When extruding the composite film , the expansion coefficients of the extruded adhesive layer, ink layer and printing substrate are inconsistent. During the cooling process, the stress and dislocation between the layers are caused, which is easy to cause the compound to be weak. So, what caused these problems, and how to solve them?
Causes and solutions of poor adhesion fastness (peel strength) in extrusion compounding
1. The viscoelasticity of the extruded melt is insufficient. The melt index of the resin is too small. An extruded resin with appropriate density and melt index should be selected.
2. The thermal oxidation of the melt is insufficient, the polarity is low, and the adhesion is not good. The temperature of the extruder is low, the speed of the production line is too fast, the density of the resin is too high, and the melt index is too low, which can reduce the oxidizing ability of the melt. Therefore, it is necessary to appropriately increase the temperature of the extruded body and reduce the traction winding speed. Use resins with high melt index and low density.
3. Caused by substrate factors. The surface treatment of the substrate is insufficient, the surface tension is low, and the additives in the substrate migrate to the surface at high temperature, forming a weak layer. For paper, moisture absorption also causes a decrease in adhesion; for aluminum foil, attention should be paid to the surface cleanliness, the wettability of the surface of the substrate should be tested in advance, and the material should be kept well.
4. The adaptability of the ink is not good. Mainly in the following aspects: the ink does not match with the AC agent, a coating agent, an amount of less than normal AC, AC agent is absorbed by the ink out of the adhesion between the small part of the substrate and the ink, the ink of low softening point resin, ink additives with Precipitation at high temperature. Therefore, it is very important to choose the right ink to suit the extrusion process.
5, AC factors agent. The wettability of the AC agent to the substrate is not good, the AC agent expires and deteriorates, the AC agent is insufficiently dried, the AC agent is not suitable for the substrate, the AC agent coating amount is not enough, and the AC agent thermal reaction is not enough. It is possible to solve the bad adhesion caused by AC agent by taking corresponding measures to the above factors .
6. The temperature is low during compound pressurization. The temperature of the resin should be increased, and the fluidity of the resin melt should be increased. The extruded melt curtain should be slightly biased towards the rubber pressure roller. It should not touch the cooling roller first to prevent the melt curtain from being cooled before it is attached to the substrate. Wood preheating.
7. Insufficient compound pressure. Can increase the pressure of the pressure roller, generally lower plastic film, higher paper pressure. The pressure of the pressure roller should be evenly applied.
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