Corrugated box is one of the most commonly used packaging materials for express transportation and protecting goods. Corrugated board is twice as thick as card paper of the same weight, resulting in significantly higher lateral compressive strength. Therefore, it is used in large quantities for the packaging of deliveries. I would like to take you through the knowledge of corrugated boxes.
History of Corrugated Boxes
It all began in 1856 when Edward G. Healy and Edward E. Allen patented a method of pleating paper to give it a wavy appearance. The purpose of introducing this paper inside top hats was to make them more durable and comfortable to wear. In 1871, Albert L. Jones was the first to use pleating paper as a protective packaging material. It was used to wrap glass bottles and kerosene lamp chimneys. The patent of Jones was improved by Oliver Long in 1874 by adding two sheets of pleating paper as liners, holding the pleating paper in the middle, thus creating the first corrugated board. Henry Norris and Robert Thompson produced the first corrugated boxes in the United States in 1894. In 1895, Jefferson T. Ferres invented the first corrugator, which is still in use today. Nowadays, more than 90% of the world’s goods are packaged in corrugated boxes.
The Process for Making Corrugated box
Corrugated board is commonly made from logs, bamboo, wheat grass, reeds, wheat straw, and recycled paper. The process of converting raw materials into corrugated board requires the cleaning of the raw materials. After treatment, the raw material is stirred by a repulper to form fibers, which are then dried after impurities are removed to form paper. A corrugator transforms the paper into corrugated board, which is slotted, die-cut, and glued into corrugated boxes.
About the flute
It is commonly known as three-layer corrugated board, which consists of face liner, pleating paper (called flute in the industry), and inner liner. The wavy structure of the flute makes the board 60-70% hollow. Depending on the height and density of the flute, corrugated boards can be classified as A, C, B, and E, and the following table summarizes their characteristics and data.
| Type | Height Of Flute | Number Of Flute | Feature |
| A | 4.5-5.5mm | 115 flutes per meter | Good cushioning for lighter products |
| B | 2.5-3mm | 154 flutes per meter | Flatter surface for printing, suitable for heavier products |
| C | 3.5-4mm | 125 flutes per meter | Weaker overall performance than A |
| E | 1.2-2.2mm | 286 flutes per meter | Suitable for folding boxes, enabling complex printing to be achieved |
Additionally, they can be combined based on their characteristics to achieve complementary functions. For example, combining to form AB type corrugated board, BC type corrugated board, or AC type corrugated board.
About the liner
The most commonly used papers for the liner are kraft paper and test paper. A corrugated board’s inner liner is usually made from test paper, whereas its outer liner is made from kraft paper. Kraft paper is more expensive than test paper, but it is of higher quality. Kraft paper is primarily made from virgin chemical pulp fibers derived from wood and can be processed to have a variety of colors and textures. Additionally, it has a flatter surface, which makes printing easier. Furthermore, kraft paper is more resistant to tearing and bursting than test paper, thus providing better protection for goods.
About the printing
Printing on corrugated boxes can be done in two basic ways: pre-printing and direct printing. The term “direct printing” refers to printing directly on the box. Pre-printing is the process of printing outer liner paper first and then combining it with other parts.
In direct printing, flexographic printing, offset printing, and screen printing is commonly used.
- Flexographic printing: In general, flexographic printing lines or printing slotting machines are used to print directly on corrugated board using water-based inks. The printers are suitable for printing large formats and general quality requirements based on text and lines. Because flexographic printing involves light pressure, it has little effect on the strength of the corrugated board, resulting in a stronger finished product
- Direct offset printing: It has the advantage of high printing quality, low printing costs, and short loading and adjustment times; this process can ensure good carton molding and also complete fine outer liner printing.
- Screen printing: although the resolution of the print is not high, the image accuracy is low, the ink color is thick, the color saturation is high, and the visual effect is strong, especially for spot colors
- Digital printing: this method is more suitable for small batches since it is more expensive and takes longer than the above mentioned printing methods when printing large quantities
Printing methods commonly used for pre-printing include flexible printing, offset printing, plastic gravure printing, and coated paper gravure printing.
