The analysis of polyethylene cable insulation using microspectrophotometry

The use of a microspectrophotometer system allows the direct in-situ analysis of the composition of small features and regions of interest in polyethylene insulated electrical cables. The Nanometrics Nanospec™ model 10 and model 20 microspectrophotometers allow the investigator to cover the UV/VIS/IR spectrum with a spatial resolution of better than 2 microns under favorable conditions. The method is entirely nondestructive and involves little more sample preparation than is required for a conventional microscopic examination of cable insulation. This paper presents examples of the range of applications to which this method can be applied. The analysis of the interior composition of voids can be determined as to whether water, dicumyl peroxide, air, acetophenone, or some other compound is present. The migration of antioxidants and crosslinking agents in freshly manufactured and used cables is studied. The compositional variation in various regions of cable insulations which were insufficiently homogenized during manufacture will be presented. The direct analysis of such localized regions is nearly impossible using conventional IR spectroscopy due to the requirement for a comparatively large sample size and the difficulty of extracting regions of interest from the insulation.