Corrugated paper and carton strength test and analysis (a)

A: Strength test and analysis of corrugated board

Corrugated paper is the main material for manufacturing various cartons and packaging. The quality and strength of corrugated paper will directly affect the quality of cartons or packaging. The requirements for the quality and strength of corrugated paper are affected by the limitations and limitations of the production process and operations. On the other hand, the requirements for the products to be packaged and the intended use are required. Therefore, strict determination of various aspects of the strength of corrugated paper in packaging printing and production is a very important part, to ensure product quality and performance has a very important significance.

Sampling is the first step in accurate measurement of corrugated cardboard. Sampling should be able to represent the characteristics of the entire batch as much as possible, but it should be as small as possible. China's standard is set at 3% to 5%, and sampling can also be based on specific production scale and conditions. After sampling, the paper plate is processed so that the measured data is obtained under a specific condition, and such data can be compared under the same conditions. The humidity and temperature of air have a great influence on the physical and mechanical properties of paper and board. It is necessary to do proper conditioning before measurement. Below we introduce the strength indicators and test methods for corrugated paper.

1. Corrugated cardboard and carton board ring crush strength

It is difficult to determine the compressive strength of the base paper or paperboard along the width of the web (ie, perpendicular to the thickness of the paper). Because the thickness of paper or paperboard is very small, it is difficult to apply pressure on a flat paper in a direction perpendicular to its thickness, and it is difficult for the paper or paperboard to maintain its shape stability. If paper or cardboard is enclosed in a ring shape, its shape stability is much better when pressure is applied. Therefore, the raw paper or cardboard is enclosed in a ring, and then its compressive strength is measured. This is the ring pressure strength of the base paper or paperboard. Measurements were performed on a small pressure tester.

2. The flat compressive strength of corrugated core

The main function of the corrugated core is to maintain a certain thickness of the cardboard when the corrugated cardboard is deformed under pressure, so that the cardboard obtains a greater moment of inertia. This effect of corrugated papers is closely linked to the reliability of corrugated paper made on single-sided machines. Corrugated paper cores should be able to withstand stress and strain, and form uniform contour corrugations at high speeds, and they can be firmly attached to face paper.

This effect of the corrugated core can be measured by the flat compressive strength of the corrugated corrugated core. The flat crushing strength of the corrugated core is determined by first pressing the corrugated paper at a certain temperature and a certain pressure with a corrugation tester to form a corrugated shape. The flat pressure test was then performed on a small tester to determine its load carrying capacity and expressed in KN (kgf).

3. Flatness of corrugated cardboard

One of the intrinsic properties of corrugated cardboard is that it has a greater moment of inertia than normal paperboard. When the corrugated cardboard is subjected to a relatively high moment of inertia, maintaining its original thickness is a prerequisite for maintaining its inherent characteristics. Therefore, the ability of corrugated cardboard to withstand flat load without crushing is an important strength indicator for corrugated paperboard. This index is particularly important for the elasticity of corrugated board in use, and for maintaining the original thickness of the board in various manufacturing processes of the carton.

The flat compressive strength of the corrugated board is expressed in terms of the force acting perpendicularly on the unit area of ​​the board, and the unit is kPa. The flat compressive strength of the corrugated cardboard can be measured by using a small-scale pressure tester using a round specimen with a diameter of 5.13 cm.

4. Corrugated board side pressure strength

A corrugated box is different from a paper bag in that it is applied as a rigid container and maintains a certain shape when used. A major form of corrugated box damage is crushing and losing rigidity. A large amount of research work has shown that an indicator that reflects the rigidity of a carton is the compressive strength of the carton and is directly related to the side-press strength of the corrugated cardboard.

The side pressure strength of corrugated board is the ability of the board to bear the compressive load in the direction of the corrugation, expressed as the force per unit length. The unit is N/m. This index can be used to compare the production under similar conditions, but not the same batch. The quality of the product can also be used to compare the side pressure strength of corrugated board produced from different materials.

The side pressure strength can be measured with a small pressure tester. The area of ​​the upper and lower platens is 100mm*100mm, and the other requirements are the same as those for determining the flat compressive strength. Another need for two rectangular metal guides holding the sample, length 100mm, cross-section 20mm * 20mm.

5. Bursting degree

Burst resistance has always been considered as an important quality indicator of corrugated board and its components (core paper, face paper and liner paper). In the early days, even the entire quality specification of corrugated board was mainly based on the bursting resistance. Although current specifications have noted such indicators as side pressure strength, the determination of burst resistance still has great significance. Because the cardboard is subjected to stress similar to that used in the bursting test during use. Burst strength is the load of paper or paperboard when it is not broken, it means the ability of paper or paperboard to withstand external pressure without breaking. The bursting resistance is measured with a bursting tester.

6. Pierce strength

Puncture strength can be used to measure the resistance of corrugated cardboard when it is damaged by sharp objects. It is a comprehensive indicator. Recent studies have shown that the tear strength in both longitudinal and transverse directions of the paper is related to the corrugating medium, and the flat compressive strength of the corrugated medium has an important influence on the strength of the corrugated paperboard. The puncture strength has recently become more and more important, and many countries have included this indicator in the quality specifications of corrugated paper.

The puncture strength was measured with a puncture tester. The tester uses a pendulum-mounted pendulum to determine the ability of the paperboard to resist puncture by varying its positional energy before and after penetrating the paperboard, converting the amount of potential energy into kinetic energy to pierce and tear the paperboard. To indicate the puncture strength of paper or cardboard.

7. Adhesive strength

Adhesion strength refers to the bond strength of corrugated paper with face paper or paper. Apply a vertical pulling force perpendicular to the surface of the paper or corrugated medium until the two are separated. The maximum load that the interface of the binder or binder fiber can withstand before separation is the bond strength of the sample, also known as the peel strength, in units of N.

Adhesive strength can be measured with a small pressure tester. The tensile force applied to the paper and the corrugated medium is generated by inserting the upper and lower sets of inserts of the corrugated medium. Therefore, this test is also referred to as the strength test of the cemented pin.
The model of the test rod depends on the type of corrugated board being tested. A long group of test bars is inserted on the lower side of the corrugated medium, and a short group of test bars are inserted below the corrugated medium. The upper side is then pulled up and the lower one is pulled down to measure the adhesive strength of the weaker side of the two adhesive surfaces. When a long set of test bars is inserted into the upper or lower side of the core paper at intervals, and the short set of test bars are also on the same side of the insert core paper, the adhesive strength of the side connected to the test bar can be measured.

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