Different sheets should choose different materials for plastic coating. For example, materials for PP coating cannot be coated with ABS, and materials for ABS coating cannot be coated with PA, etc. The plastic coating TPE on the market can be divided into the following categories: PP coating, ABS coating, PETG coating, PC coating, PA coating, etc.
Thickness of TPE coating layer:
In most plastic coating rubber and plastic products, the wall thickness range of 1.5-3.0mm will ensure a good bonding effect. If the TPE glue position is too thin, the injection molding process is difficult, the bonding strength is low, and the touch is weak. If the TPE glue position is too thick, on the one hand, the cost is high, and on the other hand, it is easy to cause shrinkage, bubbles and other defects.
The thickness of the TPE glue position should be as uniform as possible to achieve the molding cycle. The connection between different wall thicknesses should be slow to reduce the problems caused by liquid flow, such as air marks and bubbles.
In large corners, an inclination (radius of 0.5mm) should be used to reduce local stress. Deep closed brake air chambers or curved parts that cannot be vented should be avoided. If necessary, sufficient venting grooves (0.015-0.025mm) can be added at the end of the TPE glue position. Insufficient venting may cause safety hazards such as trapped air, burning glue, and insufficient adhesion.
Adding snap-on structures or making some appropriately designed deep convex and concave parts on the sheet is very helpful in improving the bonding effect of TPE.
Treatment of mold surface:
The mold should be polished to obtain a smooth or clear surface.
In order to achieve the dull appearance of thermosetting rubber surface, a rough mold surface is required. Generally speaking, the rough surface of the mold core after discharge machining (EDM) will produce a better product appearance and make demolding easier. Grinding methods such as steam blasting, sandblasting or shot blasting, as well as chemical etching, can also be used to produce surfaces with different glossiness and appearance.
To facilitate demolding, a demolding coating can be applied to the core or mold, for example, a layer of PTFE (polytetrafluoroethylene) pre-impregnated nickel can be applied after it has been sandblasted or processed by EDM.
The sheet should be free of mold release agents. The surface of the sheet should be cleaned to minimize contact with dust.
The production temperature of TPE plastic pellets should be based on the measured melting temperature of the plastic pellets, rather than the surface temperature of the plastic machine.
If TPE is required to be coated on an alloy product, an effective adhesive can be used as an auxiliary.
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