SPECIAL REPORT 96-26

Further Studies on the Softening of

Rigid PVC by Aqueous Solutions of

Organic Solvents

Louise V. Parker and Thomas A. Ranney October 1996
Abstract: In this study, small pieces of PVC well casing

were exposed to relatively low activities (or relative

solubilities) of TCE and methylene chloride for 12

months. PVC pieces were also exposed to aqueous

solutions containing several organic chemicals that

were either solvents or swelling agents of PVC. In

addition, small pieces of PVC were exposed to aqueHow to get copies of CRREL technical publications:

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ous solutions containing organic chemicals that were

either PVC solvents or swelling agents and were totally

miscible in water. These studies revealed that there is

an interactive effect among these chemicals when

dissolved in water. However, softening does not appear to occur in any solutions where the sum of the

relative solubilities is less than 0.1.
Special Report 96-26

Further Studies on the Softening of

Rigid PVC by Aqueous Solutions of

Organic Solvents

Louise V. Parker and Thomas A. Ranney October 1996

Prepared for

U.S. ARMY ENVIRONMENTAL CENTER

SFIM-AEC-ET-CR-96156

Approved for public release; distribution is unlimited.

US Army Corps

of Engineers

Cold Regions Research &

Engineering Laboratory
PREFACE

This report was prepared by Louise V. Parker, Research Physical Scientist, Applied

Research Division, Research and Engineering Directorate, U.S. Army Cold Regions

Research and Engineering Laboratory (CRREL), Hanover, New Hampshire, and

Thomas A. Ranney, Staff Scientist, Science and Technology Corporation, Hanover,

New Hampshire. Funding for this work was provided by the U.S. Army Environmental Center (USAEC), Aberdeen Proving Ground, Maryland, Martin H. Stutz, Project

Monitor.

We thank Martin Stutz and AEC for their support of this work; Robert Forest,

CRREL, for carefully cutting the PVC pieces; and Daniel Leggett and James Cragin,

Research Chemists at CRREL, for their technical reviews of this manuscript.

This publication reflects the personal views of the authors and does not suggest or

reflect the policy, practices, programs, or doctrine of the U.S. Army or Government

of the United States. The contents of this report are not to be used for advertising or

promotional purposes. Citation of brand names does not constitute an official

endorsement or approval of the use of such commercial products.

ii
CONTENTS

Page

Preface ........................................................................................................................ ii

Introduction ............................................................................................................... 1

Methylene chloride studies ................................................................................ 2

Trichloroethylene studies ................................................................................... 3

Studies on aqueous solutions that contain several organic solutes.............. 4

Aqueous solutions containing organics that are miscible in water .............. 4

Purpose of this study ............................................................................................... 5

Materials and methods ............................................................................................ 6

Long-term methylene chloride study ............................................................... 6

Long-term TCE study .......................................................................................... 6

Studies on aqueous solutions that contain several organic solutes.............. 7

Studies on aqueous solutions containing organics that are miscible

in water .......................................................................................................... 8

Results and discussion ............................................................................................. 8

Long-term methylene chloride studies ............................................................. 8

Long-term TCE studies ....................................................................................... 9

Studies on aqueous solutions that contain several organic solutes.............. 10

Studies on aqueous solutions containing organics that are miscible

in water .......................................................................................................... 16

Conclusions ............................................................................................................... 19

Literature cited .......................................................................................................... 19

Appendix A: Percent weight gain in PVC exposed to various neat

organic chemicals ......................................................................................... 21

Abstract ...................................................................................................................... 23

ILLUSTRATIONS

Figure

1. Flory-Huggins isotherms for various values of χ and approximate

composition for softening of PVC at room temperature .................. 2

TABLES

Table

1. Literature values for the Flory-Huggins interaction parameter, χ ........ 1

2. Relative solubility and molarity of PVC solvent and swelling

agents used in the test solutions ........................................................... 7

iii
iv

Table Page

3. Listing of 18 PVC solvent and swelling agents used in studies

and their aqueous solubilities ................................................................ 7

4. Hardness readings and percent weight gain of PVC exposed to

methylene chloride solutions ................................................................. 8

5. Hardness readings and percent weight gain of PVC exposed to

TCE solutions ........................................................................................... 10

6. Hardness readings and percent weight gain of PVC exposed to

aqueous solutions of several organic solutes (short-term study) ..... 12

7. Hardness readings and percent weight gain of PVC exposed to

aqueous solutions of methylene chloride and TCE ............................ 13

8. Hardness readings and percent weight gain of PVC exposed to

aqueous solutions of several organic solutes (first long-term

study) ......................................................................................................... 14

9. Hardness readings and percent weight gain of PVC exposed to

aqueous solutions of several organic solutes (second longterm study)................................................................................................ 14

10. Hardness readings and percent weight gain of PVC exposed to

acetone solutions ...................................................................................... 16

11. Hardness readings and percent weight gain of PVC exposed to

aqueous solutions of methylene chloride and acetone ...................... 18
INTRODUCTION

It has been known for some time that some

neat (undiluted) organic solvents can dissolve or

swell PVC well casings and screens. Products that

can dissolve PVC are referred to as PVC solvents,

and products that do not dissolve PVC but can

cause it to swell are referred to as swelling agents

of PVC. There has been concern that PVC casings

and screens might be degraded by well water

containing ppm and ppb levels of these chemicals. In the past few years, we have conducted a

series of studies (Taylor and Parker 1990, Parker

et al. 1992, Parker and Ranney 1994, 1995) to address this issue.

The solvent interaction parameter (χ) used in

the Flory-Huggins equation* has been commonly

used as a measure of the solvent or swelling power

of a particular organic solvent (Berens 1985, Vonk

1985, 1986, Jenkins et al. 1986). Table 1 gives χ

values for a number of organic chemicals that

were derived experimentally† by Berens (1985) at

30°C and by Vonk (1985) at 20°C. PVC is reported

to be softened only by solvents with a χ value less

than 1 (Berens 1985) or 1.2 (Vonk 1985); the lower

the number the greater the solvent or swelling

power. Also, a neat solvent with a χ value less

Further Studies on the Softening of Rigid PVC

by Aqueous Solutions of Organic Solvents

LOUISE V. PARKER AND THOMAS A. RANNEY

* The Flory-Huggins equation relates activity (a) to the volume fraction (V1) of the organic chemical in the polymer as

follows:

ln (a) = ln V1 + (1 – V1) + χ(1 – V1) 2

where χ is the Flory-Huggins interaction parameter.

† Berens (1985) and Vonk (1985) derived χ by exposing PVC

to different activities of organic chemicals in vapor and solution.

Table 1. Literature values for the Flory-Huggins

interaction parameter, χ.

From From

Organic chemical Berens (1985) Vonk (1985)

acetone 0.61 —

aniline — 0.87

benzene 0.83 0.83

2-chloroaniline — 0.58

3-chloroaniline — 0.61

chlorobenzene — 0.66

chloroform 0.64 —

1,2-chlorotoluene — 0.74

1,3-chlorotoluene — 0.69

1,4-chlorotoluene — 0.75

1,2-dichlorobenzene — 0.63

1,3-dichlorobenzene — 0.74

1,1-dichloroethane < 0.68 —

1,2-dichloroethane < 0.55 0.56

1,2-dichloropropane 0.68 0.65

di-isopropylketone — 0.56

ethylbenzene — 0.89

n-methylaniline — 0.59

methylene chloride < 0.53 0.55

methyl ethyl ketone — 0.54

nitrobenzene — 0.54

propylbenzene — 1.91

1,1,2,2-tetrachloroethane — 0.59

tetrachloroethylene 1.17 1.58

toluene 0.80 0.82

1,2,4-trichlorobenzene — 1.52

1,1,1-trichloroethane 0.85 0.92

1,1,2-trichloroethane < 0.56 0.58

trichloroethylene 0.88 0.90

1,3,5 trimethylbenzene — 2.52

vinyl chloride 0.98 —

xylene 0.88 —

1,2-xylene — 0.76

1,3-xylene — 0.87

1,4-xylene — 0.86
than 0.5 reportedly can completely dissolve PVC

(Berens 1985). According to Vonk (1985), PVC is

nearly inert to organic solvents if their χ value is

greater than 3 (e.g., alcohols, aliphatic hydrocarbons, and organic acids).

According to Berens (1985), at ambient temperatures, rigid PVC can be softened only by PVC

solvents or strong swelling agents at activities

greater than 0.5. The less aggressive the solvent

(i.e., the higher the χ value), the higher the activity required to cause softening. Figure 1 shows

the isotherms Berens derived using the FloryHuggins equation for various values of χ and the

approximate softening range for PVC at 30°C.

Berens predicted that for lower temperatures (such

as those commonly encountered in groundwater), slightly higher activities would be needed to

cause softening.

The activity of an organic chemical in aqueous

solution can be approximated by dividing the concentration of the compound in solution (Cw) by

its solubility in water (Cws) (Berens 1985, Vonk

1986, Holsen 1988). However, the true relationship between activity (a), Cw, and Cws is:

 

a

Cw

Cws = γ

where γ is the activity coefficient (Holsen 1988).

According to Holsen (1988), γ is equal to unity

when there are no interacting forces between the

molecules; these forces become important at high

but still unsaturated conditions. At lower concentrations, γ has been considered equal to unity

partially because of the lack of experimental data.

Therefore, at high concentrations or when there

are interacting forces between the molecules, estimates of activity using solubility may be inaccurate.

In this paper, we will use the term “relative

solubility” to express Cw/Cws and thus estimate

activity. However, we should point out that there

also can be significant imprecision with this term.

While it is known that aqueous solubilities vary

with temperature, we have also found that for

some organic compounds, the reported solubility

can vary 1 or 2 orders of magnitude at the same

temperature. Montgommery and Welkom (1990)

have compiled aqueous solubility data from a

number of sources. As an example of the variability we have observed, two of the values they report for the solubility of 1,1-dichloroethylene at

25°C are 273 mg/L and 5,000 mg/L.

Berens (1985) concluded that if aqueous solutions of solvents are going to cause softening of

rigid PVC, the pure (or neat) solvent must be able

to soften or dissolve PVC and must exist in solution at a concentration that exceeds one-half its

solubility in water (activity > 0.5). However, one

criticism of Berens’ work is that the various test

(activities) solutions he used in his experiments

were prepared by dissolving the organic solvents

in polyethylene glycol and thus he never actually

tested aqueous solutions of these organic solvents.

