296 Science and Human Welfare
with the war effort. A process, to make new Nylon out of old,
has been completed—thus converting ladies’ used Nylon
hose into parachute cloth and similar materials.
Early in the defense program the Army and Navy evolved
a beautiful pair of ground glass goggles mounted in precisely
machined metal frames. Even before the approved design
went into production it was clear that they could not be pro-
vided either in time or in required quantity. Here a crisis
was averted by the Polaroid Corporation, which had de-
veloped a new process for finishing the surface of cellulose
acetate sheets which gave the plastic the optical qualities of
fine ground and polished glass. The result was the inter-
changeable plastic lens in a snug-fitting frame of molded
synthetic rubber. For protection against wind, a clear,
“Wind-foil” lens is worn. When the sun grows bright and
glare becomes bothersome, the Polaroid “Glare-foil” lens is
snapped into place.
A very important use of Plexiglas is for the production of
hoods for pilots and gun turrets on airplanes where high
visibility is so essential.
Laminated safety glass is a result of much research.
Ceramic chemists worked out suitable formulae for the glass.
Chemists developed the plastics which are being used in the
interlayer, evolved the plasticizers that render this interlayer
flexible, and invented compositions to make the plastics ad-
here to the glass. The plastic interlayer employed in the
original “Triplex” was cellulose nitrate. This material de-
composed under the influence of the shorter wave-length
portion of solar radiation, turned brown, and lost its adhesion
properties. Cellulose acetate, which is now used, is not ap-
preciably affected by sunlight and does not decompose.
When broken, the glass fragments remain anchored to the
plastic and also yield to applied force. A new laminated glass,