Table 1. Equilibrium swelling and interaction parameters for PVCorganic liquid
systems. (After Berens 1985.)
Interaction
Weight
Volume
Time*
parameter
χ
Compound
gain (%)
fraction (V1)
(hr)
Methylene chloride
>800**
>0.89
2
<0.53
Chloroform
227
0.68
6
0.64
Carbon tetrachloride
0
~0
(280)
--
1,1-dichloroethane
132
0.61
6
<0.68
1,2-dichloroethane
700**
>0.86
6
<0.55
1,1,1-trichloroethane
67
0.42
600
0.85
1,1,2-trichloroethane
>400**
>0.80
10
<0.56
Trichloroethylene
70
0.40
5
0.88
Tetrachloroethylene
35
0.23
800
1.17
1,2-dichloropropane
176
0.68
20
0.68
Benzene
50
0.44
12
0.83
Toluene
5060
0.450.49
15
0.80
Xylene
42
0.40
100
0.88
Acetone
170
0.75
2
0.61
Methanol
~1.0
--
(300)
--
Ethanol
~0.1
--
(300)
--
i-propanol
~0.5
--
(300)
--
n-hexane
~0.6
--
(160)
--
Vinylchloride
~30
0.33
--
0.98
* Time to apparent equilibrium, 24-mil (0.6-mm) PVC sheet, or duration of experiment in paren-
theses.
** Soluble.
periments were prepared by dissolving the or-
of (PVC) solvents are necessary to confirm Berens's
ganic solvents in polyethylene glycol, so he never
predictions. While Vonk did use aqueous solu-
actually tested aqueous solutions of these organic
tions of organics in his studies, we have been un-
solvents. Since it is possible that the partitioning
able to find a thorough discussion of his meth-
of these organic solutes between the dissolved
ods that is available in English.
state and the polymer could differ between gly-
Our laboratory has conducted several studies
col and water, studies that use aqueous solutions
to test Berens's predictions for aqueous solutions
(Parker et al. 1992, Parker and Ranney 1994). In
our first study (Parker et al. 1992) we looked for
1.0
softening of PVC exposed to aqueous solutions
containing various activities of methylene chlo-
ride. According to Vonk (1985) the χ value for meth-
0.8
ylene chloride is 0.55. However, according to
Berens (1985) the χ value is less than 0.53. Thus,
0.6
depending on which χ value you use, methylene
χ=0
V1
chloride is either a solvent or a good swelling agent
of PVC. [We have observed pieces of PVC well
Rubbery
0.4
casing dissolve when placed in neat methylene
0.5
chloride (Ranney and Parker, 1995). Thus it ap-
Softening Range
pears that the true χ value for methylene chlo-
0.2
1.0
ride is less than 0.5.] In this study (Parker et al.
Glassy
1.5
1992), small pieces of PVC well casing were ex-
posed to solutions with a range of activities [1.0,
0
0.2
0.4
0.6
0.8
1.0
Solvent Activity
0.8, 0.6, 0.4, 0.2 and 0.0 (controls with only wa-
ter)] for 33 days. Samples exposed to the 1.0- and
Figure 1. FloryHuggins isotherms for various
0.8-activity solutions became rubbery and could
be bent easily by hand within 4 and 22 days, re-
ening of PVC at room temperature. (After Berens
spectively. This agrees well with Berens's predic-
1985.)
2
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