Since one would expect that the partitioning of

these organic solutes between the dissolved state

and the polymer would differ between glycol and

water, studies that use aqueous solutions of PVC

solvents should be conducted to confirm Berens’

predictions. While Vonk did use aqueous solutions of organics in his studies, we were unable to

find a thorough discussion of his methods that

was available in English. Therefore, our laboratory conducted a series of studies (Parker et al.

1992, Parker and Ranney 1994, 1995) to confirm

Berens’ predictions for PVC solvents and swelling agents in aqueous solutions. Following is a

summary of our findings to date.

Methylene chloride studies

The first test solutions that were tested contained methylene chloride. Vonk (1985) reported

that the χ value of methylene chloride is 0.55,

while Berens (1985) did not give a value for χ but

reported that it is less than 0.53. We (Ranney and

Parker 1995) have observed pieces of PVC well

casing dissolve when placed in neat methylene

chloride. Thus, if Berens (1985) is correct in sayχ = 0

0.5

1.0

1.5

Softening Range

Rubbery

Glassy

1.0

0.8

0.6

0.4

0.2

0 0.2 0.4 0.6 0.8 1.0

V1

Solvent Activity

χ = 0

0.5

1.0

1.5

Softening Range

Rubbery

Glassy

1.0

0.8

0.6

0.4

0.2

0 0.2 0.4 0.6 0.8 1.0

V1

Solvent Activity

Figure 1. Flory-Huggins isotherms for various

values of χ and approximate composition for

softening of PVC at room temperature (from

Berens 1985).

2
ing that any organic chemical with a χ value less

than 0.5 can dissolve PVC, the true χ value for

methylene chloride remains undefined but is less

than 0.5.

In a previous study (Parker and Ranney 1994),

we found that after one week of exposure, PVC

pieces exposed to aqueous solutions of methylene chloride with a relative solubility of 0.6 had

hardness readings that were significantly lower

than the control samples, and these samples were

rubbery in that they could easily be bent by hand.

(In all our studies, we use a Barcol Impressor to

determine hardness.) Samples exposed to solutions with a relative solubility of 0.8 were also

similarly affected, with significant changes in the

hardness readings after only four hours. While

these findings agree with Berens’ (1985) predictions for PVC exposed to aqueous solutions with

an activity of 0.8, Berens would not predict that

PVC exposed to solutions with an activity, or relative solubility, of 0.6 would become rubbery unless the true value of χ was very close to 0. We

were not able to find in Berens’ paper how he

determined softening.

In a subsequent study (Parker and Ranney

1994), we were able to determine that there were

significant changes in the hardness readings of

test pieces that were exposed to aqueous solutions of methylene chloride with relative solubilities of 0.4, 0.2, and 0.1 for 20 weeks. However,

none of these samples were actually rubbery or

pliable. We concluded that it appeared that softening had begun to occur at much lower relative

solubilities, or activities (0.1 to 0.4), than had been

previously reported or predicted by Berens (1985).

Because we conducted our own solubility tests to

confirm the aqueous solubility of methylene chloride, we do not feel that our test results can be

explained away by assuming the solubility value

we used is incorrect.

According to Berens (1985), diffusion of organic permeants is slowest (Fickian) at activities

less than 0.25. However, Vonk (1985, 1986) felt

that diffusion would be Fickian for the poorer

PVC swelling agents (e.g., alkylated aromatics) at

activities less than 0.25, but for the solvents and

the better swelling agents (i.e., anilines, chlorinated hydrocarbons, ketones, and nitrobenzenes)

the activity should be less than 0.1. If this is the

case, we would not expect to observe any changes

in the hardness readings of samples exposed to

solutions of methylene chloride (a solvent) with

relative solubilities less than 0.1. The results from

this study tend to support this hypothesis since

the hardness readings of the samples that were

exposed to solutions with a relative solubility of

0.05 were not significantly different from the controls.

We proposed that only partial softening occurs

at the lower relative solubilities (0.1 to 0.4) and

that these samples will never actually become rubbery or pliable. Examination of Berens’ isotherms

(Fig. 1) indicates that some samples do become

partially softened but never actually become rubbery. We concluded that a longer-term study was

necessary to resolve whether softening progresses

further with time, and the lowest relative solubility at which softening occurs.

Trichloroethylene studies

We conducted another series of studies using

trichloroethylene (TCE). TCE is a common environmental pollutant and is a relatively good swelling agent of PVC. There is close agreement between the χ value of Berens (1985), 0.88, and that

of Vonk (1985), 0.90. When we (App. A, Ranney

and Parker 1995) subjected small pieces of PVC

well casing to neat (undiluted) TCE, we found

that the test pieces showed signs of swelling and

softening after only one day. However, TCE did

not dissolve the PVC pieces. Thus, our experimental work appears to confirm that TCE is a

good swelling agent of PVC but that it is not a

solvent.

We conducted two studies where pieces of PVC

were exposed to aqueous solutions of TCE with a

range of relative solubilities (0.2 to 1.0) (Parker

and Ranney 1994). Samples that were exposed to

solutions with relative solubilities of 0.8 and 1.0

had Barcol readings that were significantly lower

than the controls. The samples that were exposed

to the solutions with a relative solubility of 0.8

never became pliable or rubbery, while those exposed to the 1.0 relative solubility solutions were

pliable by the end of the study (77 days). Generally, the results for TCE agree with what would

be predicted using Berens’ isotherms (Fig. 1): PVC

would be softened by TCE when the activity, or

relative solubility, is 0.8 or greater and would

become rubbery if the relative solubility was 0.95

(at 30°C).

Samples that were exposed to solutions with a

relative solubility of 0.6 had hardness readings

that were significantly different from the controls

in the first study (68 days) but not in the second

study (77 days). We were not certain why the

results for the two studies differed. We thought

that if the unsoftened samples had been given

3
more time that softening might have occurred, or

it might have been due to the heterogeneous nature of PVC. We noted that at the lower relative

solubilities, the test pieces continued to gain

weight, and therefore equilibrium was not

reached. We concluded that a longer-term study

should resolve the lowest relative solubility that

can soften PVC.

Studies on aqueous solutions that

contain several organic solutes

One question that has not been addressed in

the literature is what effect does an aqueous solution that contains several different PVC solvents

or swelling agents have on PVC. This is an important question for the groundwater monitoring industry since most contaminated groundwater contains several organic contaminants, each at ppb

or ppm levels. In cases where there is only one

organic solute in a solution, there can be interactions between the organic and the polymer, the

organic and water, and among the organic molecules. In cases where there is more than one

organic solute, there can be all those interactions

as well as interactions among the various organic

solutes (i.e., a and b, b and c, a and c, etc.). We

have conducted several studies that have looked

at softening by solutions containing multiple organic solutes.

In the first study, we (Parker and Ranney 1994)

found that after two days’ contact, the hardness

readings of samples exposed to an aqueous solution that contained three PVC solvents or swelling agents were significantly lower than those of

the controls, and these samples were rubbery. The

test solution contained methylene chloride, 1,1,2-

trichloroethane, and 1,2-dichloroethane, each with

a relative solubility of 0.3. The χ values for these

three compounds are reported to be less than 0.6

(Table 1). At this relative solubility, Berens would

predict that none of these organic solutes should

be able to soften PVC by themselves. Our own

studies (Parker and Ranney 1994) have shown

that methylene chloride was able to cause softening at a similar relative solubility (0.4), but it took

eight weeks. The test solution in this study behaved more like a test solution containing methylene chloride at a relative solubility of 0.8, which

softened the PVC pieces almost immediately

(Parker and Ranney 1994).

In a follow-up study (Parker and Ranney 1995),

an aqueous solution that contained 18 PVC solvents and swelling agents, each with a relative

solubility of 0.05, softened PVC. There was a significant change in the Barcol readings after only

one day, and after 14 days several of the test

pieces were noticeably softened when tested

manually, although none actually became pliable.

It is clear from these studies that there is a cumulative or possibly synergistic effect when several

PVC solvents and/or swelling agents are present

in an aqueous solution.

We thought that the sum of the relative solubilities (or activities) of the organic solutes in the

test solution might prove to be useful in estimating the ability of a solution to soften PVC. In this

study (Parker and Ranney 1995), the sum of the

relative solubilities of the organic solutes was 0.9.

This solution was more aggressive than a solution containing a PVC swelling agent (the TCE

solution) with a relative solubility of 1.0, but less

aggressive than a solution containing a PVC solvent (the methylene chloride solution) with a relative solubility of 0.8 (Parker and Ranney 1994).

Although it does not explain how the organic

solutes interact with the polymer, water, or each

other, the sum of the relative solubilities does

give some measure of the ability of an aqueous

solution containing two or more organic solutes

to degrade PVC.

We concluded that there were a number of

unanswered questions, such as 1) whether a mixture of organic solutes that are at even lower relative solubilities could soften PVC, 2) whether PVC

solvents and swelling agents have any synergistic

effect on other, poorer swelling agents, and 3)

what happens in solutions that contain a number

of solutes with varying but very low relative

solubilities?

Aqueous solutions containing

organics that are miscible in water

Another issue that had not been addressed in

the literature prior to our studies was whether

aqueous solutions of PVC solvents and swelling

agents, which are also completely miscible in water, can soften PVC. It is impossible to calculate

the relative solubility of these solutions, because

this involves dividing the analyte’s concentration

by an infinitely large number. We have conducted

several studies that look at this issue.

In our most recent paper (Parker and Ranney

1995), PVC test pieces were exposed to varying

concentrations of aqueous solutions containing

one of four organic chemicals that were totally

miscible in water: acetone, tetrahydrofuran,

dimethylformamide, and pyridine. Acetone is a

good swelling agent of PVC (χ = 0.61 [Berens

4
1985]). There are no χ values available for the

other three chemicals, but tests by our laboratory

indicate that they are all PVC solvents (App. A,

Ranney and Parker 1995). In fact, tetrahydrofuran

is commonly used as a component of PVC glues.

We (Parker and Ranney 1995) found that the

test solutions containing tetrahydrofuran were the

most aggressive. After seven days, a 60% solution

(8.4 M) dissolved the PVC pieces. By the end of a

20-week study that used lower concentrations,

the hardness readings of the samples exposed to

the lowest concentration tested (0.01% or 0.0014

M) were significantly lower than the controls.

However, none of these samples were noticeably

softened when tested manually, even the samples

exposed to the highest concentration tested (10%

or 1.4 M). Although there is a lot of variability in

the weight change data, by the end of the study

there was no additional weight gain in the samples

that were exposed to the 1.0, 0.1, and 0.01% solutions. This may indicate that these solutions have

reached equilibrium. If this is the case, then we

would not expect any additional softening to occur.

