Repair Systems — 03 — Facade & External Envelope
Mapeflex PU45 two-part polyurethane movement joint sealant
Technical product reference for Mapeflex PU45 two-component polyurethane sealant by Mapei Australia. Chemical cure independent of ambient humidity — suitable for large-scale facade joint resealing, low-humidity environments, and air-conditioned buildings. Accommodates ±35% joint movement. Requires accurate two-component mixing per manufacturer ratio; pot life approximately 45 minutes at 23°C. Bond breaker backer rod and primer required.
What is Mapeflex PU45 two-part polyurethane sealant?
Mapeflex PU45 is a two-part chemically curing polyurethane sealant rated ISO 11600 F 35 HM — accommodating ±35% of the joint width in movement. Used when one-part sealants at ±25% are insufficient for the expected joint movement range. Requires on-site mixing of A and B components in the correct ratio. Higher movement rating than standard 1-part products but adds site complexity through mixing requirements and limited pot life. Requires polyethylene foam backer rod and primer on porous substrates.
Supplier reference — Mapeflex PU45 polyurethane sealant
Mapeflex PU45 — two-part polyurethane movement joint sealant
Two-part moisture-resistant polyurethane sealant — ISO 11600 F 35 HM — ±35% movement accommodation — requires A+B mixing on site — high-movement masonry facade joints
Mapeflex PU45 — key technical data
| Attribute | Value |
|---|---|
| Supplier | Mapei Australia |
| Product | Mapeflex PU45 |
| Components | Two-part (A+B) |
| Cure mechanism | Chemical cure (A+B reaction) |
| ISO class | F 35 HM |
| Movement accommodation | ±35% |
| Shore A hardness (cured) | ~45–50A |
| Elongation at break | >300% |
| Service temp range | −40°C to +90°C |
| Paintable | Yes — after full cure |
| Primer required | Yes — Mapei primer on porous substrates |
| Bond breaker required | Yes — PE foam backer rod |
| Joint width:depth ratio | 2:1 |
| Traffic bearing | No |
- Wide movement joints (>20 mm) in masonry facades where ±25% LM products are insufficient for the expected movement range
- Parapet junctions and coping joints with large thermal cycling — dark parapets in hot climates
- Joints at material change-of-plane junctions with high differential thermal movement
- Specify Mapeflex PU45 when the joint movement class required exceeds ±25% — typically for joints wider than 20 mm or joints subject to high thermal movement
- Calculate expected joint movement from AS 3700 movement joint spacing and thermal range; if ±35% class required, use this product
- Confirm mixing ratio capability on site — two-component products require careful handling; ensure applicator has correct equipment and training
- Mixing ratio is critical — do not estimate; use measured dispensing equipment for two-part mixing
- Pot life limits batch size — mix only what can be applied within the pot life window
- Higher modulus (HM) means higher stress is transmitted to joint faces — confirm substrate bond strength is adequate
- ISO 11600 — Classification and requirements for joint sealants — F 35 HM designates facade grade, ±35%, high modulus
- AS 3700 — Masonry Structures — movement joint spacing and sealant requirements for masonry facades
- NATSPEC worksection 05 32 00 — Sealants — project specification requirements for sealant work
- Failed high-movement joint sealant in masonry parapet or wide movement joint where standard ±25% products have torn
- Movement joints in precast concrete facade panels specified at ISO 11600 F 35 or higher movement class
- Replacement of polysulfide or two-part sealants in existing high-movement joints during facade remediation
- Dense fired clay brick and engineering brick — prime porous surfaces per Mapei TDS
- Precast concrete and in-situ concrete — prime per TDS; confirm primer for dense concrete surfaces
- Rendered masonry — confirm render is cured and primed before sealing
Do not confuse Mapeflex PU45 with:
- Sikaflex-11FC+ — a one-part moisture-curing polyurethane sealant by Sika rated ±25% movement; simpler application, no mixing required; preferred for small or isolated joint repairs where two-part complexity is not justified
- Tremco Dymonic FC — a one-part high-movement polyurethane sealant rated ±35% movement; no mixing required; preferred where one-part convenience is needed at high movement class
- Mapeflex AC4 — a different Mapei sealant product line; confirm the correct Mapeflex grade for the specified joint class before ordering
- Silicone sealants — different polymer chemistry with different paintability and adhesion characteristics; not interchangeable with polyurethane on masonry movement joints
- Epoxy joint fillers — rigid, no movement accommodation; not appropriate for live movement joints in masonry facades
Disclaimer
This page provides general technical information only. Sealant selection, joint geometry, mixing ratio, pot life and movement class must be confirmed against the project's joint design, substrate type and exposure conditions per ISO 11600 and AS 3700. Confirm current product data with the Mapei TDS before specifying or applying.