Basic knowledge collection III of the hottest cart

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Basic knowledge collection of carton base paper (III)

waterproof performance

the waterproof performance of carton board and corrugated core paper is an indispensable property of corrugated boxes. The waterproof performance of box board paper is called water absorption by the weight of water absorbed per unit area in unit time, which is generally expressed in g/m2/2mins. Its test method is called Cobb sizing test. The water absorption of the front and back sides of box board paper is equally important. The waterproof performance of corrugated core paper is called sizing or water resistance. Its test method is to put the corrugated core paper sample into a glass dish containing ammonium thiocyanate solution, Drop several drops of ferric chloride solution on the surface of the sample. When the two solutions are in contact, it will turn red. The gumming degree is expressed by the penetration time (SEC) of the two solutions

wet strength refers to the strength retained by the base paper after it is immersed in water for 24 hours or placed in high temperature (above 40 ℃) and high humidity (95%r.h.) air for a considerable time, which is called wet strength. Generally, the wet burst resistance, wet tensile strength, wet ring pressure, etc. of base paper are tested. This performance is produced by the paper factory when making paper, adding the wet strength agent into the paste, and generating a waterproof layer between the fibers after heat treatment to prevent the penetration of water, that is, to produce the wet strength effect. If corrugated boxes need to be stored in a high humidity environment for a long time or refrigerated, they need to use base paper with wet strength treatment to be competent

effect of relative humidity on the physical strength of base paper

the physical strength test of base paper is in accordance with the provisions of the national standard gb10739 pulp, paper and paperboard sample treatment. ① Before the sample is prepared, it should be dried to about half of the water content in the standard condition (the drying temperature should not exceed 60 ℃). ② Hang the sample in the air of 20 ± 2 ℃ and 65 ± 2% RH, and make its surface fully contact with the modulated air. ③ Cardboard or paper with good waterproof performance should be prepared for 24 hours or more until there is no significant change in the total weight. All physical tests should also be carried out at the same temperature and humidity. The United States has a continental climate, so all tests are carried out under the standard state of returning the 23 ± 2 ℃ and 50 ± 2% R samples to the starting position as * sub-h. therefore, the test conditions are different, and the test values obtained cannot be compared

the base paper used in corrugated boxes is composed of plant fibers, and the moisture content of plant fibers changes with the change of ambient air conditions. When the ambient air humidity is high, the base paper will become wet, and when the humidity is low, the base paper will become dry. If placed in the air with a certain temperature and humidity for a long time, the moisture of the base paper will reach a balance state; When two sheets of paper with great moisture difference are prepared under the same temperature and humidity, the one with lower moisture content absorbs moisture; The higher the water content, the release of water, the two can reach a balanced state, but there is still a slight difference in the water content of the two. Therefore, before the preparation of the sample, the water content of the base paper sample 271 ventilation pipe should be dried to about half the water content of the standard condition, and then reabsorb the water to obtain the same water content. The changes of the base paper water absorption and release are shown in Figure 1

the moisture balance point of all kinds of paper varies with the type of pulp. When the moisture reaches the balance point at 60% R.H., the moisture of coated paper is about 6%, that of paper is about 10%, and that of base paper for corrugated box is about 9.5%

the physical strength of the base paper is greatly affected by the moisture content, and its change is shown in Figure 2. The intensity is 100 when the humidity is 65% R.H. as of 2011

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