Any new material will in the course of time be applied to the uses
for which it has special advantages, displacing older materials which
formerly served those purposes. The resulting product may sometimes be
used in the same manner as before, or the properties of the substitute
material may widen the usefulness of the finished product, or even make
possible a product almost wholly new.
Before the development of molded synthetic resins, electrical plugs and
sockets were usually made of porcelain or molded of marble dust and
shellac. In this use substitution has been almost complete. Wall plates
for electric switches and outlets were usually of brass. Today molded
tar-acid or molded urea resins are substituted in part. In neither of
these examples has the substituted material any important effect upon the
use of the product.
An example of a substitute material widening the usefulness of the
product is afforded by a new computing scale, where a molded urea resin
casing (substituted for metal in the older model) has aided in decreasing
the weight and has improved the appearance. Another example is the use
of laminated synthetic resin coil forms in radio frequency transformers
which, because of their better electrical properties at high frequencies,
have aided in the design of more compact units.
Examples of synthetic resins making possible a wholly new product are
more difficult to find, but the following will serve as illustrations:
Cast acrylate sheets to form curved cockpit enclosures for airplanes;
molded acrylate buttons for reflecting road markers; and new special
coatings, which make possible the use of metal cans for preserving foods
and beverages hitherto impossible to can without loss of flavor.
Motives for substitution.
One of the most important reasons why a manufacturer may decide to
substitute a synthetic resin for another material is the resulting
economy in the sense of economy in total costs. As a rule, the synthetic
resin will be more expensive pound for pound than the material for which
it is substituted; but frequently the manufacturing cost is enough lower
to more than make good the difference in material cost, because the resin
part will come from the mold almost in finished form, whereas the part
made of wood or metal will require considerable fabrication. In some
cases there may be a saving in marketing costs. For example, the shades
for large office fixture lights are now made of synthetic resin as well
as of opal glass. The resin shades are less expensive to ship because
they are lighter and require less expensive packing.
Another incentive toward substitution is to give novelty, and hence sales
appeal, to an old product. In many cases the use of synthetic resins fits
in with the present tendency to redesign an old-style product so that it
will be more compact, have more pleasing lines, and more color.
Still another incentive toward substitution is to give the product
greater usefulness, or lower costs in use. The great expansion in the
use of synthetic resins in surface coatings has come about because, with
these materials, coatings can be developed to fit special purposes, and
dry rapidly, which means an important saving to those who use them.
Materials displaced by synthetic resins.
The wide range of uses to which synthetic resins are now applied implies
that the materials displaced are numerous. For example, cast or wrought
iron or steel is displaced in timing gears and in many small machine
parts, such as cradle-type telephones; nonferrous metals in small machine
parts and novelties, such as inexpensive bracelets; glass in lamp shades
and in cosmetic containers; natural resins in lacquers; plastics, such
as cellulose acetate in safety glass or cellulose nitrate in colored
lacquers; other adhesives in bonding plywood; and cork or metal in bottle
closures.
In general, the quantity of material displaced is a very small part of
that material’s total market. Frequently, however, industries producing
the finished product have had to make substantial changes in their
equipment in order to use synthetic resins. This has been true in the
button industry, in the bottle closure industry, in the varnish and
lacquer industry, and in the various electrical supply industries; and
readjustment is now proceeding in the fancy container industry and in the
safety glass industry.
Competition between synthetic resins.
Any particular synthetic resin must compete for its market with other
synthetic resins, as well as with other materials. The basis of choice
or substitution will be the same as that which has already been briefly
discussed in connection with the displacement of other materials by
resins. As between a number of resins with properties fitting them for a
particular use, the total costs of using each will be compared and the
choice will go to the least expensive; but where a resin has special
advantages in a particular use it may win out over a less expensive
resin.
It should be emphasized that this battle of materials for markets
is a never-ending one. The fact that a specific synthetic resin has
achieved a certain position is no guarantee that it may not lose it
wholly or in part to some newer resin or other material. Thus cast
phenolic resin was for a time the only resin available in light colors
but urea resins became available in pastel shades and more recently
water-clear polystyrene and acrylate resins have come on the market.
