Edge-sealing hot-melt adhesive is a kind of adhesive specially used for edge-sealing of man-made sheets. It is a solvent-free thermoplastic adhesive. When the hot melt adhesive is heated to a certain temperature, it changes from solid state to melt state. When it is coated on the surface of artificial board or edge sealing material, it cools to solid state and bonds the edge sealing material to the base material.

1. Material of Hot Melt Adhesive for Edge Sealing

(1) EVA (ethylene-vinyl acetate copolymer resin) based hot melt adhesives, which can be divided into two categories: filler and non-filler. The use of EVA as base material is a common production technology of hot melt adhesives for edge sealing. Its main limitation is poor heat resistance. The ambient temperature of panel furniture sealed with EVA hot melt adhesive should not be higher than 120 degree C.

(2) POL YAMIDE (polyamide) based hot melt adhesive, which has good heat resistance and fast curing characteristics, has the main disadvantage of high price.

(3) HMPU (polyurethane) base hot-melt adhesive, which is a kind of good performance hot-melt adhesive, is the guarantee of high-quality plate edge sealing. It is expensive and requires special methods of use.

2. Viscosity of Hot Melt Adhesive for Edge Sealing

The viscosity of the edge-sealing hot melt adhesive can not directly reflect the performance of the adhesive. Generally speaking, the higher the viscosity of the edge-sealing hot melt adhesive, the better its initial adhesion strength, but the worse its coating performance. Low viscosity hot melt adhesives have better wettability because of their small amount of glue. Some hot melt adhesives with low viscosity and fast curing speed may also have high initial bond strength. For poor quality particleboard, high viscosity hot melt adhesives are needed for edge sealing. This is because the fluidity of high viscosity hot melt adhesives is poor. It is not as easy to enter the voids in the edge of particleboard as low viscosity hot melt adhesives, so that hot melt adhesives can be fully coated on the edge of the board.

3. Density of Hot Melt Adhesive for Edge Sealing

The density of edge-sealing hot melt adhesives is generally 0.95-1.6g/cm 3, and its density depends on the number of fillers (the more fillers, the greater density).  Because of the requirement of a certain glue area for edge sealing, the glue amount per unit length of filler-free hot melt adhesives with low density is less than that of filler-free hot melt adhesives. Moreover, due to the good bonding performance of the filler-free hot melt adhesive and the same edge sealing effect, it is possible that the use of the filler-free hot melt adhesive is less than that of the filler-free hot melt adhesive. In order to reduce the amount of glue coating, the edge sealing machine must have a good glue coating system.

4. Softening Point and Use Temperature of Hot Melt Adhesive for Edge Sealing

Softening point is an index of heat resistance of hot melt adhesives. The higher the softening point, the more difficult the hot melt adhesives are to melt. At the same time, softening point is also an important aspect to measure the heat resistance of panel furniture. In Europe, there has been a set of testing methods for the heat resistance of plate edge sealing, and standards for the heat resistance of plate furniture have also been put forward. France, Germany and Italy have not produced low softening point hot melt sealant on a large scale, but domestic manufacturers (including Taiwan manufacturers) still produce and provide to the domestic market, because domestic furniture manufacturers and consumers do not pay enough attention to the heat resistance of panel furniture, especially kitchen furniture. The softening point range of EVA hot melt adhesives is generally between 90 and 135 C.

The use temperature of hot melt adhesives refers to the temperature on the coating rolls of the edge sealing machine. Only at this temperature can the hot melt adhesives achieve good adhesive strength. The temperature displayed on some edge sealing machines is quite different from the actual temperature, so the temperature of the machine should be checked regularly. If the temperature of edge sealing machine is too high, the adhesive will carbonize and smoke; if the temperature is too low, the adhesive strength will decrease.

5. Opening Time of Hot Melt Adhesive for Edge Sealing and Feeding Speed of Edge Sealing Machine

The opening time of hot melt adhesive for edge sealing refers to the period from the beginning of gluing to the time before the edge sealing tape is pressed onto the base material. The opening time varies with the type of glue. Feeding speed and opening time of edge sealing machine are closely related. Both of them are very important in choosing and using hot melt adhesive. Fast feeding edge sealing machine must choose hot melt glue with short opening time, on the contrary, hot melt glue with long opening time.

For most manual edge-sealing machines, due to the manual operation of workers, it requires the hot melt adhesive to be open for a long enough time to facilitate the edge-sealing of bending parts. Hot melt adhesives are usually coated on the edge-sealing tape. In order to ensure the quality of the edge-sealing, the domestic manual edge-sealing machine also adopts the method of double-sided gluing. The temperature of the rubber can of the manual edge-sealing machine is generally controlled below 180 degrees C (the German BRANDT manual edge-sealing machine can be heated to more than 200 degrees C), so the hot melt glue with the temperature below 180 degrees C should be used. If the thin PVC seals with thickness less than 0.2mm are sealed on the manual edge sealing machine, the temperature of the hot melt adhesive used must be about 120 degrees C.