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Megaprene 40GG: A Technical Overview
Megaprene 40GG is a single-component, gun-grade polyurethane sealant designed for construction joints requiring flexibility, water resistance, and long-term durability. With ±25% joint movement capability and >400% elongation at break, this moisture-curing sealant provides excellent adhesion to most substrates including concrete, metal, timber, and fibreglass. It’s potable water safe (AS/NZS 4020), non-toxic, paintable, and resistant to fuels, chemicals, UV, and mildew. Once cured, it forms a permanently elastic joint suitable for both indoor and external use in commercial, civil, and transport applications.
>400%
Elongation at Break
Core Features & Specifications
- Elongation at break >400% (ISO 8339)
- Joint movement capability ±25% (ASTM C719)
- Potable water safe — AS/NZS 4020 certified
- Excellent chemical resistance to diluted acids, alkalis, petrol, oil (short-term)
- UV resistant, low ignitability (AS1530.3 rating: 0-1)
- Tear strength: 6.5 N/mm
- Non-toxic, low VOC <1.5g/L (Green Star eligible)
- Shore A hardness: 25
- Service temperature: -40°C to +80°C
- Skin time: ~60 min @ 23°C / Cure: 3mm per 24 hrs
The Megaprene 40GG Advantage
- AS/NZS 4020 potable water compliant — safe for contact with drinking water systems
- Ideal for structural joints exposed to mechanical stress, temperature and UV
- Forms watertight, flexible seal even in chemically aggressive or fuel-prone areas
- Compatible with powder-coated metal, concrete, aluminium, timber, fibreglass, and more
- Single-pack gun-grade format simplifies application — no mixing required
Best Practices: Do's & Don'ts
Do
- Apply between +5°C and +35°C in clean, dry conditions
- Use open-cell backing rod (Adhefoam) or bond breaker tape for joints >10mm deep
- Prime porous substrates with Supaprime for high-performance adhesion
- Tool off with moistened spatula before skin forms (~5–10 min)
- Use masking tape for clean joint edges and remove before sealant skins
Don't
- Do not use in fully confined spaces without atmospheric moisture
- Not suitable for swimming pools or aquariums
- Avoid contact with high-chlorine environments (>5 ppm)
- Do not apply on copper, EPDM, bitumen, or oily/rubber-leaching substrates
- Avoid application on wet, damp, or uncured concrete
Applications in Practice: Trade Scenarios
For Builders & Civil Contractors: Concrete & Pavement Joint Sealing
The Engineering Challenge
Expansion joints in driveways, car parks and precast structures require flexibility, water resistance, and fuel tolerance while exposed to heavy traffic and UV.
The System-Based Solution with Megaprene 40GG
Megaprene 40GG resists water, fuels, and movement. Apply into cleaned and primed joints using backer rod, ensuring full depth fill and avoiding 3-point adhesion.
Best Practice Note
Ensure concrete has cured 28+ days before application. Use polyethylene tape on flat joints to prevent 3-point adhesion.
For Fabricators & Fitout Teams: Acoustic & Cladding Integration
The Engineering Challenge
Architectural wall systems require sealing between dissimilar substrates like powder-coated panels, acoustic tiles, fibreglass, and timber — without shrinkage or bleed.
The System-Based Solution with Megaprene 40GG
Use Megaprene 40GG for a durable, non-staining joint. Prime powder coat and timber where needed, and apply in a smooth continuous bead using a triangular profile.
Best Practice Note
Pre-test on plastics, PVC, and powder-coat. Use a fine abrasive pad and Adheseal 50A for surface prep where required.
Performance Benchmark: Megaprene 40GG vs. Standard Polyurethane
| Metric | Megaprene 40GG | Typical PU Sealant | Advantage |
|---|---|---|---|
| Elongation at Break | >400% High Flex | 250–300% | Wider movement accommodation |
| Tear Strength | 6.5 N/mm Reinforced Seal | 3–4 N/mm | Greater mechanical resistance |
| Potable Water Certification | AS/NZS 4020 Safe Contact | Often not certified | Allows use in water-sensitive zones |
Frequently Asked Questions About Megaprene 40GG Polyurethane Sealant
Q: Can Megaprene 40GG be used for sealing joints in water tanks?
A: Yes, Megaprene 40GG is certified to AS/NZS 4020, making it suitable for potable water contact. It is ideal for water tank seams, plumbing penetrations, and fixtures that require drinking water safety.