- Flexographic pre-printing: Printing is performed on a whole roll of face paper, followed by finishing on an automated corrugator production line. While the printing quality and forming quality of the box are relatively high, the investment required is substantial, and it is not suitable for small batch production. Furthermore, due to the high temperatures and pressures required when processing the corrugated board after printing, special inks must be used.
- Offset pre-printing: since this technology is extremely popular, boxes for sales with small batches and high-quality requirements are now commonly printed indirectly by offset printing, i.e., the outer liner is printed first, and then the printed liner is laminated to the corrugated board. Corrugator linkage production lines are not suitable for this process, but only single facer corrugators, which have low production efficiency. In addition, the printing width is limited and the printing costs are high.
- Plastic gravure printing: If you still need to laminate after your liner printing is completed and the production batch is larger, gravure printing can be used to print on plastic film with a white background, then laminate the printed plastic film with the outer liner, and then complete the box making process according to conventional box forming procedures. Its printing effect can be compared to that of offset printing. When the production batch is larger, this process can greatly reduce the printing and material costs of the outer liner.
- Coated paper gravure printing： The process can be used when the production batch is relatively large, does not require lamination, and requires a good printing effect at a reasonable cost. First, gravure printing is used to print thinner coated paper, which is then laminated with the original outer liner, resulting in a new outer liner that is then formed into a box as usual.
How to test the quality of corrugated boxes
The most common performance tests for cartons are edge crush tests, folding endurance tests, bursting strength tests, puncture resistance tests, and compression strength tests.
- Edge crush tests: a certain width of the corrugated board is tested to determine the maximum pressure it can withstand per unit length parallel to the flute direction. Using this test, you can determine the flute strength inside the corrugated box, which directly affects the strength of the corrugated box. In a corrugated box, gravity is primarily supported by the flutes inside, and side pressure is one of the best methods of assessing the flute’s strength.
- Folding endurance tests: It is using a sample corrugated board of 150mm x 15mm specifications, for a reciprocal folding test at a 135° angle, when the paper breaks, that is, the number of folding resistance tests.
- Bursting strength tests: Refer to test the maximum pressure perpendicular to the surface that the corrugated board can withstand per unit area. In this test, the box will be tested for its ability to withstand static local extrusion in an actual transportation environment. This test can be used to understand the ability of the box to withstand the handling, loading, and unloading, impact and tearing forces in the process of circulation, and the breakage resistance of corrugated board is determined by the strength of the liner used and does not depend on the strength of the flute in the middle.
- Puncture resistance tests: using a certain shape of angle cone, this test measures the force required to pierce the corrugated board, expressed in joules (J). Check its resistance to external sudden impacts. It is designed to provide a simulation of the impact force of a box during use or transportation. In this test, corrugated board is evaluated for its ability to withstand the impact of sharp objects. Puncture resistance strength is closely related to its fiber toughness, hardness, tightness, and moisture content, as well as its glue strength and thickness.
- Compression strength tests: The objective is to determine the maximum pressure that an empty corrugated box can withstand when it is placed normally and pressed at a constant rate on both sides. In this test, the box is evaluated for its ability to withstand a sufficient amount of stacking weight and whether it can protect its goods from deformation, damage, and other undesirable phenomena caused by inadequate strength during use, handling, stacking, storage, and transportation of the product, as well as a comprehensive reflection of the box’s protection performance.
Advantages and disadvantages
After reading this far, you may already be aware that corrugated boxes have the advantages of being inexpensive, environmentally friendly, and highly protective due to their structure and raw materials. Aside from that, because technology has matured, it is easy to customize the size or print the graphics you require.
Additionally, I believe you should be aware of his shortcomings as well as his advantages. Whenever your goods are placed outdoors, you need to pay particular attention to water, since rain or other liquids dripping on the box can easily seep into the box and cause damage to the goods. The tray and tarp can be matched if the container must be stored outdoors. Moreover, in terms of appearance, although it is easy to print on the box, there will always be ridges appearance on the corrugated, so fine printing is still very difficult.
Considering the advantages and disadvantages of corrugated boxes, you can decide whether they are suitable for packaging your product.
