Plasma as a tool for enhancing insulation properties of polymer composites

Abstract

The performance of electrical insulating polymers measured by comparative tracking index can be improved by flame retardant fillers in the polymer–matrix, but is not necessary effective due to persisting surface layers. We demonstrated a method for selective etching of polyphenol–matrix composites which leads to improvement of the tracking properties. Selective etching was performed by low pressure inductively coupled oxygen plasma generated at 35 Pa. Species created in discharge were monitored in situ during the treatment by optical emission spectroscopy (OES). Their surface reactions were established indirectly from X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS) after plasma treatment. The effective etching was done by oxygen species which removed off surface polymer layer within 10 to 15 s during plasma pulse operation to prevent surface overheating. The selective polymer removal improved tracking properties of the 70% glass filler reinforced composites up to 56%, whereas the performance level decreased with the decrease in filler content. This technology provides an important enhancement of polymer–matrix composites' tracking properties and resistance of composites to electrical short-circuit fire.