. The Bell System technical journal . 376 BELL SYSTEM TECHNICAL JOURNAL use directly on latex has been employed as a control during the synthesis ofGR-S^^ This test, referred to as the vistex test, consists in adding 1 the latex sample to be examined to 100 ml. of a solvent having bothhydrophobic and hydrophilic properties, such as a mixture of 70 parts (byvolume) of xylene with 30 of pyridine, or 60 of benzene and 40 of clear solution is run through the viscometer in the usual manner and therelative viscositv used as a measure of extent of reaction. The test has the. Fig.
. The Bell System technical journal . 376 BELL SYSTEM TECHNICAL JOURNAL use directly on latex has been employed as a control during the synthesis ofGR-S^^ This test, referred to as the vistex test, consists in adding 1 the latex sample to be examined to 100 ml. of a solvent having bothhydrophobic and hydrophilic properties, such as a mixture of 70 parts (byvolume) of xylene with 30 of pyridine, or 60 of benzene and 40 of clear solution is run through the viscometer in the usual manner and therelative viscositv used as a measure of extent of reaction. The test has the. Fig. 8. -Viscometers and bath used for the determination of diluti solution viscosity ofpolymer solutions. advantage of great speed, thus providing control of the reaction, step bystep. Figure 9 shows the apparatus em[)loyed in the determination ofconcentrated solution viscosity {CSV).^ In this measurement a 15 percentsolution of the copol3nner in xylene is made by weighing the requiredquantity of GR-S into a test-tube adding the precise volume of xylene andstoppering. The solution is homogenized by moving a steel armaturethrough it in the test-tube by means of a strong electro-magnet. A traceof acetic acid is added to eliminate thixotropic effects. After completedispersion has been effected the viscosity is determined by the faUing ball SYNTHETIC KlBBEIi KESEAKCII 377 method. Branched copolymers show inordinately high concentrated solu-tion viscosities. The latter may therefore be employed as a measure ofdegree of branching or approach to gelation when supplemented by dilutesolution
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