High Pressure Laminates (HPL)

High Pressure Laminates (HPLs) are hard, dense materials made by applying heat and pressure to substrate layers impregnated with synthetic resin. When heat and pressure are applied, polymerization transforms the layers into a thermoset industrial laminated plastic. Paper, canvas and glass fabric are the most common substrates. The resins include epoxy, phenolic, melamine, silicone and polyester.

HPLs are characterized by low cost, superior heat resistance, high heat deflection temperatures and good electrical properties. Applications include electrical device, mechanical, oil & gas and power generation. Given their use in many electrical applications, the industry generally refers to the materials based on their NEMA rating (The National Electrical Manufacturers Association).

Available stock shapes include:

Sheets               .030″ – 6.00″ thick – up to 48″ x 96″
Rod                    .250″ – 4.00″ diameter – up to 48″ lengths (varies by grade)
Tube                  .250″ – 10.00″ ID and .500 – 12.00″ OD (varies by grade)

Custom sizes can be manufactured. ACI provides CNC machining of your parts to shape and length.

NEMA Overview

  • X,XX,XXX – Paper substrate/Phenolic Resin Good for washers, sleeves, switch bases and panel boards (MIL-I-24768/12-PBM, MIL-I-24768/11-PBG and MIL-I-24768/10-PBE)
  • C, CE – Canvas substrate/Phenolic Resin Used for gears, pulleys, sheaves, insulators, bushings, washers and rollers where good bond strength required (MIL-I-24768/16-FBM and MIL-I-24768/14-FBG)
  • L, LE – Linen substrate /Phenolic Resin Higher electrical dissipation factor than X and C grades. Good for radio components, fine gears and pinions.   (MIL-I-24768/15-FBI and MIL-I-24768/13-FBE)
  • G-3 – Glass Cloth/ Phenolic Resin High dielectric strength and mechanical properties. (MIL-I-24768/18-GPG)
  • G-7 – Glass Cloth/ Silicone Resin High heat and arc resistance. (MIL-I-24768/1-GSG)
  • G-9 – Glass Cloth/ Melamine Resin High arc resistance.   (MIL-I-24768/1-GME)
  • G-10, 11 – Fiberglass/Epoxy Resin Where the strength to size ratio is critical. Good for terminal boards and structural components. G11 is higher temperature version. (MIL-I-24768/2-GEE and MIL-I-24768/3-GEB)
  • FR4 and FR5 – Fiberglass/Epoxy Resin Brominated epoxy resin to reduce fire hazard. FR5 is higher temperature version. (MIL-I-24768/27-GEE-F and MIL-I-24768/27-GEB-F)


Note that not all ratings apply to all shapes.

Download PDF Properties Table

All properties are generalized. Material purchased may vary. You can request specification for products purchased.


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