Terahertz absorption spectra of antioxidants in insulating polymers

Terahertz absorption spectra were measured for nine kinds of antioxidants. The spectra were also measured for low-density polyethylene sheets that contain each antioxidant with different contents. As a result, a fingerprint spectrum appears for each antioxidant, from which the antioxidants become distinguishable and their contents can be estimated.

I. Introduction

Organic insulating polymers play important roles in various pieces of electrical apparatus. As their degradation has a risk of causing malfunctions of such apparatus or fatal accidents, many kinds of additives such as antioxidants are usually added for preventing oxidative decomposition or degradation [1]. When more than two kinds of antioxidants are used, they often exhibit positive or negative synergisms [2]. However, it is usually difficult for users of polymeric insulators to obtain information on antioxidants in polymers. Therefore, it is valuable for users to identify their antioxidants.