length changes

of pipe sections on oven heating at 90°C (l9i+°F) to determine the limit of this effect.

These changes, though slight, are in the direction indicated by the TMA measurements and were not completed since further heating produced further changes. This aging phenomenon,

which is believed to be due to stress relaxation, is probably the most serious potential

problem in the long term use of PVC, and possibly CPVC, piping. Certainly, more needs to be learned about relating the results of laboratory studies of heat effects to long time . performance in service,. Proper evaluation of the thermal stability is also important to establish whether there is a .slow loss of HCl from PVC and CPVC \inder prolonged moderate

heating with consequent degradation of physical properties and chemical resistance of

the materials [lO].

5. Summary of Results

The most important finding of this study of the effects of elevated temperatures on commercial samples of PVC and CPVC piping is the discovery of the presence of large

amounts of internal stress in the PVC-DWV piping that is relieved by dimensional changes

which taJce place at temperatures in the neighborhood of 82°C (i80°F). This effect is

critical because the temperature at which it occurs is so near the maximum hot water

temperature which may be found in residential occupancies. The permanent dimensional

changes which occiirred in the PVC piping resulted in shorter lengths, smaller diameters,

and greater wall thicknesses. While CPVC shows similar behavior, it only does so at a higher temperature, 110-120°C (230-2U8°F) which is probably enough above the maximum

expected hot water temperature for little trouble to develop from this characteristic.

Hardness measurements as a function of temperature appear to be indicative of

differences in temperature sensitivity of mechanical properties between PVC and CPVC and

can be readily measured to sufficient precision to be considered as a quantitative measure.

However, neither hardness nor its temperature coefficient have yet been directly related

to a critical performance requirement.

Thermal stability, as defined by the temperature at onset of decomposition, shows

little difference between PVC and CPVC; both begin to decompose at approximately 20k°C

(U00°F), liberating HCl. The total weight loss appears to be quantitative for the

chlorine content and may be useful as a measure of the degree of chlorination of the CPVC.

The thermal decomposition appears to only take place at a sufficiently high temperature

as to remove almost all concern about decomposition under normal use of PVC and CPVC in

plumbing systems in homes.

Accelerated aging studies using a xenon arc Weather-Ometer showed some slight

evidence of changes in properties of PVC, but the results were too scattered to allow

unequivocal conclusions to be made. This study should be continued for longer periods

of time to establish its significance.

6. Future Needs of This Program

The work reported here showed the need for long-range studies of thermoplastic

materials, both for D¥V and pressure distribution of hot and cold water, to provide a basis for the establishment of performance criteria. Studies related to the effects

of long-term use on the critical mechanical and dimensional properties are important

if predictions of expected lifetimes for the products are to be made from laboratory

tests of thermal and other properties. Some potential instability of the materials to

heat and light, leading to possible permanent deformation, would indicate the desirability

of studies of mechanisms of change of properties with time with a view to recognizing

such changes in the future.

7
An area not investigated in this study is stress-corrosion. This phenomenon, which

has resulted in failures of metals and plastics in other applications, is not very well

understood or predictable. It, therefore, needs investigation in terms of materials,

manufacturing processes, assembly parajneters, and environment. A careful survey of

problems in the industry should be made and kept up-to-date to allow the most rapid

response to problems before they become major .issues of concern.

8
Table 1 - Glossary of Technical Terms

Term Definition Reference

1. Coefficient of Expansion

2. Glass Transition

the fractional expansion per degree rise

of temperature

the reversible change in an amorphous

polymer, or in amorphous regions of a partially crystalline polymer, from

(or to) a viscous or rubbery condition

to (or from) a hard, relatively brittle

one.

[13]

[2] ASTM

D883-T2a

3. Glass Transition

Temperature (Tg)

h. Hardness

5 . Polymer

6. Softening Point

the approximate midpoint of the tempera- [2] ASTM

t\are range over which the glass tran- D883-T2a

sition takes place.

the resistance of a plastic material to [8]

compression and indentation.

a compound formed by the reaction of [l2]

simple molecules having functional groups

that permit their combination to proceed

to high molecular weights under suitable

conditions .

the range of temperature over which a [12]

plastic changes from a rigid to a soft

state.

7. Thermoplastic

8. Viscosity

a plastic which is capable of being

repeatedly softened by increase of

temperature and hardened by decrease

of temperature.

the property of resistance to flow

exhibited within the body of a material,

[12]

[2] ASTM

D883-72a

9
Table 2 - Thermoplastic Pipe Materials Studied

Designation Pipe Size

PVC-DWV

O.D,

Nominal

in.

