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Phenolic resin, one of the first fully synthetic polymers developed
Phenolic resin, one of the first fully synthetic polymers developed, is a thermosetting polymer produced from the reaction between phenol and formaldehyde. It is known for its excellent rigidity, dimensional stability, and creep resistance, as well as good electrical properties at elevated temperatures.
Key features of phenolic resin include:
- Thermal Stability: Phenolic resins are thermally stable and can be cured by crosslinking with formaldehyde donors such as hexamethylenetetramine.
- Dimensional Stability: They offer high dimensional accuracy and stability under normal atmospheric conditions, with a linear mold shrinkage of 0 to 0.01 in./in. and a coefficient of linear thermal expansion of about 8-45x10−6 in./in. °C.
- Creep Resistance: Phenolic resins have high creep resistance, meaning they can withstand loads without significant deformation over time.
- Electrical Properties: They are good electrical insulators, with a dielectric strength of 260 to 400 V/mm and a dissipation factor of 0.03 to 0.3 for general-purpose grades.
- Chemical Resistance: Phenolic resins are resistant to common solvents, weak alkalis, weak acids, hydrocarbons, and detergents, but are attacked by strong alkalis and concentrated oxidizing acids.
- Low Water Absorption: Water absorption of phenolic molding compounds is only about 0.03 to 1.75%.
- Weather Resistance: While phenolics can be used outdoors for short periods, prolonged exposure to ultraviolet light and heat can cause failure.
Applications of phenolic resins are diverse, ranging from plywood and particle board manufacturing to molding compounds for electrical applications, brake linings, industrial laminates, and decorative laminates such as "Formica". They are also used in the production of presswood, Bakelite, and as an adhesive in the manufacturing of tires and other rubber products. Phenolic resins are also known for their flame retardancy and are used in applications where fire resistance is a critical factor.
In summary, phenolic resin is a versatile material with a range of properties that make it suitable for a variety of industrial applications, particularly those requiring heat resistance, dimensional stability, and electrical insulation.
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