Paper and cardboard hygroscopicity

2019-05-05 09:12:10 325

Paper and cardboard hygroscopicity test (Kerber method)

This standard is equivalent to the International Standard ISO 535 "Determination of Water Absorption of Paper and Paperboard (Kebo Method)". 1 Subject Content and Scope of Application This Standard specifies the method for determining the surface water absorption capacity of paper or paperboard by Cobb absorber. This standard is not applicable to the accurate evaluation of the writing performance of paper or cardboard. 2 Reference to standard GB/T 450 paper and cardboard specimens using GB/T 4

This standard is equivalent to the international standard ISO 535 "Paper and cardboard - Determination of water absorption (Kebo method)".

1 Subject Content and Scope of Application

This standard specifies a method for determining the surface water absorption capacity of paper or paperboard by Cobb absorber.

This standard is not applicable to the accurate evaluation of the writing performance of paper or cardboard.

2 Reference Criteria

Adoption of GB/T 450 Paper and Paperboard Samples

GB/T 461.1 Method for the Determination of Capillary Absorption Height of Paper and Paperboard (Krim Method)

Standard atmosphere for sample treatment and test of pulp, paper and paperboard GB/T 10739

3 terminology

Cobb value: The amount of water absorbed on the surface of paper and cardboard per unit area at a given pressure and temperature within a specified time, measured in g/m2.

4 Instruments and reagents

4.1 Burt Absorption Tester

The instruments used in the test must meet the following requirements.

A. The inner section area of metal cylinder is 100 + 0.2 cm 2 (corresponding inner diameter is 112.8 + 0.2 mm), the height of the cylinder is 50 mm, and the contact part between the cylinder and the specimen should be smooth.

B. In order to prevent the leakage of water, the cover of the instrument cylinder should be provided with an elastic rubber pad or washer which does not absorb water.

4.2 Distilled water or separated water should be used in the test. During the test, the temperature of water should be kept at the same temperature as that of the surrounding atmosphere at 20 1 C or 23 1 C.

4.3 Water Absorbing Device

4.3.1 Absorbent paper should be 200-250g/m2 in quantity, and its absorption rate should be 75 mm/10 min as determined by GB/T 461.1. When the single-layer weight of absorbent paper is less than 200-250g/m2, multi-layer stacking can be used to meet the above requirements.

4.3.2 Smooth Metal Flat Roller: The width of the roll is 200 + 0.5 mm, and the mass should be 10 + 0.5 kg.

4.4 balance: Sensitivity 0.001g, measuring range should be suitable for weighing samples.

4.5 stopwatch: readable to 1s.

4.6 glass measuring cylinder.

5 Sample Acquisition, Treatment and Preparation

5.1 Samples were taken and treated according to GB/T 450 and GB/T 10739, respectively.

5.2 The treated specimens were cut into 10 circular specimens (5 on the front and 5 on the back) with a diameter of 125 mm to ensure the test area of 100 cm 2 each.

6 test steps

6.1 The test shall be carried out in the standard atmosphere specified in GB/T 10739.

6.2 Sample placement

Before placing the sample, it is necessary to ensure that the cylinder torus and the rubber pad contacted with the sample are dry. A glass measuring cylinder is used to accurately measure 100 mL distilled water and pour it into the cylinder. Then the weighed circular specimen is placed on the circular surface of the cylinder. The measured surface is in the direction of water, and the sample is pressed over the sample to fix it together with the cylinder. Turn the cylinder 180 degrees and start the stopwatch. Every five times, add a certain amount of water according to the amount of water absorbed by the paper.

6.3 Water absorption time

Water absorption time refers to the time from the beginning of water contact to the end of water absorption. This time can be selected according to the different water absorption capacity of paper or cardboard, which is in accordance with the following table. The time may be prolonged or shortened if necessary, but it should be noted in the test report. Turn the cylinder right 10-15 seconds before the end of water absorption.

6.4 Remove the sample from the cylinder and put it on a absorbent paper. Pay attention to the absorbent side of the sample. When the absorbent side is down, two absorbent papers are placed on the sample 2 seconds before the absorbent time arrives. On a flat and hard table, smooth rollers are used to make the surface of the sample glossy within 4 seconds. Quickly remove the sample and weigh it up to 0.001 g. Note that each sample can only be tested once, No. It has to be reused. Absorbent paper can be reused many times as long as its absorbability is guaranteed.

6.5 Sample Discarded

If there is still excessive water on the surface after water absorption with absorbent paper or the sample itself has been penetrated by water, the sample should be discarded. If more than 20% is abandoned, the test time should be shortened until satisfactory results are obtained, but the shortest test time should be 10 seconds.

7. Test results calculation

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

C = G - G) 100

Formula C - Kebo water absorption value;

G - Sample quality after water absorption, g;

G - Sample quality before water absorption, G.

8 test report

The test report shall include the following:

The standard number of the test basis;

Water absorption time and water temperature were used in the experiment.

The average value, standard deviation or coefficient of variation of the test results were obtained.

Operations that do not conform to the provisions of this Standard;

Number of discarded samples and reasons for discarding.

Additional notes:

This standard is proposed by the Ministry of Light Industry of the People's Republic of China.

This standard is drafted by the Institute of Paper Industry Science, Ministry of Light Industry.

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