GB/T 11718-2021Medium density fibreboard (English PDF)

3.1 Terms and definitions

The terms and definitions defined in GB/T 18259-2018 and LY/T 1717-2007 and the following apply to this document.

3.1.1 medium density fibreboard; MDF

The board that is made of wood fiber or other plant fiber, which is prepared by fiber preparation, applied with synthetic resin, and pressed under heating and pressure conditions. The density ranges from 0.65 g/cm3~0.80 g/cm3.

NOTE: The density ranges specified in this document are for guidance only. Manufacturers may classify products as MDF boards of a specified type if their density is within +/-10% of the density range and they meet all the performance requirements of a specified type of MDF board. For example, a fiberboard with a density of 0.83 g/cm3 may also be called MDF if it meets all the performance requirements of a specified type of MDF board grade.

3.1.2 general purpose medium density fibreboard

Medium density fiberboard for non-furniture or non-structural grade applications.

Example: Temporary display boards and partition boards used in exhibitions, etc.

[Source: GB/T 18259-2018, 3.2.18, modified]

3.1.3 furniture grade medium density fibreboard

Medium density fiberboard used for furniture or decoration usually requires secondary surface processing.

[Source: GB/T 18259-2018, 3.2.19]

3.1.4 load bearing medium density fibreboard

Medium density fiberboard usually used for small structural parts, or used in load-bearing conditions.

[Source: GB/T 18259-2018, 3.2.20]

3.1.5 building medium density fibreboard

Medium density fiberboard for general construction.

Example: window frames, door linings, etc.

3.1.6 dry conditions

Indoor environment or outdoor environment with protective measures. The moisture content of the material in this state is equivalent to the moisture content in an environment with a temperature of 20°C and a relative humidity not higher than 65% (or the relative humidity exceeds 65% only for a few weeks in a year).

[Source: GB/T 18259-2018, 2.54]

3.1.7 humid conditions

Indoor environment or outdoor environment with protective measures. Usually refers to an environment with a temperature of 20°C and a relative humidity higher than 65% but not exceeding 85%, or an environment with a relative humidity exceeding 85% for only a few weeks in a year.

3.1.8 humid conditions-temperate

Indoor environment or outdoor environment with protective measures. The moisture content of the material in this state is equivalent to the moisture content in an environment with a temperature of 20°C and a relative humidity higher than 65% but not exceeding 85% (or the relative humidity exceeds 85% for only a few weeks in a year).

[Source: GB/T 18259-2018, 2.55, modified]

3.1.9 humid conditions-tropical

Indoor environment or outdoor environment with protective measures. The moisture content of the material in this state is equivalent to the moisture content in an environment with a temperature of 30°C and a relative humidity higher than 65% but not exceeding 85% (or the relative humidity exceeds 85% for only a few weeks in a year).

[Source: GB/T 18259-2018, 2.56, modified]

3.1.10 high-humid conditions

Indoor environment or outdoor environment with protective measures. The moisture content of the material in this state is equivalent to the moisture content in an environment with a temperature higher than 30°C and a relative humidity higher than 85%, or in an environment where it may occasionally come into contact with water (except immersion or watering).

[Source: GB/T 18259-2018, 2.57]

3.1.11 exterior conditions

Environmental conditions under outdoor natural climatic conditions.

[Source: GB/T 18259-2018, 2.58]

3.2 Abbreviations

BL: building EXT: exterior F: fungi retardant FN: furniture; furniture making, cabinet making and joinery, as well as surface decoration of these substrates FR: fire retardant

5.3.5 Additional instructions for performance requirements of load-bearing and construction products The product performance requirements specified in Tables 11~17 are not used as characteristic values for engineering design applications. If medium density fiberboard is classified as a load-bearing board or specified for building structure application and is used as a substitute for a specific load-bearing purpose, its relevant characteristic performance shall also comply with the requirements of relevant national standards (specifications).

5.4 Formaldehyde emission limit The requirements for formaldehyde emission limits for indoor medium density fiberboard are shown in GB 18580-2017.

The formaldehyde emission of furniture grade medium density fibreboard (MDF-FN EXT) for outdoor use shall be determined by negotiation between the supplier and the purchaser.

