Paper and board absorbency test

1 Topic content and scope of application

This standard specifies the method of determining the surface water absorption capacity of paper or paperboard using a Cobb Absorber.

This standard does not apply to accurately evaluate the writing performance of paper or board.

2 Reference standards

Take GB/T 450 paper and paperboard samples

GB/T 461.1 Determination of the capillary suction height of paper and board (Krem method)

GB/T 10739 Standard atmosphere for sample processing and testing of pulp, paper and paperboard

3 Terms

Paper and paperboard surface water absorption (Cobb) value: The unit of area of ​​paper and paperboard in a certain pressure, temperature, the amount of water absorbed by the surface in the specified time, in g/m2.

4 Instruments and reagents

4.1 Brevisability Tester

The equipment used for the test must meet the following requirements.

A. The cross-sectional area of ​​the metal cylinder is 100±0.2cm2 (the corresponding internal diameter is 112.8±0.2mm), and the height of the cylinder is 50mm. The contact portion of the cylinder torus and the sample should be smooth.

B. In order to prevent water leakage, the cover of the instrument cylinder should be coated with a flexible but non-absorbent pad or gasket.

4.2 The test should use distilled or deionized water. The temperature of the water during the test should be maintained at the same temperature as the surrounding atmosphere of 20±1°C or 23±1C°.

4.3 Water suction device

4.3.1 The amount of absorbent paper should be 200-250g/m2, and its absorption rate should be 75mm/10min according to GB/T 461.1. When the absorbent paper monolayer ration is less than 200-250g/m2, multiple layers can be used to meet the above requirements.

4.3.2 smooth metal flat roller: roller width 200 ± 0.5mm, quality should be 10 ± 0.5kg.

4.4 Balance: The amount of sense 0.001g, the range should be adapted to weigh the sample.

4.5 Stopwatch: Readable until 1s.

4.6 Glass cylinders.

5 sample taking, processing and preparation

5.1 The sample is taken and processed according to GB/T 450 and GB/T 10739 respectively.

5.2 The treated specimen was cut into 10 circular specimens with a diameter of 125 mm (5 specimens on both sides) to ensure a test area of ​​100 cm2.

6 test steps

6.1 The test shall be conducted under the standard atmosphere specified in GB/T 10739.

6.2 Sample placement

Before placing the specimen, make sure that the cylinder annulus and the pad that are in contact with the specimen are dry. Use a glass graduated cylinder to accurately measure 100 mL of distilled water and pour it into a cylinder. Then place a circular test piece of a well-weighed weight on the circular surface of the cylinder. The measured surface faces the direction of water, and cover the sample with the lid. On the specimen, fix it in the cylinder. Turn the cylinder 180° and start the chronograph. For each measurement 5 times, a certain amount of water was added according to the amount of water absorbed by the paper.

6.3 Water absorption time

The water absorption time refers to the time from the start of the contact of the water with the sample until the end of the water absorption. This time, it can be selected according to the different water absorption capacity of paper or paperboard, and is in accordance with the following table. If necessary, it can be extended or shortened, but it should be noted in the test report. 10-15s before the end of water absorption, the cylinder is turned upright.

6.4 Remove the sample from the cylinder and put it on a piece of absorbent paper. Take care that the sample is water-absorbent and face down. Before the water absorption time reaches 2s, place two absorbent papers on top of the sample, on a flat and rigid table. Use a smooth roller to make a round trip in 4s to make the surface of the sample water-free. Take the sample out quickly and weigh it accurately to 0.001g. Note that each sample can only be tested once and must not be reused. Absorbent paper can be reused several times as long as it can ensure its absorbency.

6.5 Discard the specimen

If there is still excess water on the surface after absorbing water with absorbent paper or the sample itself has been permeated by water, the sample should be discarded. If more than 20% is discarded, the test time should be shortened until satisfactory results are obtained, but the minimum test time should be 10s.

7 Calculation of test results

The test results are calculated according to the following formula, expressed in g/m2, accurate to one decimal place.

C = (G - G) 100

Where: C - can Bo water absorption value;

G - the mass of the sample weighed after absorption, g;

G - mass of sample before absorption, g.

8 Test report

The test report should include the following:

The standard number on which the test is based;

Water absorption time and water temperature used in the test;

The average, standard deviation or coefficient of variation of the results obtained from the test;

Does not meet the requirements of this standard;

Discard the number of specimens and reasons for rejection.

Additional information:

This standard was proposed by the People’s Republic of China Light Industry Department.

This standard is under the jurisdiction of the Scientific Research Institute of Paper Industry of the Ministry of Light Industry and is responsible for drafting.

This standard was first published in 1964 and was first revised in 1979.

Reprinted from: Light Industry Network