Testing                                                                                                                                     Bursting Strength

Bursting Strength

General 

The popularity of bursting strength test depends not only on the ease with which the test is made but also on the combination of strength and the toughness which it measures and which serves as a measure of the serviceability of paper in various applications. It has the disadvantage, however, that it depends in a complicated way on the machine direction, tensile strength, stretch and size of the burst area. Also, it does not give any indication of the cross-direction tensile strength. Bursting strength is measured by the pressure developed behind a circular rubber diaphragm when it is forced through the paper so as to burst it.

Equipment

A tester, in which testing is done by hydraulic pressure communicated through the medium of glycerine or by compressed air to a pure gum rubber diaphragm in contact with the paper, shall be used. The gauge used shall be so chosen that the individual reading shall not be less than 25 percent or more than 75 percent of the total indicated capacity of the gauge.

NOTE - The use of hand operated hydraulic type tester is not recommended as a standard practice.

Diaphragm

The diaphragm used in the equipment shall be such that it does not materially affect the bursting pressure and shall be between 0. 35 mm and 0. 45 mm thick. The rubber sheet used shall be pure gum valcanizate containing not less than 95 percent by volume of first quality smoked sheet rubber; the only ingredients in the mix, apart from rubber, shall be those necessary to effect correct vulcanization and resistance to premature aging at normal temperatures. The pressure required to bulge the diaphragm 5 mm above the top plane of the lower clamping surface of the test instrument shall be not more than 0. 07 kg/cm2.

Burst Factor

used for comparing two papers with regard to their bursting strength and is calculated as follows:

Burst factor =Bursting strength in g/cm2 /  Substance in g/m2

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