NASA TB 26-01: Pioneering Safer Adhesives for Spaceflight Polymeric Bonding

In the high-stakes world of aerospace engineering, bonding transparent thermoplastics like polycarbonate and acrylic is crucial for spaceflight hardware, from windows to experimental systems. NASA’s Technical Bulletin (TB) 26-01, titled “Evaluation of Adhesive and Solvent Alternatives for Polymeric Bonding Applications”, delivers a comprehensive assessment of replacements for dichloromethane (DCM), a traditional solvent facing EPA Toxic Substances Control Act (TSCA) restrictions.[1][2]

Released by the NASA Engineering and Safety Center (NESC), this February 2026 report addresses a pressing challenge: solvent welding with DCM has been the gold standard for its simplicity and strength in bonding transparent polymers. However, its toxicity profile demands safer alternatives that maintain mission-critical performance. The NESC evaluated 16 adhesives across chemical families and four solvents, using standardized block shear testing per ASTM D4501 to measure bond strength on polycarbonate and acrylic substrates.[1]

The Problem with DCM and Why Alternatives Matter

Solvent welding works by partially dissolving polymer surfaces, creating a fused bond upon evaporation. DCM excels here, especially for high-molecular-weight thermoplastics used in aerospace. But regulatory pressures, including potential EPA bans, threaten supply chains and processes for spaceflight and ground systems.[1][2] TB 26-01’s goal? Identify drop-in replacements with comparable shear strength, cohesive failure modes (where the adhesive itself breaks, not the bond), and manufacturability.[1]

Testing focused on shear strength in ksi (thousands of pounds per square inch), visualized in box plots showing performance distributions. Baseline DCM set the bar high, particularly on acrylic, but alternatives closed the gap.[1]

Standout Adhesive Performers

Two-part acrylics topped the list as the most promising, delivering shear strengths matching or exceeding DCM with cohesive or substrate failures—indicating robust adhesion.[1] These adhesives balance high strength, toughness, and rapid cure, though their short pot life (usable time after mixing) requires process tweaks for large assemblies.[1]

Cyanoacrylates (super glues) shone for speed and strength, often surpassing DCM in shear tests.[1] Their single-component, fast-curing nature suits quick bonds with minimal gaps, but humidity sensitivity and short working time limit broader use.[1]

Urethanes offered moderate strength with cohesive failures on one substrate, plus longer pot life and flexibility—ideal for tolerant processes.[1] Epoxies provided easy handling and long pot life but lagged in strength, showing adhesive failures.[1]

UV-curable adhesives intrigued with unlimited pot life and fast cure for transparent materials, but light penetration issues and fixture adhesion hampered results. The report urges process refinements.[1]

Solvent Alternatives Fall Short—For Now

Four solvents were screened using Hansen solubility parameters (from Hansen’s handbook) and toxicity data.[1] DCM remained king, especially on acrylic. Alternatives, including a promising cyclic ketone, showed fusion but weaker mechanics, particularly for tougher polycarbonates. Non-halogenated options need more modeling and screening.[1]

A box plot in Figure 2 highlights trends: on acrylic, cyanoacrylates and two-part acrylics cluster near DCM’s peak (around 4-6 ksi); polycarbonates show tighter spreads, with urethanes competitive.[1]

Recommendations for Engineers and Manufacturers

TB 26-01 provides actionable roadmap:

1. Prioritize two-part acrylics for demanding transparent thermoplastic bonds.[1]
2. Deploy cyanoacrylates for speed-critical tasks.[1]
3. Explore urethanes for extended working times.[1]
4. Optimize UV processes for future viability.[1]
5. Advance solvent modeling with solubility parameters.[1]
6. Standardize block shear tests for polymers.[1]
7. Control environment (humidity, prep) for repeatability.[1]

These steps ensure compliance while preserving performance. Surface prep, like cleaning, and controls amplify results across candidates.[1]

Broader Implications for Aerospace and Beyond

Beyond NASA, TB 26-01 resonates in aviation, automotive, and optics industries reliant on polymer bonds. As TSCA evolves, adopting acrylics or cyanoacrylates could preempt disruptions. The report’s data-driven approach—leveraging ASTM standards and solubility theory—sets a benchmark for adhesive qualification.[1]

For spaceflight, where failure isn’t optional, cohesive failures signal reliability. Yet gaps remain: UV adhesives need deeper trials, and high-weight polymers challenge solvents. NESC calls for ongoing R&D, aligning with NASA’s 2026 aeronautics pushes.[1][4]

Download the full PDF from NASA’s site for figures, raw data, and coupon designs (Figure 1).[1][2] This bulletin exemplifies NASA’s proactive engineering: turning regulatory hurdles into innovation drivers. As missions to the Moon and beyond ramp up, safer bonds will keep transparent components crystal clear and mission-ready.[1]

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Original source: NASA – Breaking News – TB 26-01 Evaluation of Adhesive and Solvent Alternatives for Polymeric Bonding Applications