Breaking News

Test method for water boiling resistance of plywood

Test method for water boiling resistance of plywood

1.4.3 testing method of plywood:

According to the classification of ordinary plywood, there are corresponding detection methods:

Class I plywood: that is, weather resistant plywood, which is used outdoors and can pass the boiling test;

Steps: boil in boiling water for 4h, dry at 63 ℃ for 20h, boil in boiling water for 4h, dry in the air, and conduct mechanical machine test.

Class II plywood: that is, water-resistant plywood, which is used under wet conditions and can pass the hot water immersion test at 60 ℃± 3 ℃;

Steps: boil in 60 ℃± 3 ℃ hot water for 3h, air for 10min, and conduct mechanical machine test.

Class III plywood: that is, non moisture resistant plywood, which is used under dry conditions and can pass the dry test.

1.4.4 analysis of common defects during gluing

Some defects often appear in the gluing process of plywood, which may increase the trouble of rework and repair, or reduce the gluing quality or even become waste products. The following lists several common gluing defects, analyzes their causes, and puts forward corresponding improvement measures.

① Low adhesive strength and large area opening

The main reasons are: the quality of the adhesive is not good, such as deterioration and excessive moisture; The moisture content of veneer is too high and the surface quality is poor; The bonding conditions are not well controlled, such as the hot pressing temperature is too low or part of the temperature is uneven, the pressure is insufficient, and the hot pressing time is too short, which makes the adhesive layer not fully cured; Insufficient or too long aging time will also reduce the adhesive strength. Henan Jianjie industrial flour can replace flour products, namely industrial flour. In the process of plywood application, all kinds of properties are better than flour, and the price is favorable.

Improvement measures: first, replace the adhesive, select a formula with low water content or add flour and soybean flour appropriately to absorb water; Second, improve the quality of veneer and strictly control the moisture content of veneer; Third, adjust the hot pressing process, increase the hot pressing temperature, extend the hot pressing time, and appropriately increase the pressure; Fourth, regularly check the equipment, ensure the accuracy of the rotary cutter, and check the steam passage and steam supply of the hot pressing plate.

② Bubbling and local degumming

The main reasons are: the depressurization speed is too fast: the moisture content of the veneer is too high; The hot pressing time is insufficient or the local temperature of the pressing plate is too low; There are blank spots, inclusions and stickiness during gluing; The pine veneer has poor air permeability, the hot pressing temperature is too high, and the pine resin vaporizes, resulting in glue opening.

Improvement measures: first, adopt multi-stage depressurization process and strictly control the depressurization speed; Second, reduce the moisture content of veneer; Third, increase the glue concentration or reduce the amount of glue; Fourth, for pine trees with poor air permeability, the hot pressing temperature below 110 ° C should be adopted; Fifth, extend the hot pressing time appropriately; Sixth, check the steam passage and steam supply of hot platen.

③ Corner falling off

The main reasons are: the aging time is too long, and the corner glue has dried up; Lack of glue at edges and corners; Lack of glue at edges and corners of small panel pressed by large panel press; When the large panel press presses the small panel, the loading position of each layer shifts, resulting in uneven pressure; Warping and deformation of hot pressed plate; The temperature at the corners of the pressing plate is too low.

Improvement measures: first, shorten aging time; Second, pay attention to the gluing operation; Third, the large press does not press small plates, and even if small plates are pressed, the pressure positions of each layer should be aligned; Fourth, when the pressing plate is warped and deformed, it can be repaired by planing the hot pressed plate; Replace the pressing plate when the deformation is large; Fifth, check the steam passage and steam supply of hot pressing plate.

④ Core plate laminated core separation

The main reasons are: manual core arrangement, inaccurate control of expansion gap between pieces of veneer; The core plate is misaligned during loading or moving; The preloading effect is not good, and the veneers are not well bonded; The edge of core plate is not straight; The edge of the core plate has ruffles and cracks.

Improvement measures: one is to realize the whole core plate or adopt the secondary gluing process; Second, the aging time of the opening of the glued core plate should be appropriate; Third, the slab is preloaded first and then loaded into the machine, which keeps stable when moving the slab; Fourth, grasp the preloading opportunity; Fifth, the core plate adopts the leveling process, and the core plate that is cut first and then dried should be aligned after drying; Sixth, improve the quality of core plate spinning and drying.

⑤ Glue penetration of plate surface

The main reasons are: the glue is too thin and the water is too much; Too much glue; The crack on the back of the veneer is too deep; The moisture content of veneer is too high; Insufficient aging time of slab; Excessive pressure during hot pressing.

Improvement measures: first, check the quality of the glue, improve the resin content of the glue, and select the formula with less water content; Second, reduce the amount of gluing and replace the worn gluing roller; Third, improve the veneer rotary cutting quality, adjust the position of the pressure gauge, and increase the rotary cutting press rate; Fourth, reduce the moisture content of veneer; Fifth, increase the aging time to evaporate part of the water in the glue solution; Sixth, reduce the hot press pressure and check the pressure gauge of the hot press.

⑥ Plywood warpage

The main reasons are as follows: when assembling billets, it does not conform to the principle of symmetry; The front and reverse directions of the face and back plate are not correct during blank assembly; The veneer is made from the stressed wood section; Warping and deformation of hot pressed plate; The plywood is stacked unevenly.

Improvement measures: first, the corresponding layers should be symmetrical when assembling billets; Second, when assembling billets, the front and back plates should face outward; The third is that the veneer that is cut out should be leveled (softened); Fourth, repair or replace the pressing plate; Fifth, plywood should be stacked flat.

如无特殊说明,文章均为本站原创,转载请注明出处。If there are no special instructions, the articles are original, if you want to use or reproduce, please indicate the original source www.plywoodinspection.com,If you find that our articles infringe on your copyrights and interests, please email us at info@plywoodinspection.com in time and we will delete it at the first time.

Check Also

Quality problems easily caused by unstable temperature of laminating and pressing in the production process of impregnated paper laminated wood flooring

Quality problems easily caused by unstable temperature of laminating and pressing in the production process …

Leave a Reply

Your email address will not be published. Required fields are marked *