Strength, paper testing

About ten years after the publication of Barrow s tentative specifications, a survey was undertaken to develop and authenticate revised specifications for permanent/durable book paper. The resulting new specifications called for higher levels of initial strength and lower rates of deterioration, but of the thirty-two papers tested, eight satisfied all requirements, whereas there was only one a decade earlier (9,10). The minimum pH was raised from 6.5 to 7.5. This one relatively simple test would permit the elimination of some papers from consideration without any need for more complicated evaluation methods. 

The bursting strength is the hydrostatic pressure required to mpture a specimen when it is tested in a specified instmment under specified conditions. It is the pressure required to produce mpture of a circular area of the paper (30.5-mm dia) when the pressure is apphed at a controlled rate (TAPPI T403). It is related to tensile strength and extensibiUty and is used extensively throughout the industry for packaging and container grades. 

For some dipped work, wet gel strength measurement is carried out, where the gel is deposited onto preformed, tissue paper dumbeUs, and the load necessary to break the dumbeU-shaped test piece is measured. 

Creep test data when plotted on log-log paper usually form a straight line and tend themselves to extrapolation. Tlie slope of the straight line, which indicates a decreasing modulus, depends on the nature of the material (principally its rigidity and temperature of heat deflection), the temperature of the environment in which the product is used, and the amount of stress in relation to tensile strength. 

Before using the device in an operation, of course, the piece of test paper will have to be replaced by a fresh, unpunctured one of similar strength. Also, after the switch is positioned, and perhaps concealed, a further test with bulb and battery is necessary to be sure the switch is OPEN before the wires to the blasting cap and charge are connected. 

Figure 4.5 Relationship between tensile strength of paper (expressed as a breaking length) and the number of fibres which fail during the test.

A solution of a certain salt is tested with litmus paper, and the litmus turns red. What does this tell you about the relative strengths of the acid and base from which the salt is derived ... 

Impact Sensitivity — less sensitive than PA and TNT FI 120% PA. French test with 10kg weight (mouton) gave at the height of drop 2.50 meters, 50% detonations Initiation Sensitivity — 50g sample pressed to sp gr 1.23 in a paper cylinder 30mm diam required 2g MF for its detonation Power (Strength) — si more powerful than TNT, but less powerful than EDNA. Ballistic Mortar... 

As it appeared probable that the nitrous acid liberated by the sulphuric acid might remain in solution, and in consequence not instantly affect the test-paper, in experiments with the residues of tire other three gallons of the water hot water was used, and an acid of double strength. In each of these exporimente the test-paper became blue in a fow seconds. 

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