Fiberboard new national standard

The newly revised standard for medium density fiberboard (MDF), one of the three major plates, will be officially implemented. This is undoubtedly a big news in the timber industry. How to implement this standard well will undoubtedly be the concern and discussion of many people in the industry. problem.

The revision of the new standard has been separated from GB/T11718-1999 for ten years. During the decade, China's medium-density fiberboard industry has also undergone major changes, and its rapid development has become the world's largest fiberboard production base.

Combined with the characteristics of China's development, the development of medium-density fiber in China is mainly reflected in the following aspects:

1. The annual production scale of the on-line plates has become larger. There are more than 10 production lines with an annual output of over 100,000 m3.

2, production equipment continues to introduce innovation, has mature and stable domestic equipment.

3. The quality of the products has been greatly improved. Under the original standard and the national mandatory standard GB/T18580, the quality of China's medium density fiberboard has been greatly improved.

However, with the development of the industry, some problems of GB11718-1999 have become prominent: First, the increase of export trade, the trade barriers encountered by MDF at the time of export are more and more obvious, and the performance of formaldehyde limit is particularly obvious.

Furthermore, the application field of China's medium density fiberboard is also gradually expanding, which has led to the development of a series of special plates, which are in urgent need of standards. In addition, in order to make the detection of China's medium density fiberboards in line with international standards, it is also necessary to revise the corresponding test methods.

1. Main contents of the standard revision

The main content of the entire standard revision can be divided into five parts:

1.1 Added a new board type.

In GB/T11718-1999, only three types of plate types, such as indoor plate type, moisture-proof type and outdoor type, are involved. When the new standard is revised, ISO/DIS16895-2 is used to classify the plate type, and the MDF form is increased to 12 Species: According to the use, it can be divided into three categories: ordinary, furniture and load-bearing. According to the conditions of use, it can be divided into dry conditions, humid conditions, high humidity conditions and outdoor. This is also an expanding demand for medium density fiberboard applications.

1.2 Some physical and chemical performance indicators have changed.

The main performance is as follows: the water content is revised from the original standard of 4%~13% to 3.0~13.0%, which mainly considers the characteristics of the climate difference between the north and the south of China; the density is revised from the original standard of 450~880kg/m3 to 0.65~0.80g/ Cm3 (allowable deviation is plus or minus 10%), that is, the density range in the new standard becomes smaller; the superior products, first-class products and qualified products in the old standard mechanical properties are canceled and become a grade requirement.

1.3 Formaldehyde limit and test method changes.

The new standard imposes stricter regulations on the amount of formaldehyde released: perforation method: ≤8.0mg/100g, climate chamber method ≤0.124mg/m3, and a new method gas analysis method ≤3.5mg (m2·h). It can be seen from the perforation method that the new standard requires a minimum formaldehyde emission of <9.0mg/100g, which is the original standard E1 level, and the new standard has only one level, and there is no E2 level.

1.4 Part of the test method changes.

The revision of the new standard inspection method mainly refers to the ISO method and is consistent with it. Therefore, GB/T17657-1999 "Test methods for physical and chemical properties of wood-based panels and veneered panels" will be revised in accordance with the new standards.

1.5 Determination method changes.

The new standard physical and chemical performance test uses the statistical sampling test rules of statistical techniques, which is the first attempt in China's wood-based panel standards, so it has certain significance.

2. Discussion and analysis of standard revision content

2.1 density

The definition of MDF in the new standard is given by a nominal density range of 0.65 to 0.80 g/cm3. An explanation of this nominal density is given in the standard 3.1.1 annotation: if the density of the product is in the nominal Within 10% of the density range and in accordance with all performance requirements of the specified type of medium density fiberboard, the manufacturer can classify this product into this type of board.

According to the standard, the actual density is within plus or minus 10% of the nominal density range, ie, the actual density is between 0.58g/cm3 and 0.65g/cm3 and between 0.80g/cm3 and 0.88g/cm3, if The performance is consistent with the specified type of MDF, and the board can be referred to as a medium density fiberboard.

