--- title: Understanding ASTM E595 and Low-Outgassing Epoxies description: Learn how ASTM E595 tests for TML, CVCM, and WVR. Discover why low-outgassing epoxies matter for optics, electronics, and spacecraft contamination control. image: https://blog.gracoroberts.com/hubfs/Space-Low-Outgassing.png --- [![GracoRoberts](https://www.gracoroberts.com/resources/SilMid/images/WebPImages/GracoRoberts-Logo-White.webp)](https://www.gracoroberts.com/) Search [Sign In / Register Account And Quick Order](https://www.gracoroberts.com/account/) New Customer? 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In a vacuum, engineers must also control how materials behave when exposed to extreme pressure drops. That behavior centers on outgassing—the release of volatile organic compounds from a material when subjected to vacuum conditions. If these released gases condense on nearby surfaces, they introduce severe contamination risks around sensitive optics, solar arrays, sensors, and microelectronics. Testing materials to ASTM E595 provides a standardized, repeatable benchmark to evaluate outgassing behavior and select compliant adhesives for space-flight and vacuum-sensitive applications. ### What Does ASTM E595 Measure? ASTM E595 evaluates material outgassing under strict thermal and vacuum conditions—typically exposing specimens to  125 °C at 10-5 Torr for 24 hours. When reviewing test reports, three key values define material compliance: - **Total Mass Loss (TML):** The total percentage of weight a specimen loses during testing. To meet NASA low-outgassing standards, TML must not exceed 1.00%. - **Collected Volatile Condensable Material (CVCM):** The percentage of released volatiles that condense onto a nearby collector plate. NASA standards require CVCM to remain at or below 0.10% to prevent optical fogging. - **Water Vapor Regained (WVR):** The amount of water vapor a sample reabsorbs after returning to ambient humidity. This helps engineers differentiate between harmless absorbed moisture and true organic outgassing. Together, these metrics give engineering teams the objective data required to qualify materials for flight hardware. Resin Formulators maintains comprehensive ASTM E595 test data—including TML, CVCM, and WVR values—across a wide range of specialty epoxy systems. ### Why Low Outgassing Matters in Vacuum Environments ![Satellite orbiting above Earth at night](https://blog.gracoroberts.com/hs-fs/hubfs/Satellite%20orbiting%20above%20Earth%20at%20night.png?width=250&height=166&name=Satellite%20orbiting%20above%20Earth%20at%20night.png)In the vacuum of space or high-vacuum processing chambers, volatile molecules released from an adhesive migrate freely away from the bond line. When those unreacted monomers, plasticizers, or solvents deposit onto colder surrounding structures, the impact can be catastrophic. A microscopic film on an optical lens, image sensor, or satellite solar panel can degrade signal transmission, disrupt thermal control surfaces, or cause complete instrument failure. Contamination control makes outgassing performance an essential selection criterion rather than a secondary consideration. ### Selecting the Right Low-Outgassing Epoxy Passing ASTM E595 outgassing limits is a critical hurdle, but it isn't the only property that determines whether an adhesive is right for your assembly. An epoxy engineered for electronics encapsulation faces completely different operational requirements than a structural joint compound or a ultra-lightweight syntactic foam. Once low-outgassing compliance is established, engineers must evaluate: - Viscosity, pot life, and dispensing profiles - Cure schedules (room-temperature vs. elevated heat post-cure) - Continuous operating temperature ranges - Mechanical shear and peel strength - Thermal conductivity or electrical insulation - Substrate CTE matching and outgassing compatibility Because no single resin fits every application, Resin Formulators offers ASTM E595-tested formulations across multiple material categories—including structural pastes, potting and encapsulating compounds, electrically conductive epoxies, and syntactics. ### Finding the Right Material for Spacecraft and Vacuum Systems ASTM E595 test data provides aerospace and optical engineers with a clear, objective baseline for evaluating material safety in vacuum environments. Resin Formulators supplies compliant, low-outgassing epoxy systems engineered across diverse application types, supported by full technical datasheets to streamline your qualification process. #### **Ready to evaluate compliant materials for your program?** **[Explore NASA ASTM E595 Low-Outgassing Epoxy Solutions](https://www.gracoroberts.com/brands/resin-formulators/industry-and-application-specific-solutions/low-outgassing-epoxies/)** to review available material systems and test data, or contact our technical engineering team for guidance on identifying the right formulation for your mission requirements. ### Frequently Asked Questions About Low-Outgassing Epoxy Systems #### What applications are low-outgassing epoxy systems used for? Low-outgassing epoxy systems are intended for aerospace, satellite, vacuum, optics, sensors, and high-reliability electronics applications where contamination control matters. #### Which product family should I review first? Start with the product family that best matches the use case. Potting Materials support encapsulation and fill applications, Structural Pastes support bonding and repair, Syntactics support lightweight structural applications, and Electrically Conductive Adhesives support electrical assembly needs. #### When should I request a consultation? [Request a consultation](https://www.gracoroberts.com/brands/resin-formulators/technical-support/consultation-request/) when the application needs validation, the material fit is unclear, or the project calls for help matching the right Resin Formulators product to the use case. 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It provides high electrical conductivity and low viscosity for wicking into very small spaces, and is suitable for electrical circuitry, EMI shielding, and the grounding of composites." }, "name" : "What is RF 2969?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "A silver-filled epoxy is an electrically conductive adhesive used to complete electrical connections, provide EMI shielding, and ground components, including composite structures. The silver filler gives the cured epoxy high electrical conductivity while retaining the bonding and protective properties of an epoxy." }, "name" : "What is a silver-filled epoxy used for?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "Yes. RF 2969 was developed in multiple versions, including a heat-cure and a room-temperature curing formula, so the same conductive epoxy system can be matched to different production processes and component requirements." }, "name" : "Does RF 2969 come in different cure versions?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "RF 2969 has been a successful aerospace solution for over 20 years and is qualified for use on military aircraft, commercial satellite, rocket, and automotive programs." }, "name" : "Is RF 2969 qualified for aerospace and defense programs?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "Resin Formulators works directly with customers to understand both the performance requirements, such as conductivity and cure, and the practical constraints of the application. 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