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.

Physical Properties

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.

Typical Plastics Color List

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"óno 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:

Standard Sawed Sheets 12"X24"

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

Round Rods

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

Square Rods

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

Cast Sheets & Slabs

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

Cylinders & Tubes

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"