Analysis of the factors influencing bonding effect of the plywood and blockboard
Guide: The glue for panel and blockboard and plywood wood-based panel refers to the adhesive used for splicing wood products such as glued laminated wood, which is suitable for bonding the panel and blockboard and plywood wood-based panel of non structural and structural laminated wood.
1、 In terms of temperature, the working environment temperature and wood surface temperature shall be measured in time in different seasons. The temperature, to some extent, determines the speed of cross-linking reaction of plywood, blockboard and plywood. The surface temperature of wood is closely related to the holding time of plywood and blockboard. The service time of plywood, blockboard and plywood based panel adhesive varies at different temperatures: in summer, the service time of mixed plywood, blockboard and plywood based panel is 30 minutes (that is, the sooner you use it, the better); In winter, the mixed plywood, blockboard and plywood panel glue can be used for 60 minutes.
2、 The moisture content of dried wood shall be controlled within 7-12% after natural moisture regain. When the moisture content of wood is lower than 7%, it may cause the phenomenon that the wood permeability is too strong and the bonding surface lacks glue, leading to cracking. If the wood moisture content is too high, it will directly lead to poor permeability, and it is difficult to form glue nails. If the cross-linking reaction is not complete, it may cause glue opening. The critical moisture content difference of wood should be controlled within 3%.
3、 In terms of wood processing accuracy, the wood processing accuracy shall be within 0.15mm. The bonding surface of wood shall be free of processing defects of “gnawing head and tail”. Wood # EAF0F4 has good right angle. The wood bonding surface shall be free of “planing marks, sawing marks, carbonization” and other phenomena. It is strictly forbidden to use wood whose bonding surface has been polluted by oil, dust, etc. for bonding.
4、 In terms of mixing, the main agent and curing agent shall be mixed in strict accordance with the weight ratio of 100:15, and shall be fully stirred. The mixed plywood, blockboard and plywood board glue shall be used up within the operable time. It is forbidden to mix wood chips, dust and other impurities or add water when mixing glue. The main agent and curing agent shall not be mixed with each other before use. Sealed storage shall be paid attention to after taking glue.
5、 In terms of gluing, the standard gluing amount is 250-300g/m2. The open stacking time shall be controlled within 10 minutes, and the closed stacking time shall be controlled within 5 minutes. The amount of glue applied shall be guaranteed for single side glue application or double side glue application, and film formation of the layer due to drying shall be prevented. The phenomenon of waste and uneven gluing shall be avoided for brush gluing. The roller gluing or mechanical gluing shall ensure the gluing amount and prevent the problem of film formation due to too thin glue layer. For tree species that are difficult to be bonded, it is recommended to use double-sided adhesive coating.
6、 In terms of pressure, according to the different tree species and bonding area, the corresponding pressure of plywood, blockboard and plywood shall be adjusted continuously. The reference pressure coefficient is as follows: the pressure coefficient of coniferous species is 8-10kg/cm2; The pressure coefficient of broad-leaved tree species is 12-16kg/cm2. There shall be sufficient glue line overflow on the surface and end of the panel when the panel, blockboard and plywood are pressurized. When the pressure reaches the requirements, the extruded wood will make a “rattle” sound. However, the decayed wood may break at this time. On the surfaces of different panels, blockboards and plywood panels, attention should be paid to keeping the pressure of panels, blockboards and plywood panels uniform. The phenomenon of “loose ends” at the ends of jointed boards, blockboards and plywood man-made boards shall be prevented.
7、 In terms of pressure holding time, under different temperatures, the pressure holding time required for splicing different tree species should be set to different optimal values according to actual working conditions and experience. For example: low ← temperature 25 ℃ → high oak wood: prolonged ← pressure holding for 45 minutes → 40 minutes pine wood ← pressure holding for 35 minutes → 25 minutes
8、 The curing time is at room temperature (above 20 ℃), and can be reworked after 12 hours of curing. At room temperature (above 20 ℃), the finished product can be delivered after 72 hours of curing. With the decrease of curing temperature, the curing time of jointed boards, blockboards and plywood panels should be extended accordingly. It is strictly forbidden to store the patched boards, blockboards and plywood man-made boards that are not well cured in an environment below 0 ℃.
