1939: Plastics

The field of plastics was extended still further in 1939. The great variety of objects that can be made from plastics arrested public imagination; and popular magazines as well as learned journals published articles on plastics and their countless uses.

In Europe the rearmament program shifted plastic production from phenol-formaldehyde molding powder to the manufacture of laminated phenolics. Since official reports deal more with exports and imports than with production, the figures can only be guessed at. Moreover, reports on synthetic resin lump resins used for plastics and other things, such as paints and adhesives; thus, the 1938 estimate on synthetic resins was perhaps high. In view of these facts, we estimate the 1938 world production of cellulose derivative plastics at 84,000 short tons, and that of synthetic resins at 121,000 short tons.

With more thought and artistry evident in their design, plastics are now standing upon their own merits. The time is past when viewed merely as substitutes for accepted materials, they were made to simulate them. Now they are filling structural and utilitarian purposes galore.

Injection Molding Powders.

The further development of injection molding powders and multiple unit injection presses was attended with the wider use of plastics in phases of automobile construction (steering wheels, radiator grilles, instrument panels, directional signs, and window reveals). Wider use of automatic compression type presses helped in this development. Some automobile instrument boards were built by injecting molding powder around a steel insert, thus making a coating tougher than ordinary lacquer and throwing open an enormous field to thermoplastic molding powders.

Resins.

Phenol-formaldehyde thermosetting resins still lead other plastics in volume, because in part of an extended use of laminated sheets in architecture and decoration. Tremendous sculptural castings were made for the New York World's Fair. Industrial uses included music box assemblies lighted from within, impellers and rotors of pumps, chemical and sanitary piping and electric shaver cases. The use in radio cabinets was greatly increased, especially in the case of the furfural-phenol resins on account of their resistance to scorching during molding. Improved molding powders have increased production by lowering the curing time. Greater light-fastness, higher di-electric strength, greater flexibility and increased water-resistance have all been secured.

Development of urea-formaldehyde resins occurred chiefly through improvements in structural design and better control of color, these effecting a rapid growth in the use of urea plastics for illuminated signs. An increased use in laminations was evident, including large sections, such as refrigerator doors and store fronts.

Nylon.

Nylon, the new synthetic fiber introduced in 1938, was found usable as a bristle material for tooth brushes and hair brushes. In 1939 fishing leaders and surgical sutures made from this strong synthetic material were marketed.

Cellulose-Acetate.

New uses of cellulose-acetate molding powder were found in molded duck pins and shoe heels. Clarity, dimensional stability and moisture-resistance have been improved through better formulation and advanced molding technique. Cellulose-acetate rigid sheeting was used in making transparent containers for hats, garment accessories and other luxury articles. Acetate film is being employed for hot-bed frames and solarium enclosures because of its light weight and its property of ultraviolet transmission. In some places cellulose-acetate butyrate was preferred to cellulose-acetate because of its greater moisture-resistance; it was used for flat sections such as instrument panels and glove compartment doors.

Acrylic Resins.

The acrylic resins, particularly methyl methacrylate have gone ahead by leaps and bounds. Various uses have been found for both cast resins and molding powders. The widespread use of methyl methacrylate dentures in England and the United States is due to new methods of application, which make the material more easily worked by dental technicians. Highway lighting reflectors are in more general use, and spectacle lenses are now being made to prescription by molding. The edge-lighting property of methyl methacrylate resin has led to its wider use in signs and displays; and the use of 'piped light' in the surgical field is increasing. Because of the material's property of easy machining and plasticity when heated, it has been used for display fixtures, attractive because of their transparency.

Vinyl Resins.

Polyvinyl acetal resin as the interlayer in safety glass is now found in practically all automobiles manufactured in the United States, and in some of Canadian manufacture. Thus far no other important use of resins of this type exists. Other vinyl resins, including polyvinyl chloride, polyvinyl acetate and after-chlorinated polyvinyl chlorides, are used for adhesives, impregnation of fabric for wrapping pipe lines, impregnation of silk for raincoats, injection molded articles, extruded cable coatings, slide rules and triangles, book bindings, and storage batteries. Polystyrene, heretofore available chiefly in Germany, was produced in the United States and served as acid bottle adapters, cosmetic packages, refrigerator knobs and dials, transparent dishes and condenser insulation. Germany reported an estimated sale of 2,000 tons, a considerable gain over 1938.

The war makes information as to specific European developments scanty and unreliable. When it is a thing of the past, reports of extraordinary developments will probably be forthcoming. (See also CHEMISTRY.)

Machines for Molding of Plastics.

See MACHINE DEVELOPMENT.