Phenolics are thermoset resin impregnated reinforcing materials (paper, cotton fabric, glass fabric, etc.) that are cured under heat and pressure to form solid shapes having high mechanical and electrical insulating properties. High pressure laminates, as a group, are often inaccurately referred to as “phenolics” due to the wide use of phenolic resin reinforced grades such as paper/phenolic and fabric/phenolic. Actually, many other resin systems are employed including epoxy, melamine, and silicone.
Phenolic Laminates are made by applying heat and pressure to layers of paper, canvas, linen or glass cloth impregnated with synthetic thermosetting resins. When heat and pressure are applied to the layers, a chemical reaction (polymerization) transforms the separate layers into a single laminated material with a "set" shape that cannot be softened again -- therefore, these materials are called "Thermosets". A variety of resin types and cloth materials can be used to manufacture thermoset laminates with a range of mechanical, thermal, and electrical properties.
Physical strength, resiliency, ease and versatility of fabrication, and excellent electrical properties make Phenolic Laminates useful as support components in a wide range of mechanical and electrical applications. Phenolic Laminates are strong, stiff, and have high impact and compressive strengths. And, they do not soften upon re-heating, so they are easy to saw, drill, tap, and machine with ordinary tools. "FR" grades are flame retardant.
Glass-based grades have the highest dimensional stability and mechanical strength, as well as low moisture absorption. However, they are not as easily machined as paper or cotton fabric laminates.
There many are different grades(in no particular order):
G-11: Mil-I-24768/3 --Glass cloth with epoxy resin. Higher heat resistance then G-10.
G-10/FR-4: Mil-I-24768/27 --Flame retarded glass epoxy laminate.
G-9: Mil-I-24768/1 --Glass cloth impregnated with a melamine resin.
G-7: Mil-I-24768/17 --Glass cloth impregnated with a silicone resin. Flame and arc resistant.
G-5: Mil-I-24768/8 Glass cloth with melamine resin binder. Flame and arc resistant.
G-3: Mil-I-24768/18 --Glass cloth with phenolic resin. Not flame retardant.
FR-5: Mil-I-24768/28 --Glass cloth with a melamine resin. Flame and arc resistant.
XXX: Mil-I-24768/10 --Bleached Kraft paper impregnated with a phenolic resin.
XX: Mil-I-24768/11 --Bleached or unbleached paper impregnated with phenolic resin.
X: Mil-I-24768/12 --Unbleached Kraft paper with a phenolic resin.
LE: Mil-I-24768/13 --Electrical grade, fine weave cotton cloth impregnated with a phenolic resin.
CE: Mil-I-24768/14 --Electrical grade cotton cloth impregnated with a phenolic resin.
Linen: Mil-I-24768/15 --Fine weave cotton cloth impregnated with a phenolic resin.
Canvas: Mil-I-24768/16 --Cotton cloth impregnated with a phenolic resin.
Polyimide: --Glass reinforced kerimid 601 bonded laminate.
N-1: --Nylon Reinforced Phenolic.
Paper Reinforced Phenolic
These grades are composed of a paper base impregnated with a phenolic resin binder. Grade X has the lowest resin content for good impact strength (but less than the fabric grades). Grade XX has increased resin content. This decreases the impact strength, but increases the electrical strength and reduces moisture absorption. Grade XXX contains the highest resin content and therefore the best electrical properties of the paper grades. It also has minimum cold flaw characteristics.
Canvas and Linen Reinforced Phenolic
These grades are composed of a continuous cotton woven fabric impregnated with phenolic resin binder. Grade C and grade CE contain a medium weave canvas and are known primarily for their mechanical properties. These grades are not suitable for primary insulation. Grade L and LE contain fine weave linen and, like the canvas phenolic, are known mainly for their mechanical properties. The finer weave allows for machining more intricate shapes than C or CE. Although exhibiting better electrical properties than the canvas base, L and LE are not recommended for primary insulation.
G-3 (Glass Cloth / Phenolic Resin)
This material is made from woven glass cloth and high-temperature phenolic resin. It has excellent flexural, compressive and impact strengths and is capable of continuous operation over 350°F (175°C). NOTE: G-3 is not a common material.
G-5 and G-9 (Glass Cloth / Melamine Resin)
These materials are very hard, flame resistant, and have excellent electrical properties. G-5 and G-9 have high arc and heat resistance. G-9 is recommended for humid environments. They are used for switch board panels, arc barriers, circuit breaker parts, and structural electrical parts. Melamine phenolics are available in sheet, rod, and tube forms.
G7 (Glass Reinforced Silicone)
Composed of a continuous woven cloth base impregnated with a silicone resin binder, this grade has excellent heat and arc resistance. It has extremely good dielectric loss properties under dry conditions and good electrical properties under humid conditions, although the percentage of change is high.
G10 (Glass Reinforced Epoxy)
The most versatile all-around laminate, this grade is a continuous glass woven base impregnated with an epoxy resin binder. It has extremely high mechanical strength, good dielectric loss properties, and good electric strength properties, both wet and dry.
G11(Glass Reinforced Epoxy)
This grade is similar to G10/FR-4, with the addition of a higher operating temperature and improved mechanical strength at elevated temperatures.
A continous woven glass fabric laminated with an epoxy resin. This grade is extremely high in mechanical strength, has low moisture absorption and dissipation factors, and has superior electrical characteristics which are exibited over a wide range of temperatures and humidities. Grade G11 is flame retardant and at 300 degrees F retains 50% of its flexual strength while maintaining all of its electrical properties. This grade is recommended for applications where superior strength and excelent electrical properties are required at elevated temperatures. This material can be used where resistance to continuous operating temperatures of 350 degrees F is required.
N-1 (Nylon Reinforced Phenolic)
This grade is a continuous nylon woven cloth base impregnated with a phenolic resin binder. It has good electrical properties in high humidity and good impact strength, but is subject to creep and cold flow.
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