Strength test and analysis of corrugated paper and carton
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First. Strength test and analysis of corrugated paper
Corrugated paper is the main material for the manufacture of various cartons and packaging. The quality and strength of corrugated paper will directly affect the quality of the carton or packaging. The requirements for the quality and strength of corrugated paper are subject to the influence and limitation of the production process and operation, and on the other hand, the requirements for the products to be packaged and the intended use. Therefore, strict measurement of various aspects of corrugated paper strength index is very important in packaging printing and production, and is of great significance for ensuring product quality and performance.
Sampling is the first step in accurate measurement of corrugated board. Sampling should be able to represent the characteristics of the entire batch of products to the greatest extent possible, but as little as possible. China's standard is 3% to 5%, and it can also be sampled according to the specific production scale and situation. After sampling, the paper plate is processed so that the measured data is taken under a specific condition, and such data can be compared under the same conditions. The humidity and temperature of the air have a large impact on the physical and mechanical properties of paper and board. It is necessary to do proper humidity control before measurement. Below we introduce the strength index and test method of corrugated paper.
1. Ring compression strength of corrugated board and carton board
It is difficult to determine the compressive strength of the base paper or paperboard in the width direction (ie, perpendicular to the thickness of the paper). Since the thickness of the paper or paperboard is small, it is difficult to apply pressure on a straight piece of paper in the direction perpendicular to its thickness, while maintaining the shape of the base paper or paperboard. If the paper or paperboard is enclosed in a ring shape, its shape stability is much better when pressure is applied. Therefore, the base paper or paperboard is enclosed in a ring shape, and then the compressive strength is measured, which is the ring pressure strength of the base paper or paperboard. The measurements were made on a small pressure tester.
2. The compressive strength of the corrugated core
The main function of the corrugated core is to maintain the thickness of the cardboard when the corrugated cardboard is deformed under pressure, so that the cardboard obtains a large moment of inertia. The role of corrugated paper is closely related to its reliability in making corrugated on a single-sided machine. The corrugated paper core is capable of withstanding the effects of stress and strain, and forms a uniform contour corrugation at high speed erection, and can be firmly adhered to the facial tissue.
This effect of the corrugated core can be measured by the flat compressive strength of the corrugated corrugated core. The flat compressive strength of the corrugated core is determined by first pressing the corrugated base paper into a corrugated shape with a corrugating tester under a certain temperature and a certain pressure. Then, a flat pressure test was performed on a small test machine to measure the load carrying capacity, and it was expressed by KN (kgf).
3. Compressive strength of corrugated board
An inherent property of corrugated board is that it has a larger moment of inertia than a typical board. When the corrugated board is subjected to a high moment of inertia, maintaining its original thickness is a prerequisite for maintaining its inherent characteristics. Therefore, the corrugated board is subjected to a flat load without crushing, and is an important strength indicator of corrugated board. This indicator is particularly important for the flexibility of the corrugated board during use and for maintaining the original thickness of the board during the various processing of the carton.
The flat compressive strength of corrugated cardboard is expressed by the amount of force acting perpendicularly on the basis area of the cardboard, in units of kPa. To determine the flat compressive strength of corrugated board, a small pressure tester can be used with a circular sample with a diameter of 5.13 cm.
4. Corrugated board edge compressive strength
Corrugated boxes are different from paper bags in that they are used as rigid containers and are maintained in a certain shape when in use. One of the main forms of corrugated box damage is crushing and loss of rigidity. A large amount of research work has shown that an indicator of the rigidity of the carton is the compressive strength of the carton, and is directly related to the edge compressive strength of the corrugated board.
The edge compressive strength of corrugated board refers to the ability of the board to withstand compressive loads in the corrugated direction. It is expressed in units of length, in N/m. This indicator can be used to compare production under similar conditions, but not in the same batch. The quality of the product; it can also be used to compare the compressive strength of corrugated cardboard produced from different materials.
A small pressure tester can be used to measure the edge pressure strength. The upper and lower platens are all 100mm*100mm, and the other requirements are the same as those for measuring the flatness. In addition, two rectangular metal guide plates for holding the sample are required, which are 100 mm long and have a cross section of 20 mm * 20 mm.
5. Breaking strength
Burst resistance has long been recognized as an important quality indicator for corrugated board and its components (core paper, facial tissue and backing paper). In the early days, even the full quality specifications of corrugated board were based primarily on burst strength. Although the current specifications have noted indicators such as the edge pressure strength, the determination of the burst strength still has great significance. Because the paperboard is subjected to similar stresses during the use of the breaking resistance. Burst resistance is the load of paper or paperboard when it is not broken. It indicates the ability of paper or paperboard to withstand external pressure without breaking. The burst strength is measured with a burst resistance meter.
6. Puncture strength
The puncture strength can be used to measure the resistance of corrugated board to damage caused by the impact of sharp objects. It is a comprehensive indicator. Recent studies have shown that the tear strength in both the longitudinal and transverse directions of the facial tissue is related to the corrugated core paper, and the flat compressive strength of the corrugated medium has an important influence on the strength of the corrugated cardboard. 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 by a puncture strength meter. The analyzer uses a pendulum-mounted pendulum to measure the ability of the cardboard to resist puncture by changing the positional energy before and after the puncture of the cardboard, and transforming the change in potential energy into kinetic energy to puncture and tear the cardboard. To indicate the puncture strength of paper or cardboard.
7. Bond strength
Adhesive strength refers to the bond strength of corrugated paper to facial tissue or backing paper. Apply an outward pulling force perpendicular to the surface to the face paper or corrugated core paper until the two are separated. The maximum load that the interface of the binder or binder fiber before the separation can withstand is the bond strength of the sample, also known as the peel strength, in units of N.
