I. Scope of application
The joinery board delivered for use is set as a solid joinery board, the board cores are glued together, and both sides of the board are polished. According to the requirements of formaldehyde emission limit grade, the delivered products are used indoors. Five-layer joinery board consisting of two-layer surface board, two-layer middle board and one-layer core board is used for general purpose, not specifically for building.
Second, the quality requirements
(a) tree species, appearance quality and material requirements. Deliverables involved in the delivery are required to be first-class, and there are no specific provisions on the tree species used for the surface board and core board. The appearance classification standards of different tree species meet the requirements of 5.3 in GB/T5849, and appearance inspection should be carried out. Symmetrical veneers should have the same thickness, the same tree species or similar wood species, the same manufacturing method and the same grain configuration direction; The symmetrical layer veneer can be a whole veneer, or it can be spliced by veneers with equal width or unequal width along the edge; The surface plate should face outwards; The core strips of the same blockboard should have the same thickness, the same tree species or similar wood properties; Non-porous sewing tape is not allowed in the joinery board. Considering the market situation of blockboard products in China, the thickness of surface board should not exceed 0.55mm, so it is not necessary to carry out bonding strength test.
(2) Specification, size, thickness, size deviation and quality requirements of the plate core.
1. Specification, size, thickness and deviation. According to national standards, the measurement deviation of thickness should be [-0.60,0.60] (mm), and the deviation of length and width should be [0.0,5.0] (mm).
2. Verticality. According to the national standard, the deviation of verticality measurement is [0.0, 1.0] (mm/m).
3. Edge flatness. Measure the maximum deviation between the ruler (or straightened wire) and the edge of the plate with a measuring instrument, which should not exceed1mm/m. ..
4. Warping. Warp of blockboard delivered shall meet the requirements of first-class products.
5. wavy. Place a steel ruler with a length of 300mm near the board surface, and measure the maximum distance from the corrugated board surface to the ruler with a feeler gauge. The measuring position shall not be less than 20mm away from the plate edge. Take any three measured values, and the maximum value is the waviness of the joinery board, accurate to 0.05 mm.
6. Quality of plate core. At the same time of testing according to the standard, after making three samples according to the national standard GB/T5849-2006 "joinery board" 6.4. 1, make at least six 40mm×(300 ~ 500mm) samples at any position along the board length for the rest of the samples, and then observe whether there is decay and deterioration on the core rod and whether there are defects such as bark.
Third, the physical and mechanical properties
(1) water content. According to the national standard, the water content is in the range of 6%- 14%.
(2) Transverse static bending strength. Transverse static bending strength refers to the ratio of bending moment to flexural section modulus of blockboard under the maximum failure load, which reflects the bearing capacity of blockboard. According to the requirements of national standard, the average value of transverse static bending strength index is ≥ 15.0MPa, and the minimum value is ≥ 12.0MPa.
(3) Impregnation peeling performance. Impregnation peeling performance is to determine whether the adhesive layer peels off and the degree of peeling after the sample is impregnated and dried. According to the national standard, the peeling length of each surface on each adhesive layer of the specimen is less than 25 mm
(4) Surface bonding strength. Surface bonding strength refers to the ratio of the maximum breaking force of plywood surface perpendicular to the board surface to the bonding area of the specimen, which reflects the bonding quality between the surface fiber and the core fiber of plywood. According to the requirements of national standard, set the surface bonding strength index ≥0.60Mpa.
Fourth, formaldehyde emission
At present, the adhesives commonly used in plywood production in China are composed of formaldehyde, urea and other substances. Because some enterprises use inferior adhesives or unreasonable sizing technology and hot pressing technology, plywood will release free formaldehyde that does not participate in the reaction during use, which has a great impact on the safety of plywood. The world's major wood products manufacturers have restricted the formaldehyde emission, and China has also strictly restricted the formaldehyde emission of plywood.
According to the national standard GB/T5849-2006 "Blockboard", 460 samples were divided into E0, E 1 and E2 levels according to the different formaldehyde release limits.
According to China's national standards, the method of measuring formaldehyde emission from blockboard is dryer method. According to the requirements of the compulsory national standard GB 18580, the formaldehyde emission limit of E 1 class should be ≤ 1.5mg/L, and that of E2 class should be ≤ 5 mg/L.. (The second knowledge of fiberboard and plywood futures)