Degraded Rayon From a Transformer Oil Sample

This is an example of a rayon fiber that has undergone hydrothermal degradation in a transformer environment. The average polymer length is reduced with a resultant loss of birefringence and a reduction in the refractive index along the length.

Transmitted Circular Polarized Light Illumination

Rayon fiber cord is sometimes used as ties in the transformer or on leads as insulation.

This type of degradation indicates temperatures typically over 90 degrees Celsius and elevated moisture content.