TPE packaging, as the name suggests, is to wrap TPE soft rubber material on other materials. Usually, the processing method used is one-time molding using a two-color injection molding machine, or secondary molding using a common injection molding machine and rubber coating mold. So, what conditions will affect the viscosity of TPE materials?
TPE materials viscosity is influenced by the following factors:
Effectively increasing the shear rate of the plastic can reduce the viscosity of the plastic melt, but different plastics are also affected by the shear rate. When measuring the melt index, multiple pressures can be measured. If the melt index is very different, it indicates that the material viscosity is sensitive to shear height, which is suitable for injection molding materials.
Although high injection pressure can increase injection speed and obtain greater shear effect during the injection process, which seems to be favorable for reducing viscosity, from the physical meaning of pressure, pressurization will increase the melt viscosity. The reason is simple. The large molecular chains themselves maintain the rock distance between the chains, which is caused by intermolecular forces. The increase in pressure means a decrease in molecular distance. Therefore, the misalignment between the molecular chains becomes more difficult and the overall flow viscosity increases.
The same material can have different molecules and molecular weight distributions. The larger the molecular weight, the stronger the intermolecular force and the greater the reaction viscosity. When the molecular weight is the same, the viscosity of the narrow molecular weight distribution is usually smaller.
Different materials have different sensitivity to temperature. For example, when measuring the melt index, multiple temperatures can be measured. If the melt index varies greatly, it indicates that the viscosity of the material is highly sensitive to temperature and is suitable for extrusion materials.
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