Until recently tar-acid resins were without competition in laminating,
but urea resins now are used to some extent for the surface laminae and
the tar-acid resins now face a potential threat in a new product offered
to laminators. If the use of this cellulose sheet, which looks much like
blotting paper and which has lignin incorporated in it to act as a binder
in the press, should materially decrease the cost of laminated sheets, it
will mean serious new competition for the tar-acid laminating resins.
The general effect of the increase in number of types of synthetic resin
has been to modify the market outlook of the producers of each type. They
are now more inclined to view the market as being limited by the price
at which they can supply their product and by the physical properties of
each resin rather than attempt to exploit it as a universal resin for all
purposes.
Resins classified by cost.
At present the resins produced in largest volume are the alkyd resins for
use in surface coatings; the tar-acid resins for molding, laminating, and
surface coatings; the urea resins, chiefly for moldings; and the cast
phenolic resins. Roughly, the price per pound of pure resin material[12]
for these various resins may be compared as follows:
_Average sales price
of net resin, 1937
(per pound)_
Type of resin:
Cast phenolic $0.41
Tar-acid:
For molding .18
For laminating .13
For coatings .17
Alkyd .20
Urea .45
Because the cost of the filler is less per pound than the cost of the
resin, the cost of the tar-acid and urea molding powders will be less
than the figures given for the pure resin. On the other hand, wholesale
prices paid by consumers will include transportation and distribution
costs not included in the figures of manufacturers’ sales.
Vinyl resins, acrylate resins, and polystyrene resins are at present
produced in much smaller volume than those just listed. If and when the
volume of production is increased the price may be decreased. In 1937,
the price per pound of pure resin[12] was as follows:
_Average sales price
of net resin, 1937
(per pound)_
Type of resin:
Vinyl $0.69
Acrylate 1.66
Early in 1938, acrylate resins were being offered for sale at 85 cents
per pound for molding powder and $1.25 per pound for the cast material;
polystyrene resins at 72 cents per pound.
Petroleum resins, in 1937, sold for an average of 2 cents per pound net
resin content.[12] This low price puts them beyond competition of the
other synthetic resins in the uses in laminating and coating to which
they are adapted.
The physical properties of a resin and its uses.
A more expensive resin will be used in preference to a cheaper one, only
if the higher cost is more than offset by some physical property, such as
color, which makes it more desirable in a particular use. The most common
molding resin at present is the tar-acid type, but it is available only
in the darker colors and therefore has been at a disadvantage, where a
light color is desired, in competition with cellulose nitrate (celluloid)
and cellulose acetate plastics or with urea and cast phenolic resins. In
recent years the production of cellulose acetate molding compounds and
of urea resins has increased rapidly, largely under this stimulus. The
desire for color also promises well for the future of the acrylate and
polystyrene resins which are produced in water-clear grades or colored
with dyes or pigments.