The acetone solution was the next most aggressive solution (Parker and Ranney 1995). After

seven days, the hardness readings for samples

exposed to the 60% (10.2 M) solutions were significantly lower than the controls, and the samples

were pliable when tested manually (i.e., could be

bent in half easily). In a longer-term study (20

weeks) (Parker and Ranney 1995), there was no

significant change in the hardness readings of

samples that were exposed to the 2.5% (0.43 M)

and 5% (0.86 M) solutions. There was a significant change in the Barcol readings of samples

exposed to the 10% (1.7 M), 20% (3.4 M), and 40%

(6.9 M) solutions. However, none of these samples

were noticeably softened when tested manually.

Although the weight gain data were highly variable, it did appear that the samples exposed to

the 40%, 10%, and the 5% solutions had reached

equilibrium. If this is the case, we would not expect further softening to occur. However, this is

unproven at this time.

Our initial study (Parker and Ranney 1995)

showed that aqueous solutions of pyridine were

not highly aggressive. Even the 60% solution had

no effect on the hardness readings after seven

days. However, after a 20-week study (Parker and

Ranney 1995), there was a significant change in

the hardness readings for the samples exposed to

the lowest concentration tested (20% or 2.5 M).

Samples exposed to the highest concentration

tested (80% or 10 M) were actually pliable, i.e.,

easily bent in half.

The dimethylformamide solution was the least

aggressive solution. During a 20-week study

(Parker and Ranney 1995), only the test pieces

exposed to the 60 (8.2 M) and 80 percent (10.9 M)

solutions had hardness readings that were significantly lower than the controls. The samples

that were exposed to the 80% solution were also

pliable. Because there was no additional weight

gain in any of these samples during the last four

weeks of the study, equilibrium may have been

reached.

It is clear from this study that PVC solvents

and swelling agents that are completely miscible

in water can soften PVC when mixed with water.

These results are puzzling in that the aqueous

solutions of acetone were more aggressive than

the aqueous solutions of the dimethylformamide

and pyridine, and yet our laboratory studies show

that these two chemicals are more aggressive than

acetone (App. A, Ranney and Parker 1995). Therefore, we would expect that the aqueous acetone

solutions would be the least aggressive solutions.

It appears that the ability of aqueous solutions of

these chemicals does not completely correlate with

the neat chemicals’ ability to dissolve or swell

PVC. This can be related to other interactions that

occur in aqueous solution. According to Leggett

(pers. comm. 1995* ) acetone is less basic than the

other solutes and would interact less strongly with

water, and thus an aqueous solution would have

a higher activity on a molar basis.

PURPOSE OF THIS STUDY

The purpose of this study was to determine:

1) whether softening progresses further in those

solutions already showing a significant change in

hardness readings but are not yet pliable?

2) for solutions with single organic solutes, what

is the lowest relative solubility where softening

occurs?

3) for solutions with multiple organic solutes,

what is the lowest relative solubility where softening occurs?

4) for solutions with multiple organic solutes,

how well does the sum of the relative solubilities

of the solutes in the solution correlate with the

solution’s ability to soften PVC?

* D. Leggett, Research Chemist, USA Cold Regions Research

and Engineering Laboratory, Hanover, New Hampshire.

5
5) what occurs in an aqueous solution that contains a number of PVC solvents and swelling

agents at varying relative solubilities?

6) in solutions that contain several organic solutes, do solutes that are solvents and swelling

agents of PVC have some type of synergistic effect on poorer swelling agents?

7) what is the lowest concentration of acetone

in aqueous solution that can soften PVC?

8) what occurs when PVC solvents and swelling agents that are miscible in water are also

present in an aqueous solution with other PVC

solvents and swelling agents?

MATERIALS AND METHODS

Small pieces of PVC were cut from 2-in.- (5.1

cm) diameter, schedule 40 well casing. The overall dimensions of the pieces were approximately

9 × 9 × 1.1 mm (L × W × H), giving a total surface

area of approximately 2.1 cm2 and approximate

weight of 0.12 g. Special care was taken to eliminate contamination from grease or oil during the

cutting procedure. The pieces of PVC were washed

by placing them in a glass beaker containing a 2%

solution of Liquinox detergent and deionized

(Millipore) water for 30 minutes, and stirring them

intermittently with a glass rod for approximately

five minutes. The pieces were then rinsed with

copious amounts of deionized water to ensure

complete removal of the detergent, and were then

spread on paper towels, blotted, and left to air

dry.

All the test solutions were made up by adding

appropriate volumes of the neat analyte (based

on the density of the compound) to deionized

water in volumetric flasks. To prevent any losses

due to biological activity, mercuric chloride was

added to the test solution so that the final concentration was 40 mg/L. A glass-covered magnetic stirring bar was added to each flask, and the

flasks were then filled with deionized water to

within ~1 mL of the top. This left a minimal head

space once the glass stopper was inserted. The

stoppers were then wrapped tightly with parafilm

to reduce vapor loss and the solutions were mixed

for a minimum of three days on magnetic stirring

plates.

After mixing for several days, the solutions

were checked with a magnifying glass to ensure

that there were no undissolved droplets of solvent visible. Once it was determined that the

organic(s) had dissolved, pre-weighed PVC pieces

were added to 22-mL borosilicate glass vials. The

vials were then filled to capacity with the test

solution so there was no headspace, and capped

with Teflon-lined plastic caps. PVC pieces added

to deionized water served as controls. In all the

studies, there were five replicates for each type of

solution (relative solubility) and time. The test

samples were stored in the dark at room temperature. The ratio of surface area of PVC to solution

volume was 0.079 cm2/mL, and the ratio of solution volume to volume of PVC was approximately

310:1.

On the sampling day, the pieces of PVC were

removed from the solution, placed on paper towels, blotted, and allowed to air dry for one minute

before weighing (± 0.0001 g). In all cases, the pieces

of PVC were handled using stainless steel forceps. Immediately after weighing, a Model 935

Barcol Impressor was used to measure the hardness of the PVC. A description on the use of the

Barcol Impressor on rigid plastics can be found in

ASTM Standard Test Method D 2583-87 (ASTM

1988). However, the impressor employed in this

study is made for indenting softer plastics and is

not the model described in the ASTM test method.

This model was selected so that measurements

could be taken during the softening process. The

flexibility was also tested by holding the pieces

with forceps and noting the amount of force necessary to bend the sample.

In all these studies, Analysis of Variance and

Fisher’s Protected Least Significant Difference

(LSD) tests were performed on the Barcol readings and weights of the samples.

Long-term methylene

chloride study

In this study, the PVC test pieces were exposed

to aqueous solutions of methylene chloride with

the following relative solubilities: 0.01, 0.05, 0.1,

0.2, and 0.4. Contact times were 3, 6, 9, 12, 15, and

18 months. The test solutions were changed every

six months. Relative solubilities were based upon

a solubility of 19,000 mg/L. Because Montgommery and Welkom (1990) listed a range of solubility values, we conducted our own solubility tests

and then selected the published value that most

closely agreed with our findings (Parker and

Ranney 1994).

Long-term TCE study

In this study, PVC was exposed to aqueous

solutions of TCE at five relative solubilities: 0.05,

0.10, 0.20, 0.40, and 0.60. Contact times were the

6
same as the previous study, and the test solutions

were changed every six months. An aqueous solubility of 1000 mg/L (Dean 1985) was used.

Studies on aqueous

solutions that contain

several organic solutes

Short-term study

In this study, we exposed PVC to two solutions containing ten PVC solvents and swelling

agents (Table 2). Table 2 lists the aqueous solubility values we used to determine relative solubility. The sum of the relative solubilities of the organic solutes in the solutions was 0.80, the relative

solubility of each analyte varied from 0.02 to 0.15,

and the relative solubility of each analyte varied

from solution A to solution B. Contact times were

8, 24, 72, and 168 hours (seven days).

Mid-term study

The test pieces of PVC were exposed to a solution of either TCE, methylene chloride, or a combination of TCE and methylene chloride. The relative solubilities for methylene chloride were either

0 or 0.4. The relative solubilities for the TCE were

either 0, 0.2, 0.4, or 0.6. Contact times were 2, 7,

14, 28, and 56 days.

First long-term study

PVC test pieces were exposed to two aqueous

solutions of 18 organic chemicals (Table 3) that

we have found to be either solvents or swelling

agents of PVC (App. A, Ranney and Parker 1995).

Table 2. Relative solubility and molarity of PVC solvent and swelling agents used in

the test solutions.

Solubility Mol. wt. Solution A Solution B

Solvent (mg/L) (g/mole) Rel. solubility Molarity Rel. solubility Molarity

bromodichloromethane 4,5001 163.81 0.08 0.022 0.07 0.019

chlorobenzene 5001 112.561 0.04 0.002 0.10 0.004

chloroform 8,0001 119.381 0.12 0.080 0.09 0.060

cyclohexanone 23,0002 98.22 0.09 0.211 0.12 0.281

1,2-dichloroethane 8,6901 98.961 0.15 0.132 0.08 0.070

1,1,2-trichloroethane 4,5001 133.411 0.10 0.034 0.04 0.013

methylene chloride 19,0001 84.931 0.05 0.112 0.02 0.045

methyl isobutyl ketone 17,0001 100.21 0.07 0.119 0.08 0.136

nitrobenzene 1,9001 123.11 0.08 0.012 0.15 0.023

m-nitrotoluene 5001 137.131 0.02 0.001 0.05 0.002

Total 0.725 0.653

1 Value taken from Montgommery and Welkom (1990).

2 Value taken from Montgommery (1991).

Table 3. Listing of 18 PVC solvent

and swelling agents used in studies and their aqueous solubilities.

Solubility

(mg/L)

benzonitrile 2,0003

bromochloromethane 16,6912

bromodichloromethane 4,5001

bromoform 3,0101

chlorobenzene 5001

chloroform 8,0001

cyclohexanone 23,0002

dibromochloromethane 4,0001

1,2-dibromoethane 4,3003

1,2-dichloroethane 8,6901

cis-1,2-dichloroethylene 7,7003

trans-1,2-dichloroethylene 6,3003

methylene chloride 19,0001

methyl isobutyl ketone 17,0001

nitrobenzene 1,9001

m-nitrotoluene 5001

o-nitrotoluene 6002

1,1,2-trichloroethane 4,5001

1 Value taken from Montgommery and

Welkom (1990).

