Table 6a. Hardness (Barcol) readings of PVC exposed
Table 6b. Percent weight gain of PVC exposed to
to aqueous solutions of several organic solutes (short-
aqueous solutions of several organic solutes (short-
term study).
term study).
Contact time, hours
Contact time, hours
Treatment
8
24
72
168
Treatment
8
24
72
168
control
73
77
74
74
control
0.00
0.00
0.23
0.24
control
69
74
71
72
control
0.08
0.08
0.08
0.40
control
67
76
70
69
control
0.15
0.25
0.08
0.43
control
71
77
74
72
control
0.09
0.16
0.25
0.27
control
68
75
70
71
control
0.08
0.08
0.17
0.42
69.6a
75.8a
71.8a
71.6a
0.08a
0.11a
0.16a
0.35a
X
X
S.D.
0.05
0.09
0.08
0.09
solution A
63
69
58
60
solution A
64
67
62
64
solution A
1.23
2.35
3.36
5.58
solution A
65
72
62
62
solution A
1.07
2.57
3.58
5.29
solution A
69
70
65
64
solution A
1.03
2.48
3.90
5.29
solution A
64
67
64
60
solution A
1.08
2.34
3.61
5.00
65.0b
69.0b
62.2b
62.0c
solution A
1.07
2.36
3.70
5.67
X
1.10c
2.42c
3.63c
5.37c
X
solution B
67
70
63
68
S.D.
0.08
0.10
0.19
0.27
solution B
69
71
68
64
solution B
71
71
64
66
solution B
0.65
1.65
2.55
3.44
solution B
65
66
69
66
solution B
0.79
1.59
2.27
3.54
solution B
69
68
64
65
solution B
0.82
1.58
2.62
3.74
68.2a,b
69.2b
65.6b
65.8b
solution B
0.73
1.73
2.36
3.53
X
solution B
0.78
1.42
2.60
4.20
Values with different letters, taken at the same time, are signifi-
0.75b
1.59b
2.48b
3.69b
X
cantly different.
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.
ing a PVC solvent) to be, but more aggressive
ing this approach (i.e., summing the relative
than we (Parker and Ranney 1994) found a TCE
solubilities), since solution A appears to be more
solution with the same relative solubility (0.6) to
aggressive than solution B (Table 6), even though
be. Thus, there does not appear to be an enhanced
they both have the same cumulative relative solu-
or synergistic effect of the organic solutes in this
bilities. The reason solution A was more aggres-
test solution, and taking the sum of the relative
sive can be explained by the fact that the sum of
solubilities was useful in roughly predicting the
the mole fractions of the organic solutes was
ability of this test solution to soften PVC.
greater in solution A (Table 2). In addition, the
sum of the mole fractions of the four most aggres-
First long-term study
sive chemicals (cyclohexanone, 1,2-dichloro-
PVC pieces were exposed to two aqueous solu-
ethane, methylene chloride, and nitrobenzene)
tions that contained 18 organic chemicals that were
(App. A, Ranney and Parker 1995) in the test so-
either a PVC solvent or swelling agent (Table 8).
lution was also greater.
In these solutions, the relative solubility of each
chemical was either 0.01 or 0.02, and the sums of
Mid-term study
the relative solubilities of all the organic solutes
Test pieces of PVC that were exposed to a TCE
in the test solutions were 0.18 and 0.36, respec-
solution with a relative solubility of 0.2 were not
tively. After 40 weeks' exposure, the test pieces
softened during the course of this study (56 days)
exposed to the test solution with the higher total
(Table 7). However, samples exposed to a solu-
relative solubility (0.36) had significant changes
tion containing TCE with a relative solubility of
in hardness readings (but were not pliable), while
0.2 and methylene chloride at a relative solubility
those exposed to the solution with the lower total
of 0.4 were softened after seven days. Again, none
relative solubility (0.18) did not. However, there
of these samples were pliable. This test solution
was a significant increase in the weight of the test
was less aggressive than we (Parker and Ranney
pieces exposed to this test solution when com-
1994) found a methylene chloride solution with a
pared with the controls.
relative solubility of 0.6 (i.e., a solution contain-
12
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