The bond strength can be measured by a small pressure tester. The tensile force applied to the paper and the corrugated medium is produced by inserting the upper and lower sets of the corrugated rods. Therefore, this test is also called the pin bonding strength test.
The model of the test stick depends on the type of corrugated board being tested. A long set of test bars are inserted on the underside of the corrugated medium, and a short set of test bars are inserted under the corrugated medium. Then, the upper side is pulled up and the lower side is pulled down to measure the bonding strength of the weaker side of the two bonding faces. When a long set of test bars are inserted into the upper or lower side of the core paper at intervals, and a short set of test bars are also inserted into the same side of the core paper, the bond strength of the side connected to the test bar can be measured. (Figure)
Second, the performance test of the carton
Corrugated boxes can mostly replace wooden boxes, but the main reasons for not completely replacing wooden boxes are: 1. Water and moisture resistance is not as good as wooden boxes; 2. Easy to be pierced by sharp hard objects; 3. Compressive strength is not as good as wooden boxes . Especially the last point is particularly big. Therefore, it is of great significance to study how to improve the compressive strength of corrugated boxes.
Corrugated boxes are packaging containers whose testing can be carried out in accordance with the requirements of the packaging container. The main test items are:
Carton pressure test
The carton pressure test, the compression test, is the most basic test for the performance of the carton. Through this test, it is possible to determine the compressive capacity of the carton under different conditions.
The equipment used for the carton pressure test is a carton-specific pressure tester. The pressurizing area of such a test machine table is relatively large. Generally, the area of the upper and lower platens is 1.5 m*1.5 m or 1 m*1 m. One of the two pressure plates is a support plate, the position of which can be adjusted according to the size of the sample to have a suitable height, and then fastened; the other piece is a pressure plate that can slide along the guide rod. Apply pressure to the sample.
2. Drop test of the carton
The drop test is a commonly used test for general merchandise packaging and is also used in corrugated boxes. The physical strength of the contents under different drop conditions can be detected by the drop test. At the same time, the performance of the carton and the cushioning effect of the carton structure can also be determined through experiments.
The drop test is a simple and applicable test. It is suitable for packages with a total weight of less than 150kg or a smaller volume. The equipment used in the test machine is relatively simple, and the hook drop test machine or the spreader test machine can be used.
3. Bevel impact performance
For heavy or bulky packages, such as large packages weighing up to 150 kg, a bevel impact test can be used to test the impact resistance of the package and contents.
The bevel impact test mimics the strong impact loads caused by trains, car starts, braking and downhill. In addition, this test can provide similar experiments for various impact loads caused by the transportation process (such as the transportation of goods through the conveyor belt, lifting, unloading, etc.). The test device is a crash tester consisting of a slide, a pulley and a baffle.
4. Hex drum test
The hexagonal drum test is a comprehensive test of the various loads on the outside during the transportation of the carton with the contents. This test can emulate the case where the carton is transported by the conveyor belt into the warehouse, the machine compartment, the carriage, or the conveyor belt transports the carton from one floor to the other. The tumbling and falling of the carton in the testing machine is arbitrary and there is no certain rule. This natural drop of the carton can fall on the baffle of the drum or fall on each corner, each side and each side of the drum to provide various load tests for the carton.
Through this test, two purposes can be achieved: simulating the impact and vibration that the carton may encounter during transportation, determining the ability of the carton to withstand these shocks and vibrations; and determining the protection of the carton, inner packaging and anti-vibration material against the contents. In addition, this test is also useful for determining the reliability of the joint and closure of the carton. This test was carried out on a hexagonal drum tester.
5. Vibration and anti-vibration performance test
The carton will be subjected to vibration of different frequencies and amplitudes during transportation, which will affect the carton and the contents, such as deformation and cracking of the carton, surface wear, ink stain, etc. The vibration test can simulate the general vibration during transportation, or Perform occasional vibrations of known parameters. Due to the wide range of vibration frequencies during transportation, the test consists of two aspects: one is to place the carton on the vibrating table without being tightly clamped, and the test carton is subjected to the fatigue and high-frequency vibration caused by repeated vibration; Tighten the carton on the shaker and check that low-frequency vibrations cause resonance in the carton. This test is suitable for items such as electronic instruments that are very sensitive to low frequency vibration.
The vibrating table for the vibration test of the carton can generate a vibration frequency of 1-80 Hz and an acceleration of 0.5-10 g (g = 9.81 m/s*s). A test carton can be placed on the vibrating table, and the carton can be tied or freely moved according to the test requirements. The test can simulate the stacking of the transport process and apply a simulated force load to the specimen. The shaker should also meet the requirements for stacking cartons and the total load of the contents.
The basic method of the test is to reproduce the vibrations during transportation, such as in the train compartment, in the car compartment, and in the aircraft cabin under experimental conditions. The load of vibration depends on the type of transport.
When testing the vibration resistance of the carton, the number of patterns is adapted to the actual situation. The stacking quantity of the carton is generally not less than three, and the total stacking height should depend on the type of transportation. The stacking height of railway transportation is generally 2.5m, the car is 2m, and the air transportation is 1.5m. The termination time of the test is determined by the breakage rate of the carton. The degree of damage includes the seam of the carton and the damage of the bonded box wall.
6. Spray test
The corrugated box is sprayed under the specified conditions according to the prescribed time and the amount of water sprayed, and the intrusion ability of the carton to withstand water and the protection ability of the carton for the contents are determined.
7. Other tests
Including weather resistance test and friction performance test.