This section is from the book "Plastics In The School And Home Workshop", by Andrew Jules Lockrey. Also available from Amazon: Plastics In The School And Home Workshop.
While the process sounds comparatively simple, it is by no means feasible to attempt to cast objects in cast resin outside the plant, as every factor must be kept under strict control not usually possible without unusual care and expensive equipment. True, a jar of liquid cast resin will harden if left on a hot radiator for a couple of weeks, but this is by no means "cast resin", and the cost of the liquid is as much as the finished material. Universities such as Columbia University and testing laboratories have occasionally cast and vulcanized the material successfully, in connection with photo elastic strain analyses, etc., but their equipment and resources are of course far beyond that of the average homeworkshop or school.
The specific gravity of cast phenolic resins is 1.29, about one and a quarter times the weight of water. The compressive yield point is around 10,000 pounds per square inch, and the tensile strength about 8,000 per square inch. The dielectric strength is about the same as that of mica. The weight per cubic inch is .048, a 1" square rod 20" long weighing a pound.
The material is non-inflammable, absorbs no moisture, being completely homogeneous; it resists alcohol, oils and common acids. It is tasteless and odorless, and the colors are fast. The material is an extremely poor conductor of heat.
Following is a detailed list of its physical characteristics.
(Prepared by Modern Plastics, checked by U. S. Bureau of Standards).
Properties | Cast Resins |
Specific Gravity | 1.27-1.32 |
Specific Volume, cubic inch per lb | 20-23 |
Tensile Strength, lbs. per sq. inch | 8000-12000 |
Compressive Strength, lbs. per sq. inch | 15000-30000 |
Impact Strength, ft. lbs. per sq. inch. | 1-2.5 |
Modulus of Elasticity, lbs. per sq. inch x 10^5 | 5-25 |
Thermal Conductivity, 10^-4 cal., per second | |
centimeter degree centigrade | 3-5 |
Thermal Expansion, 10-6 per degree centigrade | 2.8 |
Specific Heat, cal. per degree centigrade gram | 0.3-0.4 |
Heat Resistance, ° F | 160° |
Water Absorption, % by weight, 48 hrs. | 0.01-0.05 |
Volume Resistivity (a) (b) (c) (d) | 2 X 10^8 |
Breakdown Voltage, 60 cycles, volts per | |
mil (instantaneous) | 300-450 |
Dielectric Constant, 106 cycles | 5-7 |
Power Factor, radio frequencies | 1-4.5 |
Power Factor, e and f | 0.5-8.0 |
Refractive Index ND | 1.5-1.7 |
Burning Rate | Nil |
Effect of Age | None |
Effect of Light | Practically No effect |
Effect of Weak Acids | No effect |
Effect of Strong Acids | No effect |
Effect of Weak Alkalis | None |
Effect of Strong Alkalis | Slight pitting |
Effect of Solvents | None |
Metal Inserts | None |
Machining Qualities | Excellent |
Clarity | Opaque, translucent |
Color Possibilities | Water clear |
(a) Megohms centimeters.
(b) 10^10 ohms per cubic centimeter.
(c) At 30° centigrade 10^10 ohms per cc.
(d) Surface at 50% relative humidity.
(e) 60 cycles.
(f) Audio frequencies.
Cast resins are available in some two or three hundred colors and color combinations, including transparent, translucent and opaque colors in both the plain and mottled form. Any darker color can be mottled with a lighter color, although mottles are usually white. The material is also available in water-clear, to which a touch of transparent blue is occasionally added for the same reason that bluing is used in laundry. The opaque colors are usually mineral, and the transparent colors aniline. Transparent colors, as a rule, cost about ten percent more than the translucent and opaque colors. Following is a partial list of the colors offered by one manufacturer.
Jet Black, Cherry Red, Green Quartz, Brown Onyx, Amethyst, Slate Blue, Jade Green, Natural, Rose Quartz, Carnelian, Peacock Blue, Horn, Middy Blue, Coral, Morocco Red, Grass Green, Brazilian Onyx, Mottled Green, Turquoise, Old Ivory, Navy Blue, Black & White, White Coral, Capucine, Yellow, Dk. Wine, Black Onyx, Pale Amber, Mahogany Brown, Bt. Green, Buttercup Yellow, French Beige, Natural Onyx, Lipstick Red, Lime Green, Dk. Green Quartz, Queen Blue, Leafmold Brown, Hindu Green, Cinnabar Lacquer, Tango Yellow, Lilac Tint, Green &White, Blue &White, Blossom Pink, Sky Tint, Night Blue, Bitter Orange, Cocktail Blue, Carioca Brown, Pompadour Blue, Bt. Orange, Alpine Blue, Pearl White, Spring Lilac, Chili Brown, French Violet, Orange Onyx, Shell Onyx, Carnelian Onyx, Butter Scotch, Bulgarian Green, National Onyx, Oak Brown, Dove Grey, Golden Orange, Commodore Blue, Signal Red, Azure Blue, Mottled Wine, Royal Copenhagen, Mottled Green, Cocktail Red, C & R Amber, Beige Onyx, Opal, Onyx Base, Base and Black, Base and Green, Base and Brown, Base and Blue, Rooster Red, Br. Green Mottled, Blue Crystle, Demi Shell, Dark Amber, Dark Sapphire, Casco Emerald, Dark Emerald, Amethyst, B. M. Rose, B. M. Amber, B. M. Emerald, B. M. Ruby, B. M. Sapphire, B. M. Topaz, Pink Quartz, Amber Quartz, Dark Brown, Royal Blue, Dark Green, Wine,
French Shell, White Crystle, Jade Quartz, Sapphire Quartz, Translucent Black, Slate Gray, New Amethyst, Frosted Crystle, Lavender Quartz, Oyster White, White Quartz.
