British common corrugated paper, cardboard and carton testing equipment and test methods
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So far, there has not been any scientific and accurate detection of the characteristics and composition of corrugated cardboard. This is because there are many uncertainties in the detection process, or depending on the processing method of paper, cardboard and carton. In addition, in the inspection area, the temperature, humidity, operation of the detection device and changes in the contents of the carton are also the reasons. One. However, it would be wise to establish some guidance testing methods and pick out those testing methods that are important for comparing certain materials, paperboard and applications.
Paper
In order to standardize various conditions affecting paper performance, it is necessary to control various conditions reasonably and effectively. In the United Kingdom, for example, the test is usually carried out at a room temperature of 50% relative humidity and 23 °C. Samples should be placed properly within 24 hours prior to testing.
Water absorption measurement
The accepted test method is the Cobb method, but this method is only applicable to facial tissue. First, the metal ring or cylinder that is opened at both ends is clamped on the paper of a given area and weight, so that the paper weight effectively closes one end of the metal ring or the cylinder. Measure the amount of water (usually 25ml) and pour it into the water storage area. After the specified time, drain the residual water. At this time, we can reweigh the paper sample and know the difference in front and back weight to calculate the water absorption rate, so as to compare the water absorption of different papers. The usual test time is about one minute, and the time is adjusted only when the paper is particularly hygroscopic.
The water drop method can be applied to all papers. This method is easier, but the results are not accurate enough, but you can test it anytime, anywhere, and compare different papers. Usually, a circle is drawn on the paper for marking, and a small amount of water is dropped into the center of the circle, and the water absorption of the paper is calculated by measuring the water absorption time, that is, the time when the circle is wet.
Air permeability test (measurement of paper hole number)
The usual method is the Gurley test, which still requires time measurement, but this time measures the time during which the air is passed through a defined area of the paper (used as a layer of membrane) at a specified pressure.
The fixed area on the paper is defined by the ring gauge. The compressed air then passes through the "separator" at a specified pressure and the amount of gas permeated can be measured with a manometer. The air permeability is usually expressed in units of "ml/min". The Bendsten test method is similar to this law.
Ring compression strength test (RCT) and derived other test methods (CCT and SCT)
For testing, a 152 mm (6 in) long, 12.7 mm (1/2 inch) wide paper strip was placed in the annular groove of a thick steel plate. The steel sheet is laid flat, and the length of the paper strip is just right to form a roll along its annular groove. A horizontal steel plate is placed over the paper roll, and then the paper roll is continuously pressed until the paper roll is crushed. The applied pressure is the RCT index of the paper, usually in "Newton" units. This method is mainly used to test facial tissue, but it can also be tried to test corrugated medium. The RCT index of these papers provides a good reference for the final edge strength of the paperboard to be formed in the future.
Corrugated Compressed Strength Test (CCT)
This method is specifically used to measure corrugated paper. As in the corrugated core paper flatness test (CMT), the paper passes through the cold-pressed corrugated core paper forming machine and becomes the same core paper as the tile line. As with the RCT test procedure mentioned above, the formed core paper is also subjected to pressure, and its compressive strength can be calculated at the moment of being crushed.
Short moment compressive strength test (SCT)
Neither the RCT test nor the CCT test can be repeated because the shape or vertical state of the paper may change when pressed, and the results will not be accurate when tested. Therefore, in order to maintain the consistency of the test, a test method for short-term compressive strength of paper has been developed. The 15 mm wide paper strip was firmly flattened with two splints leaving a 0.7 mm (0.030 inch) free paper gap in the middle. One of the splints moves under the hydraulic pressure along the plane of the strip to the other splint, pressing the narrow strip in the middle, and also measuring the pressure when the paper is crushed. This test can be done in both the machine direction (MD) and the machine vertical direction (CD).
Corrugated core paper flatness test (CMT)
In the early stage of corrugated board production, the industry believes that it is necessary to determine the flat compressive strength of different corrugated core papers, so the corrugated medium paper test device came into being. This time, a 152 mm × 12.7 mm (6 inch × 1/2 inch) paper tape was used to put the paper tape into a cold-pressed core paper forming machine similar in function to a single-sided machine to become a core paper. The core paper can also be formed by the action of a hot roll on a single-sided machine, but it should be stored for a period of time after the tape is applied. The tape is applied to imitate the single-sided cardboard, ensuring that the core paper does not deform after being removed from the single-sided machine. This single-sided tape can then be placed under pressure and used as an RCT test and a CCT test. After the tape is pressed, there may be two crushing conditions in the CMT test - either the "expanded" shape or the side damage. In this way, the core paper and the facial tissue can be compared and tested. Similarly, you can use the single-sided paper actually produced on a single-sided machine to test, compare the actual value of CMT and the theoretical value.
Perform the “hot paper” test. Pass the sample paper through a hot single-sided machine crepe stick and then place it between the splints and repeat the above steps.
Moisture test
For moisture testing, the widely used tool is a hand-held hygrometer. Calibrate the paper color or surface finish (affecting the divergence of light) before using the hygrometer. In addition, refer to the instructions provided by the manufacturer.
Scott interlayer adhesion strength test
The sample is glued to the metal base at one end and to the top angular member at the other end. The vertical face of the angled member is tapped with a pendulum pendulum until it is separated from the paper. The energy required to achieve this separation goal is often "joules per square meter".
Other tests done by the paper mill include pH testing, paper brightness and smoothness testing.
Burst resistance test (also applicable to corrugated board)
The common method is the Mullen test method, in which a stretched hydraulic elastic circular aperture is provided, and a similar paper or cardboard sample is placed on top of it, and the wafer sample is just clamped on the aperture. . The liquid pressure at which the sample ruptures is recorded, the so-called sample Mullen test value, usually in units of "kJ/m2".
