Do TPE Pellets Require Surface-Modified Fillers?

Whether fillers in TPE pelletizing need pre-surface modification depends on the filler’s properties (activity and surface area), the performance requirements of the final TPE product (mechanical strength, appearance, processing precision), and the filling ratio. The following explains when modification is essential and when it can be skipped.

1. Core Principle

The main purpose of filler modification is to improve compatibility between inorganic fillers and the non-polar TPE matrix.

• Highly active or high surface area fillers tend to agglomerate and show poor dispersion due to high surface energy.

• Low-activity fillers at low loadings can rely on compatibilizers and lubricants in the formula instead of pre-treatment.

2. When Pre-Modification Is Necessary

Pre-treatment is recommended (usually via silane or titanate coupling agents) in the following cases:

(1) Filler characteristics:

For fillers like nano SiO₂, fumed silica, precipitated silica, fine calcium carbonate (>2000 mesh), and nano CaCO₃, pre-modification with KH-570 or NDZ-101 (0.5–2% of filler weight) helps prevent agglomeration and ensures even dispersion.

(2) High-performance applications:

Pre-modify when TPE products require:

• Superior mechanical properties (tensile, tear strength, elasticity);

• Smooth surface finish (no specks or roughness);

• High precision (thin-wall extrusion, precision injection molding).

Surface treatment improves interfacial bonding and reduces processing instability.

(3) High filler loading (≥20 phr):

When filler content is 20 phr or more, pre-modification becomes essential to prevent increased melt viscosity, high torque, and poor product toughness.

3. When Pre-Modification Is Not Necessary

You can skip pre-treatment when:

(1) Using low-activity fillers such as coarse calcium carbonate (<1250 mesh), talc (<500 mesh), or mica powder, which have low surface energy and weak agglomeration tendencies.

(2) Producing low-cost or general-purpose TPE where filler is added mainly for cost reduction or density control, not for performance enhancement.

(3) Low filler content (≤15 phr):

Compatibility can be maintained using PP-g-MAH or SEBS-g-MAH compatibilizers and lubricants, forming a bridge between filler and matrix while improving dispersion.

4. Practical Tips

• Use coupling agents as the first choice; combine with stearic acid (0.5–1%) for high-load systems to balance bonding and flow.

• If skipping pre-modification, pre-mix TPE with compatibilizer and lubricant before adding filler to prevent agglomeration.

• For special fillers (e.g., silica, nano powders), pre-treatment is still advised when high transparency or mechanical strength is required.

Summary

Surface modification of fillers in TPE compounding and pelletizing is not always mandatory—but for high-performance, high-loading, or fine particle systems, pre-treatment significantly enhances dispersion, stability, and product quality.

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