Folding strength, paper testing

Folding endurance under tension (10) is a favorite physical property for research on paper permanence and is the basis for the TAPPI method (16). Application of the mechanism involved in this test procedure, however, is unknown in practical uses for paper. Comparisons among product choices and estimates of their useful life should be based upon tests that assess physical properties of practical interest. Retention of reflective brightness, tear strength, tensile energy absorption, and... 

The basic mission of the Physics and Biology Laboratories is to test paper treated with products used in the restoration process. Physics is in an air-conditioned room, maintained at 60% relative humidity at 21°C, equipped with machines for testing folding endurance, tensile, and burst strength of paper. Biology runs tests, primarily with culture media, to determine the susceptibility of the treated paper to attack by microorganisms these are identified and a determination is made on how to avoid or eradicate them. Aging chambers are available for tests made by the laboratories. 

The data in Table V show that the control group for JCPA-60 paper had low strength folding endurance test values at 20% and 30% relative humidities. At 40% relative humid-... 

The control group of Allied Superior paper was categorized as high strength at 20% relative humidity, and at 80% relative humidity, the folding endurance test values had increased 9.56 times. 

The ideal mechanical test would be one in which the properties related to the use of the paper were tested. Although weak papers have low tensile strength it may be of more interest to measure how they behave when folded. A test that measures the tensile strength after one fold has been proposed. 

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