Special PU sealant for building exterior walls refers to single/two-component, moisture/reaction cured polyurethane sealant, graded according to JC/T 482-2022, suitable for waterproofing, weather resistance, and displacement resistance requirements of exterior wall concrete/metal/curtain wall joints. Choosing the right displacement level and modulus type for the core, combined with standardized construction, can significantly improve durability.
1、 Core grading and selection (must see for exterior walls)
According to JC/T 482-2022, based on displacement capacity and modulus classification, priority is given to selecting ≥ ± 35% for exterior walls, and * * ± 50% * for temperature difference/earthquake zones.
table
Key parameters of the project: Recommended configuration and selection of exterior walls
Displacement capacity level 50 (± 50%), 35 (± 35%), 25 (± 25%), 35/50 curtain wall/expansion joint selection level 50; Choose level 35 for ordinary exterior walls
Modulus type LM (low modulus, ≤ 0.4MPa), HM (high modulus,>0.4MPa) vertical seam LM; horizontal seam HM dynamic seam prioritizes low modulus to avoid three sided wrapping
Liquidity non sagging type (N), self leveling type (L), non sagging type (N). Vertical exterior walls must be N-type to prevent flow
Single component (I), multi-component (II), single component (conventional); Double component (high requirement) single component construction is fast; Two component strength/stronger weather resistance
Key performance: Elastic recovery ≥ 70%, sagging ≤ 3mm, surface dryness ≤ 24h, no damage to bonding after artificial climate aging, elastic recovery ≥ 80%, crack resistance, aging resistance is the key to the service life of exterior walls
2、 Applicable and Not Applicable Scenarios
✅ Applicable: concrete exterior wall expansion joints, metal/stone curtain wall joints, window frame and wall joints, roof grid joints, and comprehensive pipe gallery/tunnel exterior wall joints.
❌ Not applicable: structural stress bonding (choose structural adhesive), main stress joints of glass curtain walls (choose silicone structural adhesive), long-term immersion without displacement of pool bodies (choose polysulfide adhesive).
3、 Five step construction method (anti cracking core)
Grassroots treatment: remove floating dust/oil stains, dry and free of floating ash; Interface agent for concrete and anti rust primer for metal.
Seam design: width to depth ratio of 2:1; Add backing rod and leave two sides bonded to avoid wrapping on three sides.
Compatibility testing: Make small samples of coated glass, stone, and insulation layer to prevent contamination/loss of adhesion.
Glue application: Single component can be used and opened at any time, and dual components can be mixed in proportion; Fill with no bubbles and shape.
Maintenance and finished product protection: Avoid rain before the surface dries; Single component surface drying for 24 hours and complete solidification for 7 days; Avoid stepping on or contaminating.
