Tips for Adjusting Melt Flow of TPE During Pelletizing And Product Manufacturing

Optimizing the melt flow rate (MFR) of thermoplastic elastomer (TPE) is crucial for ensuring excellent processability, stable production, and high-quality final products. Below are practical tips on how to adjust and control the melt flow of TPE materials during pelletizing and injection molding.

1. Adjust the oil content in the base resin

• Proper oil filling:

• Adding oil significantly improves the flowability of TPE compounds. Depending on the properties of the base resin (such as SEBS or SBS grades) and specific performance requirements, adjust the oil content accordingly.

• Generally, a higher oil content leads to better melt flow, but excessive oil may cause small molecules (like white oil) to migrate or bleed out.

• Using high-viscosity white oil helps balance flowability and mechanical properties.

2. Optimize the formulation

• Choose plastic phases wisely:

In TPE formulations, selecting PP or PS with a higher melt flow index (MFI) improves melt flow. Using low MFI resins will reduce flowability.

•  Adjust filler type and loading:

Different fillers (such as calcium carbonate, talc, or silica) impact melt flow differently. Increasing filler content usually decreases flowability. Fine-tuning the type and amount of filler helps balance mechanical strength and processability.

• Use lubricants effectively:

Adding internal or external lubricants (like stearic acid or silicone) enhances melt flow. However, excessive use may lead to surface blooming or reduced mechanical performance.

3. Modify processing conditions

• Adjust pelletizing temperature and screw shear rate:

• For linear SEBS, melt flow mainly depends on the screw shear rate: higher shear improves flowability.

• For star-shaped SEBS, melt flow is influenced more by temperature: higher temperature increases flowability.

• Be cautious to prevent thermal degradation or uneven mixing.

• Control temperature precisely during production:

• Both excessively high and low temperatures can cause unstable melt flow. Using intelligent temperature control systems helps monitor and maintain consistent temperatures in real time.

• Maintain stable injection speed:

• In injection molding, fluctuations in injection speed can lead to inconsistent melt flow and defects. Keeping a stable speed ensures uniform mold filling. Slightly increasing the speed may also help fill complex mold cavities.

• Set appropriate holding (packing) time:

• Proper holding time improves part density and appearance, ensuring complete mold filling and minimizing shrinkage or sink marks due to flow variations.

By optimizing oil content, formulation, fillers, and processing parameters, TPE manufacturers and molders can achieve better melt flow control, enhance production stability, and improve product quality.

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