What Is Phenolic Laminate?
Phenolic laminate is a thermoset composite — layers of reinforcing substrate (woven glass fabric, paper, or canvas) impregnated with thermosetting resin (phenol-formaldehyde or epoxy), then cured under heat and pressure. Unlike thermoplastics, phenolic laminates do not melt or soften when reheated and maintain structural integrity to their service temperature limits.
The reinforcement type and resin system determine the NEMA grade designation and resulting properties — making grade selection the most critical specification decision.
Key Phenolic Grades
Woven fiberglass + epoxy resin. Highest-performance general-purpose grade. Excellent electrical insulation, low moisture absorption, high mechanical strength. Standard for PCB substrates and electrical components in wet environments.
Similar to G-10 with higher-temperature epoxy. Retains flexural strength at elevated temperatures. Specified for motor windings and transformer insulation in high-temperature environments.
Cotton canvas + phenolic resin. Lower electrical performance but superior machinability and impact resistance. Standard for bushings, gears, jigs, and structural components.
Finer weave than CE producing smoother surface finish and better dimensional consistency. Preferred for precision bushings, bearing components, and electrical panels.
XX / XXX (Paper grades): Paper reinforcement with phenolic resin. Lower mechanical strength but excellent machinability and moderate electrical insulation. Used for electrical panels, terminal boards, and general-purpose insulating in dry indoor environments.
Key Properties
Electrical insulation: High dielectric strength and volume resistivity across a range of voltages and frequencies. Glass-reinforced grades maintain properties even after moisture exposure.
Dimensional stability: Does not creep significantly under sustained load — reliable where tight clearances must be maintained over long service periods.
Temperature range: ~250°F (120°C) for standard phenolic grades, over 300°F (150°C) for G-10 and G-11. Combined with flame resistance, this makes phenolic standard in electrical switchgear, transformers, and motors.
Machinability varies significantly. Canvas and linen grades (CE, LE) machine freely. Glass-reinforced grades (G-10) are significantly more abrasive and require carbide tooling. All grades produce fine particulate dust requiring respiratory protection.
Applications
Frequently Asked Questions
What is the difference between G-10 and Garolite?
Garolite is a trade name. Garolite G-10 refers to the same NEMA G-10 grade as any other G-10 product. Properties are defined by the NEMA standard, not the brand.
What is the difference between G-10 and FR-4?
Nearly identical properties. FR-4 includes a flame-retardant additive meeting UL 94 V-0. For most structural/electrical uses they're interchangeable. FR-4 is required where UL flammability rating is specified.
Is phenolic safe to machine?
Not hazardous electrically, but dust — especially from glass-reinforced grades — is a respiratory and skin irritant. Requires respiratory protection, dust collection, and skin protection.
Can phenolic be used outdoors?
Glass-reinforced grades (G-10) perform well in wet environments. Paper and canvas grades absorb moisture and should not be used outdoors. For outdoor electrical insulation, G-10 or G-11 with surface treatment is correct.
Where can I buy phenolic?
Plastic-Craft Products stocks G-10, CE, LE, and other grades in sheet, rod, and tube at West Nyack, NY. No minimum orders. Call (845) 358-3010 or email [email protected].
Ready to Order Phenolic Sheet, Rod, or Tube?
Plastic-Craft stocks G-10, Garolite, CE, LE, and other phenolic grades — cut to exact dimensions or machined to print with no minimum orders and ISO/AS9100D certified quality.
(845) 358-3010