Wall

Thickness, Nominal

in.

Sched. ho

(ASTM)

Sched. UO

Sched. 30 "Thin Wall"

( non-standard

)

SDR 11

(ASTM 28U6-69T)

1 1/2

2

1/2

1.900

2.375

U.T5

CFVC-Pressure

0.625

0.13h

0.163

O.lUU

0.068

10
Table 3 - Properties of Thermoplastic Pipe Materials

Density, g/ml [8]

% CI, calc. theoretical

Glass Transition, Tg, °C [5]

Softening Point, Ts, °a [5]

Decomposition, Td, °C [5]

Linear Coeff, of

Expansion/°C (55-65°C) [8]

Injection Molding [8]

Temp. , °C

Hardness [8]

PVC

1.35 - l.i+5

56.5

80 (1t6°F)

80 (176°F)

170 (338°F)

5.0-18.5 X 10

-5

150-210

(302-UlO°F)

65-85 Shore D

CPVC

1.1+5 - 1.58

72.9

170 (338°F)

6.8-7.6 X 10"^

190-218

(37ii_U2l+°F)

117-122 Rockwell

Note: The sources of this infomation are indicated by the numbers in brackets.

11
Table k - Change in Hardness (Shore D) of PVC

and CPVC Piping vith Temperature

a) 1 1/2" PVC-DW

26°C 38°C U5'.5°C 52°C 58°C 65°C

Temperature* (78.8°F) (l00.1+°F) (113. 9°P) (l25.6''F) (136.1+®F) (1I49OF)

Av. of 10 85.73 8I4.85 83.13 82.28 60.9^ 79.97

measurements

Std. Dev. 0.30 0.16 0.27 O.U3 0.26 O.i+1

Av. Std. Dev. 0.30

b) 1/2" CPVC-Pressure Tubing

Temperature* (78.8°F) (lOO.i+°F) (lllt.8°F) (130.6°F) (ll+3.6°F) (l58°F)

Av. of 10 85.97 Qh.gk 8U.58 81+. 01 82.1+8 81.56

Std. Dev. 0.15 0.08 0.30 0.09 0.27 0.33

Av. Std. Dev. 0.20

* Surface Temperature of Pipe Sample

12
Table 5 - Weight Loss Study for

HCL Content of PVC

Time of Heating Temperature Weight Loss, % hrs. °C' °F Sample 1 Sample 2

0 0 0

0.5 2U0 52.

U

50.8

1.0 5i^.l

, 53.8

2.5 55.1 55.0

5.5 55.5 55.9

7.0 300 532 58.0 58.5

7.5 57.9 58.3

(Final Av. 58.1)*

•Theoretical HCl Content, 58.1^

13
Table 6 - Weight Losp Study for

HCl Content of CPVC

Time of Heating Temperature Weight Loss, % hrs. °C Sample 1 Sample 2

0 n\j n\j

0.5 280 536 63.1 60.2

1.0 63.1 62.0

1.5 62.7 62.3

2.0 65.0 61+.

2

It.O 65.it 65.5

7.0 65.5 65.3

(Final Av. 65 M*

* Theoretical HCl content for CPVC of one CI per carbon atom would be 75.0^. Therefore,

the results above correspond to 87^ of theoretical chlorination of PVC to CPVC.

Ik
Table 7 - Dimensional Changes of PVC-DWV

Piping on Thermal Aging at 80°C (1T6°F)

Diameter , internal

.

Wall Thickness

Time, Length, in. in.

hr. in. End 1 End 2 End 1 End 2

0 2.156 1.3hk 1.350 0.159 0.156

2.159 1.3h6 1.3i+5 0.153 O.15U

2.157' 1.3i+5 1.3i+6 0.153 0.15^+ Av. 2.157 1.3i+7 I.3I+9 0.15i+

ih6 2.128 1.329 1.325 0.161 0.156

2.131 1.332 1.325 0.162 0.161

2.133 1.330 I.33U 0.158 0.160

2.132 1.331 1.330 0.156 0.157

Av. 2.131 1.331 1.322 0.159 0.158

Increase -1.2^ -1 .6% +2. 9%

15
Table 8 - Decreases in Length (AL) of Piping

on Heating to 90''C (19^+°?)

Length, cm Material Time . .Sample A Sample B

hr.

1 1/2" PVC 0 90.6 91.2

DWV 2ii 89.5 90.0

50 89. i+ 89.9

73 89.5 89.9

_ AL, ^ 1.3

2" PVC 0 91.1+ 90.5

i : 21+ 90.5 89.6

50 90. li 89.5

• 72 90.