2 Value taken from Montgommery (1991).

3 Value taken from Dean (1985).

The solubilities of these 18 chemicals are also

given in Table 3. The protocol for this experiment differed from our other experiments in

that smaller test pieces (~9 × 9 × 0.9 mm) that

were left over from our previous studies (Parker

and Ranney 1994, 1995) were used. These dimensions made the total surface area 1.9 cm2,

7
RESULTS AND DISCUSSION

Long-term methylene

chloride studies

Table 4 gives the hardness readings and percent weight gain data for samples exposed to aqueous solutions with relative solubilities of 0.01, 0.05,

0.10, 0.20, and 0.40. After 18 months’ exposure,

there was no significant change in the hardness

readings of samples that were exposed to aqueous solutions of methylene chloride with relative

solubilities that were less than 0.1. With one exTable 4a. Hardness (Barcol) readings of PVC exposed to methylene chloride solutions.

Relative Contact time, months

solubility 3 6 9 12 15 18

0.00 71 74 78 77 78 78

0.00 71 73 79 77 78 80

0.00 72 73 78 78 76 79

0.00 73 74 76 76 78 80

0.00 73 74 80 78 78 78

 

X 72.0 73.6 78.2 77.2 77.6 79.0

0.01 73 74 78 77 78 79

0.01 72 74 79 79 77 79

0.01 71 72 80 76 78 80

0.01 70 73 77 78 79 79

0.01 74 73 78 77 77 78

 

X 72.0 73.2 78.4 77.4 77.8 79.0

0.05 72 74 76 77 76 77

0.05 72 74 78 78 79 80

0.05 71 73 79 76 78 79

0.05 70 73 76 76 76 78

0.05 70 72 77 78 77 78

 

X 71.0 73.2 77.2 77.0 77.2 78.4

0.10 71 74 76 76 76 77

0.10 72 74 79 74 78 76

0.10 71 74 77 77 75 78

0.10 72 73 78 76 76 77

0.10 71 73 80 75 74 75

 

X 71.4 73.6 78.0 75.6* 75.8 * 76.6*

0.20 71 73 77 75 73 77

0.20 71 74 76 76 74 76

0.20 70 72 77 75 73 74

0.20 71 73 76 73 74 74

0.20 72 73 74 77 73 73

 

X 71.0 73.0 76.0* 75.2* 73.4* 74.8*

0.40 69 72 74 74 73 71

0.40 70 72 77 74 72 72

0.40 71 71 76 75 71 74

0.40 70 72 76 75 71 74

0.40 69 73 76 73 72 73

 

X 69.8* 72.0* 75.8* 74.2* 71.8* 72.8*

*Significantly different from controls.

the approximate weight 0.09 g, the ratio of surface area to solution volume 0.076, and the solution volume to PVC volume approximately 386:1.

Another difference with this experiment was that

the Teflon-lined caps were lined with aluminum

foil to prevent any losses due to sorption by caps,

and as a result mercuric chloride was not added

to the test solutions because it would degrade the

aluminum foil. The relative solubility of each of

the analytes was either 0.010 or 0.020. The sum of

the relative solubilities of the organic solutes was

either 0.18 or 0.36, respectively. Samples were

taken after 20 and 40 weeks’ contact.

Second long-term study

In this study, pieces of PVC were

exposed to four aqueous solutions

of the same eighteen PVC solvents

and swelling agents (Table 3). This

time the relative solubility of the

analytes was either 0.001, 0.005,

0.010, or 0.020. This makes the sum

of the relative solubilities of the organic solutes either 0.018, 0.09, 0.18,

or 0.36, respectively. Samples were

taken after 3, 6, 9, 12, 15, and 18

months, and the test solutions were

changed every six months.

Studies on aqueous solutions

containing organics that are

miscible in water

Long-term acetone study

In this study, pieces of PVC were

exposed to aqueous solutions that

contained the following percent acetone: 0.5%, 1%, 5%, 10%, and 20%

(w/v). Contact times were again 3,

6, 9, 12, 15, and 18 months. The test

solutions were changed every six

months.

Short-term study with acetone

and methylene chloride

PVC was exposed to different solutions containing methylene chloride and acetone. The relative solubility of the methylene chloride was

0.4, while the concentration of acetone in the solution was either 0%,

0.5%, 1.0%, 5.0%, 10%, or 20% (w/

v). Contact times were 2, 4, 7, 14,

and 21 days.

8
Hardness readings of samples that were exposed to aqueous solutions with a relative solubility of 0.1 were significantly lower than the controls after one year. Samples exposed to solutions

with higher relative solubilities (0.2, 0.4) softened

earlier in the study. However, none of these

samples were pliable. Presumably

these materials become slightly softened but never become pliable or

rubbery. This conclusion is supported by the fact that there does

not appear to be much additional

weight gain after the first three to

six months for any of the samples

exposed to the solutions with relative solubilities of 0.10 and 0.20 and

after 12 months in samples exposed

to solutions with a relative solubility of 0.40. This may mean that the

test pieces have reached equilibrium

with the test solution, and thus we

do not expect any further changes.

We also observed that softening

occurred more slowly for the samples exposed to solutions with relative solubilities of 0.10 and 0.20 than

what we observed previously (Parker and Ranney 1994). This is most

likely a result of the pieces being approximately 20% thicker in this

study.

Long-term TCE studies

Table 5 gives the results of exposure to aqueous solutions of TCE

with relative solubilities of 0.05, 0.1,

0.2, 0.4, and 0.6. The samples exposed

to the solutions with relative solubilities of 0.6 and 0.4 had significant

changes in their hardness readings;

however, they did not become pliable. It should be noted that TCE

has never before been shown to be

active at such a low relative solubility, and that it took more than a year

before significant changes in hardness were detected in those samples.

There were also significant changes

in the weights of the samples exposed to the solutions with relative

solubilities of 0.4 and 0.6.

It is clear from this and the previous study that small but measurable changes occur in the weight

Table 4b. Percent weight gain of PVC exposed to methylene chloride solutions.

 Relative Contact time, months

solubility 3 6 9 12 15 18

0.00 0.13 0.24 0.26 0.20 0.33 0.17

0.00 0.26 0.28 0.17 0.09 0.00 0.32

0.00 0.15 0.35 0.35 0.28 0.25 0.19

0.00 0.17 0.35 0.26 0.16 0.27 0.16

0.00 0.25 0.35 0.27 0.14 0.20 0.26

 

X 0.19a 0.31a,b 0.26a 0.17a 0.21a 0.22a

S.D. 0.06 0.05 0.07 0.07 0.13 0.07

0.01 0.35 0.18 0.26 0.26 0.35 0.17

0.01 0.17 0.26 0.35 0.34 0.17 0.24

0.01 0.25 0.27 0.41 0.36 0.16 0.21

0.01 0.34 0.36 0.35 0.27 0.08 0.18

0.01 0.41 0.42 0.42 0.35 0.34 0.08

 

X 0.30a 0.30a 0.36a 0.32a,b 0.22a 0.18a

S.D. 0.09 0.09 0.06 0.05 0.12 0.06

0.05 0.44 0.25 0.40 0.34 0.27 0.35

0.05 0.34 0.33 0.40 0.34 0.33 0.50

0.05 0.34 0.44 0.36 0.31 0.24 0.17

0.05 0.34 0.44 0.33 0.61 0.33 0.41

0.05 0.24 0.25 0.34 0.34 0.25 0.28

 

X 0.34a 0.34a,b 0.37a 0.39b,c 0.28a 0.34a,b

S.D. 0.07 0.09 0.03 0.12 0.04 0.13

0.10 0.33 0.41 0.62 0.53 0.72 0.43

0.10 0.37 0.41 0.55 0.42 0.52 0.64

0.10 0.43 0.62 0.53 0.50 0.59 0.52

0.10 0.26 0.69 0.64 0.54 0.60 0.58

0.10 0.32 0.37 0.69 0.69 0.51 0.44

 

X 0.34a 0.50b 0.60b 0.54c,d 0.59b 0.52b,c

S.D. 0.06 0.14 0.06 0.10 0.08 0.09

0.20 0.75 1.01 0.74 0.74 0.82 0.60

0.20 0.72 0.64 1.11 0.59 0.87 0.67

0.20 0.87 0.76 0.66 0.61 0.92 0.58

0.20 0.61 0.60 1.00 0.81 1.05 0.61

0.20 0.65 0.75 0.83 0.85 0.84 0.59

 

X 0.72b 0.75c 0.87c 0.72d 0.90c 0.61c

S.D. 0.10 0.16 0.19 0.12 0.09 0.03

0.40 1.33 1.39 1.69 2.38 2.37 2.18

0.40 1.51 0.79 1.91 2.15 2.13 2.01

0.40 1.65 1.01 1.66 1.94 1.67 2.20

0.40 1.99 1.25 1.36 2.26 2.50 1.41

0.40 1.43 1.39 1.66 1.67 2.01 1.97

 

X 1.58c 1.17d 1.66d 2.08e 2.14d 1.95d

S.D. 0.26 0.26 0.19 0.28 0.32 0.32

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly different.

ception, there was also no significant change in

the weight change data. These results support

our hypothesis that softening will not be detected

at activities where diffusion is reported to be slowest (Fickian), i.e., for PVC solvents and better swelling agents less than 0.1 (Vonk 1985, 1986).

9
Table 5a. Hardness (Barcol) readings of PCE exposed to TCE

solutions.

Relative Contact time, months

solubility 3 6 9 12 15 18

0.00 70 74 77 76 80 80

0.00 72 73 78 77 78 77

0.00 71 74 80 78 79 78

0.00 71 72 77 74 78 79

0.00 71 71 77 75 78 79

 

X 71.0 72.8 77.8 76.0 78.6 78.6

0.05 70 73 74 76 78 79

0.05 71 74 75 75 79 78

0.05 71 72 77 75 78 79

0.05 71 72 78 78 79 78

0.05 72 73 79 74 78 78

 

X 71.0 72.8 76.6 75.6 78.4 78.4

0.10 70 74 77 76 79 79

0.10 71 74 76 74 76 80

0.10 70 72 73 77 77 78

0.10 71 72 80 78 78 78

0.10 69 73 80 77 78 78

 

X 70.2 73.0 77.2 76.4 77.6 78.6

0.20 71 72 75 78 77 77

0.20 71 73 76 74 78 77

0.20 69 73 74 75 79 79

0.20 71 74 79 75 76 79

0.20 72 72 75 74 77 78

 

X 70.8 72.8 75.8 75.2 77.4 78.0

0.40 71 72 77 74 77 76

0.40 71 73 75 76 76 78

0.40 71 74 74 75 76 76

0.40 69 72 78 76 74 76

0.40 70 73 73 74 74 78

 

X 70.4 72.8 75.4 75.0 75.4* 76.8*

0.60 68 71 75 73 75 76

0.60 70 70 73 72 75 75

0.60 70 71 74 73 74 77

0.60 68 70 75 74 75 75

0.60 69 72 72 75 73 77

 

X 69.0* 70.8* 73.8* 73.4* 74.4* 76.0*

*Significantly different from controls.

and hardness of samples exposed to aqueous solutions of PVC solvents and swelling agents, and

that these changes occur at lower relative solubilities than was predicted by Berens.

