BRIGHTNICKELPLATING UNIT WITH ALL RACKS“KOROSEAL” COATED
Recent Developments with ICoroseal F. IC. SCHOENFELD, A. W. BROWNE, JR., AND S. L. BROUS The B. F. Goodrich Company, Akron, Ohio upon a variety of conditions such as time, temperature, pressure, purity of monomer, nature of catalyst, presence of modifying agents, and mechanical conditions prevailing during the polymerization reaction. Semon (6) disclosed new and useful compositions based on one type of polymerized vinyl chloride, and Brous and Semon (9) presented the general properties of a class of products bearing the generic name “Korosea1.” These “Koroseal” stocks are thermoplastic and therefore can be shaped by means of heat and pressure. They can be milled on hot roll mills, calendered to various gages, extruded through hot dies, and molded to different shapes in flash or plunger type molds. Furthermore, they can be made into cements with special solvents for treating fabrics and papers. I n general, the processing technique used for “Koroseal” stocks is similar to that employed for rubber stocks, with the exception that “Koroseal” does not require vulcanization. Unlike rubber, “Koroseal” does not deteriorate from contact with air, ozone, light, and oxidizing chemicals; does not swell in oils or in most solvents; and can be made nonflammable. “Koroseal” has a further advantage over rubber in that it can be made glass-clear. On the other hand, “Koroseal” is not as resilient as vulcanized rubber or as resistant to abrasion a t elevated temperatures.
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Koroseal” plastics exhibit a wide range of physical, chemical, and electrical properties which can be modified by the use of suitable plasticizers, loading pigments, and special compounding ingredients. Essentially rubberlike “Koroseal” stocks may be milled, calendered, extruded and molded without vulcanization into a variety of enduring products. “Koroseal” is especially valuable for uses requiring resistance to water, acids, alkalies, oxidizing agents, and corrosive chemicals.
I
N RECENT years much research work has been done on
synthetic rubbers and synthetic rubberlike materials. The desire for national self-sufficiency undoubtedly has stimulated these developments in foreign countries. I n the United States the primary consideration has been the desire to secure materials having properties superior in certain respects to those of vulcanized natural rubber, with national self-sufficiency as a secondary incentive. Limestone, coal, salt, petroleum, and sulfur have been used as the basic raw materials for the synthesis of the majority of rubberlike products now available commercially. One of the intermediates which can be prepared from these raw materials is vinyl chloride, CH2=CHC1, made by combining acetylene and hydrogen chloride by passage over a contact catalyst, or from ethylene dichloride, CICH2--CH&l, by partial dehydrohalogenation, either by treatment with aqueous alcoholic caustic (1) or by a vapor-phase catalytic process. That vinyl chloride will polymerize was discovered many years ago. More recent work shows that the physical and chemical properties of the polymeric products are dependent
Physical Properties Brous and Semon (2) showed PLASTICIZER COMPOUNDINQ. how wide a range of properties can be obtained merely by elasticizing a special polyvinyl chloride with 10 to 60 per cent of a single plasticizer-in this case, tricresyl phosphate. Graphs were given to show how the durometer hardness may 964
AUGUST, 1939
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965
hundred different o r g a n i c m a t e r i a l s h a v e been evaluated as plasticizers for polyvinyl chloride in the Goodrich laboratories. These i n c l u d e h y d r o c a r b o n s , chlorohydrocarbons, ethers, chloroethers, ketones, esters, chloroesters, and organic sulfur compounds. Esters oomprise by far the largest and most important group of plasticizers, although many ketones and organic sulfur compounds are quite satisfactory. Ethers as a class are not so effective as esters or ketones. Aromatic hydrocarbons are fair plasticizers; aliphatic hydrocarbons are seldom used. It would be far beyond the scope of this paper to discuss the effect of all of these plasticizers on
TABLEI. EFFECTOF AMOUNTOF PLASTICIZER ON PHYSICAL PROPERTIES OF “KOROSEAL” Vol Tricresyl Tear FlexiPhos- HardElonga- Resist011 Gasoline Hear bility phatea nessb Tensile Strengthc tiond ancee Extract/ Extractg Lossh Limiti KO./ Lb./ 8q. em. sq.zn. % K O /cm. % % % OC. 1.0 20 0.3 -4.8 142.8 3320 190 96 233 50 1.3 7 8.8 78.5 2.5 270 80 211 3000 75 1.3 -6 15.9 53.6 6.3 330 68 147 2100 100 1.4 -22 19.7 28.6 17.9 490 49 98 1400 150 0 Per 100 volumes of polyvinyl chloride. b Shore Durometer T y p e A 30’ C. c Force required to’break stAndard dumbbell a t 30” C. d Ultimate elongation a t 30’ C. e Force (in kg. per om. thickness) required t o tear s t a n d a r d sample a t room temperature. f P e r cent loss i n weight after immersion in oil for 14 days a t 50’ C. g P e r cent loss i n weight after immersion i n motor gasoline for 14 days a t room temperature. h P e r cent loss i n weight after heating i n a n air-circulating oven for 14 days a t 105” C . i Temperature at which a standard strip under a constant weight will bend through a n angle of 30’ i n 2 minutes.
