Synthetic resins and their raw materials / A survey of the types and uses of synthetic resins, the organization of the industry, and the trade in resins and raw materials, with particular references to factors essential to tariff consideration. Under the general provisions of section 332, title III, part II, Tariff act of 1930.

by United States Tariff Commission

Resins obtained from urea and thiourea, if imported, would probably be classified under paragraph 11 of the Tariff Act of 1930. The present rate of duty under this classification is 4 cents per pound and 30 percent ad valorem.

There has been no importation of these resins. This is due principally to the international licensing arrangements which usually include the allocation of markets.

Exports are not shown separately in official statistics.

6. ACRYLATE RESINS

A new development of widespread importance in the synthetic resin industry is the commercial production of the polymers of certain derivatives of acrylic acid. The commercial exploitation of the acrylates is another example of the belated realization of the value of substances known for many years. Acrylic acid has been known for about a hundred years, and the polymer of methyl acrylate was first described in 1880. It was not until 1927, however, that a suitable method for their commercial production was developed. The study of the many derivatives of acrylic and methacrylic acids leads to the conclusion that those of greatest practical application in the resin field are the lower esters, such as methyl and ethyl, polymerized separately or together.

Colorless transparency, stability against aging, thermoplasticity, and chemical resistance to many reagents are the general characteristics of the acrylate resins. In consistency they range from soft, sticky, semiliquids to hard, tough, thermoplastic solids. Since these widely varying properties are obtained by control of manufacturing conditions, rather than by the use of plasticizers, the resins retain their initial properties indefinitely. Aging and weathering have no effect as they are stable under exposure to heat, light, and oxidizing agents. The methacrylates are harder and tougher but less elastic than the acrylates.

Properties and uses.

The acrylate resins are marketed in a number of forms, such as solutions in organic solvents, dispersions in water, solid cast sheets, rods and tubes, and molding powders. All of these are distinguishable from many other resins by their colorless transparency, adhesive qualities, great elasticity, and chemical resistance. The brilliant water-white color makes it possible to secure masses having a high degree of light transmission and great optical clarity.

The earliest commercial use of the acrylate resins was in laminated safety glass marketed as Plexigum in the United States and as Luglas and Sigla in Europe. The extensibility and elasticity of the resin film gives the laminated glass a flexible or yielding type of break when subjected to a hard impact. Having excellent adhesion to glass there is no need of an auxiliary cement to bond the resin to the glass, nor is it necessary to seal the edges since the resin has good resistance to moisture. The acrylate resin used for this purpose is in the form of a viscous solution in an organic solvent. A film is applied to each sheet of glass, the solvent removed by drying, and the sheets are pressed together.

The harder acrylic resins are used in the form of solid thermoplastics. Methyl methacrylate is of special interest. As the monomer is a mobile liquid it can be cast-polymerized to a solid of any desired shape in predesigned molds or produced in finely divided form for use as molding powder. The cast resin is marketed in this country as Crystalite, Plexiglas and Lucite, and in England as Diakon.