Page 97 - Carrahers_Polymer_Chemistry,_Eighth_Edition
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60 Carraher’s Polymer Chemistry
Since it is difficult to measure the molar volume, its equivalent the molecular weight (M) divided
by density (D), is substituted for V as shown in the following equation:
∆ H − RT 1/ 2
δ = D v M (3.5)
Because the law of mixtures applies to the solubility parameter, it is possible to easily calculate
the solubility parameter of blended liquids forming mixtures that can serve as solvents. For exam-
ple, an equal molar mixture of n-pentane (δ = 7.1 H) and n-octant (δ = 7.6 H) will have a solubility
parameter value of 7.35 H (simply [7.1 + 7.6]/2).
The solubility parameter of a polymer is generally determined by noting the extent of swelling or
actual solution of small amounts of polymer in a series of solvents and comparing the solubility val-
ues of the ones that swell or dissolve the polymer and assigning the polymer a solubility parameter
value that is close to the solvents that dissolve/swell the polymer. The solubility parameter can also
be determined by adding a nonsolvent to a polymer solution and by noting the amount of nonsolvent
needed to begin to precipitate the polymers.
Since polar forces are present in polar solvents and polar molecules, this must be considered
when estimating solubilities with such “nonregular” solvents and polymers. Hydrogen bonding,
a special case of secondary polar bonding, is also important for some solvents and polymers and
again will infl uence the solubility parameters. Thus, special solubility values have been developed
for polar and hydrogen-bonding solvents (Tables 3.1 and 3.2).
Plasticizers help the flexibility of polymers and are chosen so that they do not dissolve the poly-
mer but rather allow segmental mobility to occur. Through experience, it is found that the solubility
TABLE 3.1
Solubility Parameters (δ) for Typical Solvents
Poor Hydrogen Bonding Moderate Hydrogen Bonding Strong Hydrogen Bonding
Dimethylsiloxane 5.5 Diisopropyl ether 6.9 Diethylamine 8.0
Difl uorodichloromethane 5.5 Diethylether 7.4 n-Amylamine 8.7
Neopentane 6.3 Isoamyl acetate 7.8 2-Ethylhexanol 9.5
Nitro-n-octane 7.0 Diisobutyl ketone 7.8 Isoamyl alcohol 10.0
n-Pentane 7.0 Di-n-propylether 7.8 Acetic acid 10.1
n-Octane 7.6 sec-Butyl acetate 8.2 m-Cresol 10.2
Turpentine 8.1 Isopropyl acetate 8.4 Analine 10.3
Cyclohexane 8.2 Methylamyl ketone 8.5 n-Octyl alcohol 10.3
Cymene 8.2 Ethyl acetate 9.0 t-Butyl alcohol 10.9
Carbon tetrachloride 8.6 Methyl ethyl ketone 9.3 n-Amyl alcohol 10.9
n-Propylbenzene 8.6 Butyl cellosolve 9.5 n-Butyl alcohol 11.4
p-Chlorotoluene 8.8 Methyl acetate 9.6 Isopropyl alcohol 11.5
Decalin 8.8 Dichloroethylether 9.8 Diethylene glycol 12.1
Xylene 8.8 Acetone 9.9 Furfuryl alcohol 12.5
Benzene 9.2 Dioxane 10.0 Ethanol 12.7
Styrene 9.3 Cyclopentanone 10.4 N-Ethylformamide 13.9
Tetraline 9.4 Cellosolve 10.5 Methanol 14.5
Chlorobenzene 9.5 N,N-Dimethylacetamide 10.8 Ethylene glycol 14.6
Ethylene dichloride 9.8 1,2-Propylene carbonate 13.3 Glycerol 16.5
p-Dichlorobenzene 10.0 Ethylene carbonate 14.7 Water 23.4
Nitroethane 11.1
Acetronitrile 11.9
Nitroethane 12.7
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