U

89.6

AL, % 1.1 1.1

I4" PVC 0 91.6 - DWV ...

"

. 90.2 -

. - .

' 50 90.1 - 90.0

AL, % 1.7

1/2" CPVC 0 82.8 82.2

Pressure 21; 82.7 82.1

50 82.7 82.0

73 82.7 82.0

AL, % 0.1 0.2

16
References

1. National Sanitation Foundation Standards, Standard No. ih . Published by National

Sanitation Foundation, Ann Arbor, Michigan, October (1965)-

2. 1972 Annual Book of ASTM Standards, Parts' 26 and 27, Plastics-Specifications; Methods

of Testing Pipe; Film; Reinforced and Cellular Plastics; Fiber Composites. Published

by American Society for Testing and Materials, I916 Race Street, Philadelphia,

Pennsylvania 19103.

3. Instruction Manual, 9OO Thermal Analyzer and Modules, Section 11 - 9^1 TMA and

Accessories, E. I. Du Pont de Nemoiirs and Co., Inc. Instrument Products Division,

Wilmington, Delaware 19898.

h. Thermoanalytical Methods of Investigation by Paul D. Garn. Published by Academic Press

Inc., Ill Fifth Ave., New York, N. Y. 10003 (1965).

5. The Chemical Structure and Thermal Characteristics of Polymbers by V. V. Korshak,

translated by J. Schmorak. Published by Israel Program for Scientific Translations,

Jerusalem (l97l).

6. Handbook of Plastics Test Methods, by G. C. Ives, J. A. Mead and M. M. Riley.

Published by The Chemical Rubber Company, 189OI Cranwood Parkway, Cleveland, Ohio

i+Ul28 (1971).

3 f - 7. A%ias Fade-Ometer and Weather-Ometer , Atlas Electric Devices Company, Ulli+ N. Ravenswood Ave., Chicago, Illinois 60613.

8. Modern Plastics Encyclopedia, Volume k'J , No. lOA, October 1970. Published by

McGraw-Hill, Inc., 330 W. l+2nd St., New York, N. Y.

9. Analytical Chemistry of Polymers, Ed. by Gordon M. Kline, Volme XII of High

Polymers Series. Published by Interscience Publishers, Inc., 250 Fifth Ave.,

New York, N. Y. (1959).

10. Autoxidation and Antioxidants, Volume I and II, Ed. by W. 0. Lundb^rg. Published by

Interscience Publishers, Inc., 250 Fifth Ave., New York, N. Y. (1962).

11. Literature Survey on Thermal Degradation, Thermal Oxidation, and Thermal Analysis of

High Polymers, PLASTEC Note 7, by David W. Levi, Picatinny Arsenal. Available from

Defense Documentation Center (DDC), Cameron Station, Arlington, Va. 2231^-

12. A Glossary of Plastics Piping Terms, Tech. Rpt. PPI-TRI-Nov. I968, Plastics Pipe

Institute, 250 Park Ave., New York, N. Y. 10017.

13. Chambers Technical Dictionary, 3rd Edition, The MacMillan Company, New York, N. Y.

1^+. Fire Endurance Tests on W^ls and Plumbing Chases Containing Either Metallic or Non-metallic Drain, Waste, and Vent Systems. W. J. Parker, NBSIR "jh-hh^. National

Bureau of Standards.

17
Fig. 1 Thermomechanical Analjyzer (TMA)

A - sample area and probe

B - recorder and controls

H - heater

L - load

18
Fig. 2 Thermomechanical Analyzer (Detail)

Close-up view of probe and sample with heater

P - probe

S - sample

B - base '•

; H - heater

19
CIRCUMFERENTIAL

LONGITUDINAL

TRANSVERSE

J I I ' ' I I I I 1 1 1 F 68 104 138 173 208 243 279 315 351 387

20 40 60 80 iOO 120 140 160 ISO 200

TEMPERATURE

3 TMA Curves on Pipe Samples

- ' a - PVC DWV Pipe

Measurements made on three samples according to orientations

shown in figure 12. Conditions of test: lOg. load on ball

tip probe, heating rate 10°C/min. starting at rqom temperature

in air, the probe displacement scale is 0.2mV/in. or 6.8 mils/inch

of chart

.

20
TRANSVERSE

"F 68 104 138 173 208 243 279 315 351 387

*C 20 40 60 80 100 120 140 160 180 200

TEMPERATURE

Figure 3 TMA Curves on Pipe Samples

B - CPVC Pressure Pipe

Measurements made on three samples according to orientations

shown in figure 12. Conditions of test same as for A.

