The Phenolic bonded paper laminated tube V3520 is made by the paper of pure wood purl, which is coiled as basal material with phenolic resin as adhesive, then to be reeled and hot-pressed at high temperature, and finally cured to thermoset  phenolic laminated tube.

Its thermal class is E, with higher dielectric property at dry conditions, used as insulating structural parts at dry conditions or in transformer oil for electrical equipments

Its surface should be smooth without delamination、bubble and ridge. The marks of finishing and creases under the tolerance is allowed. The slight uneven color、scrape、tearing drop and a few impurities which are not retard the electric resistance are also allowed. The slight crease、bubble and imprint of core die on inner wall are permitted. The end surface should be cut trimly.

The surface is coated with insulating varnish of huminity-proof and oil resistance. The color is natural, light snuff color or henna color.

The material of V3520 should not be delaminated and detached when being sawed, drilled, lathed(not included screw thread lathing) and milled.