Paper and board thickness test
Measuring the thickness of paper and cardboard will use a micrometer, which can control the pressure and adjust the anvil properly.
Paper and cardboard weight test
Paper mills often use sensitive test scales to measure the weight of unit paper and compare it with the factory standards. When the gram weight and the thickness are measured, the paper density is immediately known. This method can also be used for the determination of the weight of cardboard.
Cardboard
Edge strength test (ECT)
This test is quite important, and it can be seen from the stacking strength of the carton after the carton is made of such a cardboard box, in which the shape of the erected carton is also erected. This test is similar to the CCT, CMT, RCT, and FCT tests, where the tape is pressed and the ends of the tape are absolutely horizontally parallel and perpendicular to the axis. The ECT value is the pressure value measured when the cardboard is crushed.
The ECT value can be estimated slightly by adding the RCT value of each paper to the CCT value of the corrugated medium (taking into account the paper shrinkage). Add 10% to the ECT value for the first-time bonded, structurally thick composite corrugated board.
Flat compressive strength test (FCT)
During the test, the cut circular cardboard sample was placed and placed under pressure. As with the CMT test, there may be two cases of crushing - if not, it is most likely due to the skew.
Bond Strength Test (PAT)
This test has been used for a long time to test the bond strength of corrugated medium and facial tissue. A common tool is a special "comb". The length of the protruding needle on the "comb" is twice the width of the cardboard, and the diameter is just right between the turns of the cardboard to be tested. Insert a "comb" from each side of the rectangular cardboard sample, and then apply pressure to the two "combs" to separate them, that is, force the upper and lower papers to try to separate the facial tissue and the core paper. The pressure value at which the corrugated medium and the paper are torn is the PAT value of the board to be tested. The bond strength of each face paper can also be measured separately, depending on which side of the paper the needle is inserted into.
After corrugated core paper and facial tissue are torn open, it is necessary to check whether the test is actually used to invalidate the bond, or whether the interlayer adhesion strength of the paper is problematic, and the latter is generally the case.
Puncture strength test
The test element used was a pendulum with a pointed tool that was dropped from a predetermined angle during the test to allow it to puncture the cardboard sample. The degree of puncture will show the burst strength of the board tested and the value will be displayed on a meter.
Carton
Carton compressive strength test
This test requires a lot of pressure to determine the potential stacking strength of the finished carton—that is, how high the carton filled with the item can be stacked. This depends not only on the compressive strength of the top of the carton against the bottom, but also on the weight of the contents and its characteristics. If the main containers of the contents (such as cans, bottles) have a structural vertical strength and are closely arranged in the carton, it will help to increase the compressive strength of the carton. Of course, the pressure on the carton at the bottom of the carton stack determines the required carton compressive strength.
The results of this test are often far from the actual results. The reason for this difference is that the quality of the cardboard is different, especially the bond strength of each board is different, or the vertical cardboard surface of the carton is often deformed. These phenomena can occur during the filling process and occur during the sealing process, mainly because the cardboard press line is not clear enough, is difficult to identify, or the indentation is incorrect due to improper or damaged crimping tools. When folding the flap, it should be clean and clean, otherwise the cardboard near the pressure line will be bulged, and it may be crushed under the action of vertical pressure.
However, the compressive strength of the carton also depends on the ECT value and perimeter of the carton and the thickness of the carton board. The McKee formula is commonly used to calculate the compressive strength of a carton. The formula is as follows:
BCT (kg) = 1.515 × ECT 0.57 × T0.87 × (L + W) 0.47
Among them, ECT is the edge pressure strength (kg / cm), T is the cardboard thickness (mm), L, W are the length and width (millimeter) of the carton.
Drop test
This type of testing is not only for cartons, but also for the overall protective performance test of the contents of the contents and some of the packaging. In the first 50 years of the last century, the test method appeared somewhat “rude”: throwing the test carton from the second or third floor windows onto the concrete pavement in the factory, and watching the results with the naked eye or taking pictures. Later, people put the carton on the trolley and slammed down a hard surface along a slope or ramp, or rolled over the carton contained in the drum to pass it over the obstacle. Nowadays, people have developed new seismic testing equipment.
Many electronic product manufacturers now specify the requirements for drop testing, and they do not allow any damage to the contents. As mentioned earlier, this test is not only about the outsourcing carton itself, but also the overall testing of the packaging design, packaging materials and specifications.
Some laboratory tests are necessary for comparative measurements (if not absolute) and can also be referred to as a means of quality control.
However, in fact the most important test is most likely to be done by the operator. The test area is mainly near the paper flyover (testing the bond strength of single-sided paperboard), and when the first bonded cardboard is laid off, the test paperboard can get a lot of useful information, such as the bond strength, whether the cut is square, Whether the paperboard is foamed or not, the compressive strength of the paperboard, whether it is sufficiently dry, and whether there is warpage or the like. Although machine builders have succeeded in making the machine no longer require too much skill, they still require operators to understand some of the skills and board principles, and the space for operators to use their technical expertise is getting smaller and smaller. In addition, formal training of operators is also important, because the machine testing methods learned will come in handy, and the results of testing in the laboratory will come out later, which is inevitable and understandable. In most cases the results have not yet come out and the test has been completed. Nowadays, many manufacturers have long omitted the test, and most of the testing equipment has been disposed of, leaving only the carton compressive strength testing device, the flat compressive strength detecting device and the cardboard thickness measuring device. In some of the larger manufacturers, it is only in the center of the region or the headquarters to do some testing.