The type and amount of adhesive on the improvement of bending stiffness
The type and amount of glue have a significant impact on the bending stiffness of plywood.
1.Glue type
Commonly used glue types include:
*Urea-formaldehyde resin adhesive: has good bonding strength, but poor heat resistance and moisture resistance.
*Phenolic resin adhesive: has excellent heat resistance and moisture resistance, but slightly lower bonding strength.
*Melamine formaldehyde resin adhesive: has high bonding strength and heat resistance, but poor moisture resistance.
*Isocyanate adhesive: has extremely high bonding strength and water resistance, but is more expensive.
2.Adhesive dosage
The adhesive dosage is usually expressed in grams per square meter (g/m2). The appropriate adhesive dosage is critical to ensure sufficient bond strength and bending stiffness.
*Low adhesive dosage: usually results in insufficient bond strength, which reduces bending stiffness.
*High adhesive dosage: Although it can improve bond strength, it also increases cost and weight and may cause adhesive oozing.
3.Experimental studies
Several experimental studies have shown that the type and amount of adhesive have the following effects on the bending stiffness of plywood:
*Adhesive type: Phenolic resin adhesive and isocyanate adhesive have the highest bending stiffness, followed by urea-formaldehyde resin adhesive and melamine formaldehyde resin adhesive.
*Adhesive amount: Within a certain range, the increase in adhesive amount is positively correlated with the increase in bending stiffness. However, when the adhesive amount is too high, the increase in bending stiffness decreases.
4.Recommended dosage
Generally speaking, for plywood with a thickness of 3-6 mm, the recommended dosage of adhesive is as follows:
*Urea-formaldehyde resin adhesive: 120-160 g/m2
*Phenolic resin adhesive: 100-140 g/m2
*Melamine formaldehyde resin adhesive: 120-160 g/m2
*Isocyanate adhesive: 80-120 g/m2
The actual amount of adhesive should be adjusted according to the specific application, adhesive type and other factors.
5.Conclusion
The proper adhesive type and dosage selection is crucial to improve the bending stiffness of plywood. Phenolic resin adhesives and isocyanate adhesives have the highest bending stiffness, while urea-formaldehyde resin adhesives and melamine formaldehyde resin adhesives have certain bonding strength and temperature resistance. Increasing the amount of adhesive generally improves the bending stiffness, but the dosage should be optimized to balance the cost, weight and performance requirements.
Part 3 Layer structure design optimization to improve bending stiffness
Layer structure design optimization to improve bending stiffness
1.Optimize layer thickness distribution: By adjusting the thickness of each layer of plywood, the stiffness moment of inertia of the overall structure can be changed, thereby improving the bending stiffness.
2.Use plywood of different strength grades: Using materials of different grades (such as strength and elastic modulus) in the plywood layer can customize the performance of the layer according to specific force requirements and optimize the bending stiffness distribution.
3.Optimize the layer sequence arrangement: The arrangement order of plywood layers will affect the bending resistance of the overall structure. By optimizing layer sequence, the force can be balanced, stress concentration can be reduced, and thus the bending stiffness can be improved.
Optimize interlayer adhesive to improve bending stiffness
1.Choose high-performance adhesive: Adhesive plays a vital role in the bending performance of plywood. Choosing adhesive with high shear strength and elastic modulus can effectively transmit interlayer shear force and improve bending stiffness.
2.Optimize adhesive distribution: The adhesive is evenly distributed between layers to ensure the overall strength of the plywood. By optimizing the adhesive coating process, stress distribution can be uniform and bending stiffness can be improved.
3.Use reinforcement ribs or reinforcement layers: Adding reinforcement ribs or reinforcement layers between plywood layers can further enhance interlayer bonding and improve bending stiffness.
Optimizing layer structure design to improve bending stiffness
The bending stiffness of plywood mainly depends on its layer structure and material properties. By optimizing the layer structure design, the bending stiffness of plywood can be effectively improved. The following are several layer structure design optimization strategies:
1.Core material selection
The core layer is the central layer of the plywood, and its material has a significant effect on the bending stiffness. Materials with high elastic modulus and bending strength, such as spruce, fir and poplar, are ideal core materials. These materials can resist large bending deformations, thereby improving the overall stiffness of the plywood.
2.Optimization of core thickness
The core thickness directly affects the bending stiffness of plywood. Generally speaking, thicker cores have higher stiffness. However, increasing the thickness of the core will also lead to increased weight and cost of plywood. Therefore, it is necessary to balance stiffness and cost to determine the optimal core thickness.
3.Surface material selection
The surface is the outer layer of the plywood, and its material also has an impact on the bending stiffness. Materials with higher hardness and strength, such as hardwood and particleboard, can improve the surface stiffness of the plywood. These materials can resist surface scratches and wear, thereby improving the overall durability of the plywood.
4.Optimization of surface thickness
Surface thickness is critical to the bending stiffness of plywood. Thicker surface layers provide higher stiffness, but also increase the weight and cost of the plywood. The optimal surface thickness depends on the plywood intended application and economics.
5.Optimize the number of plies
The number of plywood layers affects its bending stiffness. Generally speaking, the more plywood layers there are, the higher the stiffness is. However, increasing the number of plywood layers will also make the plywood heavier and increase the cost. Reasonably determine the number of plywood layers to meet the stiffness requirements and control costs.
6.Layer sequence optimization
The layer sequence refers to the order in which the layers are arranged in the plywood. Different layer sequences have different effects on bending stiffness. Symmetrical layer sequences usually have higher stiffness than asymmetric layer sequences. This is because symmetric layer sequences can better resist bending deformation.
7.Optimize the direction of wood grain
The direction of wood grain in each layer of plywood will also affect the bending stiffness. Wood grain parallel to the bending direction can provide higher stiffness. Therefore, in the surface and core layers of plywood, the wood grain should be arranged parallel to the expected bending direction.
8.Glue type optimization
The glue type has an effect on the bending stiffness of plywood. High-strength glues, such as phenolic glue and epoxy glue, can provide higher strength and stiffness. Glue application uniformity and glue layer thickness also affect the bending stiffness of plywood.
9.Pressing process optimization
The pressing process has a significant impact on the bending stiffness of plywood. High pressure and longer pressing time canincrease the density and strength of plywood, thereby improving its bending stiffness.
By applying these layer structure design optimization strategies, the bending stiffness of plywood can be significantly improved.
The optimized plywood is widely used in construction, furniture, transportation and industry, meeting the load-bearing and stiffness requirements in different application scenarios.