In addition to the above colors, most companies also make a mixed color, called variously "variegated", "jazz", "random", etc., which consists of the small remainders of the various color-batches run during the day, all poured into the same molds. Occasionally some very weird effects are encountered in this "color"—no two pieces ever being alike. Some companies offer a discount on this material.
All of the chemicals of which cast resins are made, incidentally, are produced in the United States, and the original patents which lead up to the development of the product, as well as most of the subsequent patents of importance, were granted in this country, so that cast resins are a completely "all-American" product.
Sizes and Weights of Rods, Sheets, Tubes Following is an abbreviated table of standard sizes in which cast resins are available:
Thickness in inches | Approx. Lbs. Per Sq. Ft. | Thickness in inches | Approx. Lbs. Per Sq. Ft. |
1/8 | .85 | 5/8 | 4.27 |
3/16 | 1.28 | 11/16 | 4.68 |
1/4 | 1.71 | 3/4 | 5.13 |
5/16 | 2.13 | 13/16 | 5.53 |
3/8 | 2.56 | 7/8 | 5.98 |
7/16 | 2.98 | 15/16 | 6.38 |
1/2 | 3.42 | ....... | ....... |
9/16 | 3.83 | 1 | 6.84 |
Diameter | Length | Weight per Unit |
3/8" | 6" | .034 |
3/8" | 12" | .065 |
7/16" | 12" | .098 |
1/2" | 14 1/4" | .137 |
9/16" | 20" | .235 |
5/8" | 17 5/8" | .261 |
3/4" | 19 3/4" | .433 |
7/8" | 21" | .60 |
1" | 20" | .74 |
1 1/8" | 20 3/4" | .96 |
1 1/4" | 20 5/8" | 1.2 |
1 3/8" | 20 1/2" | 1.35 |
1 1/2" | 21 1/2" | 1.75 |
1 3/4" | 20 1/2" | 2.30 |
2" | 20 1/2" | 3.10 |
2 1/4" | 16 1/4" | 2.90 |
2 1/2" | 16 1/4" | 3.70 |
3" | 18" | 5.85 |
3 1/4" | 16" | 6.30 |
3 3/4" | 14 7/8" | 7.45 |
3 7/8" | 12 5/8" | 6.98 |
4" | 12 5/8" | 7.23 |
5" | 12 1/8" | 11.0 |
6" | 11 1/2" | 15.35 |
Length | Weight per Unit | |
7/16" reg | 12" | .116 |
1/2" reg | 12" | .147 |
5/8" | 12" | .223 |
3/4" | 12" | .328 |
7/8" | 20 1/2" | .76 |
1" | 21" | 1.0 |
1 1/4" | 21" | 1.55 |
1 1/2" | 20 7/8" | 2.19 |
1 3/4" | 21" | 3.96 |
2" | 21" | 3.94 |
2 1/4" WS3 | 14 1/2" | 3.43 |
4" | 12 1/4" | 8.50 |
Thickness | Length | Width | Weight per Unit |
3/16" | 8" | 6" | .45 |
1/4" reg | 15 1/2" | 6" | 1.15 |
5/16" | 16" | 6" | 1.38 |
3/8" reg | 16" | 6" | 1.79 |
7/16" | 16" | 6" | 2.11 |
1/2" reg | 16" | 6" | 2.23 |
5/8" | 16" | 6" | 2.86 |
3/4" reg | 16" | 6" | 3.43 |
7/8" | 16" | 6" | 4.00 |
1" | 16" | 6" | 4.47 |
cyl | O.D | I.D. per Unit | Weight Length | |
#1 | 2 1/2" | 2" | .75 | 8 1/2" |
#2B | 3 1/8" | 2 5/8" | .90 | 8 1/4" |
#3 | 3 1/2 | 2 5/8" | 1.75 | 8 |
#5B | 5 5/8 | 2 1/8" | .75 | 8 1/4" |
#7 fl | 3-3/16" | 2 5/8" | 1.00 | 8-7/16" |
#10M | 2 3/4" | 2 3/8" | .62 | 8" |
#12 | 3 7/8" | 3 1/8" | 1.84 | 9 1/8' |
#13 | 1-15/16" | 1-7/16" | .58 | 8 1/2" |
#15 | 3" | 2 | 1.42 | 8 3/8" |
#18 S | 3" | 2 5/8" | .80 | 8 3/8" |
#29 | 2 7/8" | 2 1/4" | .87 | 8" |
#65 | 4" | 2 7/8" | 2.40 | 8 1/2" |
CP 1 | 1 3/8" | 1 | .325 | 6" |
CP 2 | 1 1/2" | 15/16" | .31 | 3 7/8" |
CP 3_ | 1" | 1/2' | .115 | 6" |
 
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