[Chinese Packaging News] When extruding and compounding, the coefficient of expansion of the extruded adhesive layer, ink layer, and printing substrate is inconsistent. During the cooling process, the stress and misalignment between the layers are caused, and the composite is liable to be weak. Then, what causes these problems and how can they be solved?
Reasons and Solutions for Bad Adhesion (Peel Strength) in Extrusion Compounding
1, the lack of viscoelasticity of the extruded melt. The melt index of the resin is too small and an appropriate density and melt index of the extruded resin should be selected.
2. Insufficient thermal oxidation of the melt, low polarity, poor adhesion. The temperature of the extruder is too 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 to reduce the oxidizing ability of the melt. Therefore, the temperature of the extruded body must be appropriately increased to reduce the traction winding speed. Use a resin with a high melt index and a low density.
3, caused by the substrate factor. The surface treatment of the substrate is insufficient, the surface tension is low, and the additives in the substrate migrate to the surface at a high temperature to form a weak layer. For paper, moisture absorption also causes a decrease in adhesion; for aluminum foils, attention should be paid to the surface cleanliness, and the wettability of the substrate surface should be tested in advance in production, and care should be taken in the storage of the materials.
4, the ink's adaptability is not good. There are mainly the following aspects: ink and AC agent do not match, AC coating agent is less, AC agent is absorbed by the ink part, the adhesion between the substrate and the ink is small, the ink resin softening point is low, the ink additive High temperature precipitation. Therefore, it is very important to choose the right ink for the extrusion process.
5, AC agent influencing factors. The AC agent has poor wettability to the substrate, the AC agent expires, the AC agent is insufficiently dried, the AC agent is not suitable for the substrate, the amount of the AC agent is insufficient, and the thermalization reaction of the AC agent is insufficient. It is possible to solve the adhesion failure caused by the AC agent by taking appropriate measures against the above factors.
6, when the composite pressure is low. The temperature of the resin should be increased to increase the fluidity of the resin melt. The extruded melt curtain should be slightly biased toward the rubber pressure roller, and it must not first hit the cooling roller to prevent the melt curtain from being cooled before being attached to the substrate. Preheat the material.
7, composite pressure is insufficient. The pressure of the pressure roller can be increased, generally the plastic film is lower, and the paper pressure is higher. Pressure roller pressure should be applied evenly.