I&EC REPORTS & C O M M E N T S Treated fillers advance thermoset technology Closing the immiscibility gap in glasses A new plan for industrial education
Stronger Metal-Filled Resins Small amounts of silane coupling agents, added to metal and nonmetal fillers, result in improved tensile, flexural, and compressive strengths for a number of filled-resin systems. These improved properties make items such as metallic coatings, patching and caulking compounds, and other specialty items more competitive and of greater consequence in our value-conscious markets. Silane coupling agents are already in use to produce stronger glass fiber-resin composites, and as primers for metals which are to be covered with a variety of coatings. Union Carbide’s Silicones Division now claims that these concepts can be extended to upgrade the metal-filled resin systems and has taken out six patents on such processes. The properly selected silane is effective in such thermosetting systems as polyesters, epoxies, melamines, and phenolics. The use of aminoand epoxy-functional silanes in aluminum-filled epoxy resins is typical of the results obtained after extensive testing. Test specimens, such as that shown in the photograph, were cut from mixes of about 40y0 commercial resin-hardener systems filled with about 60% aluminum needles. Three silane derivatives (Union Carbide’s A-1100, A-186, and A-187) were added to the commercial resin in the amount of 1%, by weight, based on the epoxy resin alone. The resulting comparative data are shown in Table I. O n the avcrage, a 94% improvement in flexural strength was achieved before and a 150y0improvement after exposure of the filledresin system to boiling water. The corresponding improvements in the compressive strengths were 57y0
and 69Oja before and after the boiling water exposure. I t isn’t necessary to add the silanes to the mix itself. The metallic fillers may be precoated before being incorporated into the resin, thereby permitting storage of all the
TABLE I.
mix ingredients until they are ready for use. Test samples were made by adding A-1100 to metal powder followed by thorough milling, heating, and screening. The effects of treating the metal filler are shown in Table 11.
PROPERTIES OF ALUMINUM-FILLED EPOXIES
Flexural Strength (p.s.i.) Silane Additive
Initial
None A-1100 A-186 A-187
620 1240 1240 1110
TABLE II.
1
After 72 hr. in boiling water
1
Compressive Strength (p.s.i.)
!
1
Initial
470 1310 1200 1030
2110 2970 3700 3230
After 72 hr. in boiling water 2100 3220 3990 3430
EFFECTS OF ADDING SILANES TO METAL FILLERS IN EPOXIES
I A-1100 (%w) Ultimate tensile ( p s i . ) Tensile modulus ( p s i . ) Ultimate compression Compression modulus
I
Mix. No. la None 4500 1.1 X 106 15,800 1.0 x 106
0,008 6900 1 . 0 X 106 19,900 1.0X106
M i x No. 26 None 4600 1.04X106 15,700 1.04X108
0.003 7200 1.14X106 18,800 1.19X106
a M i x No. l is composed of 120parts of aluminum powder added to 100 parts of a commercial resinlhardener. b M i x No. 2 is composed of 288 parts of iron powder added to 100parts of a commercial resin/hardener.
Test specimens such as this, shown after rupture in a flexural test, were used to demonstrate improvements in physical properties obtained by small additions of silane coupling agents to 0.25 X 0.025 in. aluminum needles used to reinforce epoxy resins VOL. 5 7
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I&EC REPORTS
Easy. If that drop is a Dow Corning@ silicone defoamer. And many times, one drop will defoam much morefrom eighteen gallons of phenolformaldehyde to thirty-six gallons of tall oil, for example. Supplied in compound, fluid or emulsion form, these silicone defoamers stop wasteful, hazardous, costly foam-overs in both aqueous and nonaqueous systems. They reduce production and maintenance costs; help improve product quality, too; are equally effective with most types of mechanical systems. Prove the efficiency of these defoamers in your plant. Send for your FREE Evaluation K i t - plus detailed brochure. Mail the coupon below today, or write Dept. 5222, Chemical Products Division, Dow Corning Corporation, Midland, Michigan 48641.
DOW CORNING CORPORATION
KH of bow Corning
silicone
defoamers Dept. 5222, Chemical Products Div. Dow Corning, Midland, Mich. 48641 Send my Kit, plus detailed brochure to: TITLE COMPANY ADDRESS
STATE
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The substantially improved physical and chemical properties of the resin-metal systems should prove a boon to the designers using structural plastics. One particular use, still in the developmental stage, is the filling of filament-wound, glass fiber-resin composite structures for pressure vessels. Still another suggested use for the improved properties of the metalfilled systems is in the tool and die industry. I t is claimed that costly metal molds are being replaced with cheap, easily produced molds made from the filled resins. For low value products, there probably is some market potential. However, the dimensional stability required for intricate castings and molded parts, such as lock tumblers, and the absolute necessity for long service molds may be placing too heavy a demand on the resin systems at this stage in their development.
