Aramid Paper

Toughness and thermal class in one sheet

Aramid paper is the workhorse of Class H machine insulation. It holds its dielectric strength at 220 °C continuously, it does not melt, and unlike most films it survives being pushed into a stator slot without splitting. That combination is why it appears wherever a winding has to be both hot and handled.

• Thermal class 220 (Class H) as standard, with Class C grades available
• Inherently flame resistant, charring rather than melting or dripping
• High tear and edge-tear strength through automated slot insertion
• Stable in transformer oil, varnishes and impregnating resins
• Retains properties after long-term thermal ageing and irradiation

Calendered and uncalendered forms

The same fibre is supplied in two very different papers, and picking the wrong one is the most common specification error we see.

Calendered

Hard-pressed under heat to a dense, smooth sheet. Higher dielectric strength per unit thickness, dimensionally stable, and the right choice for slot liners and phase separators.

Uncalendered

Low-density and conformable, with high resin uptake. Used where the paper has to follow a curve or absorb impregnating resin: wrapping, layer insulation and honeycomb core stock.

Our RHOARAMID portfolio

Supplied as slit rolls, sheets or die-cut parts to your drawing.

Where it is specified

Aerospace

Honeycomb core for structural and interior panels, and API laminate insulation in generators, actuators and power distribution where weight and flammability are both constrained.

High-end motors

Slot liners, phase separators and closing wedges in traction and industrial motors running Class H, including inverter-driven machines where the laminate carries a polyimide core for corona resistance.

Transformers

Layer and barrier insulation in dry-type and cast-resin transformers, and in oil-filled units where the higher thermal class allows a smaller core for the same rating.