ISO 7781:1996
Rubber, raw styrene-butadiene - Determination of soap and organic-acid content

Standard No.

ISO 7781:1996

Release Date

1996

Published By

International Organization for Standardization (ISO)

Status

Withdraw

Replace By

ISO 7781:2001

Latest

ISO 7781:2017

Scope

This International Standard specifies a method for the determination of the soap and organic-acid content of raw styrene-butadiene rubber (SBR). The method depends on the extraction of the organic acids and soaps from the rubber by means of a solvent. In practice, therefore, it is convenient to determine both organic-acid and soap contents on separate portions of the same solvent extract. Since the soaps and organic acids present in the rubber are not single chemical compounds, the method gives only an approximative value for the soap and organic-acid content. The method is applicable to all types of styrene-butadiene rubber, but slight modifications are required for oil-extended rubbers. 3 Principle A weighed test portion of the rubber, in the form of thin strips, is extracted by ethanol-toluene azeotrope, or ethanol-toluene-water mixture. After making up to standard volume, an aliquot portion of the extract is withdrawn and titrated with standard acid for determination of soap and with standard alkali for the determination of organic acid. With oil-extended rubbers it may be necessary to employ a second aliquot portion of the diluted extract as a control in order to detect the colour change at the end-point. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 4.1 Ethanol-toluene azeotrope (ETA) Mix 7 volumes of ethanol with 3 volumes of toluene. Alternatively, mix 7 volumes of commercial grade ethanol with 3 volumes of toluene, and boil the mixture with anhydrous calcium oxide (quicklime) under reflux for 4 h. 4.2 Ethanol-toluene-water mixture

ISO 7781:1996 history

• 2017 ISO 7781:2017 Styrene-butadiene rubber, raw - Determination of soap and organic-acid content
• 2008 ISO 7781:2008 Styrene-butadiene rubber, raw - Determination of soap and organic-acid content
• 2001 ISO 7781:2001 Styrene-butadiene rubber, raw - Determination of soap and organic-acid content
• 1996 ISO 7781:1996 Rubber, raw styrene-butadiene - Determination of soap and organic-acid content
• 1986 ISO 7781:1986 Rubber, raw styrene-butadiene; Soap and organic acid content; Determination