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Fishing for Fundamentals New rubber skin may be boon to boating I HE PORPOISE is a unique animal— he isn't very pretty, to be sure, but some of his features can't be dupli cated anywhere. For instance, he has a definite personality—he is playful and fun-loving, and ex tremely intelligent compared with other "lower" forms—so intelligent that he is reported to have actually spoken human phrases to a scientist, who utilized the porpoises' highly developed "sonar" system. But his most amazing attribute is his ability to maneuver and swim with so little effort. A former German scientist, Dr. Max O. Kramer, noticed this. Ac cording to his observations, the por poise has only 10% of the calculated "drag" caused by water that he should have according to his odd shape. Dr. Kramer began to look for the answer. He obtained a sample of porpoise skin, and analysis showed the queer fish is covered with a soft, squashy hide, a '/ic-inch hydraulic layer, elastic and ducted, which eliminates turbulence and therefore cuts drag to a near minimum. Dr. Kramer set out to duplicate this skin and came up with a rubber coating approaching the effectiveness of a porpoise covering. It consists of a thin layer of rubber supported by a multitude of tiny rubber pillars. Interconnecting channels are filled with a free-flowing oil, the channels facing the surface of the coated ob ject. The channels give the coating flexibility, and the liquid provides the necessary damping to suppress drag-causing turbulence. A 5 0 % drag reduction has already been ob30 A
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The porpoise is a b l e to swim r a p i d l y and maneuver well because o f his hydraulic hide. A rubber duplication o f his skin allows up to 5 0 % reduction of d r a g due to turbulence
tained on a test object towed under water. U.S. Rubber scientists have also demonstrated a 30% reduction in drag on high speed, planning-type surface boats. "Boundary layer stabilization" is what the chemical engineer working with fluid dy namics theory would call it. Considering that 70 to 90% of the propulsive force is consumed in overcoming drag due to the object itself, think what would happen to the speed of a submarine with a por poiselike coat : Subs could travel at 70 miles per hour (60 knots) with the present engines. Improved power plants could propel underwater craft at speeds up to 210 miles per hour (180 knots). This means commuter and cargo subs could operate regard less of hurricanes, typhoons, and other surface storms. The free-flow principle should also apply to appli cations in flight and to passage of fluids through pipes and pipelines. The future looks so bright for the material that U.S. Rubber Co. plans to produce the material under the
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trade-name Lamiflo as soon as some of the practical production and appli cation problems can be worked out. They feel that this coating could be as important to high-speed water transportation as the pneumatic tire is to land transport. Wonder what the porpoise said to the scientist? J.B.P.
Urethane Takes to the Fairways Cross-linked elastomer and its solution provides surface for miniature golf β \
MINIATURE GOI.F COURSE w o u l d
seem to be an unlikely proving ground for an advance in polymer chemistry. But for testing the weathering and wearing powers of a surfacing material, it is hard to beat. As fans swarm to the "links" and
Many ideas and projects—big and little—can influence you, give you ideas for use in your work, and provide useful information for "current awareness." Each month I/EC's field editors and Washington staff select for detailed report and analysis, designed for easy reading, some of the most timely, in research and commercial development, process design, engineering, production, and marketing areas in the chemical process industries. We present also our comments on other interesting happenings of business and professional interest.
The Chemical World Today courses, stretching from Florida up hack and putt their way around, through North Carolina, Kentucky, they unwittingly add insult to the Ohio, and Illinois. injury already being done by snow, rain, and sunshine. Coating miniature golf courses is just one of the uses for CX-1046, Maintaining a good playing surstill a development material, acface has always been a headache for cording to Goodyear staff chemist miniature golf course owners. Most Henry Pace. The material is unare happy to get one year of wear usual in that it is a solution of a high from carpeting. And slate chips molecular weight, cross-linked urerequire constant raking and mainthane type of polymer. tenance. Dr. Pace points out that this may Now with some "fairways" in their sound paradoxical—solution of crossthird season of play, Goodyear Tire linked elastomer. But, he says, the & Rubber feels it has come up with an answer to the problem in its elastomer meets all the requirements of substances in this class. "Virtually CX-1046 urethane solution. T h e cross-linked" elastomers are either solution has been used to experimentally coat the surfaces of 14 dissolved or disintegrated by solvents
Carol Schneider and Bob Cook o f Ravenna, Ohio, try their skill at Rolling Acres Beach Club miniature golf course. The concrete course is t o p p e d with urethane film a n d grit, giving artificial greens which a r e only a little faster than grass greens.
