GB/T17657-2013 Test Method for Physical and Chemical Properties of Artificial Board and Decorative Artificial Board: Determination of Internal Bonding (Bonding) Strength.
11 Determination of internal bonding strength
11.1 Principle
The internal bonding strength is a measurement of the tensile strength of the specimen surface to withstand uniformly distributed tensile force until failure. The internal bonding strength is the ratio of the maximum breaking force perpendicular to the surface of the specimen to the area of the specimen.
11.2 Instruments and equipment
Artificial board universal testing machine. png
11.2.1 Universal mechanical testing machine. The testing function applies a tensile force perpendicular to the surface of the specimen through a fixture (see Figure 14), and selects an appropriate load range according to product requirements, with a measurement accuracy of 1% of the load value. At least one 11.2.2 clamp head, which can be metal, hardwood, or hardwood plywood, is used in two fixtures. The clamp head is matched with the fixture, and the specimen is bonded to the clamp head (see Figure 14). The density of hardwood or hardwood plywood is greater than 600kg/m ³。
11.2.3 Vernier caliper, with a division value of 0.1mm and a range of 0mm~150mm.
11.2.4 Stop watch.
11.3 Test pieces
11.3.1 Specimen size
Length l=(50 ± 1) mm. Width b=(50 ± 1) mm.
11.3.2 Specimen balance treatment
If necessary, place the test piece and hardwood or hardwood plywood clamp in an environment with a temperature of (20 ± 2) ° C and a relative humidity of (65 ± 5)% until the mass remains constant. The difference between the two weighing results after a 24-hour interval does not exceed 0.1% of the mass of the test piece, which is considered to be a constant mass.
In some cases, such as conducting cyclic tests or immersion tests in a humid state, another equilibrium treatment condition can be specified. In this case, refer to the corresponding standards for implementation.
Artificial board constant temperature and humidity box. png
11.4 Method
11.4.1 Measure the width and length of the specimen at the centerline of its length and width (see 1).
11.4.2 Adhesion between test piece and clamp head: Apply epoxy resin adhesive or melted hot melt adhesive or similar adhesives evenly on the surface of the clamp head, and bond the test piece and clamp head together according to Figure 14. Remove the adhesive extruded from the adhesive layer. If hot melt adhesive is used, sand the textured side of the hard fiberboard until a smooth surface is obtained. If the mesh side is not sanded off, epoxy resin adhesive can be used
Unit in millimeters
blob.png
explain:
1 Metal clamp head
2 card heads (Jincheng, hardwood or hardwood plywood);
3 Hardwood plywood clamp heads (not suitable for thin sheets);
4 specimens:
5 automatic centering ball socket connection:
Note: t ≥ 15mm
Figure 14 Schematic diagram of internal bonding strength measurement device
During bonding, additional stress caused by moisture and/or high temperature rise in the adhesive can have an impact on the specimen and should be avoided as much as possible.
Note: The following combination proof is applicable:
Bonding of hot melt adhesive and epoxy resin to metal card heads:
Adhesion of hot melt adhesive, epoxy resin, PYAC, UT, resorcinol with hardwood and hardwood plywood card heads.
If the test piece is subjected to cyclic testing or immersion testing pre-treatment in a humid state, some adhesives are not suitable for bonding between the test piece and the clamp head. If the specimen is pre treated and bonded to the clamp head, the upper and lower surfaces of the specimen should be slightly sanded to eliminate surface roughness during the pre treatment period. To prevent damage to the adhesive layer during stretching, sufficient time is required for the adhesive to cure and the moisture content of the specimen to be evenly distributed before measurement.
Based on experience, if hot melt adhesive is used, it can cure quickly: if epoxy resin is used, it needs to cure for 24 hours; If other adhesives are used, it will take approximately 72 hours to cure. During this period, the glued components were placed in an equilibrium treatment room with a temperature of (20 ± 2) ℃ and a relative humidity of (65 ± 5)%. After taking out the test piece from the balance treatment room, the test is completed within 1 hour:
For specimens or glued components that undergo cyclic testing or immersion testing in a humid state, as well as inspection during the humid phase, no balancing treatment is performed.
If inspecting thin plates (thickness<8.0mm) or high-density boards (>800kg/m ³）， It is recommended to use a metal clamp head. Experience has shown that using wooden card heads in this situation results in high variability.
11.4.3 Place the component in the clamping device and load it until the specimen is damaged. The entire test should be uniformly loaded, and the specimen should be damaged within (60 ± 30) seconds from the start of loading. Record the maximum load value, accurate to 1%.
11.4.4 If there is partial or complete damage to the adhesive layer or card head during testing. The result is invalid. A new test piece should be taken from the original sample for retesting.
11.5 Expression of Results
11.5.1 Calculate the adhesive strength inside the specimen according to equation (10) to the nearest 0.01MPa:
blob.png (10)
In the equation:
σ—— The adhesive strength inside the specimen, in megapascals (MPa);
Fmax – maximum load at failure of the specimen, in Newton (N):
L – length of the test piece, in millimeters (mm);
B – specimen width, in millimeters (mm):
11.5.2 The internal bonding strength of a board is equal to the arithmetic mean value of the internal bonding strength of all test pieces in the same board, accurate to 0.01MPa.