TABLE 17.—_Synthetic resins and other plastics: Properties that affect
appearance_
-----------------------+---------+-------------+-----------+-------------
Type |Machining| Clarity | Color |Burning rate
|qualities| possibilities
-----------------------+---------+-------------+-----------+-------------
Synthetic resins: | | | |
| | | |
Tar-acid—Formaldehyde:| | | |
| | | |
Molded, wood flour | Fair to | Opaque | Limited | Very low
filler. | good | | |
| | | |
Molded, mineral | do | do | do | Nil
filler. | | | |
| | | |
Molded, fabric | do | do | do |Approximately
filler. | | | | nil
| | | |
Laminated, paper | Fair to | do | do | Very low
base. |excellent| | |
| | | |
Laminated, fabric | do | do | do | do
base. | | | |
| | | |
Laminated, asbestos | do | do | do |Approximately
cloth base. | | | | nil
| | | |
Cast |Excellent|Transparent, | Unlimited | Very low
| |translucent, | |
| | opaque | |
| | | |
Tar-acid—Furfural: | | | |
| | | |
Wood flour filler. | Fair to | Opaque | Limited | do
| good | | |
| | | |
Mineral filler. | do | do | do | Nil
| | | |
Fabric filler. | do | do | do | do
| | | |
Urea—Formaldehyde. | Fair |Translucent, | Unlimited | Very low
| | opaque | pastel |
| | | shades |
| | | |
Vinyl, unfilled. | Good |Transparent, | Unlimited | Nil
| |translucent, | pastels |
| | opaque | to black |
| | | |
Vinyl, filled. |Excellent| do | do |Approximately
|(organic | | | nil
| filler) | | |
| | | |
Acrylate |Very good|Transparent | Unlimited | Slow
| |(95% light | |
| |transmission)| |
| | | |
Polystyrene | Poor to |Transparent, | do | do
| good | opaque | |
| | | |
Other plastics: | | | |
| | | |
Shellac compound. | do | Opaque | Limited, | High (wood
| | | pastels | filler)
| | | excluded |
| | | |
Cold molded: | | | |
| | | |
Nonrefractory. | Poor | do |Dark colors| Nil
| | | only |
| | | |
Refractory. | do | do | Gray | do
| | | |
Rubber compounds: | | | |
| | | |
Chlorinated rubber. | |Translucent, | Unlimited | do
| | opaque | |
| | | |
Modified isomerized | Good |Transparent | do | Slow
rubber. | | | |
| | | |
Hard rubber. | Fair | Opaque | Limited | Medium
| | | |
Casein | Good |Translucent, | Unlimited | Very low
| | opaque | |
| | | |
Cellulose compounds: | | | |
| | | |
Ethyl cellulose | do |Transparent, | do | Slow
| |translucent, | |
| | opaque | |
| | | |
Cellulose acetate | do | do | do | do
sheet | | | |
| | | |
Cellulose acetate | do | do | do | do
molding | | | |
| | | |
Cellulose nitrate | do | do | do | Very high
-----------------------+---------+-------------+-----------+-------------
-----------------------+---------------+--------------+-----------
Type | Effect of age | Effect of |Refractive
| | sunlight |index No[1]
-----------------------+---------------+--------------+-----------
Synthetic resins: | | |
| | |
Tar-acid—Formaldehyde:| | |
| | |
Molded, wood flour | None | Light shades |
filler. | | discolor |
| | |
Molded, mineral | do | do |
filler. | | |
| | |
Molded, fabric | do | do |
filler. | | |
| | |
Laminated, paper | Improves | Lowers |
base. | mechanical | surface |
| and | resistance |
| electrical | |
| properties | |
| | |
Laminated, fabric | do | do |
base. | | |
| | |
Laminated, asbestos | do | |
cloth base. | | |
| | |
Cast | Hardens | Colors | 1.5-1.7
| slightly | may fade |
| | |
Tar-acid—Furfural: | | |
| | |
Wood flour filler. | do |Light shades |
| | discolor |
| | |
Mineral filler. | do | do |
| | |
Fabric filler. | do | do |
| | |
Urea—Formaldehyde. | do | None | 1.54-1.6
| | |
Vinyl, unfilled. | Strength | Darkens | 1.53
| unaffected | |
| | |
Vinyl, filled. | None | Discolors |
| | |
Acrylate | do | None | 1.49
| | |
Polystyrene | do | Yellows | 1.67
| | |
Other plastics: | | |
| | |
Shellac compound. | | None |
| | |
Cold molded: | | |
| | |
Nonrefractory. | | |
| | |
Refractory. | | |
| | |
Rubber compounds: | | |
| | |
Chlorinated rubber. | Slight | Darkens | 1.56
| embrittlement | |
| | |
Modified isomerized | None | Slight |
rubber. | | surface |
| | crazing |
| | |
Hard rubber. | do | Discolors |
| | surface, |
| | resistivity |
| | decrease |
| | |
Casein | Hardens | Colors |
| slightly | may fade |
| | |
Cellulose compounds: | | |
| | |
Ethyl cellulose | Slight | Slight | 1.47
| | |
Cellulose acetate | do | do | 1.49-1.50
sheet | | |
| | |
Cellulose acetate | do | do | 1.47-1.50
molding | | |
| | |
Cellulose nitrate | Slight |Discolors and | 1.50
| hardening | becomes |
| | brittle |
-----------------------+---------------+--------------+-----------
[1] Specified refractive degree.
