Discussion on properly reducing the standard value

2022-09-29
  • Detail

Discussion on appropriately reducing the standard value of corrugated box strength

at present, people have different opinions on the quality evaluation of corrugated boxes for transportation and packaging of export goods (hereinafter referred to as corrugated boxes): some complain about their poor quality, some think that their standard value is set too high, and some suggest omitting oneortwo of their performance inspection items. So, is the above statement based? Is the proposal feasible? Which kind of commodity packaging corrugated box performance indicators can be slightly reduced? How much is it appropriate to reduce the value? These problems not only need a large number of test results as the basis, but also need the practical verification of actual transportation, storage, loading and unloading, and can be implemented only after the demonstration and approval of experts organized by relevant departments. Therefore, it is a prudent and rigorous problem. This article tries to take the liberty of talking about some personal views on the above issues, for reference only

the author counted and analyzed the test records of nearly 1000 batches of corrugated boxes for this purpose. The results showed that about 58% of the corrugated boxes met the requirements of the original commodity inspection industry standard Sn/t0262, and about 42% of the corrugated boxes failed due to the non-compliance of individual items. Among these unqualified items, the appearance accounts for 5%, the bursting strength accounts for 6.6%, the puncture strength accounts for 9%, the edge pressing strength accounts for 27%, the bonding strength accounts for 52%, and the pressure resistance accounts for 0.4%, which is basically similar to the statistical results published in relevant domestic newspapers. It can be seen from the above statistical results that the highest undesirable frequency is the bonding strength, followed by the edge pressing strength. These two are the items that are not required by the United States, Japan and Taiwan at present. Among the above-mentioned unqualified rate of cartons, the packaging of food and electrical appliances accounts for about 5-7% respectively, while the vast majority is in shoes, hats and clothing, especially shoe boxes, accounting for more than 80%. When people don't understand the reasons for the high failure rate of cartons, there will naturally be many doubts, misunderstandings and different views. Therefore, it is necessary to analyze these reasons first

I. reasons

1. In the objective aspect: since the 1980s, China's corrugated box production has just started, the plant equipment is simple, the production process is backward, the quality of raw and auxiliary materials is not high, and the inspection standards and management measures have not kept up with each other. Some production enterprises have unfair business competition, pushing down prices, cutting corners, shoddy goods, and shoddy goods. The quality of corrugated boxes was once seriously affected, Coupled with the relatively backward means and means of transportation, brutal loading and unloading and other reasons, the packaging is damaged and the goods are destroyed, causing economic losses of more than 10 billion yuan to the country every year, seriously affecting the reputation of China's foreign trade, and to a certain extent, causing people the impression that the quality of corrugated boxes is too poor

2. In terms of Subjectivity: corrugated boxes are also the most responsible for the damage of goods caused by some human factors. First of all, when there are accidents such as carton cracking and stacking, which affect the packed goods, people first blame the poor quality of the cartons. The author believes that this blame is sometimes one-sided. The poor quality of cartons is an important reason for the above accidents, but it does not mean that the quality of damaged cartons must be poor. Some people don't pay attention to and care for the packaging, stack and cut improperly, and load and unload barbarously. Even the most qualified cartons can't resist those "inadvertent" man-made damage or barbarous loading and unloading. Second, a considerable number of carton users pay more attention to products than packaging. They often try to reduce the packaging cost, reduce the quality and limit the price according to the sales, transportation and internal packaging (shoebox or lining) of their products, and require the production of general cartons. In order to win business, carton manufacturers are too accommodating to customer requirements. They often say, "the customer's requirements are the standards". They don't produce according to the standards at all. In order to make profits, they have to reduce the quantity and grade of paper, which will inevitably affect the quality of cartons. These undoubtedly also give people the impression of poor quality corrugated boxes

3. there are too many required inspection items, and the main items are not prominent. At present, the inspection of corrugated boxes by the inspection and quarantine department is mainly based on GB5033, 5034 and industry standards Sn/t0262, 0608, 0714, 0715, 0717, 0718, 0720, etc. the inspection items of corrugated boxes in each standard are slightly different, but the basic requirement is that in addition to the appearance inspection, 98 light defects and 3 heavy defects) should also be inspected for their burst resistance, puncture, edge pressure, The adhesive strength and pressure resistance are tested (stacking, vertical impact drop test), and the wet burst test is also required in Sn/t0714. The general judgment is "if the appearance inspection, performance inspection and type inspection are all qualified, the inspection batch is qualified; as long as there is one unqualified item, the inspection batch is unqualified". These requirements are understandable to ensure the quality of export cartons, reduce the damage of export commodities and improve China's foreign trade reputation. However, in the implementation of the above standards, many people also reflected the unreasonable problems of some provisions of the standards, mainly including: ① the same standard value of adhesive strength of 588n/M is stipulated regardless of the type of goods packed (such as food, fragile goods or shoes, hats and clothing) and the quality and value of the contents, and no matter what cartons and models; ② Compared with the United States and other countries or regions, China requires too many mandatory inspection items, which are not targeted and primary and secondary. On the contrary, it is not conducive to the improvement of carton quality, and some even cause waste of packaging materials and high costs

