Testing of Flexible Packaging Materials

 Paper and Paper Board

The types of test for paper and paper boards are almost same. But there are certain test like stiffness which is conducted for paper board only.

Significance and Tests of Important Parameters

(a) 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 weighing balance. At least, ten readings are taken and then take the average value and expressed in gms/square meter .

(b) Moisture Content

Significance : It is necessary to understand the presence of moisture content in 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).

(c) Thickness

Significance : This test is important to measure the thickness of an individual sheet which affect the total thickness of board used in packaging.

Test Method : In the laboratory, the single sheet as test specimen is measured at several points by means of a micro meter and an average value is calculated.

(d) Bursting Strength

Significance : This test is performed to determine the resistance of a paper against to 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 kilo pascals.

(e) Water Absorption Test

Significance : This gives an indication of resistance to water absorption (normally referred 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.

(f) 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 meter, and that is expressed as breaking length.

Breaking Length (meter) =( Tensile Strength)/( Grammage) ×1000

(g) Stiffness to Bend

Significance : The test signifies the rigidity of the test sample. Normally, the test is carried out for paper board.

Test Method : One end of the test specimen is clamped on jaws and then allow to bent at 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.

(h) Tear Resistance

Significance : The resistance against tearing of paper is measured.

Test Method : The specimens are clamped on the jaws of 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.

Plastic Films and Laminates

Significances and Tests of Important Parameters

(a) Caliper or Thickness

Significance : To measure the thickness of the film in millimeter or micrometer or micron.

Test Method : The centre portion of the test specimen is placed in between the flat jaws of micrometer to check the uniformity of thickness. (Reference IS: 1060 (Part –I) – 1966.

(b) Density

Significance : To check the specific gravity or density or the ratio of mass upon volume.

Test Method :

The detail test method is described in IS : 2508 - 1987.

(c) Tensile Strength and Elongation at Break

Significance : To measure the force require to break the test specimen while the samples are kept under tension in between the jaws of tensile machine.

Test Method : Two ends of the test specimen are clamped in the machine at the grips separated by 50mm. Start the machine at the pre adjusted speed of 500 mm/min and note the load and elongation at break. Tensile strength is expressed as kg/cm2 or Mn/m2 and elongation at break are expressed as percentage.

(d) Dart Impact Resistance

Significance : To measure the impact resistance of the plastic film by measuring the load or dart at which 50 percent of the specimen fail when tested by this method.

Test Method : The details are described in IS : 2508 – 1987.

(e) Co-Efficient of Friction or Slip

Significance : It is the ratio of the frictional resistance to the normal pressure acting on two surfaces in contact.

Test Method : A sled of 120 mm square is allowed to move over the plastic film and record the frictional force acting at the contact surface. The value is expressed in Newton. Calculate the dynamic coefficient of friction using the mean load represented by the straight line.

(f) Determination of Gloss

Significance : To measure the percentage of reflectance of light at a particular angle where the angle of incident light and the angle of reflectant light will be the same. This is an optical property of plastic film.

Test Method : The gloss meter is set up to 450. Take reading with plastic film by replacing the standard used for calibrating the instruments. Repeat the test for five times with different specimens. It is expressed as specular gloss at 450.

(g) Determination of Haze

Significance : The haze of the specimen is the percentage of transmitted light which is passing through the specimen deviates from the incident beam by forward scattering. This is also an optical property of the film.

Test Method : Illuminate the specimen by unidirectional beam making an angle with the direction of its axis not exceeding 30. Determine the reading with haze meter and then expressed in percentage.

(h) Peel Bond Strength for Flexible Laminate

Significance : To measure the tackiness between the two substrate of the laminate in terms of force.

Test Method : The two ends of the test specimen where one end clamped at the jaws of Tensile machine by keeping the gauge length of 50 mm. Run the test at the speed of 300 mm/min and record the force in gm/15 mm width and then calculate the average from the graph. (Ref. ASTM F-88)

 Aluminium Foils

Significance and Tests of Important Parameters

(a) Thickness or Caliper

Significance : To measure the thickness of the aluminum foil or web.

Test Method : Properly calibrated dead weight micrometer is used to measure thickness.

(b) Pin Hole Test

Significance : To ascertain the number of pinhole exists in the aluminum foil.

Test Method : The aluminum foil is checked by means of an illumination equipment where a tungsten lamp is positioned in a cylindrical structure and all the surroundings are covered with black paper. The test specimens are placed at the top end of the cylinder and then observed the pinholes against the light.