We can mix the masterbatch and chips in the melt injector and observe the mixing of the two polymers. Use the knowledge of polymer blending to analyze the plasticization and dispersion process of the two components in the above blending process. The masterbatch and chips are fully compatible, so the melt mixing between them only requires dispensing and mixing. For this mixing to be effective, stress must be transferred from one material to another. When the viscosity of the materials is similar, stress transfer is easiest, while when the viscosity of the two materials differs too much and the viscosity is low (in the system composed of masterbatch, especially black masterbatch and slices, the melt viscosity of slices is generally lower than that of masterbatch. When the component content is large, the low viscosity component may "swamp" the high viscosity component, making stress transfer in the melt quite difficult. Even if the energy is increased (increasing the rotation speed or increasing the temperature, etc.), it is difficult to melt the high viscosity polymer, which will lead to the presence of unplasticized particles in the melt. The temperature is too high so that the polymer is overheated and these particles cannot be eliminated. In summary, it is necessary to make the masterbatch and slices have similar viscosities in the plasticizing environment of the melt ejector to obtain a well-plasticized and dispersed melt. On the other hand, the melt dispersion of masterbatches and slices can be improved by increasing the plasticizing capacity of the equipment, such as reducing the depth of the groove to achieve "thin layer" plasticization, which can achieve plasticization of masterbatches and slices. The melt viscosity is very different when slicing. Melt evenly.
Precautions for using masterbatches Items:
1. When using masterbatch for injection molding, the injection molding machine used is preferably a screw type, otherwise uneven coloring will occur due to poor mixing;
2. Increasing the extrusion back pressure and improving the mixing effect of the screw can make the masterbatch diffuse more evenly.
3. There are many solemn and elegant high-end colors, and some such as imitation porcelain and flash colors, which must be very bright in the mold to show their effects.
4. During operation, if the masterbatch is found to stick to the hopper wall, this is caused by static electricity. The hopper can be grounded to eliminate static electricity and will not be caused by process problems.
5. Masterbatch will absorb moisture after a period of time, especially PET/ABS/PA/PC, etc., and it should be dried according to the same process requirements as the color particles to meet the water absorption requirements.
Due to the nature of PET materials, environmentally friendly materials have poor weather resistance; during processing, if the masterbatch (titanium dioxide) stays in the feed section of the high-speed mixer or extruder for too long, even if a high-efficiency antioxidant is added, part of the surface treatment layer will be damaged due to severe friction. Plastic products. , light stabilizer, the actual anti-aging performance of the product will also be compromised; since most antioxidant light stabilizers are powder crystals, it is not easy to add them to PET pellets. It is recommended to add some tougheners or tackifiers separately.
For crystalline polymers such as polyester, the flow changes from solid to flow, and the process only changes from crystallization to melting. Therefore, when the plastic changes from a state with a lower apparent density to a melt, the volume suddenly decreases, so the corresponding compression ratio must be set in the melt plasticization section. If the compression ratio is too small, the air in the polyester chips is difficult to discharge, which will cause oxidation, yellowing, and gas.
