Physical properties tests of paper and cardboard
Paper and Paper Board
The types of test for paper and paper boards are almost the same. But there is ascertain test like stiffness which is conducted for paper board only.
Significance and Tests of Important Parameters
1. Grammage
Significance: It specifies the mass of a unit area of a sheet of paper or paper board and it is expressed in gms per square meter.
Test Method: The test method is described in Indian Standard 1060-Part-I (1987). Cut the test specimen of size 10cm x 10cm and then take the weight in the weighing balance. At least, ten readings are taken and then take the average value and expressed in gms/square meter.
2. Moisture Content
Significance: It is necessary to understand the presence of moisture content in the paper which affect the other properties of paper such as printing, absorbency etc.
Test Method: This test method is described in Indian Standard IS 1060-Part-I (1987).
3. Thickness
Significance: This test is important to measure the thickness of an individual sheet which affect the total thickness of the board used in packaging.
Test Method: In the laboratory, the single sheet as test specimen is measured at several points by means of a micrometre and an average value is calculated.
4. Bursting Strength
Significance: This test is performed to determine the resistance of a paper against rupture in use.
Test Method: The apparatus generally used “the Jumbo Muller Tester” is either motor driven or hand driven. The testing is done by means of hydraulic pressure communicated through the medium of glycerin or by compressed air to a pure gum rubber diaphragm in contact with the paper. The test values are expressed in kg/cm2 or pound/sq inch or kilopascals.
5. Water Absorption Test
Significance: This gives an indication of resistance to water absorption (normally referred to as cobb value). In this, the quantity of water absorbed by a specified area of paper surface when in direct contact with water over a period of time is measured.
Test Method: The details are given in IS: 4006 – Part – I, 1987.
6. Breaking Length
Significance: It signifies that when a paper roll is hanged and allowed to fall, then the extent of the length of paper at which the paper breaks on its own weight is measured in meters, and that is expressed as breaking length.
Breaking Length (meter) =( Tensile Strength)/( Grammage) ×1000
7. Stiffness to Bend
Significance: The test signifies the rigidity of the test sample. Normally, the test is carried out on a paper board.
Test Method: One end of the test specimen is clamped on jaws and then allow to be bent at a 15-degree angle. Measure the force required to bent the sample without cracking, measures the resistance against bending. Stiffness is expressed in either Kenley or Taber or mN.
8. Tear Resistance
Significance: The resistance against tearing of paper is measured.
Test Method: The specimens are clamped on the jaws of the Elmendorf Tear Tester. 25% of the specimen is cut by means of a knife inbuilt in the tear testing equipment. Then, the pendulum is released to tear the balance 75% of the test specimen. The force required to tear the paper is measured from the recording scale. The tear resistance is expressed as gms force.