The coefficient of friction of printing and writing papers is an indicator of the ease with which the top or bottom sheet of a stack of paper will slide across the succeeding sheet, such as occurs on the infeed of a printing press or the sheet transport into a copier machine. A minimum coefficient of friction is required to prevent double-feeding of any sheets.

Since each sheet is removed from the stack only once, a single slide of each pair of specimens is performed and the value recorded.

FIG. 1 Schematics for Two Horizontal Plane Instruments

1.1 This test method describes a horizontal plane procedure for the determination of the coefficient of static and kinetic friction of paper measured when sliding against itself.

1.2 Although this test method is basic in concept, the precision statement has been developed on uncoated writing and printing papers. While the use of this test method is recommended for those grades only, it may be used with other types of papers giving specific attention to special paper characteristics and with the understanding that the precision and bias may not be the same.

1.3 The horizontal instrument requires some means of movement of the specimen in relation to the surface upon which it rests. The coefficient of friction (COF) is measured directly from the resistance to tangential motion and the applied weight pressing two pieces of paper together.

1.4 Static COF relates to the force required to initiate movement between two surfaces while kinetic COF relates to the force required to cause continuation of the movement at uniform speed.

1.5 An inclined plane method is described in Test Method D 4918, which gives similar results for static COF but Test Method D 4918 cannot be used for the determination of kinetic COF. The choice of approach depends on the equipment available and the means of measurement.

1.6 The determination of this characteristic for corrugated and solid fiberboard is described in Test Methods D 4521 and D 3247. These test methods differ in that in Test Methods D 4521 and D 3247, the two specimens are allowed to slip upon one another three times before the force measurement is determined, while in this test method the determination is made on the first slip.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.