New Type of Phase Behavior I n liquid-solid systems, especially binaries, the appearance of more than one liquid phase is usually manifested either in the two-phase region or above the liquidus. However, another type of liquid immiscibility recently has been recognized as the result of work done at the U. S. Air Force Office of Aerospace Research Metallurgy and Ceramics Laboratory. The 1939 patent for the preparation of Vycor glass, issued to Hood and Nordberg, stated that the initial composition within the NaZO-B203Si02 system exhibited two immiscible glass phases, even though further work on the system didn’t reveal such immiscibility. I n the early 1950’s a closely related system (SiOzNa2BR013) was being investigated by the Air Force in connection with work on the polymorphism of silica. The liquidus of the related system
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INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
was distinctly S-shaped, and electron micrography of the system subsequently revealed that two liquid glass phases do exist at temperatures which are below the liquidus and partially within the solid region. The investigators postulated that the immiscibility was of a previously
STABLE LIQUID
COMPOSITION Na,B,O,
/
SiO,
unknown type and substantiated the postulate after producing the complete phase diagram as shown above. The unusual two-phase region (crosshatched area) is referred to as the “immiscibility gap.” Having finally closed the “immiscibility gap,” the investigators are now searching for other systems exhibiting the same behavior. The clue to such a metastable state is, apparently, the S-shaped liquidus.
Industrial Plants and Classrooms The department of metallurgy at Ohio State University will launch an experimental program in graduate education under a $95,000 grant from the Ford Foundation. Mars G. Fontana, chairman of the department, in announcing the program said that it would culminate in a master’s degree and the graduate
(Continued on page 76)
Recognize your mixing problem? I I I I I I I I I I I I I I I I I I I
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I&EC R E P O R T §
What’s the P/U* I
w h e n it comes to bad smells, a fellow can be painfully iinpopular: P / U -terrible. But stop. If you’re looking for the solution to a pressing industrial air pollution problem, Cairox@ potassium permanganate could be the answer. Cairox has been used successf u l l y against t h e strongest chemical odors from rendering and asphalt plants, livestock feedlots and fish processing plants. Low-dosage Cairox treatment has worked in all cases. You can solve the most persistent and the most difficult odor problems inexpensively and effectively with this powerful but safe oxidant. Potassium permanganate is known to oxidize a wide
range of organics and many inorganics- including troublesome sulfides or mercaptans, amines, sulfur dioxide, nitric oxides and aldehydes. Simple, positive air pollution control is now possible with the application of Cairox in air washers, or sprayed in solu. tion on the odor source. If you haven’t started yet, don’t waste time, do the job with Cairox. If you’ve tried ineffective meth. ods, look to Cairox for success and for savings. Technical assistance is available from our staff, Tell us about your problems, we’ll help you to find the solution. Call or write today. Ask for File 1032. “Population/Unhappiness
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
research. Other programs, more easily iden-
have actually been put into effect, Yale’s multidegree program was one response but its results are unknown. I n view of the usually futile attempts of a number of organizations to establish some kind of consistent examination of the educational requirements of industry, it is a refreshing change to observe a group actually doing something without resorting to the ponderous machinery of the Government.
A Theory of Explosions T h e advent of explosive cladding, vessel coating, and other processes involving controlled explosions, as well as the natural concern over explosion hazards, have made theoretical studies of explosions more than an academic pastime. Gray and Yang [J. Phys. Chem. 69 ( 8 ) , 2747 (1965)] point out that neither of the well established mechanisms for explosions in gases is satisfactory. T h e thermal theory is incapable of yielding kinetic data or explaining purely chemical events such as inhibition or sensitization. The branched-chain theory of Semenov cannot account for the effect of added chain carriers on explosion limits-i.e., they predict that the explosion limit is independent of the initial condition of the system. T h e investigators have attempted to unify these two theories by simultaneously considering the kinetic equation of the chain reaction and the energy conservation equation of the system. By considering the equations simultaneously, one can deduce a considerable amount of semiquantitative and qualitative information about potentially explosive materials. The restrictive assumptions of both previous theories are removed, and the resultant generalization explains phenomena previously unexplained. Vessel coating and difficulties in reproducing results, for example, seem to be very sensitive to the temperature The behavior of the system. temperature behavior is usually highly nonlinear with time and causes geometry to assume a much greater importance than previously suspected.
a Ust ni uyro=urocessin..i. C A L C I N I N G & OXIDIZING RARE E A R T H S IN ONE O P E R A T I O N
at Mountain Pass
.The Mountain Pass, California, mine of The Molybdenum Corporation of America is the only mine in the U. S. worked regularly just for rare earths. Through test work, using a Skinner Pilot Plant Furnace, a unique process was developed which permits calcining and oxidizing t h e rare earths in one operation. Based on these results a 10’ dia. 6 hearth Skinner Furnace was installed at Mountain Pass. The operation is a very successful one, met-
allurgically, and production is 3 tons or more per hour. Test service and 70 years processing experience available to help you solve pyro-processing problems. drying, roasting, cakining, decomposing, incinerating.
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Write for Skinner Catalog No. 163.
MINE & SMELTER SUPPLY CO.
Dept. IES-3, 3800 Race St., Denver, COIO.80216 Area Code 303/244-4353
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