A curtain wall asks its sealants to do two very different jobs: hold the glass structurally to the frame for decades, and keep rain and air out of the building envelope. Choosing one product for both roles is the most common specification mistake we see. This guide walks through the selection logic our technical team uses with distributors and facade contractors.

1. Separate the Two Roles: Structural vs Weather Sealing

Structural glazing sealants carry permanent mechanical loads. They bond glass panels to aluminium frames and must maintain adhesion and cohesive strength under wind load, thermal movement and long-term dead load. Weather sealants, by contrast, fill movable and stationary joints to block water and air; their priority is movement capability and weathering resistance, not load bearing.

Never specify a weather sealant for structural bonding. The reverse also applies: a high-modulus structural adhesive is unnecessarily stiff for a perimeter weather joint and can transfer stress the joint was never designed to take.

2. Ask for Recognised Standards, Not Just a Data Sheet

For structural glazing, request type-test evidence against a recognised standard:

  • GB 16776-2005 — the Chinese structural silicone sealant standard, widely referenced in projects across Asia, the Middle East and Africa.
  • ASTM C1184 — the North American standard for structural silicone sealants.
  • EN 15434 — the European product standard for structural glazing sealants.

For weather sealing, GB/T 14683 and ISO 11600 classifications (such as 25LM or 35HM) tell you the movement capability and modulus class at a glance. A manufacturer that can hand you third-party type-test reports for each standard has already done most of your risk assessment for you.

3. Read the TDS Like an Engineer

A technical data sheet is only useful if you know which numbers matter. For curtain wall work, check these five:

  • Sag (slump) — low sag keeps the bead in place on vertical joints. Look for ≤ 3 mm.
  • Tack-free time — affects site scheduling and dust pickup. Values of 0.1–3 h are typical.
  • Elastic recovery — higher recovery means the joint returns to shape after movement. Look for ≥ 80%.
  • Tensile modulus — reported at 23°C and −20°C. Confirm it matches the modulus class you specified.
  • Adhesion after conditioning — immersion, cold-heat cycling and UV exposure results should all report cohesive, failure-free performance.

As a concrete example, DUDI 9000, our high-performance curtain wall structural sealant, is type-tested to GB 16776-2005 as a 1MG grade: density 1.36 g/cm³, sag 0 mm, tack-free 0.1 h, elastic recovery 95% and tensile modulus 1.13 MPa at 23°C, with no adhesion failure under immersion, thermal cycling or UV exposure. The full third-party report is downloadable on our Quality Reports page.

4. Check the Substrates, Then Test on Them

Glass and anodized aluminium are the reference substrates in most standards, but real projects add coated glass, Low-E surfaces, powder-coated frames and gaskets. Coatings and PVdF finishes can change surface energy enough to affect adhesion. Always run a compatibility and adhesion test on the actual project substrates before production — reputable suppliers will support this and issue a project-specific recommendation.

The Short Version

Structural loads need a certified structural grade (1MG/HM class) with third-party reports; weather joints need the right movement class; and both need substrate testing on the real project materials. Get those three right and the sealant will outlast the warranty.