NOTE.—The values for the properties in this table are based upon
maximum and minimum figures submitted to Modern Plastics by a
number of manufacturers of each type of material. Differences in
test procedures and sizes of test specimens may lead to erroneous
conclusions in some cases if direct comparisons are attempted.
Special grades of materials are often available which excel in
one particular property.
Source: Modern Plastics, vol. 15, no. 2, opp. p. 120. October
1937.
TABLE 18.—_Synthetic resins and other plastics: Molding properties_
------------------------------+--------------+-------------+-------------
| General | Compression | Compression
Type. | molding | molding | molding
| qualities | temperature | pressure
------------------------------+--------------+-------------+-------------
| | _°F._ |_Pounds per
| | | square inch_
Synthetic resins: | | |
Tar-acid—Formaldehyde: | | |
Molded, wood flour filler | Excellent | 280-360 | 1,600-4,500
Molded, mineral filler | Excellent | 270-350 | 1,600-6,000
| to fair | |
Molded, fabric filler | Good to fair | 270-330 | 3,000-8,000
Laminated, paper base | | 250-365 | 1,000-3,000
Laminated, fabric base | | 250-365 | 1,000-3,000
Laminated, asbestos cloth | | 250-325 | 1,000-3,000
base | | |
Cast | | |
Tar-acid—Furfural: | | |
Wood flour filler | Excellent | 330-400 | 1,000-3,000
Mineral filler | do | 330-360 | 1,000-3,000
Fabric filler | Good to fair | 300-360 | 1,000-3,000
Urea—Formaldehyde (alpha | Excellent | 290-325 | 1,500-6,000
cellulose filler) | | |
Vinyl, unfilled | Good | 240-275 | 1,500-2,000
Vinyl, filled | Excellent | 250-300 | 2,000-2,500
Acrylate | do | 285-315 | 1,500-5,000
Polystyrene | Good | 280-325 | 300-2,000
Other plastics: | | |
Shellac compound | do | 240 | 1,000-1,200
Cold molded: | | |
Nonrefractory | Fair | |4,000-12,000
Refractory | do | |4,000-12,000
Rubber compounds: | | |
Chlorinated rubber | do | 200-225 | 2,000-5,000
Modified isomerized rubber| Good | 260-300 | 1,200-4,000
Hard rubber | Fair | 285-350 | 1,200-1,800
Casein | Poor | 200-225 | 2,000-2,500
Cellulose compounds: | | |
Ethyl cellulose | Excellent | 212-300 | 1,000-5,000
Cellulose acetate sheet | do | 210-320 | 500-5,000
Cellulose acetate molding | do | 250-350 | 500-5,000
Cellulose nitrate | Good | 185-250 | 2,000-5,000
------------------------------+--------------+-------------+-------------
------------------------------+-------------+--------------+-------------
| Injection | Injection | Compression
Type. | molding | molding | ratio
| temperature | pressure |
------------------------------+-------------+--------------+-------------
| _°F._ | _Pounds per |
| | square inch_|
Synthetic resins: | | |
Tar-acid—Formaldehyde: | | _|
Molded, wood flour filler | 275-375 | 2,000-10,000 | 2.5-3.0
Molded, mineral filler | 275-350 | 2,000-15,000 | 2.2-7.1
Molded, fabric filler | | | 2.5-11.0
Laminated, paper base | | | 1.5-3.0
Laminated, fabric base | | | 1.5-3.0
Laminated, asbestos cloth | | |
base | | |
Cast | | |
Tar-acid—Furfural: | | |
Wood flour filler | 250-290 | 300-5,000 | 2.5-3.0
Mineral filler | 250-290 | 300-5,000 | 2.5-6.0
Fabric filler | 250-290 | 300-50,000 | 4.0-15.0
Urea—Formaldehyde (alpha | | | 3.0
cellulose filler) | | |
Vinyl, unfilled | | | 2.0
Vinyl, filled | | | 1.5-3.5
Acrylate | 325-475 | 3,000-30,000 | 2.0
Polystyrene | 300-375 | 3,000-30,000 | 2.5
Other plastics: | | |
Shellac compound | | |
Cold molded: | | |
Nonrefractory | | | 2.5
Refractory | | | 3.5
Rubber compounds: | | |
Chlorinated rubber | | | 2.0-3.0
Modified isomerized rubber| | | 3.0
Hard rubber | 180-220 | 2,000-5,000 | 4.0-6.0
Casein | | |
Cellulose compounds: | | |
Ethyl cellulose | | | 2.2-2.9
Cellulose acetate sheet | | |
Cellulose acetate molding | 300-440 | 3,000-30,000 | 2.0-2.8
Cellulose nitrate | | |
------------------------------+-------------+--------------+-------------
------------------------------+-------------------+-----------
| Mold | Effect
Type. | shrinkage | on metal
| | inserts
------------------------------+-------------------+-----------
| _Inches per inch_ |
Synthetic resins: | |
Tar-acid—Formaldehyde: | |
Molded, wood flour filler | 0.006-0.010 | Inert.
