Meet NASA Low Outgassing Standards With Adhesives for Aerospace and Optical Systems

Key Takeaways

• Low outgassing adhesives are essential in aerospace and optical applications to prevent contamination and ensure functionality.
• Nasa's ASTM E595 standard sets strict limits for Total Mass Loss (TML) and Collected Volatile Condensable Materials (CVCM).
• Proper handling, mixing, and curing of adhesives are crucial for achieving low outgassing performance.
• Specific adhesives like Master Bond's EP30-2 are designed to meet these stringent requirements.
• Understanding the outgassing process can help manufacturers enhance product reliability in critical applications.

In the aerospace and optical systems sectors, the reliability of components is of utmost importance. One significant concern that can jeopardize performance is outgassing, which refers to the release of volatile substances from cured adhesives over time. These substances can contaminate sensitive components, leading to failures and diminished functionality. To combat this issue, NASA has established stringent low outgassing standards that many manufacturers aim to meet.

Outgassing can occur when residual solvents, unreacted monomers, or other chemical species escape from an adhesive. This phenomenon is particularly concerning in environments where contamination could severely impact performance, such as in space applications or high-vacuum scientific equipment. To quantify outgassing, the industry relies on the ASTM E595 test, developed by NASA. This test exposes a cured adhesive sample to high vacuum and elevated temperatures, measuring both Total Mass Loss (TML) and Collected Volatile Condensable Materials (CVCM). To comply with NASA's low outgassing requirements, materials must exhibit less than 1% TML and less than 0.1% CVCM.

Applications requiring low outgassing adhesives include optical assemblies, such as cameras and telescopes, where clarity is essential. Fogging caused by outgassing can obscure optics, rendering them ineffective. Similarly, semiconductor manufacturing tools and aerospace electronics demand materials that minimize outgassing to ensure long-term reliability and performance.

One notable adhesive that meets these stringent requirements is Master Bond's EP30-2. This versatile system is designed for various applications across aerospace, electronics, and optical industries, particularly where optical clarity and low outgassing are critical. However, achieving the specified outgassing performance requires careful attention to the adhesive's storage, mixing, and curing processes.

For two-part adhesive systems, it is vital to use the correct mix ratio and to mix thoroughly to ensure a complete reaction. Following recommended cure schedules is also essential; applying heat during curing—at temperatures between 150°F and 200°F—can significantly enhance cross-linking and reduce outgassing. For UV-curable adhesives, ensuring complete curing involves using the correct lamp wavelength, adequate intensity, and appropriate exposure time, avoiding shadowed areas that could inhibit the curing process.

If contamination appears on optical surfaces or if outgassing test results exceed expectations, it may indicate an incomplete cure. The first step in troubleshooting is to verify that the adhesive has reached its specified Shore hardness. If necessary, extending the heat cure can improve cross-linking and further reduce outgassing.

Master Bond offers a range of adhesives that meet NASA's low outgassing standards, including EP30-2 and EP21TCHT-1, which have been successfully used in ultra-high vacuum environments. For applications requiring UV curing, specialty formulations such as UV16 are available, as well as dual-cure systems like UV22DC80-10F, which initiate curing with UV light and complete the process with heat.

In conclusion, low outgassing adhesives play a vital role in ensuring the reliability and performance of aerospace and optical systems. By adhering to NASA's stringent standards and employing proper handling techniques, manufacturers can mitigate the risks associated with outgassing and deliver high-quality products that meet the demands of critical applications.

FAQs

• What is outgassing?
  Outgassing is the release of volatile substances from cured adhesives over time, which can contaminate nearby surfaces.
• Why is low outgassing important in aerospace applications?
  Low outgassing is crucial in aerospace applications to prevent contamination of sensitive components, which can lead to failures.
• How is outgassing measured?
  Outgassing is measured using the ASTM E595 test, which evaluates Total Mass Loss (TML) and Collected Volatile Condensable Materials (CVCM).
• What are some adhesives that meet NASA's low outgassing standards?
  Examples include Master Bond's EP30-2 and EP21TCHT-1, which are designed for demanding vacuum applications.
• How can manufacturers ensure low outgassing performance?
  Manufacturers can ensure low outgassing performance by following proper mixing and curing procedures, as well as selecting the right adhesive formulations.