Phenolic Micarta board resins are formed by condensation polymerization of phenol and formaldehyde. They are thermoset resins which are commonly filled with organic and inorganic fillers, fibers and fabrics. Phenolic resins are classified as either resoles or novolacs. Resoles are produced by using an excess of formaldehyde at an alkaline pH. They are sold in liquid form as water or solvent solutions and are cured using heat and an acid catalyst. Resoles are used in panels, pultrusion and prepregs. They are commonly reinforced with paper, cloth or glass fabrics. Novolacs are produced by using an excess of phenol at an acid pH. They are supplied as solid products and require the addition of a cross-linker such as hexamethylenetetramine (HMTA) to cure the resin. Novolac resins are used as compounds for compression and injection molding, and are commonly reinforced with glass fiber and other fillers.
As a class, phenolic compounds are characterized by low cost, superior heat resistance, high heat deflection temperatures, good electrical properties, flame resistance, excellent moldability and dimensional stability, and good water and chemical resistance. They are of interest to the building and transportation industries due to their fire retardancy, low smoke generation and low smoke toxicity.
Special purpose phenolics are formulated to meet specific requirements such as maximum dimensional stability at high temperature (in automotive transmission valves), cracking resistance (pump housings), stability in steam environments (steam irons, coffee makers), electrical resistance (high voltage switch gears) or good machining qualities (fine tooth gears).
Other applications of Micarta board include bonding, impregnating and coating formulations. Phenolic tackifiers are used in synthetic rubbers for tires and hoses. Solvent cements based on phenolics are used as structural adhesives for metal-torubber bonds and for bonding vinyls to various substrates.
• Motor housings
• Pistons and packing rings
• Handles for pots and pans
• Seals and gaskets
• Automatic transmission rings
• Marine switch board panels
• Automotive ignition components
• Marine relay bases
• Motor housings
• Punch parts
• Thermostat housings
• Insulating washers
• Communication instruments
• Gears and pinions
• Components for aircraft instruments
• Radio and television terminal boards