4. the standard of adhesive strength is not perfect, which directly affects the qualification rate of cartons. There are many factors that affect the bonding strength of corrugated boxes. In addition to the quality of the adhesive itself, the quality of the paper, the moisture content of the paper, the mounting quality and the detection method, it is also related to the conversion and evaluation of the test results. The old gb6548-86 standard has been replaced by the new international GB/t6548-1998 method for determining the adhesive strength of corrugated boards. The calculation formula of the results of the old standard is inconsistent with the left and right units, that is, n/m=n/cm2. When there is no way to rely on it, people usually follow the calculation method introduced in relevant books or training courses, that is, the bonding strength a = f/(0.025x ridge number). This formula can be referred to as the "single ridge length" calculation method, where a - bonding strength, n/m ridge; F - the average value of the strongest force required when the sample is completely separated), N; Number of ridges? The number of ridges on the sample. When converting the adhesive strength value of the same test value, there will be great differences due to people's different values of the number of ridges, which is directly related to the evaluation of the adhesive strength of a batch of cartons. Now the specified 25mm × Taking 80mm sample as an example, some take all the complete number of ridges on the sample, such as a, C, and b ridge types, and the number of ridges of the three are generally 8 ~ 9, 10 ~ 11, and 12 ~ 13 respectively. If the average value of F measured by a batch of c-ridge type samples is 160n, and the number of ridges is 11, the bonding strength value of the sample is 582n/m ridge after calculation, and the result is unqualified; In some cases, take the actual number of peeled edges on the sample. For the same edge type, it is generally 2 less than the number of full edges. If f is still 160n, and the number of C-shaped edges is 9, then the value is 711n/m edges, which greatly exceeds the standard value. The calculation formula of adhesive strength in the new standard is: P = f/L, where p - adhesive strength, n/m; F is the same as above; L - the size of the long side of the sample (l=0.0080m). From the unit of the formula in the new standard, it seems to be no different from the calculation method of "single ridge length" adopted by people, but there is only one less word "ridge", but the meaning reflected in the formula is completely different. The latter can be referred to as "area" calculation method for short. Although on the surface it represents the bonding strength on the sample with a length of 1m, in fact, the width of the included sample is 25mm. If f = 160n, the strength value of any ridge type is 2000N/m. According to 5.2.2 of GB/t6544-1999 corrugated board for packaging materials, the standard still stipulates that "the bonding strength of corrugated board should not be less than 588n/M". It can be seen that there is no new qualified value corresponding to the new standard for stable and reliable performance. This value is obviously equal to 6kgf/10cm specified in gb5034, and the strength mentioned above is used as the judgment standard value? Since there is no qualified judgment value of bonding strength corresponding to the new standard, the calculation results of the new standard can only be compared under the same corrugated paperboard, losing the role as a judgment basis. Although some laboratories indicated that the results were tested and calculated according to the new standard GB/t6548-1998, the standard value could not be listed on the report, and people could not judge whether the bonding strength of this batch of corrugated board was qualified. In addition, both calculation methods ignore that different strength levels are related to the width of bonding line of different ridge types, which further explains the irrationality of specifying the same standard value. Therefore, the current calculation of the bonding strength of corrugated board can be said to be in a situation where there is no standard to rely on

II. Analysis of test results

1. The relationship between bonding strength and pressure resistance, edge pressure strength. The tested samples (10 batches) are corrugated boxes of the same specification produced by the same manufacturer, the same raw material and the same paper quantitative grade. The adhesive is corn starch, which is prepared into adhesives with different strengths through different water ratios and additives. After testing, the relationship between the adhesive strength value of 10 batches of samples and the values of pressure resistance, bursting strength, cutting strength and edge pressure strength is represented by a curve (see the attached figure), The results are as follows: ① the relationship between adhesive strength and pressure resistance. The test shows that the pressure resistance, as a comprehensive indicator of the quality of corrugated boxes, is not only related to the paper quantity, grade, corrugated type, box type, height, printing, nail distance, moisture and other factors, but also affected by the adhesive strength. It can be seen from Figure 1 that the anti pressure increases or decreases with the bonding strength within a certain range. When the bonding strength increases to a certain value, the anti pressure will quickly stabilize, and when the bonding strength decreases to a certain value, the anti pressure will sharply decrease. ② The relationship between the adhesive strength and the edge pressing strength. Theoretically, the edge pressing strength reflects the pressure resistance of the corrugated box from another angle, which is related to the adhesive strength in addition to the thickness of the surface paper (including core paper and corrugated paper), corrugated type and paperboard. It can be seen from Figure 2 that the relationship between adhesive strength and side pressure strength and the relationship between adhesive strength and pressure resistance have similar characteristics

2. The relationship between adhesive strength and bursting strength and cutting strength. Both bursting strength and cutting strength are used to measure the breaking resistance of cartons. The difference is that the former belongs to static strength and the latter belongs to dynamic strength. With the same quantitative grade and corrugated board with different bonding strength, through the above amphoteric energy test, it can be seen from Figure 3 and Figure 4 that although the bonding strength changes greatly, the bursting strength and puncture strength basically fluctuate in a small range. It can be seen from this that once the paper used for the carton is determined, the strength values of the above two will basically remain unchanged, resulting in a reduction of about 21% in vanadium slag production

after consulting relevant data and combining the analysis of test results, even if different materials, specifications and other conditions are changed, only the specific test value is changed, but the relationship between the bonding strength and other properties is consistent

III. actual usage

1. After nearly ten years of efforts, the relevant departments have formulated relevant laws and regulations and standards, strengthened supervision and management, issued a series of policies, and taken effective measures, such as implementing the system of license fatigue testing machine equipped with corresponding experimental fixtures, classification management assessment and minimum quantitative paper limit for export carton production enterprises, so as to lead export carton production enterprises to an orderly competition mechanism

Copyright © 2011 JIN SHI