-
~~~
__ PLASTICIZERS ON PHYSICAL PROPERTIES OF “KOROSEAL” Tear FlexiElonga- ResistHeat bility Strength tion anoe Loss Limit
TABLE 11. EFFECT OF SIX
be varied from 100 to about 15, the tensile strength varied from 9000 to 1000 pounds per square inch, and the elongation varied from 2 to 500 per cent. I n addition, changes occur also in tear resistance, oil resistance, .gasoline resistance, heat behavior, and low-temperature flexibility of these compounds. Table I shows the effect of varying the volume of tricresyl phosphahe (per hundred volumes of polyvinyl chloride) on these physical properties. Numerous other plasticizers can be
p ~ ~ $% ? ;:A
B
C
D
E F
73
76 84 68 69 71
X o . / $ q . em. L b . / s q . i n . 156 2220 146 2070 160 2280 94 1340 112 1590 112
1590
~
% 350 365 325 380 395 340
Kg./cm. 61.2 63.0 77.6 42.1 42.0 52.3
% 2.3 6 8 26.3 32.3 6.6 8.0
C. -3 -1 i-9
-24 -22 -17
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FIGURE 1. EFFECTOF PIGMENTS ON HARDNESS OF “KOROSEAL”
FIGURE3. EFFECTOF PIGMENTS ON ELONGATION OF “KOROSEAL”
Af;;
0
!ENTON!; CHANNEL BLACK C
0
K
A I
L
t
.
VOL. 31, NO. 8
P I G M E NCTO M P O U N D I N GThe . term “pigment” is used here in the same sense that it is used in rubber compounding. It refers not necessarily to a “color,” but to any material, other than a plasticizer or solvent, which may be added to ‘(Koroseal.” It includes inorganic powders such as whiting and clay, and organic materials such as factice, rosin, oils, and waxes, etc. A wide variety of these materials has been tested in “Koroseal” for the purpose of discovering specific effects, and to serve as a basis for the compounding of commercial products. I n most cases, increasing loadings of dry pigments have a hardening effect on “Koroseal.” Pigments may be grouped in terms of the hardness imparted to the base recipe (Table 111). I n addition t o their hardening effect, certain pigments produce specific effects, such as increase in tensile strength (channel black, micronized graphite, fine silica) ; increase in tear resistance (Thermax, P-33) ; and increase in oil resistance (clay, bentonite clay, K gum rosin).
I
GUM ROSIN THERMAY WHITING
25 20
I
0
I
IO VOLUMES
I
I
I
1
20 30 40 OF PIGMENT (PER 100 VOl%
I P.V.Cy
FIGURE 2. EFFECTOF PIGMENTS ON
TENSILE STRENGTH OF “KOROSEAL”
I 0
I
I
I
I I
I
10 20 30 40 50 BO VOLUMES OF PIGMENT (PER 100 VOLS.P.V.C,\
u TLMPERKW
FIQURE 4. EFFECTOF PIGMENTS ON TEARRESISTANCE OF “KOROSEAL”
Specific physical properties resulting from the use of these plasticizers (89 volumes of plasticizer per 100 volumes of polyvinyl chloride) are summarized in Table 11. I n general, plasticizers for polyvinyl chloride fall into two distinct classes, when grouped according to the properties of the resulting ‘(Koroseal” compounds : Class I, typified by plasticizers A, B, and C, give “Koroseal” compounds which are somewhat harder than those of class 11, and have higher tensile strength, higher tear resistance, and lower heat loss. Plasticizers of class 11, typified by plasticizers D and E, give somewhat softer stocks, with higher elongation and greatly improved flexibility at low temperatures. Intermediate between these two classes i r e materials like plasticizer F which combines good tear resistance, low heat loss, and low temperature flexibility. Mixtures of plasticizers are sometimes used to obtain properties intermediate between those of single plasticizers. I n most cases, the effects are additive.
