# Evaluation of Thermal Stability and Thermal Transitions of Hydroxyl-Terminated Polysiloxane/Montmorillonite Nanocomposites

## TL;DR

This study examines how adding modified clay to a silicone material affects its thermal properties, showing improved heat resistance and potential for high-temperature applications.

## Contribution

The novel contribution is demonstrating how varying clay modification levels influence thermal stability and dispersion in polysiloxane nanocomposites.

## Key findings

- Cloisite 20A, with higher organic modification, showed better dispersion and greater thermal stability in nanocomposites.
- Nanocomposites exhibited increased onset and maximum degradation temperatures compared to pure silicone.
- Cold crystallization temperature decreased with reinforcement, while glass transition and melting temperatures remained stable.

## Abstract

Condensation-type polysiloxane composites with montmorillonite (MMT) of different organic modifications were prepared in this study. X-ray diffraction (XRD) characterization revealed that the higher degree of organic modification in Cloisite 20A, compared to that in Cloisite 30B, resulted in a larger interlayer spacing between the clay platelets. This facilitates the insertion of elastomer chains between the layers, enabling easier exfoliation and dispersion in the elastomeric matrix. Differential scanning calorimetry (DSC) showed that the reinforcing agents used reduced the cold crystallization temperature of the condensation-type polysiloxane while leaving the glass transition and melting temperatures nearly unaffected. Additionally, the nanocomposites exhibited slightly lower crystallization and melting enthalpies compared to pure silicone. Thermogravimetric analysis (TGA) showed that incorporating the two organically modified clays (Cloisite 20A and Cloisite 30B) into the condensation-type polysiloxane significantly improved the thermal stability of the resulting nanocomposites. This improvement was reflected in the significant increase in the onset and maximum degradation rate temperatures across all examined reinforcement ratios. It was observed that a higher degree of organic modification in MMT (Cloisite 20A) resulted in a more efficient dispersion in the PDMS matrix and enhanced the thermal stability of the composites. These PDMS nanocomposites could be suitable as protective coatings for devices exposed to elevated temperatures.