Analysis of the relationship between carton strength and production factors (I)

The strength of corrugated cartons is an important technical indicator for the quality inspection of packaging containers. The level of these indicators reflects the quality of raw materials on the one hand and the quality of processing techniques on the other. The production process shows that to improve the strength of corrugated cartons, it is not enough to rely on purchased raw materials. The quality control of the production process is also an important part of improving the strength of corrugated cartons. Therefore, correctly understanding and understanding the relevant factors that affect the strength of corrugated boxes is of great significance for better production and product quality improvement.

Raw Paper Technical Index and Its Relation to Corrugated Box Strength

Quantitative quantification, also known as grammage, is the weight per square meter of paper, expressed in g/m2. The quantitative calculation formula is: the weight of the sample/area of ​​the sample. Quantitative is an important index to measure the physical properties of paper. In general, the paper has a high basis weight, and its tensile strength, ring pressure strength, tear strength, stiffness and thickness are relatively high. Making corrugated boxes with high-quantitative paper materials has relatively higher compressive strength. Therefore, to make a high-strength corrugated carton, selecting a high-quantity paper material is often one of the basic requirements of the customer.

Tightness It refers to the weight per cubic centimeter of paper, expressed in g/cm3. Its calculation formula is:

Tightness = quantitative / (thickness × 1000)

The tightness of the paper reflects the degree of densification of its fibrous tissue structure. Boxboard and corrugated paper have high tightness values, and their burst strength, ring pressure strength, puncture resistance, and tensile properties are relatively good. Then, the overall strength of the carton is relatively high. However, if the tightness is too large, the paper material is likely to be brittle, especially for whiteboard paper. If the tightness value is significantly larger than the standard, the folding endurance performance will be reduced. Therefore, the use of white paper for the surface layer of corrugated cardboard, should not use the high degree of tightness of the white paper, so as not to affect the folding box carton folding degree.

Ring compression strength The standard sample length (longitudinal) 152 ± 0.2mm, width 12.7 ± 0.1mm, take 10 tablets for testing, 5 of which were tested outwards facing outwards. The other five sheets were tested with the reverse side facing out into the circular tray. After that, the ring pressure strength of the base paper can be obtained by formula conversion. In general, cartons made from paper with good crush strength are relatively high in strength. The formula for calculating the crush strength is: RF/152. In the formula, R denotes the ring crush strength in kN/m; F denotes the force value read in crushing the sample, unit N; and 152 denotes the length of the sample in mm. The standard value of the ring pressure index in the national standard is an important index to measure the compressive performance of the base paper. It refers to the ratio of the ring pressure strength and the basis weight of the base paper and the unit is N·m/g. The calculation formula for this indicator is: Rd=1000R/W. In the formula, Rd denotes the ring pressure index, R denotes the ring pressure strength, and W denotes the basis weight of the sample, and the unit is g/m2. How the ring pressure index of the base paper affects the overall strength of the carton to a great extent, especially the impact on the compressive strength of the carton.

Sizing When paper or cardboard is produced, apply a certain amount of colloidal material such as rosin gum to increase the water resistance of the paper. This production and processing process is called sizing. The degree of sizing is a measure of the quality of the glue. According to the national standard, the ink scribe method and the surface absorption weight method can be used for detection. The factory can also use the “drip method” to detect the degree of sizing on paper. The practice is: a little water on the paper surface, if the speed of water droplets infiltration, indicating that the degree of sizing is not good; if the water droplets are not prone to seepage phenomenon, water droplets floating on the paper, indicating the degree of sizing is good. The base paper for making corrugated boxes requires a good degree of sizing, so that it is not easy to absorb moisture, the moisture content of the carton is stable, and the strength of the carton can be better ensured.

Moisture content The so-called moisture content refers to the content of water in paper or paperboard, expressed as a percentage, and its calculation formula is:

Moisture content = (sample weight - weight after drying) / sample weight

The moisture content has a great influence on the strength of the carton box, so this is also the main reason why the moisture content has become one of the three important defects inspection items of the carton. When the moisture content of the carton is high, its resistance to puncture compressive strength and burst strength will be relatively reduced. Corrugated paper has a certain degree of pressure resistance, tensile resistance, puncture resistance, and folding endurance. If the moisture content is too high, the paper will appear soft, poor in stiffness, and poor in pressure and adhesion. If the moisture is significantly lower than the lower limit of the standard value, the cracking phenomenon will occur easily when pressing. If the moisture content of corrugated paper and linerboard is too large, the corrugated board machined by one-sided machine is prone to curl. When the next process is combined, foaming and degumming are likely to occur, and the strength of the carton will be significantly reduced.

The folding-resistant carton is a kind of packaging container, and the flap needs to be frequently opened. This requires that the paper should have a certain folding-resistant ability. The paper's transverse folding resistance measures the paper's 1350 angle reciprocating folding test for 150 × 15mm specimens under a certain tension, speed, and angle conditions. When the paper is broken, it is the number of inspections of the folding resistance. . The pulp properties of the linerboard and folded paper, the moisture content of the paper, the tightness, the fiber length and the fastness of the binding force, and the influence of factors such as the storage time and temperature of the base paper largely determine the resistance of the base paper. Discounts. Therefore, to improve the folding performance of the carton, it is an important part to ensure the quality of raw materials.

(to be continued)