Testing method for water boiling resistance of plywood
Improvement measures: Firstly, replace the adhesive, choose a formula with low water content, or add flour and soybean powder appropriately to absorb water; The second is to improve the quality of veneer and strictly control the moisture content of veneer; The third is to adjust the hot pressing process, increase the hot pressing temperature, extend the hot pressing time, and appropriately increase the pressure; The fourth is to regularly inspect the equipment to ensure the accuracy of the rotary cutting machine, and check the steam path and supply situation of the hot pressing plate.
② Bubbling and local degumming
The main reasons are: the pressure reduction speed is too fast; the moisture content of the veneer is too high; Insufficient hot pressing time or low local temperature of the pressing plate; There are blank spots, inclusions, or sticky stains when applying glue; Pine veneer has poor breathability, high hot pressing temperature, and resin vaporization, resulting in glue opening.
Improvement measures: Firstly, adopt a multi-stage depressurization process and strictly control the depressurization speed; Secondly, reduce the moisture content of the veneer; Thirdly, increase the adhesive concentration or reduce the amount of adhesive applied; Fourthly, for tree species such as pine with poor air permeability, a hot pressing temperature below 110 ℃ should be used; Fifth, appropriately extend the hot pressing time; Sixth, check the steam path and supply condition of the hot pressing plate.
③ Corner detachment
The main reasons are: the aging time is too long, and the edge glue has dried up; Lack of adhesive at the edges and corners; Large area press presses small area panels with missing adhesive at the edges and corners; When the large face press presses the small face plate, the loading positions of each layer shift, resulting in uneven pressure; Warping deformation of hot pressed plate; The temperature at the corners of the pressing plate is too low.
Improvement measures: Firstly, shorten the aging time; Secondly, pay attention to the gluing operation; The third is that the large press does not press the small plate, and even if the small plate is pressed, the compression positions of each layer should be aligned; Fourthly, when the pressure plate is warped and deformed, it can be repaired by planing the hot pressed plate; When the deformation is large, the pressing plate needs to be replaced; Fifth, check the steam path and supply condition of the hot pressing plate.
④ Core plate stacking and separation seam
The main reasons are: manual core arrangement, inaccurate grasp of the expansion gap between zero pieces of single boards; When installing or moving the board, the core board is misaligned; The preloading effect is not good, and the bonding between the veneers is not good; The edge of the core board is uneven; The edge of the core board has ruffles and cracks.
Improvement measures: Firstly, achieve the whole core board or adopt a secondary adhesive coating process; Secondly, the aging time of the opening of the coated core board should be appropriate; The third is to implement pre pressing before loading the slab, and maintain stability when moving the slab; Fourth, grasp the timing of preloading; Fifth, the core board adopts a leveling process, and the core board that is cut first and then dried should be aligned with the edges after drying; Six is to improve the quality of core plate rotary cutting and drying.
⑤ Board surface adhesive penetration
The main reasons are: the glue is too thin and there is too much water; Excessive glue application; The crack on the back of the veneer is too deep; The moisture content of the veneer is too high; Insufficient aging time of slab; Excessive pressure during hot pressing.
Improvement measures: Firstly, check the quality of the glue, increase the resin content of the glue, and select a formula with low water content; Secondly, reduce the amount of glue applied and replace worn glue rollers; The third is to improve the quality of veneer rotary cutting, adjust the position of the pressure gauge, and increase the rotary cutting and pressing rate; Fourth, reduce the moisture content of the veneer; Fifth, increase the aging time to evaporate a portion of the moisture in the adhesive solution; Sixth, reduce the hot pressing pressure and check the pressure gauge of the hot pressing machine.
⑥ Plywood warping
The main reasons are: the symmetry principle is not followed during the assembly of billets; The front and back directions of the blank assembly are incorrect; The veneer is made from stressed wood segments; Warping deformation of hot pressed plate; Plywood stacked unevenly.
