# Effect of Accelerated Thermal Aging on the Dispersion Stability of Fine-Denier Silicone Emulsions for Carbon Fiber Precursor Processing

## TL;DR

This study shows that using a colloid mill to make silicone emulsions improves their stability during thermal aging, which is important for carbon fiber production.

## Contribution

The study demonstrates that high-shear colloid mill emulsification enhances thermal and dispersion stability of silicone emulsions for carbon fiber processing.

## Key findings

- Colloid mill emulsification produces smaller and more stable silicone droplets compared to mechanical dispersers.
- Thermal aging at 50–70 °C affects dispersion stability but not the chemical structure of the emulsions.
- Colloid mill emulsions maintain stable microstructure under elevated temperatures, making them suitable for PAN fiber processing.

## Abstract

What are the main findings?
Fine-denier silicone emulsions were prepared using disperser and colloid mill methods.Colloid mill emulsification produced smaller and more stable droplet sizes.Thermal aging at 50–70 °C mainly affected dispersion stability, not chemical structure.

Fine-denier silicone emulsions were prepared using disperser and colloid mill methods.

Colloid mill emulsification produced smaller and more stable droplet sizes.

Thermal aging at 50–70 °C mainly affected dispersion stability, not chemical structure.

What are the implications of the main findings?
Emulsification method strongly governs thermal stability of silicone emulsions.Stable dispersion at 3–5% concentration is suitable for PAN fiber processing.Colloid mill processing improves process stability in carbon fiber manufacturing.

Emulsification method strongly governs thermal stability of silicone emulsions.

Stable dispersion at 3–5% concentration is suitable for PAN fiber processing.

Colloid mill processing improves process stability in carbon fiber manufacturing.

Fine-denier silicone emulsions play an important role in the polyacrylonitrile (PAN) precursor treatment process by reducing surface tension and preventing fiber fusion during thermal stabilization and carbonization. These emulsions are typically prepared by dispersing polydimethylsiloxane (PDMS) polymers with various functional groups into water through different emulsification methods. In this study, two types of silicone emulsions—one prepared using a mechanical disperser and the other using a high-shear colloid mill—were manufactured on a pilot scale and systematically compared. Thermal aging was conducted at 50 °C and 70 °C for approximately one month, and changes in particle size, dispersion stability, and physicochemical properties were evaluated. The colloid-mill emulsification method produced smaller and more uniform silicone particles and exhibited superior thermal and dispersion stability relative to the mechanically dispersed emulsion. NMR relaxation, Turbiscan multiple light scattering, and viscosity measurements confirmed that the colloid-mill emulsion maintained a stable microstructure with minimal aggregation even under elevated-temperature storage. These results demonstrate that high-shear emulsification is an effective approach for producing fine-denier silicone emulsions with enhanced stability, making the colloid-mill method a more reliable and practical route for preparing silicone-based oiling agents used during PAN precursor processing in carbon fiber manufacturing.