What is electrical insulation pressboard？

Colortrieve - What is Pressboard?

Presa | High Frequency drying +forming machine for pressboard insulation collars | Energy Industry

Acco 2 inch Red Pressboard Report Covers - 4 sizes

T4 High-Density Insulation Paperboard Manufacturer. Pressboard for Transformer #manufacturer

What does pressboard mean?

Check This Pressboard Report Cover Out! A Must-Have!!!