The main factors that affect the compressive strength of cartons are: ① raw material quality; ② moisture; ③ box type and flute type; ④ printing and opening; ⑤ processing technology.
a. Raw material quality
The kellicutt formula is used to calculate the compressive strength of cartons based on the ring crush strength of corrugated cardboard, which is an indicator of the compressive strength of cartons. The ring pressure strength is the bonding strength between the core paper and the surface paper or lining paper. The raw material is the main factor affecting the ring pressure strength. It is related to the quantity, tightness, moisture, etc. of the raw material. The grades of containerboard paper and corrugated base paper mainly include A, B, C, D, E, etc. Under normal circumstances, the grade matching principle should be followed when selecting materials. The grade selection of containerboard paper and corrugated base paper should be similar. At the same time, the boxboard The basis weight of paper and corrugated base paper should be maintained within the range of 21, so as to ensure the overall quality level of raw materials and the quality of corrugated board. Of course, corrugated board is volatilized by the surface paper, core paper and lining paper bonded together, so the factors of adhesive and core paper should also be considered. The appropriate moisture content, tightness and uniformity of the core paper are conducive to the adhesion with the surface paper and lining paper. The good adhesive performance of the adhesive and the appropriate thickness of the adhesive layer are conducive to improving the compression resistance of the corrugated box. strength.
B.Moisture
The production environment, storage environment, use environment, weather, climate and other factors of the cartons will all affect the moisture content of the cartons. In order to ensure the compressive strength of the cartons, the impact of the external environment on the water content of the cartons should be avoided as much as possible.
The initial moisture content of corrugated base paper will directly affect the board-making quality of corrugated cardboard. If the moisture content is high, the base paper will be soft, but the tensile strength will be relatively reduced; if the moisture content is low, the base paper will be dry, and the top of the corrugated corrugated board will easily crack during corrugation. In the production of corrugated cardboard, the moisture content required to obtain the best strength value is generally 6% to 8%. The traditional method of determining moisture is the drying and weighing method at 105°C, using an oven and a balance. This method is the standard method.
C. Box type and corrugated type
Box type refers to the type of box and the size ratio of boxes of the same type, which have a significant impact on compressive strength. Some cartons are made of double-layer corrugated cardboard, and their compressive strength is significantly higher than that of single-layer boxes of the same specifications. Under the same conditions, the higher the box, the worse the stability and the lower the compressive strength.
In people's consciousness, they often think that the larger the flute type, the higher the compressive strength of the carton, and it is easy to ignore the impact of the flute type on the deformation. The larger the flute type, the greater the compressive strength and deformation of the carton; the smaller the flute type, the smaller the compressive strength and deformation of the carton. If the carton is too large, but the flutes are very small, the carton will be easily stained during the compression test; if the carton is too small, but the flutes are very large, the deformation will be too large during the compression test, and the buffering process will be long and effective. The deviation between the force value and the final force value is too large.
D. Printing and opening
Printing will cause certain damage to corrugated cardboard, which will reduce the compressive strength of the carton. The size of the pressure and the size of the bearing area are a major factor affecting the compressive strength of the carton. If the printing pressure is too high, the corrugations will easily be crushed and the flute height will be reduced. Especially when printing at the pressure line, in order to force and clear printing at the pressure line, the entire cardboard will be crushed and the compressive strength of the carton will be greatly reduced. Therefore, printing here should be avoided as much as possible. When printing graphics and text on the full page or around the carton, in addition to the pressing effect of the impression roller on the corrugated cardboard, the ink also wets the paper surface, which in turn reduces the compressive strength of the carton. When a general carton is fully printed, its compressive strength drops by about 40%.
For products that require ventilation in packaging, opening holes on the box surface or punching handle holes on the side of the box will reduce the strength of the carton, especially if the opening area is large or biased to one side, etc., the impact will be more obvious.
E. Processing process deviation
Through experiments, it was found that under the same conditions, for every 1mm widening of the transverse pressure line of the carton, the compressive strength of the carton decreases by 90N-130N, and the deformation increases by about 2mm. If the pressure line is too wide, the force value of the carton will increase slowly during the 1 compression test, the effective force value will be small, and the final deformation will be large. In order to ensure the compressive strength, we should try our best to improve the production process and reduce the impact of each process on the compressive strength of the carton. Improper crimping during the box making process, too deep grooves, weak bonding, etc. will also reduce the compressive strength of the box.
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