Dry heat gluing is carried out in a hot press. During the gluing process, temperature, pressure and time are three important factors influencing the hot pressing process. They are interrelated and mutually influential, in addition to Tree species and the type of rubber used are closely related.
The so-called hot pressing cycle means that the pre-formed slabs are loaded into the hot press one by one or at the same time, the press is closed, boosted, and kept under a certain pressure for a period of time, and the pressure is started after the adhesive layer is solidified. After the opening, the slab is removed, thus completing a hot pressing cycle. During the whole hot pressing cycle, the adhesive is in full contact with the wood under pressure, heating increases the temperature of the slab, the water is redistributed, the wood is compacted, the rubber layer is solidified, and the steam is discharged during pressure relief, so that the moisture content of the finished product is reduced. Specified value.
The general hot press cycle can be carried out in three stages:
In the first stage of the jujube pressurization stage, from the loading of the plate to the complete closing of the press, the slab is not subjected to external pressure after being loaded into the press, and the rubber layer near the hot plate is warmed up quickly. At this time, it is in the boosting stage. The stage slab is glued without sufficient contact, so at this stage, if the glue layer is cured, the desired bond strength is not achieved. Therefore, this period should be as short as possible.
The second stage of the jujube pressurization stage is the time from the closure of the press to the beginning of the pressure relief, which depends on the rubber grade, the slab moisture content and the thickness of the board. When the platen temperature is 105-120 ° C, the urea-formaldehyde resin plywood needs 30-50 seconds per mm thickness and the pressure is 1-1.2 MPa.
The third stage of the jujube depressurization stage, this stage can also be carried out in three stages. At this stage, attention should be paid to controlling the depressurization speed of the press. The first stage is the pressure from which the maximum pressure drops to the equilibrium between the steam pressure in the slab and the pressure of the hot platen. When the two pressures are equal, that is, at equilibrium pressure, the second phase of the pressure reduction is entered. At this time, the inner rubber layer of the slab is subjected to a large stress, which is caused by the shrinkage of the rubber layer and the conversion of moisture in the slab into a gas-forming stress, which is sufficient to destroy the structure of the slab in the event of sudden pressure drop. Therefore, at this stage, the pressure should be slowly reduced to allow the steam to escape. The third stage is the expansion of the pressure plate. For the multi-layer plywood to reduce unnecessary compression, the pressure reduction time can be advanced.
The so-called hot pressing cycle means that the pre-formed slabs are loaded into the hot press one by one or at the same time, the press is closed, boosted, and kept under a certain pressure for a period of time, and the pressure is started after the adhesive layer is solidified. After the opening, the slab is removed, thus completing a hot pressing cycle. During the whole hot pressing cycle, the adhesive is in full contact with the wood under pressure, heating increases the temperature of the slab, the water is redistributed, the wood is compacted, the rubber layer is solidified, and the steam is discharged during pressure relief, so that the moisture content of the finished product is reduced. Specified value.
The general hot press cycle can be carried out in three stages:
In the first stage of the jujube pressurization stage, from the loading of the plate to the complete closing of the press, the slab is not subjected to external pressure after being loaded into the press, and the rubber layer near the hot plate is warmed up quickly. At this time, it is in the boosting stage. The stage slab is glued without sufficient contact, so at this stage, if the glue layer is cured, the desired bond strength is not achieved. Therefore, this period should be as short as possible.
The second stage of the jujube pressurization stage is the time from the closure of the press to the beginning of the pressure relief, which depends on the rubber grade, the slab moisture content and the thickness of the board. When the platen temperature is 105-120 ° C, the urea-formaldehyde resin plywood needs 30-50 seconds per mm thickness and the pressure is 1-1.2 MPa.
The third stage of the jujube depressurization stage, this stage can also be carried out in three stages. At this stage, attention should be paid to controlling the depressurization speed of the press. The first stage is the pressure from which the maximum pressure drops to the equilibrium between the steam pressure in the slab and the pressure of the hot platen. When the two pressures are equal, that is, at equilibrium pressure, the second phase of the pressure reduction is entered. At this time, the inner rubber layer of the slab is subjected to a large stress, which is caused by the shrinkage of the rubber layer and the conversion of moisture in the slab into a gas-forming stress, which is sufficient to destroy the structure of the slab in the event of sudden pressure drop. Therefore, at this stage, the pressure should be slowly reduced to allow the steam to escape. The third stage is the expansion of the pressure plate. For the multi-layer plywood to reduce unnecessary compression, the pressure reduction time can be advanced.
Regular, long-term use can strengthen & harden natural nails allowing you to grow healthy, beautiful nails!Seals the natural keratin layers together at the nail's edge, preventing nail splitting, chipping & peeling, leaving nails smooth with no jagged edges.glass files file in both directions, the fine grit permanently etched abrasive surface allows precise filing, target specific areas & shape the nails with ease.
Glass Nail File,Glass Nail File Set,Nail File Glass,Glass File Nail
Yangjiang Yangdong Kartie Beauty Tools Product Factory , https://www.kartierbeauty.com