which at best only cause CX-1046 to swell. It is possible, Dr. Pace adds, that this is a "missing link" between linear and crossed-linked polymers. The solution is a true, single-component, shelf-stable system of the polyurethane family of compounds, and the formulation is not based on castor oil. When the solvent evaporates it leaves a completely cured elastomer film. All of the isocyanate, hydroxyl, and other reactive hydrogen groups have reacted completely before the elastomer is dissolved. The secret behind putting the cross-linked polymer into solution, says Dr. Pace, is what might be called a dissolution agent, used along with the solvent dimethylformamide. In amounts of 1% or less, the agent will cause the elastomer to go into solution. But, Dr. Pace points out, the elastomer is not soluble in the dissolution agent. The solution that forms is a light amber sirup containing 30 to 40% urethane elastomer and having a Brookfield viscosity of 2000 to 8000 centipoises. One other common solvent besides dimethylformamide can be used: dimethylsulfoxide. However, for a solution with equivalent solids content, the viscosity is usually about four times greater. According to Dr. Pace, the solution gives a film that adheres well to natural and synthetic rubbers, polyvinyl chlorides), fabrics, wood, leather, and concrete. Although the adhesion to metals is good, he says, it is not adequate for industrial use. The solution can be applied by roller-coating, spreading with a doctor blade, spraying, brushing, or dipping. A typical film formed from the material has a tensile strength of 2500 to 5500 p.s.i., and elongation of 850 to 950%. Colored G r e e n
For the miniature golf course application, Goodyear uses both VOL. 52, NO. 8 ·
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solution, colored green, a n d 9- to 12-mesh, solid u r e t h a n e grit, also colored green. Solution goes onto the concrete golf course surfaces with a roller. After it dries, a second coat is applied. T h e grit, sifted t h r o u g h a screen, goes over this coat while still wet. T h e n , after a light rolling with a wooden roller, the surface is left to d r y for a couple of hours and excess grit swept u p for use later on. T h e bottom p a r t of each particle dissolves into the film, welding it tight. Even a wire brush will not loosen the particles, say D r . Pace. T h e base film for best results should be a b o u t 7 to 10 mils thick. D r . Pace points out t h a t the ure t h a n e is not p e r m a n e n t u n d e r the beating that a golf course takes. Rut a n owner can expect at least two seasons, a n d some of the experi
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mental surfaces are in their third. Even two seasons, says D r . Pace is quite a n i m p r o v e m e n t over con ventional covering—and at a cost of $4.50 to $5.00 per square yard, equivalent to the cheaper grades of carpeting. An a d d e d ad v a n t a g e : T h e u r e t h a n e is easy on m i n i a t u r e course golf balls, most of which are polyethylene. For resurfacing, solvent is used to soften the old grit. T h i s then be comes the base coat for new grit. G o o d y e a r does not actually get into the surfacing business, but just supplies the material. Donald C h a m b e r l a i n , owner of a course in R a v e n n a , O h i o — t h e first to be u r e t h a n e - c o a t e d —acts as a distribu tor a n d does the coating. M i n a t u r e golf course surfacing, while one of the more unusual appli cations for the solution, is only one of
Keep It Clean with Silica Colloidal silica fills voids in porous surfaces to minimize clinging dirt par ticles VrfOLLOiDAL siLTCA has taken on still another j o b . This time it is reducing dirt accumulation on painted surfaces, a n d in t u r n reducing m a i n t e n a n c e costs. T h e key—ex tremely fine particle size of the silica, a b o u t 17 ιημ, or smaller t h a n most dirt particles which r a n g e from a b o u t 20 ιημ u p . Applied to a painted or other porous surfaces, the silica fills the pores, thus keeping out dirt. A n y surface which has imper fections t h a t act as soil rcccpter sites is a c a n d i d a t e for the colloidal silica t r e a t m e n t , according to D u Pont w h o sells the material in a concentrated form. Diluted one p a r t to 14 parts water, the concen trate gives 15 gallons of colloidal silica which will cover 2000 s q u a r e feet of surface at a cost of 0.25 cent per square foot, says D u Pont. 32 A
After a surface is dry a n d free from grease, oil, or other foreign material, a water suspension of the silica m a y be sprayed, brushed, roller-coated, m o p p e d , or even wiped on the surface. O n drying, the silica particles coalesce to form a continuous film. Particles of trans parent silica fill the soil receptor sites. Getting the coating as thin as possible
m a n y possible uses. Cornell Aero nautical Laboratories has evaluated CX-1046 a n d has rated it along with the best-known coating materials for protecting high-speed aircraft against wind a n d rain erosion. Also, says D r . Pace, laboratory tests indicate that, because of its excellent filmforming properties, it should m a k e a good inner surface coating to leakproof p n e u m a t i c structures, such as blimps, life rafts, a n d tires. O t h e r possibilities: coating for dipped goods such as gloves, flocking adhesive, silk screening inks for rubber, p a p e r coating, leather coat ing, a n d fabric reinforcing. Still a n o t h e r use, says D r . Pace, would be for filaments, which m a y be formed by extruding the solution t h r o u g h spinnerets into a n alcohol or water bath. T h i s is still highly develop mental. J.H.K.
gives the best protection, says D u Pont, a d d i n g t h a t thick coatings " m u d c r a c k " on drying. Drying takes 5 to 15 minutes. T h e aged film is insoluble in sol vents or in water. Detergent wash ing solutions used for wall cleaning will not h u r t the film, although abrasive washing powders will re move it. According to D u Pont, exterior painted surfaces u n d e r test show almost as good as the original sur(Continued on page 33 A)
O i l storage tank painted a pastel blue and t r e a t e d with Du Pont's Soil Retardant Finish based on colloidal silica shows relatively little dirt accumulated after twelve months exposure.
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