21
Figure h Thermogravimetric Analysis Apparatus (TGA)

B - microbalance

T - sample chamber

R - recorder

22
'Fig. 5 Thermogravimetric Analyzer (Detail)

Close-up of sample crucilDle, sample chamlier, and furnace.

S - sample in platinum toat

T - sample chamber

F - furnace

23
10

^5 50 io5-—^5 206 ^50 ^(^6 355"

^ =^5 sfe 1^5 sio SAMPLE TEMPERATURe.*C

Fog. 6 TGA Curves on Pipe Samples

A - Measurements on PVC DWV in air and in vacuiun as indicated. Heating rate 2°C/rain. for both

qurves.

2k
ok- 50 ICX) 150

B

200 250 300 350 400 450 500 550

...J 600 SAMPLE TEMPERATURE.'C

Fig. 6 TGA Curves on Pipe Samples

Measurements on CPVC pressure pipe in vacuum. Heating

rate same as above. Similar curve obtained in air.

25
Fig. T Hardness Apparatus

S V. sample

T - thermocouple

V - support block

A - hardness gage support arm

G - hardness gage

B - circulating constant temperature bath

26
Slum

S

Fig. 8 Hardness Apparatus (Detail)

Close-up of hardness indentor before application of test

Mark on pipe sample represents 5 mm (approx. 0.2 inch).

S - sample

I - indentor of hardness gage

A - hardness gage support arm

27
Fig. 9 Weathering Apparatus - Interior

S - sample

L - xenon arc lamp

R - rain simiilator (wetter spray)

28
29
B - after heating

Upper sections are 1 1/2" pipe

Lower sections are U" pip^

30
EXTRUSION

DIRECTION

Pig. 12 Orientation of Pipe Material

Section A shows sample out for TMA with three directions

of interest for measurement of thermal movements.

31
Fig. 13 Hsirdness as a Function of Temperature

t - PVC DWV pipe

Vertical bars indicate ±1 standard deviation for each point.

Each point is average of 15 measurements. The regression

equation for the data is: K - -.155 T + 90.13 with

correlation coefficient of 0.990 and where H is the hardness,

(Shore D), and T is the temperature, (°C). ^ - CPVC pressure pipe

Vertical bars indicate ±1 standard deviation for each point.

Each point is the average of 15 measurements. The regression

equation for the data is : H 0.099 T + 88.80 with a correlation coefficient of 0.97*+.

USCOMM-NBS-DC

32
NBS-l 14A i>=iH V. 7-73)

J S. D ::'^T . OF CO^M.

BldLlOGRAPHIC DATA

SHEET

1. PL HLK ATION OR REPuRT Nn. NBSIR 74-6102. Gov't Acccs-.ion No.

3. R L-i 1 ;i , en

t

' >. Ac . siun No.

4. TITLL AXl) subtitle

Investigation of Procedures for Determination of Thermal

Performance Characteristics of Plastic Piping Used in

Housing

5. Publ ic.uion i).it _- November 1974

6. Pertormin^ Or^ani/.ation (-ode

7. AUTfK'Ki S^ Max Tryon8. Pcrtormini; Organ. Report ."^"O. NBSIR 74-610

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proiccr/ 1 ask/ ''''ork Unit No. 4623387

11. Contract/Grant .No.

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

Office of Research and Technology

Department of Housing and Urban Development

Washington, D.C. 20410

13. Type ot Report & Period 7/7Z-6/73

Interim

14. Sponsoring Agency Code

15. SUPPLE.MENTARY NOTES

16. ABSTR.ACT (A 200-word or less (actual summary ol most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The rapid growth of the use of thermoplastic pipe for plumbing in housing has

prompted a study to determine the critical factors affecting the performance

of the pipe materials. The emphasis in this preliminary study is on thermal

properties such as the softening point, relaxation of thermal stress, glass

transition temperature, hardness-temperature relationship, and decomposition

temperature. The techniques used were thermal mechanical analysis (TMA)

thermogravimetric analysis (TGA) , and hardness. Preliminary results obtained

on several pipe samples of PVC and CPVC commercial samples are reported.

17. KEY VORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Chlorinated polyvinyl chloride; hardness; internal stress; polyvinyl chloride;

thermogravimetric analysis (TGA) ; thermal mechanical analysis (TMA) ; thermoplastic

pipe; thermal properties.

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(THIS REPORT)

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45

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