By MORRIS SANDERS
In approaching the subject of plastics in future building, definition and review of the all too simple word "plastics" is first in order.
In its basic connotation, the term refers to any material capable of being shaped or molded. Natural resins such as copal, rosin, and shellac, tars and asphalt, even glass, ceramic, and plaster can thus actually be termed plastics. But we choose to limit the word today to those plastic materials that are made, or at least, tailored by man; to new molecular creations that were born in the laboratories of our modern industrial scientists. Most of these synthetic plastics may be subjected to heat and pressure and thus molded to a desired form. Some, the so-called thermoplastics, may be molded and remolded with subsequent treatments of heat and pressure; others, the thermosetting plastics are primarily cured when properly molded, and apparently "set" much in the manner of concrete.
Altho "moldability" is the outstanding characteristic of all plastics, whether thermosetting or thermoplastic, a very large proportion of the materials is never actually put to molding uses. Some are first cast and then cut and machined; a great amount of the thermoplastics is extruded at diameters ranging from inches to thousandths of an inch. And a very large percentage of all plastics is used in the forms of coatings, adhesives, films, and bonding agents.
In beginning a study of the plastics field, the layman is con-
-219-
