ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Microgel consists of branched molecules of colloidal dimensions, formed by gelation occurring within the confines of a latex particle. Thermodynamically, microgel is expected to be soluble in a “good” solvent, such as benzene. Experimentally, it is found that carefully dried microgel-containing polymers are completely soluble in benzene. Detection of microgel by solubility measurements requires the conversion of microgel to macrogel (gel of macroscopic dimensions) prior to the solubility measurement. This can be accomplished by heating under a variety of conditions. Milling of the polymer before heating aids in this conversion.A Standard Procedure is recommended for the determination of microgel in standard GR-S rubber: the polymer (preferably coagulated in ethanol) is milled for about 10 passes, with the addition of 2% of phenyl-beta-naphthylamine; the milled polymer is heated for 12 hours in a vacuum oven at 80°, then placed inside a box of wire screen and immersed in benzene for 40 hours to extract the sol portion.Solutions of microgel in benzene can be fractionally precipitated by addition of ethanol or nitroethane. The fractionation is, primarily according to molecular weight rather than degree of cross-linkage. Viscosity and light-scattering measurements of the fractions show that the polymers are of high molecular weight and are cross-linked.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1951.120060405
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