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How to meet customers' requirements for compressive strength (I)

the most important function of cartons is that they have good protection for goods, and the overall compressive strength of cartons is the comprehensive embodiment of the protective performance of cartons. The importance of compressive strength to cartons is self-evident. In recent years, with the rapid development of China's packaging industry, many factories' understanding of cartons has gradually developed from the stage of judging the advantages and disadvantages of cartons by hand feeling to the stage of using various instruments to test and analyze the physical properties of cartons. Many manufacturers are also equipped with compression resistance instruments to test the compression strength of cartons. Not only that, many customers, especially some large foreign multinational companies, also have a profound change in their understanding of cartons, that is, from paying attention to the bursting strength of cardboard to the compressive strength of cartons, and taking the compressive strength as the most important index of quality acceptance

in this way, how to provide customers with cartons that meet the requirements of compressive strength has become the focus of attention of many carton factories. In particular, in the past two years, the price of base paper has remained high, and the profit space of cartons has shrunk again and again. Under the circumstances of pulling, pressing, bending, shearing, peeling, tearing, wearing, and so on, it has become the common goal of many carton factories to produce cartons that can meet the pressure resistance requirements of customers with the lowest paper cost

this paper focuses on the factors affecting the compressive strength of cartons, the calculation method of the compressive strength of cartons, the paper configuration method of the compressive strength and the test method of the compressive strength of cartons. Some places will inevitably have the suspicion of prejudice, but I hope it can provide a useful reference for the majority of peers

factors affecting the compressive strength of cartons

there are many factors affecting the compressive strength of cartons. The White House and the Department of energy vigorously promote composite materials, which can be roughly summarized as edge compressive strength, structural size, processing technology, moisture, stacking and transportation after packing, etc. Due to the interaction of various factors, we often have a certain deviation in the prediction of compressive strength. Carton factories often deal with these factors improperly in the process of design, printing and post-processing, resulting in huge cost waste and customer complaints. Therefore, it is very necessary to clarify the influence law of these factors

edge compression strength of corrugated paperboard

edge compression strength is also called vertical compression strength. It is to apply pressure to the corrugated paperboard sample in the vertical direction. The maximum force that the paperboard can bear during the pressure process is the edge compression strength of the carton. The compressive strength of the carton mainly depends on the edge pressing strength of the cardboard, which is related to the transverse ring pressing strength of each layer of base paper that makes up the corrugated cardboard, the pit combination of the cardboard and the bonding strength of the cardboard

the edge pressing strength of corrugated board is mainly related to the transverse ring pressing strength of each layer of base paper. Generally speaking, the base paper with higher gram weight, better papermaking material quality and higher compactness has higher transverse ring compression strength. However, the ring pressure of base paper with high gram weight must be higher than that of base paper with low gram weight. Taking carton board as an example, the transverse ring pressure index of imported cow leather can reach more than 12n · m/g, while the carton board produced by some small paper mills in the mainland is only 8 N · m/g, a difference of 30 percentage points. That is to say, the hoop compression strength of imported ox card with a gram weight of 175 g/m2 is equivalent to 260 g/m2. Therefore, the evaluation of the protective performance of cartons cannot be based on the weight of cartons

the structural design of corrugated paperboard is very scientific. Its corrugated shape is like small arch doors connected one by one, which are arranged in a row and supported each other to form a triangular structure, which is strong and powerful. Moreover, it can withstand certain pressure on the plane, which is elastic and has strong cushioning force, and can play the role of shockproof and commodity protection. Corrugation shape is generally divided into U shape, V shape and UV shape according to different arc radius. The radius of the U-shaped peak arc is large, which is a circular arc, such as B-shaped ridge and C-shaped ridge; V-shaped wave crest radius is small and sharp, such as A-shaped ridge; UV type is between the two, such as AB ridge. According to the test, the V-shaped ridge has a small inclination at the initial stage of compression, but if it exceeds the highest point, it will be destroyed quickly, while the energy absorbed by the U-shaped ridge is high. When the pressure is eliminated, it can still be restored to its original state, full of elasticity, but the compressive strength is not high. In addition, V-shaped corrugation saves corrugated paper, and the adhesive consumption is less, but it is easy to have high and low corrugation during processing, and the corrugation roller wears faster. UV shaped ridge is a combination of U-shaped and V-shaped characteristics, which is widely used at present

