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Standards Development
This document specifies a method for the qualitative analysis of the organic acids in raw emulsionpolymerization styrene-butadiene rubber (E-SBR) using a gas chromatograph combined with mass spectrometer (GC-MS).
It is applicable to the identification of fatty acids and rosin acids (including disproportionated rosin acids).
The determination of the soap and organic-acid content of raw styrene-butadiene rubber (SBR) is specified in ISO 7781:2017.
SBR is the largest-volume synthetic rubber produced and consumed. It can be classified into emulsion SBR (E-SBR) and solution SBR (S-SBR) according to the polymerization process. During the polymerization of E-SBR, fatty acid soap and rosin acid soap are used as an emulsifier, these soaps will be converted to free fatty acids and rosin acids when the latex is flocculated. So E-SBR generally contains 4 to 7 percent of organic acids.
The content and type of organic acids in ESBR both have important effects on the products. E-SBR with more levels of fatty acids has faster cure rate than that of rosin acids, while rosin acids can bring the polymer better tack than fatty acids. It’s important for manufactures of E-SBR products to understand the variations of organic acids among different batches of raw materials.
ISO 7781:2017 resolves the quantitative analysis of organic acid, but it can’t be applied to identify the composition of the organic acids in E-SBR. It’s worthwhile to develop a standard method to identify the organic acids in E-SBR.
This document (ISO 7781-2) would not only provide a resolution for identifying the organic acids, but also can be used to measure the approximate percentage of each acid by comparing the chromatographic peaks. This document would be a good complementary to ISO 7781:2017.
The new work item proposal on splitting ISO 7781 in two parts was agreed at the plenary meeting of TC45/SC3 held in November 2023.
— Part 1 is the present standard which is a quantitative analysis ;
— Part 2 will be a qualitative analysis
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