Introduction to Splicing Glue
Panel adhesive refers to the adhesive used to splice wood products such as glued laminated timber. The main agent of panel adhesive suitable for non structural and structural laminated timber is specially made polyvinyl acetate lotion with waterproof effect, and the curing agent is generally isocyanate. The main color is a milky white viscous liquid, and the curing agent is light brown. The main adhesive for splicing can generally be used alone as finger bonding adhesive.
Characteristics of panel adhesive
1. Control of Wood:
1）. Moisture content control: below 14%;
2）. Maintain the flatness of the joint surface, without any wavy, curved, or twisted surfaces. For easily deformed wood (such as oak, water chestnut, etc.), it must be finished on the same day if it is flattened, and re flattened if it is flattened overnight;
3）. Before splicing, it is necessary to remove all wood ash and dust from the surface of the wood.
2. Method of adjusting glue:
1).When preparing the curing agent, the amount of glue to be adjusted should be determined based on the size of the glue container. Only one-third of the volume of the glue container can be used for adjustment, otherwise it will cause the glue to react and bubble, resulting in overflow.
2）. It is recommended to use a flat bottomed circular plastic bucket for glue mixing, as this container can easily mix the curing agent evenly.
3）. Do not add water or other substances to the glue, otherwise it will cause solidification or a sharp decrease in strength.
4）. The splicing adhesive mixed with curing agent is generally required to be used up within 12 hours (the effect is more significant after foaming).
5）. Unused curing agents must be strictly sealed and stored, without water mixed in, to avoid hardening and scrapping.
Once the dosage of the curing agent is confirmed, it cannot be changed arbitrarily, otherwise it will seriously affect key functions such as adhesive strength and water resistance.
3. Control of glue application amount:
The user should determine the amount of glue to be applied based on the temperature and humidity of the space at that time. When the space temperature is low, the humidity is high (below 80%), and the wood is hard, the amount of glue applied should be less; When the space temperature is high, the humidity is low (below 60%), and the wood is soft, the amount of glue applied should be more.
4. Glue application method:
Due to the high viscosity (consistency) of the glue, it is recommended to use a manual glue applicator, a pig brush, or a rubber scraper for uniform glue application. The glue application amount is generally controlled between 150g-250g/m (120g-150 g/m for hardwood and 120g-250 g/m for softwood). After applying glue to the workpiece, it should be spliced as soon as possible to prevent the surface of the glue from forming a film, so as to avoid false splicing and easy glue cracking.
5. Method and duration of pressurization:
Regardless of the compression method used, it is necessary to maintain uniform pressure at multiple points within a range of 30-50cm. The time control for pressurization depends on the temperature and air humidity at the work site. Except for the pressurization time of 30-40 minutes for the disc splicing machine, other pressurization methods are normally defined as 2-4 hours (below 60% humidity at 25 ℃). When assembling panels under high temperature and low humidity conditions, the pressurization time can be shortened to about one hour; Otherwise, it will take 4 hours or more.
6. Inspection during pressurization:
During pressurization, attention should be paid to preventing the wooden strips from being pulled out (unevenness and small heads are prone to occur). If they are pulled out, they should be loosened and reset, and cannot be forcibly reset under pressure; Check if there is any glue overflow in the joint. If there is no glue overflow, it indicates that the amount of glue applied is insufficient or the waiting time for pressing after applying glue is too long. If this phenomenon occurs, it should be corrected immediately. The pressure inspection process cannot be ignored.
7. Maintenance period after unloading:
In the process of solid wood splicing or tooth joint, in order to prevent glue cracking, the spliced workpieces must undergo stacking and curing after unloading. According to different climatic conditions for different types of wood, a curing time period should be set to ensure the normal use of the next process. We recommend that the curing time be set at 3-5 days when piling and curing under low temperature, high humidity, and hard wood conditions, and 1-2 days when piling and curing under high temperature, low humidity, and soft wood conditions.
8. Unused residual adhesive treatment:
If the splicing adhesive mixed with curing agent cannot be used up temporarily, it must be sealed and stored temporarily, waiting for the next use (not exposed to air for a long time to prevent dry skin), which will not affect the splicing quality.
