Evaluation of Thermal Characteristics of Rubber O-Rings

Importance of the Topic

Rubber O rings play a critical role in preventing leaks in piping and vessel systems used for transportation and storage of gases and liquids. Selecting the appropriate material based on temperature range, pressure resistance and chemical stability is essential for ensuring long term safety and performance in demanding environments.

Study Objectives and Overview

This study presents a comprehensive thermal evaluation of four common rubber O ring materials including ethylene propylene rubber EPDM, nitrile rubber NBR, fluororubber FKM and silicone rubber. The aim is to characterize low temperature behavior heat resistance filler content and thermal expansion using differential scanning calorimetry DSC thermogravimetric analysis combined with differential thermal analysis TG DTA and thermomechanical analysis TMA.

Methodology and Instrumentation

• DSC measurements were performed on a DSC 60 Plus with built in nitrogen cooled bath down to -140 °C using aluminum crimp cells to determine glass transition and crystallization temperatures.
• TG DTA experiments employed a DTG 60 instrument under nitrogen and air atmospheres from room temperature to 650 °C to assess decomposition onset weight loss and residual ash content.
• TMA tests utilized a TMA 60 in expansion mode under a small compressive load of 10 mN from -30 °C to 50 °C to measure coefficients of linear thermal expansion.

Main Results and Discussion

• DSC revealed glass transition temperatures of -34.3 °C for EPDM -35.7 °C for NBR and -23.8 °C for FKM. Silicone rubber exhibited a crystallization event at -61.5 °C indicating good low temperature flexibility.
• TG DTA showed 1 percent weight loss onset temperatures ranking FKM highest followed by EPDM NBR and silicone. Under nitrogen the combined weight loss indicated organic component content highest in FKM. Air testing highlighted carbon black content most prominent in NBR.
• TMA results in the 0 to 50 °C range produced linear expansion coefficients in the order silicone rubber > FKM > NBR > EPDM demonstrating the lowest thermal expansion in EPDM.

Benefits and Practical Applications

The multi instrument approach provides a reliable basis for selecting O ring materials by correlating cold flexibility heat endurance filler composition and dimensional stability. This ensures optimized seal performance in refrigeration cryogenic chemical and dynamic applications.

Future Trends and Potential Applications

Advances in miniature calorimeters high throughput TG DTA and integrated TMA modules will enable rapid screening of novel elastomer blends and nanocomposites. Coupling thermal analysis data with computational modeling can predict long term aging behavior and seal life in diverse service conditions.

Conclusion

A systematic thermal characterization using DSC TG DTA and TMA highlighted distinct performance profiles for EPDM NBR FKM and silicone rubber O ring materials. These insights facilitate informed material selection to enhance safety reliability and longevity of sealing components.

Reference

• Shimadzu Corporation Application Note Evaluation of Thermal Characteristics of Rubber O Rings 2023