Edge sealing hot melt adhesive is a kind of adhesive specially used for edge sealing of artificial boards. It is a solvent-free thermoplastic adhesive. When the hot melt adhesive is heated to a certain temperature, it changes from a solid state to a molten state. When it is applied to the surface of the wood-based panel substrate or the edge sealing material, it cools to a solid state, and the edge sealing material and the substrate are bonded together. For the selection and use of edge sealing hot melt adhesive, the following aspects must be paid attention to:
Edge sealing hot melt adhesives can be divided into three categories according to the different base materials:
(1) EVA (ethylene-vinyl acetate copolymer resin) base material hot melt adhesive, this hot melt adhesive can be divided into two types with filler and without filler. ,
(2) POL YAMIDE (polyamide) base material hot melt adhesive, this kind of hot melt adhesive has the characteristics of good heat resistance and fast curing, but the main disadvantage is that it is expensive.
(3) HMPU (polyurethane) base material hot melt adhesive, which is a kind of hot melt adhesive with the best performance, and is the guarantee of high-quality sheet edge sealing. It is expensive and requires special usage.
The viscosity of the edge sealing hot melt adhesive does not directly reflect the performance of the adhesive. In general, the higher the viscosity of the edge sealing hot melt adhesive, the better its initial tack strength, but the worse the coating performance. Low-viscosity hot melt adhesives have a smaller amount of glue and better wetting properties. Some hot melt adhesives with low viscosity and fast curing speed may also have high initial tack strength. For particleboards with poor quality, hot melt adhesives with higher viscosity should be used for edge sealing. This is because high viscosity hot melt adhesives have poor fluidity and are not as easy to enter the pores of the edge of particleboards as low viscosity hot melt adhesives. , so that the hot melt adhesive can be fully coated on the edge of the board.
The density of edge sealing hot melt adhesive is generally 0.95-1.6g/cm3, and its density depends on the amount of filler (the more filler, the higher the density). Since a certain area of gluing is required for the edge sealing of the sheet, the amount of gluing per unit length of the unfilled hot melt adhesive with low density is smaller than that of the filled hot melt adhesive. And because the unfilled hot melt adhesive has better bonding performance and achieves the same edge sealing effect, it is possible that the unfilled hot melt adhesive is used in a smaller amount than the filled hot melt adhesive. In order to reduce the amount of glue, the edge banding machine must have a good glue system.
The softening point is an indicator of the heat resistance of the edge-sealing hot melt adhesive. The higher the softening point, the less likely the edge-sealing hot-melt adhesive will melt. At the same time, softening point is also an important aspect to measure the temperature resistance of panel furniture. In Europe, there has been a set of testing methods for the heat resistance of panel edge sealing, and a standard for the heat resistance of panel furniture has also been proposed.
The use temperature of edge-sealing hot-melt adhesive refers to the temperature at which the gluing roller of the edge-sealing machine is glued. Only at this temperature, the hot-melt adhesive can achieve the best adhesive strength. There is a considerable error between the temperature displayed on some edge banding machines and the actual temperature, so the temperature of the machine should be checked regularly. If the temperature of the edge banding machine is too high, the glue will be carbonized and smoked; if it is too low, the adhesive strength will be reduced.
The opening time of the edge-sealing hot melt adhesive refers to the period of time from the beginning of the gluing of the edge-sealing machine to the time before the edge-sealing tape is pressed to the substrate. The opening time varies with the type of glue. The feeding speed of the edge banding machine is closely related to the opening time, both of which are very important in the selection and use of hot melt adhesives. The fast-feeding edge banding machine must choose a hot melt adhesive with a short open time, and vice versa, a hot melt adhesive with a long open time.
For semi-automatic or automatic hot melt adhesive machines, because the substrate and the edge banding tape are glued and pressed, the edge banding band must be cut off, trimmed and polished up and down and other mechanical processes soon. During these processes, the edge banding band To withstand mechanical cutting forces, hot melt adhesives are required to have a short opening time and a high initial tack strength. Especially for thicker edge banding materials (such as thick solid wood edge strips), due to the large cutting force, if the initial bond strength of the hot melt adhesive is not enough, cracks will occur between the board and the edge band.