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At a Glance: Key Applications
Use RLA Flex Pro MS for: Sealing high-movement expansion joints, perimeter sealing of window and door frames, bonding in vibrating structures, sealing wall and floor penetrations, and use in sanitary applications.
RLA Flex Pro MS: A Technical Overview
RLA Flex Pro MS is a premium, single-component sealant engineered with advanced Silane-Modified Polymer (MS) technology. Unlike traditional polyurethane and silicone sealants, it is free from solvents, isocyanates, and PVC, ensuring very low VOC emissions and enhanced operator safety. This moisture-cured system provides exceptional, primerless adhesion to a broad spectrum of common construction materials, including concrete, metals, and plastics. Its formulation delivers a permanently elastic, highly durable seal that withstands the demanding conditions of Australian job sites, from extreme temperature fluctuations to high UV exposure.
Comparative Performance Overview
| Metric | RLA Flex Pro MS | Standard Polyurethane | Advantage |
|---|---|---|---|
| Elongation at Break | 400% | ~250-350% | Superior flexibility accommodates higher structural movement without cohesive failure, crucial for expansion joints. |
| Chemistry & Safety | Isocyanate-Free MS Polymer | Contains Isocyanates | Eliminates a key respiratory sensitiser, improving workplace health and safety without compromising performance. |
| UV Resistance | Excellent Colour Stability | Prone to yellowing/chalking | Maintains its colour and integrity on UV-exposed facades and window frames, preventing premature degradation. |
| Service Temperature | -50°C to +120°C | -30°C to +80°C | A significantly wider operational temperature range ensures performance in all Australian climate extremes. |
Using RLA Flex Pro MS in a Complete System
RLA Flex Pro MS is engineered not just as a standalone product, but as a critical component within a larger engineered assembly. Its primary function is to provide a flexible, weatherproof seal that accommodates movement between building elements. For waterproofing applications, it is approved for use as a bond breaker prior to the application of RLA acrylic membranes, preventing three-sided adhesion and allowing the membrane system to perform as designed. When designing joints, the use of a compatible backer rod (open-cell polyurethane is recommended for faster curing) is critical to achieve the correct width-to-depth ratio and prevent sealant failure. It is also compatible with most paint systems once fully cured, allowing for seamless aesthetic integration, although a field test is always recommended due to the variability in paint formulations.
How RLA Flex Pro MS Prevents Common Failures
Prevents Joint Splitting (Cohesive Failure)
With an exceptional 400% elongation at break, FLEX-PRO MS absorbs significant thermal and structural movement. This prevents the sealant body from splitting or tearing under stress, a common failure point for less flexible products in dynamic joints.
Prevents Adhesion Loss on Damp Surfaces
Its advanced MS Polymer chemistry allows for application on moist, non-porous surfaces. This overcomes a common challenge on job sites where residual dampness can compromise the bond of conventional sealants, saving time and reducing call-backs.
Prevents Bubbling & Gassing
As a solvent-free and isocyanate-free formulation, it cures without producing gas bubbles that can create pinholes and compromise the seal's integrity, a known issue with some polyurethane sealants, especially when applied in warm conditions.
Core Features & Specifications
- Advanced MS Polymer Base: Delivers superior durability and flexibility compared to traditional silicones and polyurethanes, and is free of harmful isocyanates.
- 400% Elongation at Break: Accommodates extreme joint movement, making it ideal for expansion joints, vibrating structures, and dissimilar materials.
- Shore A Hardness of 32: Provides the optimal balance of toughness to resist damage and flexibility to absorb movement, ensuring a durable yet pliable seal.
- Wide Service Temperature Range (-50°C to +120°C): Guarantees stable performance across all Australian climate zones, from alpine cold to direct summer sun on dark facades.
- Excellent UV Resistance: The sealant remains colourfast and will not degrade or become brittle when exposed to harsh sunlight, ensuring long-term aesthetic and functional performance.
- Paintable Formulation: Can be painted over with most systems once fully cured, allowing for perfect colour matching with adjacent surfaces for a seamless finish.
The RLA Flex Pro MS Advantage
- Enhanced Site Safety: Being completely free of isocyanates, solvents, and acids significantly reduces health risks for applicators.
- Increased Productivity: Achieves primerless adhesion on most common substrates and can be applied to moist surfaces, saving critical preparation time on site.
- Ultimate Versatility: A single product can be used for a vast array of applications, from concrete control joints to sanitary sealing, simplifying inventory for contractors.
- Long-Term Asset Protection: Its superior weather resistance and flexibility prevent water ingress and structural damage, reducing the need for costly future remedial work.
- Acoustic Performance: Its elastic properties help to dampen sound transmission, making it suitable for sealing joints where acoustic performance is a requirement.
Applications in Practice: Trade Scenarios
For Builders: Sealing Pre-Cast Concrete Panel Joints
The Challenge: Pre-cast panel joints are subject to significant thermal expansion and contraction, requiring a sealant with high movement capability to prevent failure. Adhesion to concrete without extensive priming is critical for efficiency.
The Product Solution: RLA Flex Pro MS provides 400% elongation, easily handling the dynamic movement of large panels. It bonds directly to clean concrete, while its 3mm/24hr cure rate ensures a robust seal develops efficiently. Its service temperature range of -50°C to +120°C guarantees performance year-round.
Pro-Tip: For joints over 12mm wide, maintain a 2:1 width-to-depth ratio. Use an open-cell polyurethane backer rod to allow moisture to access the back of the joint, enabling a faster, more uniform cure.
For Glaziers & Carpenters: Perimeter Sealing of Window Frames
The Challenge: Creating a durable, weatherproof seal between dissimilar materials like anodised aluminium or PVC frames and masonry or timber surrounds. The seal must resist constant UV exposure without yellowing or cracking.
The Product Solution: FLEX-PRO MS excels with its primerless adhesion to both porous (brick, timber) and non-porous (aluminium, PVC) substrates. Its excellent UV stability ensures it won't break down, and its paintability allows for a clean, integrated finish that matches the facade.
Pro-Tip: For window frames, ensure a minimum joint width of 10mm. After application, tool the sealant to a concave profile to ensure positive water shedding and maximum adhesion to the sides of the joint.
Certifications & Regulatory Compliance
RLA Flex Pro MS is a non-hazardous substance according to Safe Work Australia criteria, making it a safer choice for trade professionals. It is formulated with very low VOC content to help meet air quality standards. All installations should be carried out in accordance with relevant Australian Standards and local building codes to ensure full system compliance.
Storage & Shelf Life Considerations
To ensure optimal performance and a 12-month shelf life, store RLA Flex Pro MS in a cool, dry, well-ventilated location, out of direct sunlight. Keep containers sealed and upright when not in use. For best gunnability and tooling, it is recommended to store the material between +10°C and +40°C before application, which is particularly relevant for maintaining consistency in the variable Australian climate.
Frequently Asked Questions About RLA Flex Pro MS
Q: How does Flex-Pro MS handle the high movement in concrete expansion joints compared to a standard sealant?
A: RLA Flex Pro MS is engineered with 400% elongation at break, providing significantly more movement capability than many standard sealants. This superior elasticity allows it to repeatedly stretch and compress during thermal cycles without splitting or losing its bond, ensuring the long-term integrity of the joint.
Q: As a waterproofer, can I confidently use this as a bond breaker under RLA's acrylic membranes?
A: Yes, absolutely. RLA Flex Pro MS is specified for use as a compatible bond breaker for all RLA acrylic membranes. