Standard Test Method for Rubber—Determination of Gel, Swelling Index, and Dilute Solution Viscosity

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Standard Test Method for Rubber—Determination of Gel, Swelling Index, and Dilute Solution Viscosity


SCOPE:


1. This test method covers the determination of the dilute csolution viscosity (DSV), the gel characteristics, and the swelling index of raw non-oil-extended and non-pigmented
SBR and NBR.
2.This test method may be used to determine the DSV and gel characteristics of rubbers other than SBR and NBR,however, solvents other than 2-butanone and toluene may be required

 This test method is not intended for the measurement of micro gel.

 SIGNIFICANCE

1.These tests are particularly useful for quality control in the production of synthetic rubbers.



2 Percent gel is a measure of the amount of insoluble rubber present in the chosen solvent. Gel may be introduced intentionally in some rubbers. Variations from a normal level indicate changes in the polymerization system.



3 Swelling index is a measure of the type of gel. Gel with a low-swelling index is referred to as “hard gel” and usually  indicates the presence of material that does not break down


the presence of a “loose gel” that may be broken down easily     by milling.

4 In low-gel or gel-free rubbers, the DSV correlates   directly with the molecular weight. Since the viscosity is   measured only on the soluble portion of the rubber, the use of   DSV to predict molecular weight in rubbers having high gel  value is meaningless.




Designation: D 3616 – 95 (Reapproved 2004)

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