Studies on aqueous

solutions that contain

several organic solutes

Short-term study

In this study, we exposed PVC to two solutions containing ten organic chemicals that were

either a PVC solvent or swelling agent (Table 2).

The ten organic chemicals were selected based on

published χ values (Berens 1985, Vonk 1985) and

on our own tests, where small pieces of PVC casing were subjected to neat organic chemicals (App.

A, Ranney and Parker 1995). The sum of the relative solubilities of the organic chemicals in the

two solutions was the same, 0.80. However, the

relative solubility of each analyte varied from 0.02

to 0.15 and the relative solubility of each analyte

varied from solution A to solution B.

Both solutions caused rapid (within one day)

10
Table 5b. Percent weight gain of PVC exposed to TCE solutions.

Relative Contact time, months

solubility 3 6 9 12 15 18

0.00 0.26 0.00 0.26 0.17 0.27 0.17

0.00 0.23 0.25 0.25 0.21 0.17 0.25

0.00 0.25 0.25 0.33 0.33 0.34 0.09

0.00 0.17 0.39 0.08 0.25 0.16 0.18

0.00 0.26 0.35 0.33 0.16 0.08 0.33

 

X 0.23a 0.25a 0.25a 0.22a 0.20a 0.20a

S.D. 0.04 0.15 0.10 0.07 0.10 0.09

0.05 0.25 0.25 0.25 0.17 0.36 0.16

0.05 0.32 0.32 0.26 0.34 0.26 0.19

0.05 0.08 0.42 0.17 0.26 0.27 0.16

0.05 0.18 0.33 0.17 0.33 0.26 0.34

0.05 0.20 0.26 0.27 0.25 0.42 0.24

 

X 0.21a 0.32a 0.22a 0.27a,b 0.31b 0.22a

S.D. 0.09 0.07 0.05 0.07 0.07 0.07

0.10 0.26 0.29 0.25 0.25 0.33 0.09

0.10 0.25 0.16 0.17 0.18 0.26 0.20

0.10 0.18 0.29 0.34 0.27 0.35 0.16

0.10 0.25 0.39 0.51 0.40 0.17 0.34

0.10 0.18 0.33 0.18 0.17 0.17 0.34

 

X 0.22a 0.29a 0.29a,b 0.25a,b 0.26a,b 0.23a

S.D. 0.04 0.08 0.14 0.09 0.08 0.11

0.20 0.34 0.41 0.00 0.35 0.34 0.28

0.20 0.35 0.24 0.27 0.24 0.42 0.25

0.20 0.35 0.34 0.34 0.41 0.25 0.27

0.20 0.26 0.25 0.36 0.34 0.35 0.34

0.20 0.34 0.25 0.17 0.41 0.18 0.34

 

X 0.33b 0.30a 0.23a 0.35b 0.31a,b 0.30a,b

S.D. 0.04 0.08 0.15 0.07 0.09 0.04

0.40 0.33 0.30 0.43 0.40 0.53 0.57

0.40 0.33 0.41 0.42 0.44 0.44 0.33

0.40 0.41 0.41 0.41 0.52 0.40 0.34

0.40 0.40 0.34 0.43 0.47 0.33 0.25

0.40 0.32 0.27 0.29 0.59 0.54 0.34

 

X 0.36b 0.35a 0.40b 0.49c 0.45c 0.37b

S.D. 0.04 0.07 0.06 0.07 0.09 0.12

0.60 0.75 0.65 0.66 0.94 0.86 0.83

0.60 0.57 0.72 0.88 0.90 0.75 0.72

0.60 0.61 0.49 0.65 0.90 0.78 0.55

0.60 0.60 0.43 0.74 0.78 0.82 0.63

0.60 0.66 0.68 0.75 0.78 0.74 0.53

 

X 0.64c 0.60b 0.74c 0.86d 0.79d 0.65c

S.D. 0.07 0.12 0.09 0.07 0.05 0.13

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly different.

changes in the hardness readings of PVC, although

none of these samples actually became pliable

(Table 6). The ability of the solution to soften PVC

appears to be correlated with the sum of the relative solubilities of the organic solutes, since the

behavior of the two test solutions was between

that of a methylene chloride solution (i.e., a solution with a PVC solvent) with a relative solubility

of 0.8 and a TCE solution (a solution with a swelling agent) with a relative solubility of 0.8. There

does not appear to be a synergistic effect with this

solution, i.e., the ability to soften PVC does not

appear to be enhanced beyond a simple cumulative effect.

However, the data (both weight change and

hardness values) also show the limitations of us11
ing this approach (i.e., summing the relative

solubilities), since solution A appears to be more

aggressive than solution B (Table 6), even though

they both have the same cumulative relative solubilities. The reason solution A was more aggressive can be explained by the fact that the sum of

the mole fractions of the organic solutes was

greater in solution A (Table 2). In addition, the

sum of the mole fractions of the four most aggressive chemicals (cyclohexanone, 1,2-dichloroethane, methylene chloride, and nitrobenzene)

(App. A, Ranney and Parker 1995) in the test solution was also greater.

Mid-term study

Test pieces of PVC that were exposed to a TCE

solution with a relative solubility of 0.2 were not

softened during the course of this study (56 days)

(Table 7). However, samples exposed to a solution containing TCE with a relative solubility of

0.2 and methylene chloride at a relative solubility

of 0.4 were softened after seven days. Again, none

of these samples were pliable. This test solution

was less aggressive than we (Parker and Ranney

1994) found a methylene chloride solution with a

relative solubility of 0.6 (i.e., a solution containing a PVC solvent) to be, but more aggressive

than we (Parker and Ranney 1994) found a TCE

solution with the same relative solubility (0.6) to

be. Thus, there does not appear to be an enhanced

or synergistic effect of the organic solutes in this

test solution, and taking the sum of the relative

solubilities was useful in roughly predicting the

ability of this test solution to soften PVC.

First long-term study

PVC pieces were exposed to two aqueous solutions that contained 18 organic chemicals that were

either a PVC solvent or swelling agent (Table 8).

In these solutions, the relative solubility of each

chemical was either 0.01 or 0.02, and the sums of

the relative solubilities of all the organic solutes

in the test solutions were 0.18 and 0.36, respectively. After 40 weeks’ exposure, the test pieces

exposed to the test solution with the higher total

relative solubility (0.36) had significant changes

in hardness readings (but were not pliable), while

those exposed to the solution with the lower total

relative solubility (0.18) did not. However, there

was a significant increase in the weight of the test

pieces exposed to this test solution when compared with the controls.

Table 6b. Percent weight gain of PVC exposed to

aqueous solutions of several organic solutes (shortterm study).

Contact time, hours

Treatment 8 24 72 168

control 0.00 0.00 0.23 0.24

control 0.08 0.08 0.08 0.40

control 0.15 0.25 0.08 0.43

control 0.09 0.16 0.25 0.27

control 0.08 0.08 0.17 0.42

 

X 0.08a 0.11a 0.16a 0.35a

S.D. 0.05 0.09 0.08 0.09

solution A 1.23 2.35 3.36 5.58

solution A 1.07 2.57 3.58 5.29

solution A 1.03 2.48 3.90 5.29

solution A 1.08 2.34 3.61 5.00

solution A 1.07 2.36 3.70 5.67

 

X 1.10c 2.42c 3.63c 5.37c

S.D. 0.08 0.10 0.19 0.27

solution B 0.65 1.65 2.55 3.44

solution B 0.79 1.59 2.27 3.54

solution B 0.82 1.58 2.62 3.74

solution B 0.73 1.73 2.36 3.53

solution B 0.78 1.42 2.60 4.20

 

X 0.75b 1.59b 2.48b 3.69b

S.D. 0.07 0.11 0.16 0.31

S.D. = standard deviation

Values with different letters, taken at the same time, are

sigificantly different.

Table 6a. Hardness (Barcol) readings of PVC exposed

to aqueous solutions of several organic solutes (shortterm study).

Contact time, hours

Treatment 8 24 72 168

control 73 77 74 74

control 69 74 71 72

control 67 76 70 69

control 71 77 74 72

control 68 75 70 71

 

X 69.6a 75.8a 71.8a 71.6a

solution A 63 69 58 60

solution A 64 67 62 64

solution A 65 72 62 62

solution A 69 70 65 64

solution A 64 67 64 60

 

X 65.0b 69.0b 62.2b 62.0c

solution B 67 70 63 68

solution B 69 71 68 64

solution B 71 71 64 66

solution B 65 66 69 66

solution B 69 68 64 65

 

X 68.2a,b 69.2b 65.6b 65.8b

Values with different letters, taken at the same time, are significantly different.

12
Table 7a. Hardness (Barcol) readings of PVC exposed to aqueous solutions of methylene chloride

(MC) and TCE.

 Relative

 solubility Contact time, days

MC, TCE 2 7 14 28 56

control 75 70 73 79 76

control 73 71 74 76 74

control 74 73 75 78 75

control 73 74 72 77 75

control 76 75 73 76 77

 

X 74.2 72.6 73.4 77.2 75.4

0, 0.2 72 73 74 78 76

0, 0.2 74 75 73 77 75

0, 0.2 75 74 71 72 74

0, 0.2 74 72 70 76 75

0, 0.2 73 71 72 78 74

 

X 73.6 73.0 72.0 76.2 74.8

0, 0.4 74 69 74 74 76

0, 0.4 73 70 74 78 75

0, 0.4 74 73 74 78 75

0, 0.4 74 71 73 73 73

0, 0.4 73 72 70 78 75

 

X 73.6 71.0 73.0 76.2 74.8

0, 0.6 73 73 72 77 74

0, 0.6 75 71 73 75 75

0, 0.6 76 72 68 79 74

0, 0.6 74 68 70 78 73

0, 0.6 75 71 73 77 74

 

X 74.6 71.0 71.2 77.2 74.0 *

0.4, 0 76 68 75 74 74

0.4, 0 72 72 70 78 73

0.4, 0 74 73 71 76 72

0.4, 0 73 71 69 78 73

0.4, 0 75 71 72 73 72

 

X 74.0 71.0 71.4 75.8 72.8*

0.4, 0.2 73 66 70 74 72

0.4, 0.2 76 67 69 73 70

0.4, 0.2 74 66 72 75 72

0.4, 0.2 75 66 70 72 71

0.4, 0.2 72 69 72 74 72

 

X 74.0 66.8* 70.6* 73.6* 71.4*

0.4, 0.4 73 70 70 73 70

0.4, 0.4 71 71 68 71 70

0.4, 0.4 74 68 68 74 68

0.4, 0.4 73 65 71 75 70

0.4, 0.4 74 66 69 70 69

 

X 73.0 68.0* 69.2* 72.6* 69.4*

0.4, 0.6 66 63 60 67 62

0.4, 0.6 70 64 63 63 62

0.4, 0.6 70 65 65 70 65

0.4, 0.6 68 65 64 64 61

0.4, 0.6 71 67 61 62 63

 

X 69.0* 64.8* 62.6* 65.2* 62.6*

*Significantly different from controls.