Molded, mineral filler | .002- .006 | Do.
| |
Molded, fabric filler | .003- .007 | Do.
Laminated, paper base | | Do.
Laminated, fabric base | | Do.
Laminated, asbestos cloth | | Do.
base | |
Cast | | Do.
Tar-acid—Furfural: | |
Wood flour filler | .005- .009 | Do.
Mineral filler | .002- .006 | Do.
Fabric filler | .0025-.006 | Do.
Urea—Formaldehyde (alpha | .007- .011 | Do.
cellulose filler) | |
Vinyl, unfilled | .001 | Not used.
Vinyl, filled | .000 | Inert.
Acrylate | .002- .003 |
Polystyrene | .002-.0025 |
Other plastics: | |
Shellac compound | .002 | Do.
Cold molded: | |
Nonrefractory | .000- .022 | Do.
Refractory | .000 | Do.
Rubber compounds: | |
Chlorinated rubber | |
Modified isomerized rubber| .000 | Do.
Hard rubber | |
Casein | |
Cellulose compounds: | |
Ethyl cellulose | .0003-.0007 | Do.
Cellulose acetate sheet | ([1]) | Do.
Cellulose acetate molding | ([1]) | Do.
Cellulose nitrate | |
------------------------------+-------------------+-----------
[1] Positive and injection 0.002-0.003; semipositive 0.005-0.007;
flash 0.008-0.009.
NOTE.—The values for the properties in this table are based upon
maximum and minimum figures submitted to Modern Plastics by a
number of manufacturers of each type of material. Differences in
test procedures and sizes of test specimens may lead to erroneous
conclusions in some cases if direct comparisons are attempted.
Special grades of materials are often available which excel in
one particular property.
Source: Modern Plastics, vol. 15, No. 2, opp. p. 120. October
1937.
Table 17 lists the properties which affect appearance and gives in
addition to the color range, the clarity, material, the burning rate,
the effect of age and sunlight, the refractive index, and the machining
quality of each synthetic resin.
Table 18 lists molding properties of synthetic resins. Of special
interest are the possibilities of using a resin in injection molding. The
thermoplastic resins and plastics (see softening point in table 20) are
generally preferred to the thermosetting materials for injection molding
because they permit the reuse of material otherwise wasted.
Table 19 lists the strength properties of the synthetic resins; table 20
the heat properties; table 21 the electrical properties; and table 22 the
resistance to acids, alkalies, and solvents. All of these qualities are
important in some uses and each quality may be paramount in a few. Each
material has its limitations and its special advantages and the consuming
industry must choose the one best suited to its purposes. The tie-up
between specific properties and particular uses is exemplified by vinyl
resins, which because of their great elasticity at low temperatures, are
used in safety glass, and by the polystyrene resins, which because of
their electrical properties at high frequencies, are used in laminated
electrical parts. As production of the various resins increases new uses
will probably be found for most of them.
