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ASTM D 645 / D 645M Thickness




ASTM D 645 / D 645M


Thickness of Paper and Paperboard


ASTM D 645 / D 645M Thickness covers the determination of the thickness of paper and paperboard except electrical insulating papers (see ASTM D 202). Because of the relatively high pressure 50 kPa [7.3 psi] used in this test method, it may not be suitable for measurement of tissue or other soft or low density materials, because the structure may collapse (decrease in thickness) at the prescribed pressure of 50 kPa. The values stated in either SI units or in other units shall be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system must be used independently of the other, without combining values in any way.

Significance and Use

Thickness is an important property of paper or paperboard, critical for certain end uses of paper and paperboard.  This method is useful for research work, routine control, design of end-use products, and for acceptance testing for conformance to a specification. Apparent density and other paper properties are related to thickness.


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