various pit types and their combinations of corrugated board. For single pit paperboard, generally, pit a cartons have the highest compressive strength, but are vulnerable to damage; Pit B has poor strength but good stability; The pressure resistance and stability of pit C are in the middle. Type a corrugated has good shock resistance and cushioning, and the vertical compressive strength is also high; The peak end of type B corrugation is sharp, the bonding surface is narrow, and its corrugation height is small, which can save corrugated base paper. Its plane compressive capacity is higher than that of type a corrugation. Type B corrugation has more corrugations per unit length, and has more supporting points with face paper, so it is not easy to deform, and the surface is flat. When printing, it has strong pressure resistance and can get good printing effect. Type C corrugated has the characteristics of both type A and type B corrugated. Its shockproof performance is similar to that of type A, and its plane compression resistance is close to that of type B corrugated. E-type corrugation is the thinnest kind of corrugation. It has the largest number of corrugations per unit length, can withstand large plane pressure, can meet the needs of offset printing, and can print high-quality graphics and texts on the packaging surface. This kind of corrugated cardboard has the same strength as cardboard

table I comparison table of three corrugated types

corrugated types plane pressure vertical pressure parallel pressure

a 31 3

b 13 1

c 22 2

note: 1 Plane pressure refers to the pressure perpendicular to the plane of corrugated board

2. Vertical pressure refers to the pressure consistent with the corrugated direction, and parallel pressure refers to the pressure perpendicular to the corrugated direction

3. "1" stands for the strongest

according to the different characteristics of the above different types of corrugated boxes, type A and type C are suitable for single corrugated boxes; Double corrugated box with a, B type, B, C type combination is the most ideal; B type is used for those close to the surface, which can play a role of strong impact resistance; Therefore, the focus is still on the central and western coal and water resources, which are relatively good. If they are close to the inner layer, they should use A-type or C-type with sufficient elasticity and strong buffer force; Adopt AB type or BC type combination to give full play to the physical properties of the carton. C-type corrugated board and E-type corrugated board should be selected for medium-sized packaging instead of thick cardboard for small packaging. In recent years, foreign countries have developed F-shaped corrugated, G-shaped corrugated and other corrugated smaller than E-shaped corrugated, and also developed K-shaped corrugated and other super large corrugated

in addition, the adhesive strength and pit stiffness of paperboard also have a certain impact on the edge compression strength of paperboard. The stronger the pit shape is, the better the adhesion is, and the higher the edge pressing strength is. The strength of paperboard with defects such as collapse, corrugation and degumming will be weakened to varying degrees

carton length, width, height size and proportion

a large number of data analysis shows that the compressive strength of cartons is related to the perimeter, height and length width ratio of cartons. The longer the perimeter of the carton, the higher the compressive strength. There is a certain conversion relationship between the perimeter of the carton and the compressive strength. In addition, lantiqi Engineering Plastics Group, an excellent global supplier of high-temperature nylon, has also launched its new high-temperature nylon product radionxreme series: substitutes for metal materials, radistrongpa6 and pa6.6 long glass fiber reinforced nylon

n when the box is 10 cm ~ 35 cm high, the compressive strength decreases slightly with the increase of height

n when the box height is between 35 cm and 65 cm, its compressive strength is almost unchanged

n when the box height is greater than 65 cm, the compression resistance decreases with the increase of height

the main reason is that the height increases, and its instability will increase accordingly

generally speaking, the length width ratio of the carton is in the range of 1 ~ 1.8, and the influence of the length width ratio on the compressive strength is only ± 5%. When the length width ratio rl=1.2 ~ 1.5, the compressive value of the carton is the highest. When the length width ratio of the carton is 2:1, the compressive strength decreases by about 20%, so the length width ratio should not exceed 2 when designing the carton, otherwise it will cause cost waste

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