||January 1, 2007
Phenolic antioxidants are commonly added to synthetic latex and latex compounds as well as to natural rubber compounds in order to protect the polymer and the finished articles against oxidation during storage, transport and service life. Typical addition levels are 0.3 to 0.5 parts by weight (pbw) in synthetic latex and 0.5 to 1.5 pbw in natural rubber latex compounds used for thin gloves or elastic thread manufacturing. Quantitative determination of the antioxidant into the latex, the latex compound or the finished product may be necessary for various purposes such as product and application development, troubleshooting studies (typically claims investigations, quality issues in production), and customer technical support. Most often such analyses are performed in order to check that the polymer contains the expected concentration of the additive or to assess how much of the additive is remaining in the polymer after storage or aging. This paper will review briefly the most commonly used technique for antioxidant quantification based on extraction followed by a chromatographic analysis and its limitations in the case of multi-component antioxidants or antioxidants blends. Another approach based on the use of differential scanning calorimetry (DSC) will then be discussed and illustrated with some results in synthetic latex.