ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The surface concentration of polymer molecules in solution has been combined with the three-component bulk-phase diagram of Strathmann et al. to describe the complete equilibrium thermodynamic precasting situation. The polymer surface concentration is estimated according to the theory of Prigogine and Marechal as used by Siow and Patterson, and is governed by the relative values of the polymer and solvent surface tension, γp and γs respectively. In general, when γp 〉 γs, the cast membrane will tend to form with the asymmetric layer on the support side; for γp 〈 γs it will tend to form on the gelation bath side. This was found to be the case for several cellulose acetate casting solutions, including the acetone/formamide mixture of Manjikian. The surface tension of cellulose acetate in the latter mixture appeared to be much lower than in single solvents such as DMSO. The effects of surface tension were used to prepare asymmetric gels of poly(phenylene oxide) and nylon 11 by cooling high-temperature solutions in which γs 〉 γp at the gel transition point.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1974.070180721
