An instrument to determine the stiffness of paper is desc ribed. The spccime n is b ent through a given angle, and the b ending moment is m eas ured as t he torque i n two l engths of piano wue, between which the clamp that holds t h e sp ecimen is suspended.Stiffness of paper is defi ned as the bendmg moment per unit of width of sp eci men p roducing uni t cur vature. This quantity was evaluated for e ight types of paper, for various lengths a nd wid th s of specimen, and for bendi ng angles from 5° to 30°. The stiffn ess val ue for a given specimen r emamed substantially constant when the width and bending angle were vari ed, but increa sed som ewhat as t he length of t he speClmen was incr eased.
This report describes means which have been developed to determine the relative serviceability of currency-type papers. A reproducible crumpling and smoothing cycle has been d eveloped with which to imitate the appearance and characteristics of worn paper currency. The changes in significant physical properties of this worn paper are then measured. An automatic, motor-driven crumpling apparatus is used, which alternately crumples and straightens out a specimen at a rate of about seven times per minute. The change in air permeability as the crumpling procedure progresses appears to be the most useful single measure thus far found of the decreasing serviceability of the paper. An air permeameter, specially designed for use in conjunction with the crumpling apparatus, is briefly described.
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