Table 7b. Percent weight gain of PVC exposed to

aqueous solutions of methylene chloride (MC) and

TCE.

 Relative

solubility Contact time, days

MC, TCE 2 7 14 28 56

control 0.08 0.16 0.16 0.00 0.25

control 0.08 0.08 0.08 0.16 0.17

control 0.40 0.17 0.08 0.17 0.09

control 0.00 0.17 0.09 0.25 0.16

control 0.09 0.16 0.00 0.16 0.16

 

X 0.13a 0.15a 0.08a 0.15a 0.17a

S.D. 0.15 0.04 0.06 0.09 0.06

0, 0.2 0.08 0.25 0.24 0.24 0.27

0, 0.2 0.08 0.16 0.25 0.24 0.23

0, 0.2 0.00 0.23 0.08 0.08 0.25

0, 0.2 0.00 0.26 0.24 0.24 0.24

0, 0.2 0.00 0.16 0.16 0.16 0.18

 

X 0.03a 0.21a 0.19a 0.19a 0.23a

S.D. 0.04 0.05 0.08 0.07 0.03

0, 0.4 0.16 0.24 0.24 0.24 0.32

0, 0.4 0.08 0.24 0.26 0.31 0.44

0, 0.4 0.18 0.17 0.24 0.17 0.41

0, 0.4 0.08 0.26 0.23 0.34 0.28

0, 0.4 0.08 0.24 0.24 0.25 0.32

 

X 0.12a 0.23a 0.24a 0.26a 0.35a

S.D. 0.05 0.04 0.01 0.07 0.07

0, 0.6 0.16 0.40 0.44 0.41 0.32

0, 0.6 0.17 0.47 0.46 0.49 0.50

0, 0.6 0.16 0.34 0.49 0.46 0.32

0, 0.6 0.17 0.25 0.37 0.48 0.32

0, 0.6 0.00 0.33 0.48 0.42 0.49

 

X 0.13a 0.36a,b 0.45a 0.45a 0.39a

S.D. 0.07 0.08 0.05 0.04 0.10

0.4, 0 0.37 0.59 0.81 1.12 1.26

0.4, 0 0.33 0.74 0.84 0.93 1.42

0.4, 0 0.24 0.73 0.99 1.06 1.18

0.4, 0 0.43 0.56 0.91 1.15 1.23

0.4, 0 0.33 0.55 0.89 1.29 1.00

 

X 0.34b 0.63b 0.89b 1.11b 1.22b

S.D. 0.07 0.09 0.07 0.13 0.15

0.4, 0.2 0.56 0.83 1.31 1.03 1.55

0.4, 0.2 0.56 1.01 1.09 1.42 1.90

0.4, 0.2 0.49 1.05 1.26 1.71 1.69

0.4, 0.2 0.51 1.02 1.22 1.53 1.62

0.4, 0.2 0.55 1.12 1.23 1.89 1.72

 

X 0.53c 1.01c 1.22b 1.52b 1.70c

S.D. 0.03 0.11 0.08 0.32 0.13

0.4, 0.4 1.04 1.91 2.11 1.79 3.19

0.4, 0.4 0.89 1.80 2.18 2.63 2.80

0.4, 0.4 0.97 1.80 1.86 3.36 2.54

0.4, 0.4 0.83 1.85 2.09 2.98 2.22

0.4, 0.4 0.49 1.74 2.21 3.12 2.38

 

X 0.84d 1.82d 2.09c 2.78d 2.63d

S.D. 0.21 0.07 0.14 0.61 0.38

0.4, 0.6 2.72 5.02 6.88 4.49 5.78

0.4, 0.6 2.35 3.80 5.05 5.07 5.48

0.4, 0.6 2.50 5.06 5.24 5.24 5.21

0.4, 0.6 2.18 5.37 4.92 5.81 5.48

0.4, 0.6 2.36 4.05 5.67 5.97 5.25

 

X 2.42e 4.66e 5.55d 5.32d 5.44e

S.D. 0.20 0.69 0.80 0.60 0.23

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly different.

13
Second long-term study

Table 9 gives the results of exposing PVC to a

test solution containing the same eighteen organic

solutes at four different relative solubilities for up

to 18 months. The relative solubility of each of the

organic solutes was either 0.001, 0.005, 0.010, or

0.020. Thus, the sums of the relative solubilities of

the organic solutes in these solutions were 0.018,

0.090, 0.18, and 0.36, respectively.

The test results show that when the sum of the

relative solubilities of the organic solutes in the

test solutions was less than 0.10, softening did not

occur. Test pieces that were exposed to organic

solutes with relative solubilities of 0.010 and 0.020

(or cumulative relative solubilities of 0.18 and 0.36)

had hardness readings that were significantly

lower than the controls but were not rubbery.

These results agree with our previous findings

for methylene chloride, i.e., softening does not

occur when the relative solubility of the analyte

in the test solution is less than 0.1. The weight

gain data also support these conclusions. Significant changes in weight were found in samples

exposed to solutions with relative solubilities of

0.01 and 0.02. Generally, there was not significant

change in the weights of samples exposed to solutions with lower relative solubilities.

Table 9a. Hardness (Barcol) readings of PVC exposed to aqueous

solutions of several organic solutes (second long-term study).

Relative Contact time, months

solubility 3 6 9 12 15 18

control 71 74 77 79 79 79

control 72 75 76 78 77 80

control 73 73 75 76 77 78

control 72 74 79 77 78 78

control 73 75 77 77 79 78

 

X 72.2 74.2 76.8 77.4 78.0 78.6

0.001 71 74 77 78 77 78

0.001 73 75 76 77 79 78

0.001 71 74 75 76 80 79

0.001 72 75 75 77 78 77

0.001 73 73 76 77 78 78

 

X 72.0 74.2 75.8 77.0 78.4 78.0

0.005 71 74 77 75 77 79

0.005 72 75 73 77 78 78

0.005 73 73 74 78 79 78

0.005 72 74 75 76 77 77

0.005 72 75 77 77 76 79

 

X 72.0 74.2 75.2 76.6 77.4 78.2

0.01 71 74 75 76 77 77

0.01 71 74 75 76 78 77

0.01 72 74 73 78 78 78

0.01 72 75 75 77 76 77

0.01 71 73 76 75 77 75

 

X 71.4 74.0 74.8* 76.4 77.2 76.8*

Table 8. Hardness (Barcol) readings and percent

weight gain of PVC exposed to aqueous solutions

of several organic solutes (first long-term study).

Relative 20 week 40 week

solubility Barcol % ∆ weight Barcol % ∆ weight

control 78 0.40 76 0.41

control 77 0.37 74 0.47

control 74 0.53 76 0.40

control 76 0.41 74 0.41

control 77 0.36 76 0.37

 

X 76.4a 0.41a 75.2a 0.41a

S.D. 0.07 0.04

0.01 74 0.59 75 0.54

0.01 74 0.50 74 0.64

0.01 76 0.61 75 0.70

0.01 76 0.56 74 0.36

0.01 77 0.47 73 0.52

 

X 75.4a 0.55b 74.2a,b 0.55b

S.D. 0.06 0.13

0.02 76 0.92 72 0.93

0.02 74 0.65 75 0.99

0.02 77 0.91 74 0.93

0.02 76 0.75 73 0.80

0.02 72 0.68 72 0.92

 

X 75.0a 0.78c 73.2b 0.91c

S.D. 0.13 0.07

S.D. = standard deviation

Values with different letters, taken at the same time, are

significantly different.

14
Table 9a (cont’d).

Relative Contact time, months

solubility 3 6 9 12 15 18

0.02 72 74 74 73 76 75

0.02 70 73 74 75 75 76

0.02 71 74 75 76 77 74

0.02 72 73 75 76 77 76

0.02 72 73 73 75 75 74

 

X 71.4 73.4 74.2* 75.0* 76.0* 75.0*

*Significantly different from controls.

Table 9b. Percent weight gain of PVC exposed to aqueous solutions of several organic solutes (second long-term study).

Relative Contact time, months

solubility 3 6 9 12 15 18

control 0.17 0.32 0.27 0.08 0.24 0.24

control 0.13 0.25 0.17 0.35 0.25 0.09

control 0.16 0.17 0.09 0.41 0.17 0.13

control 0.25 0.26 0.09 0.34 0.20 0.17

control 0.17 0.34 0.16 0.16 0.17 0.26

 

X 0.18a 0.27a 0.16a 0.27a 0.21a 0.18a

S.D. 0.04 0.07 0.07 0.14 0.04 0.07

0.001 0.17 0.25 0.13 0.26 0.18 0.18

0.001 0.26 0.17 0.17 0.24 0.33 0.27

0.001 0.16 0.33 0.17 0.34 0.25 0.16

0.001 0.17 0.26 0.32 0.24 0.25 0.38

0.001 0.27 0.34 0.17 0.33 0.20 0.07

 

X 0.21a 0.27a 0.19a 0.28a 0.24a 0.21a

S.D. 0.05 0.07 0.07 0.05 0.06 0.12

0.005 0.34 0.33 0.44 0.35 0.41 0.27

0.005 0.34 0.62 0.17 0.17 0.40 0.16

0.005 0.33 0.25 0.25 0.25 0.26 0.18

0.005 0.33 0.25 0.17 0.34 0.34 0.17

0.005 0.45 0.42 0.14 0.17 0.40 0.33

 

X 0.36b 0.37a,b 0.23a,b 0.26a 0.36b 0.22a

S.D. 0.05 0.15 0.12 0.09 0.06 0.08

0.01 0.33 0.57 0.46 0.41 0.51 0.42

0.01 0.33 0.51 0.31 0.53 0.52 0.42

0.01 0.24 0.33 0.27 0.71 0.59 0.47

0.01 0.28 0.52 0.43 0.62 0.62 0.33

0.01 0.32 0.43 0.20 0.41 0.52 0.21

 

X 0.30b 0.47b 0.33b 0.54b 0.55c 0.37b

S.D. 0.04 0.09 0.11 0.13 0.05 0.10

0.02 0.57 0.64 0.66 0.84 0.73 0.88

0.02 0.57 0.75 0.67 0.82 0.87 0.70

0.02 0.35 0.63 0.68 0.92 0.68 1.01

0.02 0.59 0.58 0.44 0.80 0.74 0.63

0.02 0.54 0.73 0.64 0.91 0.84 0.78

 

X 0.52c 0.67c 0.62c 0.86c 0.77d 0.80c

S.D. 0.10 0.07 0.10 0.05 0.08 0.15

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly different.

