Soy plastics

Fig. 17.2. Photos showing automotive parts molded from soy plastic (1939), an exhibit dash incorporating soy plastics (1940), and a plastic bodied car made from soy plastics. Photos from the Collections of the Henry Ford Museum.

SPI hardened with an aldehyde at or near the proteins isoelectric point ("pH 4.5 for soy protein) produces a material that is thermoplastic and absorbs <10% moisture during 24 h of soaking. An aqueous suspension of the formaldehyde-hardened SPI can be used as a laminating material for Kraft paper. Laminating material made from soy plastics has similar properties to the more expensive phenol and urea laminating materials, but is less water-resistant. SPI was discontinued during the early 1950s in favor of modified soybean meals used as modifiers and extenders in PF plastics. 

Despite the early enthusiasm and fanfare, soy plastics have not measured up to alternative materials. As potential began to grow for protein-based plastics after World War II, inexpensive and adequate supplies of petroleum and better-performing synthetic materials were realized. Widespread availability of synthetic polymers discouraged attempts to make improvements. For a short period (1935—1943), H. Ford used soy plastics in his popular, inexpensive automobiles, but his plan to use over 1.4 million kg (4 million lb) of soybean meal for every million cars produced never materialized. 

The potential uses of soy plastics as commodity products (e.g., eating utensils, bags, toys) were successfully demonstrated (Paetau et al., 1994a,b Wang et al., 1995 ... 

Sue, H.J. S. Wang J.L. Jane. Morphology and mechanical behavior of engineering soy plastics. 

Sue H.-I, Weng S., Jane J.-L. Morphology and mechanical behaviour of engineering soy plastics,... 

The concept of eco-fibres is not new — Henry Ford of the Ford Motor car company wore a suit made of [soya] fabric in the 1940s. He even considered a car made of soy plastic. The subsequent rise of man-made fabrics and plastics put the development of these fabrics on the back burner. As a result of this, not much has been heard of these [natural fibres] until recently. Recognition of the environmental problems caused by man-made fibres has resulted in the emergence of a large number of alternate yams, and an increasing numbers of producers and consumers are eager to explore these options. 

Soy protein can be easily isolated from soybeans and molded. Soy plastics, which for a short period were used in automotive knobs and even body panels, never saw the widespread adoption predicted by Henry Ford in the 1930s. The Second World War sent his dream of growing a car like a crop into oblivion. Yet, as bio-based materials were being phased out by a growing synthetic, petroleum-based plastics industry, soy-protein plastics were being researched at the Ford Motor Company in Dearborn, Michigan, probably propelled by its leader Henry Ford s conscience, in an effort to give back to the American farmer what Ford tractors had taken away. 

The Second World War effectively put an end to the chemurgy movement, including Ford s desire to introduce large quantities of soy plastics into automobiles. After the Second World War, cheaper and better performing synthetic petrochemical based resins replaced soy and milk based protein plastics. 

Figure 7.9 SEM images of cross sections of soy plastic sheets plasticized with different amounts of acetamide.Liu, D. and L. Zhang Structure and properties of soy protein plastics plasticised with acetamide. Macromolecular Materials and Engineering 2006, 291, 820-828. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission.

Sue HJ, Wang S, Jane JL. 1997. Morphology and Mechanical Behaviour of Engineering Soy Plastics. Polymer 38(20) 5035-5040. 

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