Heat Resistant Poly(carborane-siloxane) Adhesives

Area of Science:

• Materials Science
• Polymer Chemistry
• Adhesion Science

Background:

• Organic adhesives are widely used but fail at high temperatures due to oxidation and degradation.
• Harsh environments, such as in aerospace, require adhesives with enhanced thermal stability and robust performance.
• Existing organic adhesives lack the necessary resilience for extreme temperature applications.

Purpose of the Study:

• To develop novel high-temperature adhesives with improved thermal stability and adhesion.
• To synthesize and characterize vinyl-functionalized poly(carborane-siloxane) (PCS) based adhesives.
• To investigate the effect of crosslinking density on the thermal and mechanical properties of PCS adhesives.

Main Methods:

• Synthesis of vinyl-functionalized PCS (PCS-x%) via a one-pot method.
• Crosslinking of PCS-x% using 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane to form c-PCS-x% adhesives.
• Evaluation of thermal stability (weight loss), adhesion strength at various temperatures, and post-aging performance.

Main Results:

• All synthesized c-PCS-x% adhesives exhibited good thermal stability with <10% weight loss.
• c-PCS-75% showed the lowest weight loss (3.6%), attributed to suppressed borane volatilization and increased cohesive energy.
• c-PCS-x% adhesives demonstrated superior adhesion strength compared to linear analogs up to 250 °C.
• c-PCS-25% maintained 5.68 MPa adhesion strength after aging at 200 °C/24 h and passed a 10-min ablation test with a 1 kg load.

Conclusions:

• Topology-controlled poly(carborane-siloxane) networks provide a novel molecular design for high-temperature adhesives.
• The developed adhesives exhibit excellent thermal stability and adhesion, overcoming limitations of conventional organic adhesives.
• These advanced materials are suitable for demanding applications in harsh environments, including aerospace.