Complete Apparatus for Determination of Osmotic Molecular Weights

Abstract

The procedure and the complete apparatus for measuring molecular weights are described* and illustrated in sufficient detail to make possible constructing the equipment. By using a dozen of the static osmometers simultaneously, a complete molecular weight determination can be made in 1 to 4 days. Representative data for standard government specification GR-S polymers and for samples of German Buna S-3 subjected to various treatments illustrate the results obtained.Reproducibility of osmotic heights is of the order of 5%.

Chicle - cis- and trans-Polyisoprenes from a Single Plant Species

“…Molecular Weight. Molecular weight was determined by the method of Sands and Johnson (7). As osmosis membranes, undried regenerated cellulose film, treated in accordance with directions given by Wagner {10), was found to be satisfactory for both the caoutchouc and gutta polyisoprenes.…”

“…Literature does not mention the presence of an esterase in the latex of Hevea brasiliensis, but the presence of a lipase in the seeds of Hevea brasiliensis has been proved (1,6). Furthermore lipases have been found in the latices of other plants -for example, Euphorbiaceae, Ficus carica, Maclura Morus, Carica papaya (7,8). Gerber (%) studied the activity of enzymes, including a lipase, in the latex of Broussonetia papyrifera in the various seasons.…”

An experimental verification of gel network formation theories

“…The distribution in the milled natural rubber samples is sufficiently close to this distribution to allow the use of the theory. In addition, almost any distribution will closely approach the random distribution results after about three random scissions per weight-average molecular weight molecule.17 This theory can be expressed in its most general form, as follows, s + S*'z = ( p / q ) + (q?Jn)vl (7) where S is the sol fraction, p is the fraction of the polymeric structural repeat units that have been scissioned, q is the fraction of the polymeric structural repeat units that have been crosslinked, and is the numberaverage degree of polymerization of the polymer before crosslinking. For reasons of convenience only, cq.…”

“…I n this case q and p / q should be constant and may be determined from a plot of S + S'" versus (G)-l according to eq. (7).…”

Furfural Phenylhydrazone as Chemical Softener for GR-S

“…The second method was the more advantageous as the only added operation involved was the dispersion of furfural phenylhydrazone in the latex, while the first involved an additional milling or mixing operation and a storage period, both of which would be objectionable in large scale practice. procedure was as readily adaptable to high Mooney polymers as to regular GR-S so that they could be softened to equal the plasticity and processibility of the latter, while retaining most of the superior vulcanízate properties of high molecular weight polymers (11,17,25,42).…”