ASTM D5508 Residual Acrylonitrile Monomer in Styrene-Acrylonitrile Copolymer Resins & Nitrile-Butadiene Rubber 

What is ASTM D5508?

ASTM D5508 is a standard test method used for the detection of residual acrylonitrile monomer in styrene-acrylonitrile copolymer resins and nitrile-butadiene rubber using headspace-capillary gas chromatography (HS-CGC). The residual acrylonitrile in nitrile rubbers (NBR), styrene-acrylonitrile (SAN) copolymers, and ABS resins can be measured to determine the polymers’ appropriateness for various uses. The ASTM D5508 test method (Standard Test Method for Determination of Residual Acrylonitrile Monomer in Styrene-Acrylonitrile Copolymer Resins and Nitrile-Butadiene Rubber by Headspace-Capillary Gas Chromatography (HS-CGC)) is limited to dry rubbers and resins due to the presence of  3-hydroxypropionitrile in lattices. 

Sample Preparation Guide

According to ASTM D5508, the polymer test unit (sample) that is submitted for analysis should be a 1¾ inch (45 mm) cube. 

What are the Testing Procedure and Requirements for the ASTM D5508? 

In the ASTM D5508 test procedure, for each polymer, two dispersions (in o-dichlorobenzene) are made and sealed in headspace vials: one includes the polymer in a solvent, and the other contains the polymer, solvent, and a known standard amount of acrylonitrile (AN). Under ambient circumstances, both vials are shaken for a set amount of time. The vials are thermally equilibrated in a constant-temperature bath after shaking. 

Then, an aliquot of hot headspace gas from each vial is fed into a capillary gas chromatographic column when the timed equilibration is completed. The transfer takes place using an automated injection method. The capillary column provides the chromatographic resolution needed to separate the AN from any other volatiles present. A nitrogen-specific detector is used in ASTM D5508 testing to detect the AN response (NPD). Using a conventional addition calculation, the raw data signal is transformed into a relative RAN concentration. 

Analysis Results and Interpretation

The ASTM D5508 test technique includes the detection of residual acrylonitrile monomer in styrene-acrylonitrile copolymer resins and nitrile-butadiene rubber by using headspace-capillary gas chromatography (HS-CGC). As per ASTM D5508, the residual acrylonitrile monomer is reported in parts per billion (ng/g).

By Malhar Khole

Malhar Khole is a Material Testing Associate at MaTestLab Inc. and holds a postgraduate degree in Material Science and Technology from IIT...