g
(H’C)
FIGURE5. RESISTIVITY OF “KOROSEAL” COMPOUNDS
10
f
PROPERTIES OF “KOROSEAL” COMPOUNDS FIGURE 6 . ELECTRICAL Left, frequency = 60 cycles per second; right, 1000 cycles per second
INDUSTRIAL AND ENGINEERING CHEMISTRY
AUGUST, 1939
and even ozone a t elevated t e m p e r a t u r es without cracking. E a r l y s a m p l e s of “Koroseal” have retained their physical properties for twelve years without appreciable change. Accelerated aging tests in the Bierer bomb and Geer oven produce practically no change in tensile s t r e n g t h and elongation (Table V). “Koroseal” is unaffected by light and will endure immersion in sulfuric, nitric, or chromic acids and also in strong alkalies without deterioration (3). “Koroseal” has a flex resistance more than ten times that of rubber, if used under conditions which do not involve heating, and an a b r a s i o n resistance equal to or better than the best rubber compound. Use of “Koroseal” in contact with certain other materials must be avoided because of a solvent or swelling action. These include “KOROSEAL”-TREATED GINGHAM organic compounds BATHING SUIT c o n t a i n i n g chlorine, nitro, or amino groups and aliphatic or aromatic ketones. Gasoline and other hydrocarbon solvents do not dissolve polyvinyl chloride but tend to extract plasticizer and harden the compound, particularly a t elevated temperatures.
OF PIGMENTS ON THE HARDNESS OF TAHLE 111. EFFECT “KOROSEAL”
Polyvinyl chloride 100 vol. Tricresyl phosphate 89 60 Pigment Total 249 Hardness of unpigmented recipe 74 Group Hardness Typical Pigments I 68-72 Brown factice I1 72-76 K gum rosin I11 76-80 White factice IV 84-88 P-33, Thermax, blanc fixe, whiting, calcene V 88-92 Gastex, graphite, coarse talc, clay, lithopone, Titanox, shellac, wood flour VI 92-96 Channel black, micronized graphite, bentonite clay, mica, fine silica
These effects are best shown graphically in Figures 1 to 4 where the five pigments, channel black, Thermax, whiting, bentonite clay, and K gum rosin, are added in loadings up to 60 volumes. The effect of much higher loadings is illustrated by the effects of Thermax and whiting up to 200 volumes. I n the case of Thermax, tensile strength is maintained above 2000 pounds per square inch. Other properties change considerably as loading is increased, as Table IV shows. Many rubber softeners, such as tars, oils, and waxes, are compatible with “Koroseal” up to 10 or 20 per cent. Paraffin wax facilitates processing and gives a smooth nontacky surface on finished articles.
Electrical Properties
A simple “Koroseal” stock consisting only of polyvinyl chloride elasticized with a plasticizer does not exhibit the best possible electrical properties. As is true with other properties referred to above, the proper compounding ingredients must be used in order to develop the electrical properties desired. The improvements which can be effected are shown in Figures 5 and 6 which represent the effect of temperature on the resistivity, power factor, and dielectric constants of “Koroseals” 574 and 763. The methods used in electrical testing were similar to those developed by Fuoss (4) of the General Electric Company. LOADINGS TABLEIV. EFFECTOF HIGHPIGMENT 100 vol. 89 vol.
Polyvinyl chloride Tricresyl phosphate Pigment Thermax
As specified Whiting Tear Tear Vol. of HardElonga- resist- HardElonga- resistPigment ness Tensile strength tion ance ness Tensile strength tion ance Kg./sq. cm. Lb./sq. in. % Kg./cm. Kg./sq. cm. Lb./sq. in. % Kg./cm. ,-
0
50 100
150 200
74 84 92 95 96
169 155 169 156 151
2400 2200 2410 2230 2140
335 200 95 45 25
62.5 94 6 67.9 30.4 8.9
74 85 92 95 96
169 122 92 70 67
2400 1730 1310 1000 960
967
335 225 120 85 50
62.5 58.9 46.4 26.8 19.6
Applications and Uses I n the electrical, wire, and cable industries, “Koroseal” is ideally suited to many applications for use as insulation or sheathing. The material has high dielectric strength, complete resistance to corona cutting, good insulation resistance, and the capacity of being compounded to provide low power factor and dielectric constant. For such uses as insulation on apparatus and machinery wire, switchboard and station control cable for light and power service, and building wire, the material is finding increasing applications. “Koroseal” is being used in power and control cables both
Chemical Properties “Koroseal,” as its name implies, is outstanding among synthetic rubberlike materials for “sealing against corrosion.” The remarkable corrosion resistance of “Koroseal” arises from the chemical stability of gamma polyvinyl chloride, which, in turn, results from its absence of olefinic unsaturation and its high chlorine content. Earlier papers emphasized the resistance of “Koroseal” t o oxidation of all types, enabling this material to withstand long exposure to pure oxygen
TABLE V. ACCELERATED AGINGTESTSON “KOROSEAL”
Bierer bomb
Period of ElongaAging 100% Modulus Tensile Strength tion Kg./sq. cm. Lb./sq. in. Kg./sq. cm. Lb./sq. in. % 96 hr. 98 1390 185 2630 348
105
Geer oven
2 wk.
100
0
98 116 102
2 wk. 2 mo.