15
Table 10a. Hardness (Barcol) readings of PVC exposed to acetone solutions.

Contact time, months

Concentration (%) 3 6 9 12 15 18

control 73 74 80 77 79 81

control 71 74 79 76 77 78

control 72 73 77 77 78 78

control 71 72 78 78 78 79

control 72 74 77 79 78 80

 

X 71.8 73.4 78.2 77.4 78.0 79.2

0.5 71 74 78 77 77 78

0.5 72 75 80 78 78 76

0.5 72 73 77 76 78 79

0.5 71 73 79 77 77 79

0.5 71 72 76 77 79 80

 

X 71.4 73.4 78.0 77.0 77.8 78.4

1.0 71 73 78 77 78 78

1.0 71 74 77 76 79 79

1.0 70 74 78 78 77 79

1.0 71 72 78 76 77 78

1.0 72 73 78 77 78 78

 

X 71.0 73.2 77.8 76.8 77.8 78.4

5.0 71 73 79 76 76 77

5.0 72 72 78 76 76 78

5.0 70 72 79 78 76 77

5.0 71 73 78 77 77 76

5.0 71 74 74 76 75 76

 

X 71.0 72.8 77.6 76.6 76.0* 76.8*

10.0 71 71 76 76 75 75

10.0 71 73 75 74 74 75

10.0 72 72 74 74 75 77

10.0 70 71 76 73 74 76

10.0 71 73 75 75 73 76

 

X 71.0 72.0* 75.2* 74.4* 74.2* 75.8*

20.0 69 71 69 74 72 72

20.0 71 73 73 72 69 71

20.0 70 72 73 73 72 71

20.0 69 71 71 70 69 70

20.0 71 72 72 71 68 70

 

X 70.0* 71.8* 71.6* 72.0* 70.0* 70.8*

*Significantly different from controls.

The results from the first long-term study compare well with these findings. In the previous

experiment the Teflon-lined caps were lined with

aluminum foil to prevent substantial losses of the

organic solutes due to sorption by the Teflon liners. In this experiment there was no aluminum

liner. Thus, we concluded that the Teflon does

not appear to substantially alter the ability of the

test solutions to affect PVC.

Studies on aqueous solutions

containing organics that are

miscible in water

Long-term acetone study

Table 10 shows the results of long-term (18

months) exposure to 0.5%, 1.0%, 5.0%, 10%, and

20% solutions of acetone. By the end of the study,

the 5.0%, 10%, and 20% solutions were able to

16
Table 10b. Percent weight gain of PVC exposed to acetone solutions.

Contact time, months

Concentration (%) 3 6 9 12 15 18

0.0 0.17 0.26 0.28 0.36 0.24 0.17

0.0 0.13 0.18 0.27 0.25 0.26 0.09

0.0 0.17 0.24 0.22 0.17 0.09 0.17

0.0 0.17 0.18 0.26 0.16 0.25 0.08

0.0 0.16 0.08 0.26 0.33 0.35 0.14

 

X 0.16a 0.19a 0.26a 0.25a 0.24a 0.13a

S.D. 0.02 0.07 0.02 0.09 0.09 0.04

0.5 0.17 0.27 0.33 0.31 0.34 0.34

0.5 0.13 0.34 0.25 0.27 0.25 0.22

0.5 0.13 0.24 0.24 0.40 0.26 0.08

0.5 0.17 0.24 0.17 0.28 0.25 0.25

0.5 0.17 0.25 0.27 0.35 0.31 0.33

 

X 0.15a 0.27a 0.25a 0.32a,b 0.28a 0.24a,b

S.D. 0.02 0.04 0.06 0.06 0.04 0.10

1.0 0.26 0.32 0.33 0.33 0.26 0.27

1.0 0.15 0.25 0.33 0.26 0.27 0.18

1.0 0.27 0.25 0.27 0.26 0.24 0.27

1.0 0.26 0.25 0.25 0.27 0.25 0.20

1.0 0.27 0.25 0.24 0.26 0.25 0.18

 

X 0.24b 0.26a 0.28a 0.28a 0.25a 0.22a,b

S.D. 0.05 0.03 0.04 0.03 0.01 0.05

5.0 0.18 0.45 0.42 0.36 0.35 0.33

5.0 0.16 0.26 0.33 0.44 0.32 0.32

5.0 0.25 0.33 0.41 0.40 0.26 0.35

5.0 0.27 0.25 0.27 0.49 0.25 0.34

5.0 0.21 0.17 0.43 0.44 0.34 0.25

 

X 0.21b 0.29a 0.37b 0.43b,c 0.30a 0.32b

S.D. 0.04 0.10 0.07 0.05 0.05 0.04

10 0.33 0.50 0.49 0.49 0.51 0.52

10 0.36 0.36 0.66 0.45 0.44 0.45

10 0.26 0.49 0.64 0.70 0.42 0.51

10 0.25 0.60 0.46 0.45 0.50 0.53

10 0.34 0.46 0.40 0.43 0.27 0.40

 

X 0.31c 0.48b 0.53c 0.50c 0.43b 0.48c

S.D. 0.05 0.09 0.11 0.11 0.10 0.06

20 1.08 1.39 1.68 1.95 1.90 1.86

20 1.10 1.45 1.68 1.66 1.95 1.98

20 1.16 1.14 1.69 1.45 1.75 1.95

20 1.10 1.37 1.64 1.81 1.52 2.03

20 1.07 1.25 1.77 1.81 1.86 1.52

 

X 1.10d 1.32c 1.69d 1.74d 1.80c 1.87d

S.D. 0.04 0.12 0.05 0.19 0.17 0.21

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly different.

cause significant changes in the hardness readings and weight gain data.

Study with acetone and methylene chloride

Previously, we (Parker and Ranney 1995) observed that a 40% solution of acetone softened

PVC in seven days while a 20% solution did not.

In a different study, we (Parker and Ranney 1994)

observed that PVC was not softened after seven

days’ contact with a solution containing methylene chloride with a relative solubility of 0.4. However, in this study, a solution containing methylene chloride with a relative solubility of 0.4 (0.76%)

and 0.5% acetone softened PVC after only four

17
Table 11a. Hardness (Barcol) readings of PVC exposed

to aqueous solutions of methylene chloride (MC) and

acetone.

 MC, Acetone Contact time, days

Rel. sol. (%) 2 4 7 14 21

control 75 75 74 73 74

control 76 74 76 73 75

control 76 76 73 74 76

control 74 74 75 76 75

control 75 75 76 75 75

 

X 75.2 74.8 74.8 74.2 75

0.4, 0.0 73 72 74 73 74

0.4, 0.0 74 74 74 76 72

0.4, 0.0 76 73 76 73 75

0.4, 0.0 75 75 73 74 72

0.4, 0.0 74 76 73 72 73

 

X 74.4 74 74 73.6 73.2

0.4, 0.5 75 74 71 70 72

0.4, 0.5 76 70 68 71 72

0.4, 0.5 74 67 67 67 70

0.4, 0.5 75 69 70 75 71

0.4, 0.5 75 68 68 70 70

 

X 75 69.6* 68.8* 70.6 71.0*

0.4, 1.0 74 68 66 68 74

0.4, 1.0 74 69 72 72 71

0.4, 1.0 75 71 71 67 71

0.4, 1.0 76 67 69 74 73

0.4, 1.0 75 72 70 73 69

 

X 74.8 69.4* 69.6* 70.8 71.6*

0.4, 5.0 74 71 70 69 72

0.4, 5.0 75 68 70 68 69

0.4, 5.0 74 73 67 71 73

0.4, 5.0 74 68 69 73 72

0.4, 5.0 75 70 70 71 72

 

X 74.4 70.0* 69.2* 70.4* 71.6*

0.4, 10.0 75 72 71 63 69

0.4, 10.0 74 68 69 65 72

0.4, 10.0 74 70 70 69 68

0.4, 10.0 73 66 68 68 67

0.4, 10.0 73 67 70 69 68

 

X 73.8 68.6* 69.6* 66.8* 68.8*

0.4, 20.0 67 63 60 54 53

0.4, 20.0 71 62 54 51 54

0.4, 20.0 68 65 53 52 48

0.4, 20.0 72 58 59 58 46

0.4, 20.0 69 60 67 62 45

 

X 69.4* 61.6* 58.6* 55.4* 49.2*

*Significantly different from controls.

Table 11b. Percent weight gain of PVC exposed to aqueous solutions of methylene chloride (MC) and acetone.

