Second long-term study
Table 8. Hardness (Barcol) readings and percent
weight gain of PVC exposed to aqueous solutions
Table 9 gives the results of exposing PVC to a
of several organic solutes (first long-term study).
test solution containing the same eighteen organic
solutes at four different relative solubilities for up
Relative
20 week
40 week
to 18 months. The relative solubility of each of the
Barcol % ∆ weight
% ∆ weight
solubility
Barcol
organic solutes was either 0.001, 0.005, 0.010, or
control
78
0.40
76
0.41
0.020. Thus, the sums of the relative solubilities of
control
77
0.37
74
0.47
the organic solutes in these solutions were 0.018,
control
74
0.53
76
0.40
control
76
0.41
74
0.41
0.090, 0.18, and 0.36, respectively.
control
77
0.36
76
0.37
The test results show that when the sum of the
76.4a
0.41a
75.2a
0.41a
X
relative solubilities of the organic solutes in the
S.D.
0.07
0.04
test solutions was less than 0.10, softening did not
0.01
74
0.59
75
0.54
occur. Test pieces that were exposed to organic
0.01
74
0.50
74
0.64
solutes with relative solubilities of 0.010 and 0.020
0.01
76
0.61
75
0.70
(or cumulative relative solubilities of 0.18 and 0.36)
0.01
76
0.56
74
0.36
had hardness readings that were significantly
0.01
77
0.47
73
0.52
lower than the controls but were not rubbery.
75.4a
0.55b
74.2a,b
0.55b
X
These results agree with our previous findings
S.D.
0.06
0.13
for methylene chloride, i.e., softening does not
0.02
76
0.92
72
0.93
occur when the relative solubility of the analyte
0.02
74
0.65
75
0.99
0.02
77
0.91
74
0.93
in the test solution is less than 0.1. The weight
0.02
76
0.75
73
0.80
gain data also support these conclusions. Signifi-
0.02
72
0.68
72
0.92
cant changes in weight were found in samples
75.0a
0.78c
73.2b
0.91c
X
exposed to solutions with relative solubilities of
S.D.
0.13
0.07
0.01 and 0.02. Generally, there was not significant
S.D. = standard deviation
change in the weights of samples exposed to solu-
Values with different letters, taken at the same time, are
tions with lower relative solubilities.
significantly different.
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
72.2
74.2
76.8
77.4
78.0
78.6
X
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
72.0
74.2
75.8
77.0
78.4
78.0
X
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
72.0
74.2
75.2
76.6
77.4
78.2
X
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
71.4
74.0
74.8*
76.4
77.2
76.8*
X
14
Previous Page
