ISO 3781 Paper and Cardboard - Determination of Tensile Strength after Immersion in Water

The ISO 3781 standard published by the International Standards Organization (ISO) defines a test method for determining the wet tensile strength of paper or cardboard after immersion in water for a certain period of time. In principle, the method applies to both paper and board if a suitable soaking time is agreed between the parties involved. This standard does not apply to other lightweight, highly absorbent papers and tissue paper products that are difficult to handle or have low strength when wet.

The tensile strength test is carried out using equipment operating at a constant elongation rate of 1924 mm/min according to the ISO 2-20 standard or 1924 mm/min according to the ISO 3-100 standard. Therefore, depending on which method is chosen, only one or the other of these international standards is required to perform the test.

For the purposes of the ISO 3781 standard,

• The expression wet tensile strength refers to the maximum tensile force per unit width that a immersed test piece will withstand before breaking in a tensile test.
• The expression wet tensile strength retention refers to the ratio of the tensile strength of a wet test piece taken from the same sample in the dry, conditioned condition to another test piece.

This test method is based on the principle that the test piece of paper or cardboard under test is immersed in water for an appropriate time and the wet tensile strength is determined. From the wet tensile strength and the tensile strength in the dry, conditioned state, the retention of wet tensile strength is calculated. If the tests are carried out to evaluate a lot, the sample in accordance with the ISO 186 standard should be selected. If testing is performed on another sample type, it is necessary to ensure that the sample taken is representative of the sample taken. In addition, for tests involving dry tensile strength testing and soaking of less than 1 hour, the specimen and test pieces must be conditioned according to the ISO 187 standard. Conditioning is not required for tests involving 1 hour or longer soaking.

Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides testing services for the determination of tensile strength of paper and cardboard after immersion in water, within the scope of ISO 3781 standard, with its trained and expert staff and advanced technological equipment.