Interpret this nominal density, that is, if the fiberboard with an actual density between 0.58g/cm3~0.65g/cm3 and 0.80g/cm3~0.88g/cm3 does not meet the specified type of medium density fiberboard, it is not Medium density fiberboard, which is GB/T11718-2009, will not be suitable for its judgment.

In addition, the density of MDF produced in many production lines in China according to GB/T11718-1999 may reach 0.45g/cm3, or the fiberboard used for lower density in special applications will lose the criterion for judgment. This will form a blind spot, so national or industry standards for the introduction of low-density fiberboard should be developed as soon as possible, otherwise it is not conducive to the development of the industry. As for high-density fiberboard, there are already corresponding product standards that can be relied upon, but it also shows deficiencies.

2.2 Formaldehyde emission

The new standard imposes strict regulations on the amount of formaldehyde released, which is mainly in line with international standards, and adopts the ISO/DIS16895-2 standard for formaldehyde emission. It is undoubtedly a favorable guarantee for the environmental protection of products and the barriers to breaking export trade, which is also the key consideration for the adoption of the standard. It is undeniable that this will have a certain impact on China's medium-density fiberboard industry, which will bring some pressure to many small and medium-sized production lines.

The new standard uses three test methods in the formaldehyde test method: climate chamber method, gas analysis method and perforation method. In GB/T11718-1999 and the national mandatory standard GB 18580-2001, the method for testing the formaldehyde emission of medium density fiberboard is specified by the perforation method. This standard revision includes all three methods, and the formaldehyde emission should be consistent. Any limit value in the climate chamber method, gas analysis method or perforation method shall be selected by the supplier and the buyer.

Is it possible to understand that as long as the three limit values ​​are met, then there will be some column problems. First of all, how are the correlations between the three methods, and whether they are relevant? In the plate supervision and inspection, it is inevitable that the plate with formaldehyde emission at the boundary will be controversial.

Of course, the formaldehyde limit of medium density fiberboard is still based on the mandatory standard of 2001 before the revised version of China's mandatory standard GB18580-2001. Therefore, the revision of GB18580 is necessary to consider three methods for the detection of formaldehyde emission from the plate. In order to avoid the possible disputes over the detection of formaldehyde emission, whether the three methods for the detection of formaldehyde emission from the plate are included in the standard revision, or which method is adopted. The test should have a primary or secondary description.

2.3 Decision rules

The new standard judgment rule has a great change compared with GB/T11718-1999. This is also a pioneering decision of the artificial board judgment rule. For the first time, the statistic Qu and QL are used to judge the physical and chemical properties of the board. The calculations of Qu and QL are detailed in LY/T1717-2007. Again, the author will not clarify, only discuss the practical significance of this judgment method.

The standard stipulates that the single-side upper and lower specifications of the water absorption thickness expansion ratio, the internal bond strength, the static bending strength and the elastic modulus, the surface bond strength and the moisture resistance performance limit Qu and QL should conform to the one side of the corresponding plate type, The lower specification is limited to μu and μL. According to this need, it is noted that when the average value and the minimum value are in compliance with the index values ​​required by GB/T11718-1999, the physical and chemical properties of the sheet may not be qualified. In addition, the number of test samples is also significantly increased to achieve statistical significance. This type of judgment in the new standard focuses on the volatility between the batches of plates or the volatility of a physical and mechanical property in a board, which more reflects the quality control of the production of wood-based panels, which makes the production enterprises pay more attention to product quality. Overall uniformity.

3, summary

Overall, GB/T11718-2009 "Medium Density Fiberboard" is a standard that breaks the standard of China's plate standards, and its implementation will certainly make other relevant standards to be revised accordingly. Completing China's wood-based panel standard system is an indispensable step in the development of China's wood-based panel industry. How to integrate with internationally advanced standards, so that China's becoming a genuine wood-based board country and a strong country is a new standard revision and must be considered and considered. .

However, GB11718-2009 is a new idea after all. The standard cannot consider all aspects of the industry. Only in practice can we gradually verify and revise this standard, and China's medium-density fiber industry will also make products based on this product standard. The new level, only such a standard has its true value.

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