Q: Is priming always necessary before application?
A: Priming is not required for most surfaces. However, for critical joints or submerged conditions, use Adheseal 50A for non-porous materials and Everflex Supaprime for porous substrates like concrete and brick.
Q: Can Megaprene 40GG be painted?
A: Yes, it is paintable with most acrylic, oil, and rubber-based paints. Perform an adhesion test, especially with non-flexible coatings, which may crack due to movement of the sealant.
Q: What’s the best way to clean up after application?
A: While the product is still wet, clean tools and surfaces using Xylene. Once cured, it must be removed mechanically. Adheseal Hand Wipes are effective for skin contact.
Q: Can this product be used in hot and humid northern climates?
A: Yes, Megaprene 40GG is specifically formulated to perform in Australia’s tropical and humid zones. It resists UV, humidity, and mould growth, making it suitable for far north Queensland and NT.
Use Megaprene 40gg Gun Grade Polyurethane Joint Sealant for:
- Sealing vertical and horizontal joints in bridges and roadways.
- Sealing joints in car parks and driveways.
- Sealing joints in factory and warehouse floors.
- Sealing joints in service station driveways.
- General construction joint sealing where high flexibility and durability are required.
- Applications requiring potable water safety (AS/NZS 4020:2005).
Why Use Megaprene 40gg Gun Grade Polyurethane Joint Sealant:
- High Flexibility: Accommodates joint movement, ensuring a durable and long-lasting seal, preventing cracks and leaks.
- Fast Curing: Reduces downtime and allows for faster project completion, improving efficiency.
- Paintable: Allows for seamless integration with surrounding surfaces, providing a professional finish.
- Excellent Adhesion: Bonds strongly to most common building materials, ensuring a reliable seal, reducing the risk of failures.
- Potable Water Safe: Suitable for use with potable water, expanding application possibilities.
- Chemical Resistance: Provides durability in harsh environments, ensuring long-term performance.
Use Megaprene 40GG Polyurethane Sealant for:
- Expansion joints in precast concrete panels
- Sealing curtain walls and perimeter joints around windows
- Vehicular and marine body fabrication (metal/fibreglass bonding)
- Skirting boards, floor mouldings, and cladding
- Waterproofing below the waterline and around plumbing penetrations
Why Use Megaprene 40GG for:
- Extreme flexibility and UV stability — ideal for outdoor Australian conditions
- Water and fuel resistance — safe for vehicle, marine, and plumbing use
- Green Star compliant — meets low-VOC and potable water standards
- Time-saving single-pack format — easy to gun, tool, and finish on-site
Megaprene 40GG Polyurethane Sealant limitations:
- Not suitable for mirror bonding — use Hi-Power/MS609 with testing
- Avoid natural stone without stain testing — use S100 instead
- Do not use in totally confined spaces without air exposure — requires atmospheric moisture to cure
- Not for internal swimming pools or high-chlorine areas — chlorine max 5ppm
- Avoid use with copper, brass, and bituminous or EPDM rubber surfaces
Safety precautions when using Megaprene 40GG Polyurethane Sealant:
- Personal Protective Equipment: Wear nitrile gloves, safety glasses, long sleeves, and a respirator if ventilation is inadequate
- Ventilation: Use in well-ventilated areas; do not apply in enclosed spaces without airflow
- Handling: Avoid skin and eye contact. Do not ingest. Wash hands before eating or drinking
- First Aid: For inhalation, move to fresh air. For skin/eye contact, rinse thoroughly. If ingested, do not induce vomiting — seek medical help immediately
- Disposal: Dispose of in accordance with local regulations. Cured product may be treated as construction waste
Megaprene 40GG Polyurethane Sealant can be used on the following substrates:
- Concrete and masonry – ideal for structural expansion joints
- Brick and stone – ensure a clean, dry surface for best adhesion
- Porcelain and ceramic – roughen smooth tiles before application
- Metal (aluminium, steel) – except copper and lead; test for brass
- Timber – suitable for hardwoods and treated timbers
- Painted surfaces – remove loose or flaking paint beforehand
- Rubber and plastics – including PVC and fibreglass (test compatibility)
- Powder-coated surfaces – scuff lightly and use Adheseal 50A if needed
- Waterproof membranes – ideal for roof and deck sealing systems
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