5) what occurs in an aqueous solution that con-
were added to 22-mL borosilicate glass vials. The
tains a number of PVC solvents and swelling
vials were then filled to capacity with the test
agents at varying relative solubilities?
solution so there was no headspace, and capped
6) in solutions that contain several organic sol-
with Teflon-lined plastic caps. PVC pieces added
to deionized water served as controls. In all the
utes, do solutes that are solvents and swelling
studies, there were five replicates for each type of
agents of PVC have some type of synergistic ef-
solution (relative solubility) and time. The test
fect on poorer swelling agents?
samples were stored in the dark at room tempera-
7) what is the lowest concentration of acetone
ture. The ratio of surface area of PVC to solution
in aqueous solution that can soften PVC?
volume was 0.079 cm2/mL, and the ratio of solu-
8) what occurs when PVC solvents and swell-
ing agents that are miscible in water are also
tion volume to volume of PVC was approximately
present in an aqueous solution with other PVC
310:1.
solvents and swelling agents?
On the sampling day, the pieces of PVC were
removed from the solution, placed on paper tow-
els, blotted, and allowed to air dry for one minute
before weighing ( 0.0001 g). In all cases, the pieces
MATERIALS AND METHODS
of PVC were handled using stainless steel for-
Small pieces of PVC were cut from 2-in.- (5.1
ceps. Immediately after weighing, a Model 935
cm) diameter, schedule 40 well casing. The over-
Barcol Impressor was used to measure the hard-
all dimensions of the pieces were approximately
ness of the PVC. A description on the use of the
9 9 1.1 mm (L W H), giving a total surface
Barcol Impressor on rigid plastics can be found in
area of approximately 2.1 cm2 and approximate
ASTM Standard Test Method D 2583-87 (ASTM
weight of 0.12 g. Special care was taken to elimi-
1988). However, the impressor employed in this
nate contamination from grease or oil during the
study is made for indenting softer plastics and is
cutting procedure. The pieces of PVC were washed
not the model described in the ASTM test method.
by placing them in a glass beaker containing a 2%
This model was selected so that measurements
solution of Liquinox detergent and deionized
could be taken during the softening process. The
(Millipore) water for 30 minutes, and stirring them
flexibility was also tested by holding the pieces
intermittently with a glass rod for approximately
with forceps and noting the amount of force nec-
five minutes. The pieces were then rinsed with
essary to bend the sample.
In all these studies, Analysis of Variance and
copious amounts of deionized water to ensure
Fisher's Protected Least Significant Difference
complete removal of the detergent, and were then
spread on paper towels, blotted, and left to air
(LSD) tests were performed on the Barcol read-
dry.
ings and weights of the samples.
All the test solutions were made up by adding
appropriate volumes of the neat analyte (based
Long-term methylene
on the density of the compound) to deionized
chloride study
water in volumetric flasks. To prevent any losses
In this study, the PVC test pieces were exposed
due to biological activity, mercuric chloride was
to aqueous solutions of methylene chloride with
added to the test solution so that the final con-
the following relative solubilities: 0.01, 0.05, 0.1,
centration was 40 mg/L. A glass-covered mag-
0.2, and 0.4. Contact times were 3, 6, 9, 12, 15, and
netic stirring bar was added to each flask, and the
18 months. The test solutions were changed every
flasks were then filled with deionized water to
six months. Relative solubilities were based upon
within ~1 mL of the top. This left a minimal head
a solubility of 19,000 mg/L. Because Montgom-
space once the glass stopper was inserted. The
mery and Welkom (1990) listed a range of solubil-
stoppers were then wrapped tightly with parafilm
ity values, we conducted our own solubility tests
to reduce vapor loss and the solutions were mixed
and then selected the published value that most
for a minimum of three days on magnetic stirring
closely agreed with our findings (Parker and
plates.
Ranney 1994).
After mixing for several days, the solutions
were checked with a magnifying glass to ensure
Long-term TCE study
that there were no undissolved droplets of sol-
In this study, PVC was exposed to aqueous
vent visible. Once it was determined that the
solutions of TCE at five relative solubilities: 0.05,
organic(s) had dissolved, pre-weighed PVC pieces
0.10, 0.20, 0.40, and 0.60. Contact times were the
6
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