 MC, Acetone Contact time, days

activity (%) 2 4 7 14 21

control 0.00 0.16 0.18 0.24 0.16

control 0.00 0.17 0.08 0.33 0.17

control 0.08 0.16 0.17 0.24 0.23

control 0.08 0.25 0.16 0.25 0.16

control 0.00 0.25 0.24 0.32 0.28

 

X 0.03a 0.20a 0.17a 0.28a 0.20a

S.D. 0.04 0.05 0.06 0.04 0.05

0.4, 0.0 0.24 0.32 0.56 0.58 0.71

0.4, 0.0 0.17 0.46 0.55 0.56 0.77

0.4, 0.0 0.26 0.40 0.56 0.61 0.87

0.4, 0.0 0.23 0.55 0.33 0.54 0.76

0.4, 0.0 0.16 0.49 0.56 0.48 0.92

 

X 0.21b 0.44a,b 0.51a,b 0.55a 0.81b

S.D. 0.04 0.09 0.10 0.05 0.09

0.4, 0.5 0.16 0.57 0.62 0.84 0.70

0.4, 0.5 0.42 0.48 0.76 1.03 0.65

0.4, 0.5 0.16 0.48 0.67 0.80 0.73

0.4, 0.5 0.16 0.58 0.65 0.89 0.82

0.4, 0.5 0.26 0.33 0.63 0.95 1.01

 

X 0.23b 0.49b 0.67b 0.90b 0.78b

S.D. 0.11 0.10 0.05 0.09 0.14

0.4, 1.0 0.25 0.67 0.87 1.20 0.97

0.4, 1.0 0.29 0.83 0.73 1.12 1.01

0.4, 1.0 0.16 0.70 0.51 1.12 1.00

0.4, 1.0 0.47 0.49 0.68 1.07 1.17

0.4, 1.0 0.32 0.64 0.58 0.92 1.20

 

X 0.30b,c 0.67b 0.67b 1.09b 1.07b,c

S.D. 0.11 0.12 0.14 0.11 0.11

0.4, 5.0 0.42 0.75 0.76 0.91 1.07

0.4, 5.0 0.53 0.70 0.80 0.93 1.27

0.4, 5.0 0.44 0.59 0.80 1.09 1.13

0.4, 5.0 0.33 0.64 0.73 1.22 1.20

0.4, 5.0 0.44 0.73 0.88 1.20 1.08

 

X 0.43c 0.68b 0.79b 1.07b 1.15c

S.D. 0.07 0.07 0.06 0.15 0.08

0.4, 10.0 0.41 1.15 1.81 2.07 2.04

0.4, 10.0 0.50 1.51 1.85 1.65 1.85

0.4, 10.0 0.50 1.12 1.58 1.79 1.87

0.4, 10.0 0.83 0.80 1.51 1.78 1.97

0.4, 10.0 0.82 1.12 1.34 1.65 2.30

 

X 0.61d 1.14c 1.62c 1.79c 2.01d

S.D. 0.20 0.25 0.21 0.17 0.18

0.4, 20.0 2.33 4.53 6.46 6.64 6.34

0.4, 20.0 2.05 5.05 5.51 5.66 6.57

0.4, 20.0 2.00 4.70 5.58 5.91 7.35

0.4, 20.0 2.03 4.38 4.96 6.18 7.71

0.4, 20.0 2.49 4.00 4.70 4.94 7.37

 

X 2.18e 4.53d 5.44d 5.87d 7.07e

S.D. 0.22 0.39 0.68 0.63 0.58

S.D. = standard deviation

Values with different letters, taken at the same time, are significantly

different.

18
days’ contact (Table 11). Clearly there is a combined effect with these two organic solutes!

CONCLUSIONS

These data show that when the relative solubility of a single organic solute is less than 0.1,

there will not be any measurable effect on PVC,

either weight gain or hardness readings. For solutions that contain several organic solvents, we

have found the sum of the relative solubilities of

the organic solutes in the test solution to be a

useful, if not rudimentary, indicator of the ability

of an aqueous solution to degrade PVC. If the

sum of the relative solubilites of the organic solutes in solution is less than 0.1, there does not

appear to be any measurable effect on rigid PVC.

This relative solubility corresponds to an activity

level (0.1) where diffusion is slowest and Fickian.

At slightly higher relative solubilities (0.2, 0.4),

there are slight changes in the hardness readings,

although in the time frame of our studies (18

months and less) PVC does not become pliable or

rubbery.

We do not have any parameters that can be

used to predict the ability of aqueous solutions

that also contain PVC solvents and swelling agents

that are completely miscible in water to soften

PVC. The relative solubility cannot be used to

predict the ability of the solution to soften PVC

because this involves dividing the concentration

of the analyte by an infinitely large number. It is

interesting that a 1% solution of acetone had no

effect on the hardness readings after 18 months’

exposure, while a solution containing methylene

chloride with a relative solubility of 0.4 (0.76%)

and 0.5% acetone softened PVC after only a few

days’ contact. Clearly, further study is needed to

delineate the influence miscible PVC solvents and

swelling agents have on the softening ability of

aqueous organic solutions.

Previously Leggett and Parker (1994) used a

model based on multiparameter linear solvation

energy relationships to describe equilibrium partitioning between PVC and water for several organic compounds. Partitioning of these solutes

was related to the molecule’s acidity, polarity/

polarizability, basicity, and molecular volume. A

similar approach might prove useful here for predicting in a more meaningful way the ability of

aqueous organic solutions to soften PVC.

LITERATURE CITED

ASTM (1988) ASTM standard test method D 2583-

87 for indentation hardness of rigid plastics by

means of a Barcol Impressor. American Society

for Testing and Materials, Philadelphia, Pennsylvania, p. 337–339.

Berens, A.R. (1985) Prediction of organic chemical permeation through PVC pipe. Journal of the

American Water Works Association, p. 57–65.

Dean, J.I. (Ed.) (1985) Lange’s Handbook of Chemistry, Thirteenth Edition. New York: McGraw-Hill

Publishers.

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the equilibrium partitioning of organic contaminants between PTFE, PVC, and groundwater. Environmental Science and Technology, 28(7): 1229–1233.

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Lewis Publishers, Inc.

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Michigan: Lewis Publishers, Inc.

Parker, L.V. and T.A. Ranney (1994) Softening of

rigid PVC by aqueous solutions of organic solvents. USA Cold Regions Research and Engineering Laboratory, Special Report 94-27.

Parker, L.V. and T.A. Ranney (1995) Additional

studies on the softening of rigid PVC by aqueous

solutions of organic solvents. USA Cold Regions

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Parker, L.V., T.A. Ranney, and S. Taylor (1992)

Softening of rigid polyvinyl chloride by high concentrations of aqueous solutions of methylene

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casings to degradation by chemicals. USA Cold

19
Regions Research and Engineering Laboratory,

Special Report 95-1.

Taylor, S. and L.V. Parker (1990) Surface changes

in well casing pipe exposed to high concentrations of organics in aqueous solution. USA Cold

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Special Report 90-7.

Vonk, M.W. (1985) Permeatie van organische

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vol. 13, p. 701–714.

20
APPENDIX A: PERCENT WEIGHT GAIN IN PVC EXPOSED TO

VARIOUS NEAT ORGANIC CHEMICALS (HEEREMANS, RANNEY

AND PARKER; UNPUBLISHED STUDIES)*

Percent ∆ wt.

Solvent 4 hours 1 day 7 days 55 days

acetic acid 0.0 0.2 — —

acetone 46.5 — — 150.8

acetonitrile 1.8 5.0 11.2 13.9

benzene 2.2 5.8 23.3 47.5

benzonitrile 26.8 — — 365.0

benzyl alcohol 0.0 0.0 0.0 0.1

bromochloromethane 309.3 648.4 — —

bromodichloromethane 60.8 216.2 — —

bromoform 20.8 71.1 — —

butanol 0.0 0.0 0.0 0.0

butylamine 14.5 59.3 — —

carbon disulfide 12.0 28.0 36.5 33.9

carbon tetrachloride 0.0 0.0 0.0 0.1

chlorobenzene 11.7 52.1 — 149.7

chlorodibromomethane 57.2 165.3 — —

2-chloroethyl vinyl ether 7.5 25.6 — —

chloroform 36.2 124.2 — 205.1

cyclohexane 0.0 0.1 0.0 0.0

cyclohexanone D

1,2-dibromoethane 27.8 105.4 — —

1,2-dichlorobenzene 3.6 17.7 61.1 197.4

1,3-dichlorobenzene 3.6 13.9 47.5 100.8

1,1-dichloroethane 13.4 44.1 115.1 115.2

1,2-dichloroethane 52.6 215.5 — —

cis-1,2-dichloroethylene 87.3 253.0 — —

trans-1,2-dichloroethylene 18.7 50.7 — —

1,2-dichloropropane 10.5 30.8 — —

3,4-dimethyl acetophenone — 238.9 — —

dimethyl formamide 32.5 D

dimethyl sulfoxide 4.7 17.0 55.4 68.9

dioxane 4.2 14.3 51.0 104.7

ethanol amine 0.0 0.4 — —

ethyl acetate 23.6 85.4 — 144.4

ethyl benzene 0.8 2.1 — —

heptane 0.0 0.0 0.0 0.0

hexane 0.0 0.0 0.0 0.0

iso-butanol 0.0 –0.1 –0.1 0.1

iso-propanol 0.0 0.0 0.0 –0.1

methanol 0.0 0.0 0.1 0.3

methoxy ethanol 0.1 0.9 — —

methyl ethyl ketone — — — 238.8

* Small pieces of PVC well casing (1 cm × 1 cm) were placed in 22-mL borosilicate glass

vials, 5 mL of solvent was added, and the vials were capped with Teflon-lined plastic

caps. Prior to weighing (± 0.0001), the samples were blotted with paper towels.

— No data

D PVC dissolved

21
Percent ∆ wt.

Solvent 4 hours 1 day 7 days 55 days

methyl isobutyl ketone 18.5 92.3 — —

methylene chloride — — — 388.0

nitrobenzene 29.6 — — 488.3

o-nitrotoluene 11.9 46.1 — 474.5

m-nitrotoluene 14.5 51.1 — 479.6

propanol 0.0 0.0 0.0 0.0

pyridine 122.8 D

1,1,2,2-tetrachloroethane 6.1 32.3 — —

tetrachloroethylene 0.1 0.1 0.3 0.3

tetrahydrofuran 22.9 D

toluene 2.7 8.0 32.0 49.2

1,1,1-trichloroethane 0.2 0.5 1.6 4.0

1,1,2-trichloroethane 22.8 83.0 328.8 368.5

trichloroethylene 7.6 27.8 69.7 67.8

o-xylene 0.7 2.4 — —

m-xylene 0.6 2.3 — —

p-xylene 1.2 2.7 — —

22
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October 1996

Further Studies on the Softening of Rigid PVC by Aqueous Solutions of

Organic Solvents

Louise V. Parker and Thomas A. Ranney

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road Special Report 96-26

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31

Aqueous solutions Polyvinyl chloride Softening

Organic solvents PVC Solvents

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

In this study, small pieces of PVC well casing were exposed to relatively low activities (or relative solubilities)

of TCE and methylene chloride for 12 months. PVC pieces were also exposed to aqueous solutions containing

several organic chemicals that were either solvents or swelling agents of PVC. In addition, small pieces of PVC

were exposed to aqueous solutions containing organic chemicals that were either PVC solvents or swelling

agents and were totally miscible in water. These studies revealed that there is an interactive effect among these

chemicals when dissolved in water. However, softening does not appear to occur in any solutions where the

sum of the relative solubilities is less than 0.1.