Soybean Plastics G E O R G E H . BROTHER 1 U. S. Regional Soybean Industrial Products Laboratory2. Bureau of Agricultural Chemistry and Engineering, Agricultural Research Administration U. S. Department of Agriculture NEW candidates in the field of commercial plastics during the past five years have had to meet stiff competition with those already established. The phenolics, for example, are low-cost plastics, strong, water-resistant, and of good electrical properties. The ureas have infinite color possibilities, durability, and ease of fabrication. The cellulose plastics are even better than the ureas in range of color, and of these cellulose acetate is adaptable to injection molding. The methacrylate and polystyrene plastics have optical clarity, insulating properties, and ease of fabrication. All have set high standards, and the newcomer must show real merit in order t o find a place among them. In such a field, in spite of high requirements and standards, soybean plastics have established themselves. In combination with phenolic resins, as will be shown, they produce plastics with a wider color range than the regular phenolic molding plastics. During the present emergency, soybean meal may play an important part as a n extender for highpriority phenolic resin. Soybean plastics belong t o the industrial protein group, the principal member of which is casein derived from milk. Protein plastics are characterized b y good color possibilities, good strength, and low cost, but also by poor water resistance and by lack of permanence if subjected t o moisture. This weakness has restricted casein, the established protein plastic, t o the manufacture of buttons and other small decorative objects. The first serious attempt to develop plastics from soybeans was made by Satow, in Japan, around 1920. His product, prepared by "glutenizing" the soybean protein with aqueous caustic solutions is so unstable that it fractures spontaneously o n drying. The next important development was the much publicized soybean plastic of a prominent American automobile manufacturer. This was a regular phenolic molding compound in which 50 per cent or less of the usual wood flour filler was replaced with soybean meal. The advantages of this product over the regular phenolic molding compound were slightly better plastic flow characteristics and chemurgic implications; the disadvantage was reduced water resistance. Distributor parts, accelerator pedals, 1.Present address, Western Regional Research Laboratory, Albany, Calif. 2 Now combined with the Northern Regional Research Laboratory, Peoria, 111.
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and knobs were molded from this plastic on production scale, but not steering wheels, as is popularly believed. The publicity given to this development proved of considerable value in attracting public attention to the possibilities of soybeans in plastics. In consequence, upon the establishment of the Regional Soybean Industrial Products Laboratory by the United States Department of Agriculture at Urbana, III., plastics research was made one of the major projects for investigation. This investigation opened up two possible lines of application: refinements on the development mentioned above and an entirely new application. In the first place i t was found possible to prepare formaldehyde-hardened or tanned soybean protein which is completely thermoplastic. This development is of considerable fundamental importance because previously all protein materials had to be formed to shape in the unhardened condition and then treated with formaldehyde to render them as water resistant and permanent as possible. That process was time-consuming and expensive, and of course made the preparation of a protein molding material impossible. The soybean proteinformaldehyde thermoplastic material is a molding plastic which comes finished from the die. This material alone does not completely
meet the industrial plastics needs, because it is not suitable for injection molding. However, it was found to be perfectly compatible with phenolic resin, with which it formed a new type of plastic material. This material, in comparison with the regular phenolic wood-flour molding plastic, has greater color possibilities (since protein is a good dye base), greater plastic flow, about the same strength, and similar thermosetting characteristics (thus fitting it into the same molding cycle), but with somewhat less water resistance. More recent developments have shown that it is possible to treat the solventextracted soybean meal so that it can be mixed unhardened with t h e phenol and formaldehyde before the condensation reaction starts. The resulting product shows advantages in properties of plastic flow and water resistance over the earlier mixtures. This treatment consists in leaching out the solubles with water at the pH of the protein (4.0 to 4.6), and then heating the residue to denature the protein and dry it to 3 per cent moisture content or less. Some mixtures of the foregoing type have been put on the market by several companies, in colors ranging from red to blue. White and light pastel shades are not possible. The shades produced are not so bright as those of urea or cellulose plastics, but they are much better than
Soybeans in range 400 at Agronomy Farm, Illinois Agricultural Experiment Station. In foreground appears a wild soybean selection; in background is a Peking variety.
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application of those fundamental protein characteristics—structural and otherwise— that are primarily responsible for such properties as water absorption, plasticity, etc. With such information available, it is hoped that protein structures and prop erties may be amenable to modifications that will correct weaknesses and make available an abundance of new material with interesting plastic possibilities. This material might no longer be considered strictly as soybean protein, but it would be derived from soybean meal by economical and practical processes. The hope of large-scale commercial nonfood application of soybean meal lies in the success of this type of investigation.
Army-Navy Production Awards
Beginning at left (clockwise Shown here is the equipment used in making plastics. around room): compounding rolls. hydraulic press, mixes, and plastics flow tester.
anything previously produced with phenolics. In the present emergency, with phenol formaldehyde resin among our seriously restricted materials, this soy bean meal extender may prove of real as sistance. The other line of plastic development followed at the Soybean Laboratory was the preparation of laminated plastic ma terial from soybean protein. I t was found possible to prepare a water solution of soybean protein in formaldehyde, which upon drying is a thermoplastic formalde hyde-hardened protein. Fibrous material, such as sheets of unsized kraft paper, im pregnated with this solution and dried, may be stacked between the heated plat ens of a press and united into a laminated board with sufficient heat and pressure. The board has about the same flexural and impact strengths as phenolic lami nated material, but of course less water re sistance. However, if single sheets of phenolic impregnated paper are placed on the top and bottom of the stack of soy bean-protein-impregnated sheets when they are introduced into the press, the resulting laminated board will have ex posed phenolic faces and consequently the water resistance of phenolic plastic, ex cept on the edges. This is not serious, be cause it is necessary to protect the edges of phenolic laminated board for maximum water resistance. So far as is known, there has been no application of this soybean laminated ma terial. This might be a good time to ex tend considerably our limited supply of phenolic resins. The substitution of the formaldehyde-soybean protein for the phenolic resin not only would reduce very considerably the quantity of the latter necessary for laminated material, but the
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time of the pressing cycle could be short ened by about 2 0 to 3 0 minutes for the allphenolic laminated t o about 5 minutes for the soybean protein-phenolic material, thus also speeding production. Little or no change in present equipment would be necessary. Other emergency applications are pos sible for soybean protein, such as replace ment of casein in part of the button pro duction, as an extender for phenolic resins in plywood adhesives, and the like; but in these uses soybean protein remains in herently a protein, with all its recognized virtues and shortcomings. In the field of industrial protein technology the out standing need is for botter knowledge and
Π Ρ Η Β Texas Gulf Sulphur Co. received -*· the Army-Navy Ε flag for outstand ing accomplishments in the production of war materials in a ceremony November 2 at Newgulf, Tex. Brigadier General Ray O. Avery, Commanding Officer, Edgewood Arsenal, and Commandant, Chemical Warfare School, and Rear Ad miral P. W. Foote, United States Navy, delivered addresses. The Clarostat Mfg. Co., Brooklyn, N. Y., received the Army-Navy Ε on November 13. The company is on a 100 per cent war basis, with many of its products standard equipment in our fighting planes. The Indium Corp. of America, Utica, Ν . Υ., received the Army-Navy production award on November 12, for excellence in war production. The Armstrong Cork Co., Lancaster, Penna., is scheduled to receive the award on November 30.
Representative plastic pieces which were molded from soybean phenolic molding powder.
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