TABLE 19.—_Synthetic resins and other plastics: Strength properties_
-------------------------------+--------------+------------+-------------
Type | Tensile | Elongation | Modulus of
| strength | | elasticity
-------------------------------+--------------+------------+-------------
|_Pounds per | _Percent_ |_Pounds per
| square inch_ | | square inch_
Synthetic resins: | | | _× 10³_
Tar-acid—Formaldehyde: | | |
Molded, wood flour filler | 6,000-11,000 | | 10-15
Molded, mineral filler | 5,000-10,000 | | 10-45
Molded, fabric filler | 6,500- 8,000 | | 7-12
Laminated, paper base | 6,000-13,000 | | 5-20
Laminated, fabric base | 8,000-12,000 | | 5-15
Laminated, asbestos cloth | 9,000 | |
base | | |
Cast | 5,000-12,000 | | 5-15
Tar-acid—Furfural: | | |
Wood flour filler | 5,000-12,000 | | 10-25
Mineral filler | 4,000-12,000 | | 10-45
Fabric filler | 5,000-10,000 | | 7-12
Urea—Formaldehyde | 8,000-13,000 | | 16
Vinyl, unfilled | 8,000-10,000 | | 3.5-4.1
Vinyl, filled | 6,000-12,000 | | 3.5-8.5
Acrylate | 7,000- 9,000 | 1.0 | 6
Polystyrene | 5,500- 7,500 | 1.0 | 4.6-5.1
Other plastics: | | |
Shellac compound | 900- 2,000 | |
Cold molded | | |
Nonrefractory | | |
Refractory | | |
Rubber compounds: | | |
Chlorinated rubber | | |
Modified isomerized rubber | 4,300 | 0.013 | 4.7
Hard rubber | 4,000-10,000 | 8-15 | 5.3
Casein | 7,600 | | 5.1-5.7
Cellulose compounds: | | |
Ethyl cellulose | 2,000- 7,000 | | 2.8
Cellulose acetate sheet | 6,000-11,000 | 20-55 | 1-3
Cellulose acetate molding | 3,500-10,000 | 10-48 | 2-4
Cellulose nitrate | 5,000-10,000 | 10-40 | 2-4
-------------------------------+--------------+------------+-------------
-------------------------------+---------------+---------------
Type | Compressive | Flexural
| strength | strength
-------------------------------+---------------+---------------
| _Pounds per | _Pounds per
| square inch_ | square inch_
Synthetic resins: | |
Tar-acid—Formaldehyde: | |
Molded, wood flour filler | 16,000-36,000 | 8,000-15,000
Molded, mineral filler | 18,000-36,000 | 8,000-20,000
Molded, fabric filler | 20,000-32,000 | 10,000-13,000
Laminated, paper base | 20,060-40,000 | 13,000-20,000
Laminated, fabric base | 20,000-44,000 | 13,000-20,000
Laminated, asbestos cloth | 18,000-40,000 | 17,000
base | |
Cast | 15,000-30,000 |
Tar-acid—Furfural: | |
Wood flour filler | 28,000-36,000 | 10,000-16,000
Mineral filler | 24,000-36,000 | 8,000-14,000
Fabric filler | 26,000-30,000 | 10,000-16,000
Urea—Formaldehyde | 24,000-35,000 | 13,000-15,000
Vinyl, unfilled | | 10,000-13,000
Vinyl, filled | |
Acrylate | 8,000 | 15,000-17,000
Polystyrene | 13,000-13,500 | 6,500- 8,000
Other plastics: | |
Shellac compound | |
Cold molded | 6,000-15,000 | 5,300- 7,500
Nonrefractory |} 16,000 | 6,000
Refractory |} |
Rubber compounds: | |
Chlorinated rubber | |
Modified isomerized rubber | 8,500-11,000 | 7,000- 9,000
Hard rubber | 8,000-12,000 |
Casein | |
Cellulose compounds: | |
Ethyl cellulose | |
Cellulose acetate sheet | 4,000-16,000 |
Cellulose acetate molding | 11,000-16,000 | 5,200- 8,800
Cellulose nitrate | |
-------------------------------+---------------+---------------