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thetic rubber using a b a s e of domes tic vegetable oils not considered suitable for edible purposes, h a s been, under way at the Chicago plant of t i a e SherwinWilliams C o . for several moncfchs. Called "KemPol", the vegetable-oil 3*ubber sub stitute is a development of t i i e SherwinWilliams research laboratory's work with drying oils used i n paint manufacture. Unlike m o s t chemurgic rubbers, KemPol requires n o critical equipment for its manufacture and the volume* of produc tion will b e limited only by t h e amount of oil available. Tensile strength, elongations, and abra sion resistance of K e m P o l are n o t on a par with those of natural rubber, although in many other properties it compares so favorably with natural rubbea- as t o en able its u s e in m a n y products such as treads, m a t s , pads, erasers, gaskets, braided hose, e t c . Since no> toxic raw materials a r e used in t h e manufacture of KemPol, i t may b e used for such other products a s jar rings and various types of seals for food containers. KemPol lends itself readily- to emulsincation a n d , w i t h certain limitations, t o solutions, so t h a t a number- of success ful applications i n t h e fields of fabric coating, tapes, adhesives, s a i d sealing compounds h a v e resulted. KemPol sponges easily, offering many ;possibilities in that field. KemPol also shows consideacable prom ise a s an extender for naturaL, reclaimed, and the B u n a a n d Butyl ruJbbers, with all of which it i s readily «compatible. Possibilities are s e e n in this direction for a lasting peacetime usage, as w e l l as when used alone o r when fortified witli small per centages of reclaim. T h e customary fillers, extenders, and accelerators have been founcl to work well with K e m P o l and standard rubbermaking equipment, as found i n the aver-
left. Skid-free landings and «ake-offs on icy airport runways and in arctic regions are made possible by this new €ire in which steel coils are laced into the robber tread· The rows of steel coils are bonded into the rubber around the circumference of the tire during vulcanization in a process which made necessary the development of an entirely new method of tire construction. These tires are manufactured by B„ F. Goodrich Go. and have already been produced in considerable num bers. Many of them are in use i n our armed forces and others are now being subjected to extensive tests in domestic transport service. 306
CHEMICAL
A N D
ENGINEERING
NEWS
Rubber from Domestic Vegetable O i l s Announced age rubber plant, is entirely adequate for the pu «ose. Tensiit xength Elongation Shore hardness Elasticity
300 t o 100 t o 40 t o 50 t o
500 lbs. per sq. in. 150% 70 25
After aging 7 2 hours at 170° F. tensile strength increases about 100 per cent, elongation decreases about 33 per cent, hardness increases about 5 0 per cent, elasticity decreases about 10 per cent. Chemical and solvent resistance are, in general, similar to rubber. Water Alcohol Aliphatic hydrocarbons Aromatic hydrocarbons Dilute mineral acids Concentrated mineral acids Dilute and concentrated alkalies
N o effect N o swelling but impaired flexibility 50 per cent swelling, tender 200 per cent swelling, very tender Very slight swelling Poor resistance, especially with oxidizing acids Very poor resistance
Pigmented with black, dielectric strengths of about 185 volts per mil have been obtained. Ozone resistance is excellent, greatly superior to black rubber.
assembly lines without interruption because of a new adhesive developed b y its Plastics Department, du Pont a n nounced on March 2 . The highly-polished, optical surfaces of plastic enclosures must be carefully protected by heavy masking paper against scratching and marring during shipment, fabrication and assembly. D u e to t h e critical shortage of crude rubber used in the conventional cement, development of a less critical substitute was undertaken at the request of the War Production Board, Army and Navy. Primarily the adhesive had to seal t h e protecting paper to the plastic through all handling, shipping, fabricating and assembly, because the paper is not stripped off until the bomber or fighter is ready for its initial flight- It had to withstand extremes of temperature and humidity— outdoor assembly lines in California,
supply depots in the tropics or the arctic, warehouses in Murmansk, plants in Texas. The paper had to strip off easily, but not self-strip. It could leave no deposit of adhesive, for cleaning takes time. When aircraft production reaches its peak, hundreds of thousands of pounds of rubber will be replaced solely in masking "Lucite" methyl methacrylate resin and other acrylic plastics. Additional amounts will be used in masking other types of plastics. This new adhesive is applied to paper by the same equipment previously used for crude rubber cement. I t is being compounded by du Pont's Fabrics & Finishes Department in equipment formerly used to make commercial lacquers. T h e petroleum base is purchased from an oil company and is dispersed in various chemicals to form the adhesive.
W . J. Walton, research chemist, examines section of KemPol, a new rubber substitute.
Glycerin Recovery Process ^TLLYCERIN is recovered in soap manufacturing more quickly and economically than heretofore, a n d in substantially larger quantities, by a new alcohol process developed by t h e Fine Chemicals Division of D u Pont. Process swiftly a n d economically recovers the critically needed product from domestic fats, whereas most of it formerly was extracted from coconut oils of high glycerin content imported from islands in the Pacific. I t also marks an important step forward in the manufacture of soap, and may b e used generally after the war, the company reports. Recovery is more economical because less heat and water a r e required than for older processes, equipment is smaller and more compact, and stainless steel equipment is unnecessary since the reaction can b e carried o u t at ordinary temperatures and pressures in iron vessels. I n addition t o larger and faster recoveries, the method gives water-free glycerin that can be used directly in many processes.
Adhesive to Save Rubber TLXUNDREDS of thousands of pounds of crude rubber will b e saved and crystalclear plastic noses a n d transparent enclosures for military aircraft will flow to V O L U M E
21,
NO.
5 » » » M A R C H
10,
1943
307
