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Phenolic molding materials - some times called the workhorse of the thermosets - are high-performance engineering plastics. They are used principally in compounds containing either organic or inorganic reinforcing fibers and fillers. Color of phenolic compounds is limited to black or brown.

Phenolics are molded by compression, transfer, and injection methods, and by extrusion. Injection molding usually provides the fastest cycle times, but it may not be the most economical method for all parts. in long-fiber- filled compounds, for example, maximum tensile and flexural strengths are obtained by compression molding.

The phenolic resins are also used as bonding and impregnating materials. Bonding resins are available as pure phenolic compounds and, more often, formulated with other materials to provide special properties. The other materials are not neccessarily limited to those normally considered fillers; for example, they maymay be chemicals or elastomers.

Properties: Phenolic molding compounds are characterized by low cost, superior heat resistance, high heat-deflection temperature, good electrical properties and flame resistance, excellent moldability and dimensional stability, and good water and chemical resistance. A number of compounds provide maximum performance in specific property areas. Examples are: nonbleeding, heat resistant, impact, and electrical.

Phenolics TYPE OF COMPOUNDASTM or UL test Property General purpose Impact Non- bleeding Heat resistant Glass reinforced Electrical Special purpose* PHYSICAL D792 Specific gravity 1.35-1.46 1.36-1.41 1.37-1.38 1.36-1.75 1.41-1.84 1.7-2.0 1.37-1.75 D570 Water absorption, 24 hr X in. thick (%) 0.6-0.7 0.6-0.9 0.8-0.9 0.05-0.20 0.30-0.35 0.05-0.2 0.20-0.40 MECHANICAL D638 Tensile strength (psi) 6,500-7,000 6,000-7,000 6,000-7,000 5,000-7,000 5,000-6,000 6,000-12,000 7,000-9,000 D790 Flexural modulus (10' psi) 11-13 12 10 17-25 14 20-30 10 D790 Flexural strength (psi) 9,000-11,000 10,000 10,000 9,000-11,000 10,000 12,000-24,000 9,500 D256 Impact strength, Izod (ft-lb/in. of notch) 0.30-0.35 0.6-1.05 0.28 0.28-0.45 0.26 0.4-1.5 0.50 D785 Hardness, Rockwell E 70-95 82 82 75-88 94 92-104 76 THERMAL C177 Thermal conductivity (10- cal-cm/sec-cm²- °C) 7.1 7.9 - 16.0 - - 8.8 D696 Coef. of thermal expansion (10-'in./in.- °C) 3.95 3.56 4.40 2.60 2.80 1.80 3.60 D648 Deflection temperature (°F)
At 264 psi 275-360 270-500 370 310-400 330-380 370-550 360-430 UL94 Flammability rating, % in. V-1 HB - V-0 V-0 V-0 HB ELECTRICAL D149 Dielectric strength (V/nifl) Short time, 1/8-in. thk 350 350-400 200 400 170 400 175 D 150 Dielectric constant
At I kHz 5.2-5.3 5.2-5.4 - 4.9-6.5 11.7 4.4 7.8 D 150 Dissipation factor
At I kHz 0.04-0.05 0.04-0.06 - 0.025-0.10 0.15 0.03 0.12 D257 Volume resistivity (ohm-cm)
At 73 F, 50% RH 10¹¹-10¹² 10¹¹-10¹² 10¹² 10¹¹-10¹³ 10¹² 10¹² 10¹¹ D495 Arc resistance(s) 100 50 - 184 181 181 - *Chemical-resistant compound