What are the effects of TPE material viscosity?

1. Effect of temperature

Different TPE materials have different sensitivities to temperature. For example, when measuring the melt flow index, you can test at several temperatures. If the melt flow index varies greatly, it indicates that the viscosity of the TPE material is highly sensitive to temperature, making it suitable for extrusion materials.

2. Effect of low molecular weight additives

Low molecular weight additives can reduce the interaction force between macromolecular chains, thereby reducing viscosity and making it easier to fill the mold. This is easy to explain: small molecule additives can be understood as added mineral oil.

3. Effect of molecular weight

The same TPE material can have different molecules and molecular weight distributions. The larger the molecular weight, the stronger the intermolecular force, and the higher the viscosity. When the molecular weight is the same, a narrower molecular weight distribution often results in lower viscosity. For example, TPE base material YH503T has higher viscosity than YH502.

4. Effect of shear rate

Effectively increasing the shear rate of plastic can reduce the melt viscosity, but different plastics are affected differently by shear rate. When measuring the melt flow index, you can test at several pressures. If the melt flow index varies greatly, it indicates that the material viscosity is highly sensitive to shear, making it suitable for injection molding materials.

5. Effect of pressure

Although high injection pressure can increase injection speed and achieve high shear during the injection process, which seems beneficial for reducing viscosity, from a physical perspective, increasing pressure actually increases the melt viscosity. The reason is simple: there is already excess space between macromolecular chains due to intermolecular forces. Increased pressure reduces the distance between molecules, making the movement of molecular chains more difficult, thus increasing the overall flow viscosity.