5.5 Moisture resistance The moisture resistance performance in Table 5, Table 6, Table 8, Table 9, Table 10,

Table 12 and Table 13 specifies the requirements corresponding to three optional test

methods (Option 1, Option 2 and Option 3). Only one of the three options needs to be met, which is determined or clearly stated by the supplier and the purchaser through negotiation.

5.6 Other requirements

5.6.1 Other requirements for medium density fiberboard include but are not limited to the following indicators: screw holding force, surface absorption performance and dimensional stability.

5.6.2 When the purchaser has requirements for other test items, the performance requirements shall be determined through negotiation between the supplier and the purchaser.

6 Measurement and test methods

6.1 Measurement of dimensions

6.1.1 Measuring tools

6.1.1.1 Micrometer: graduation value is 0.01 mm.

6.1.1.2 Steel ruler: graduation value is 0.5 mm.

6.1.1.3 Steel tape measure: graduation value is 1.0 mm.

6.1.1.4 Metal wire (such as steel wire, etc.): diameter is not more than 0.5 mm.

6.1.2 Measurement of length, width and thickness of boards

6.1.2.1 The thickness of the board shall be in accordance with 8.1 of GB/T 19367-2009.

6.1.2.2 The length and width of the board shall be in accordance with 8.2 of GB/T 19367-2009.

6.1.3 Verticality measurement Perform according to 8.3 of GB/T 19367-2009.

6.2 Sampling and test piece preparation

6.2.1 Instruments

6.2.1.1 Micrometer: graduation value is 0.01 mm.

6.2.1.2 Vernier caliper: graduation value is 0.1 mm.

6.2.1.3 Balance: sensitivity is 0.01 g.

6.2.2 Methods

6.2.2.1 The sample shall be drawn in accordance with 8.2.2. The size, quantity and number of the test pieces are shown in Table 18. The size of the test pieces shall be measured in accordance with 4.1 of GB/T 17657-2013.

6.2.2.2 For the same performance test pieces, the distance between each other shall not be less than 100 mm, see Figure 1. If there are appearance defects at the test piece location, the test piece location may be appropriately staggered. If the sample size is insufficient for the test piece, another sample shall be taken from the same batch.

6.2.2.3 The test piece is not allowed to have burnt edges. The edges shall be straight and the adjacent sides shall be right angles.

The test shall be carried out in accordance with 4.14 of GB/T 17657-2013. The test piece needs to be balanced.

6.11 Determination of internal bonding strength after boiling water The test shall be carried out in accordance with 4.13 of GB/T 17657-2013. The test piece needs to be balanced.

6.12 Determination of static bending strength after immersion in water at 70°C The test shall be carried out in accordance with 4.9 of GB/T 17657-2013. The test piece needs to be balanced.

6.13 Determination of screw holding force Perform according to 4.21 of GB/T 17657-2013.

6.14 Determination of surface absorption performance Perform according to 4.28 of GB/T 17657-2013.

6.15 Determination of dimensional stability Perform according to 4.33 of GB/T 17657-2013.

7 Specification limits

7.1 The performance requirements specified in this document are the specification limits of the product. They are used to determine whether the physical and mechanical properties of the product are qualified.

7.2 For dimensional deviation, density and moisture content, the values in Table 3 are calculated based on the average value. For formaldehyde emission limits, the values given in GB 18580-2017 are calculated based on the average value.

7.3 The following physical and mechanical properties in Tables 4 to 17 are the lower specification limits uL.

- Static bending strength;

- Elastic modulus;

- Internal bonding strength;

- Surface bonding strength;

- Internal bonding strength after cyclic test;

- Internal bonding strength after boiling water;

- Static bending strength after 70 degrees C water immersion treatment.

The 5% quantile value x5% calculated from the above performance indicators of a board shall not be less than the lower specification limit uL of the corresponding board type in Table 4 ~ Table 17.

7.4 The following physical property indicators in Tables 4 to 17 are upper specification limits uu.

- Water absorption thickness expansion rate;

- Water absorption thickness expansion rate after cyclic test.

The 95% percentile value x95% calculated from the above performance indicators of a board shall not be greater than the upper specification limit uu of the corresponding board type in Table 4 ~ Table 17.

7.5 The upper and lower specification limits are calculated according to the method in