1490 1430 1390 1650 1450
174 172 185 170 174
2470 2440 2630 2420 2470
315 315 348 275 330
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as a replacement for lead LLKoroseal”-coatedpaper sheathing and as a protecfurnishes a packaging mative sheathing over lead. terial impervious to air and Underwriters laboratories moisture and resistant to have approved “Koroseal” oil, grease, sunlight, and in certain electrical applicachemicals. I n the printing tions for continuous operaindustry “Korosea1”-coated tion at 80’ C. paper is used to supply a I n the textile industry suitable cushion or printing “Koroseal” has found extencontact between the steel sive use as a roll covering surface of the impression material. It exhibits the unit and the hard surface proper frictional drag for of the type form. “Korodrafting yarns, resilience to seal” is the only material cushion against pinching, known which will withstand toughness to resist channelthe continued punishment ing or grooving from wear, of long and severe press flexibility to run in contact operation. with fluted steel surfaces, Molded a n d e x t r u d e d and resistance to oils and articles made of “Koroseal” acids used in spinning,weavhave found a wide number ing, or dyeing; moreover, i t of applications of which is capable of being ground to only a few will be mentioned. Among molded freshen the surface so as to articles are diaphragms, exproduce the desired finish on wool, cotton, or rayon. I n pansion joints, seals, and fact, recent developments packings. Flexible gaskets in high-speed high-capacity of “Koroseal” are used in textile machines make imgrease guns and in liquidfilled shock absorbers. Experative the use of ((Koroseal” since no other availtruded items include tubing able material will stand the for laboratory and factory service. operations as well as latheThe chemical inertness of cut gaskets, seals, and pack“Koroseal” makes it suitable ings. Water-clear (‘Korofor covering metal tanks to seal” makes possible transparent tubing for the brewprotect them against the actionof corrosive chemical soing industry, lutions. Rubber lining is “Korolac,” a solution of “Koroseal,” was announced used extensively for resistsome time ago as a protecance to some acids and salts, tive coating for plating racks but “Koroseal” is serving (Top) “KOROSEAL”-COVERED PIPE LINE TO RESIST SOIL used in the electrode position successfully in unusual servCORROSION of metals. Ease of appliices where rubber and other (Bottom) “KOROSEAL”-LINED TANKFOR HANDLING A MIXTURE cation, together with long materials have failed. For OF NITRICAND HYDROFLUORIC ACID USEDIN PICKLING STAINLESS STEEL service life when exposed instance, in the pickling of to the deteriorating effects stainless steel a mixture of nitric and hydrofluoric acids is used. I n early work, wood was of the various corrosive chemicals used in this induitry, are the only structural material which could be considered to responsible for an increasing number of satisfied users. handle such a corrosive mixture but wooden tanks lasted only L‘Korogel,” a highly plasticized form of “Koroseal,” has a short time. More recently steel and (‘Koroseal” have been been thoroughly tested for over four years as a matrix matecombined to give a sturdy tank which withstands both merial for the casting of plaster of Paris, portland cement, and chanical and chemical abuse. A similar unique and outstandother ceramics. Resistance to moisture, flexibility a t all ing application is that of “Koroseal”-lined tanks for handling operating temperatures, excellent aging characteristics, tochromic acid used in chromium plating. “Koroseal” is also gether with ease of operation, have made justifiable the replacement of glue compositions which were formerly used for used to cover pipe lines where soil corrosion is a factor. Transparent moisture-resistant odorless “Koroseal” is used this purpose. The applications and uses of “Koroseal” described in this for waterproofing cloth. Raincoats made of “Korosea1”-treated paper can be extended greatly as specific needs arise. New silks are now manufactured in a variety of colors. Being waterproof, ‘(Koroseal” is valuable for coating fabrics of attractive plasticizers, compounding techniques, processing methods, design and color for shower curtains and swimming suits, etc., will further improve the properties of “Koroseal,” and brightly colored curtains which may be cleaned with a damp lead to its use for many purposes which will be suggested by sponge, rainproofed evening wraps of taffeta, washable its unusual properties. upholstery of brocade, tapestries, and armure. Other products Lit erature Cited include sail and deck covers for marine service, automobile (1) Brous, S. L., U. 5. Patent 2,041,814(May 26, 1936). topping, awnings, hospital sheeting, tarpaulins, etc. Me(2) Brous, 5. L.,and Semon, W. L., IND.ENQ.CHEM.,27,667 (1935). chanical applications of “Koroseal”-coated fabrics include (3) Chem. & Met. Eng., 43, 560 (1936). belts for transmission and conveyor service, diaphragms for (4) Fuoss, R. M., J. Am. Chem. SOC.,60,451,456 (1938). meters and pumps, machine aprons, and printing blankets. (5) Semon, W.L., U. S. Patent 1,929,453(Oct. 10, 1933).
