Materials and standards

Transformer pressboard

A dense board made from pure kraft pulp, pressed and dried. It is the most common solid insulation inside oil-filled transformers.

Properties

• Thermal class A (105 °C) in transformer oil
• Thickness commonly 0.5 mm to 8 mm; thicker boards by lamination
• Can be dried and oil-impregnated with the winding
• Density roughly 1.0 to 1.3 g/cm³ depending on grade

We make from it: Pressboard strips, dovetail strips and spacers, insulation kits, clack bands. View product

Phenolic laminate (Bakelite / Hylam)

Layers of paper or cotton fabric bonded with phenolic resin under heat and pressure. Hard, rigid and dimensionally stable.

Properties

• Paper-base grades (P) for electrical use; fabric-base grades (F) for mechanical strength
• We supply F4 electrical grade as standard
• Good machinability: can be drilled, tapped and milled
• Resists transformer oil and moderate heat

We make from it: Bakelite strips and small cut parts. View product

Permawood (densified laminated wood)

Thin wood veneers bonded with resin under high pressure. Much denser and stronger than natural wood, with good insulating properties.

Properties

• High compressive strength for clamping and pressure parts
• Machinable to tight tolerances
• Low moisture absorption after drying
• Compatible with transformer oil

We make from it: Clamping blocks, cleats, pressure pads, machine components to drawing. View product

Seasoned hardwood

Natural hardwood, seasoned to reduce moisture, turned into round rods.

Properties

• Good insulating strength after drying and oil impregnation
• Straight, round and smooth after turning
• Low cost for simple support and spacing duties

We make from it: Hardwood rods 6 mm to 16 mm diameter. View product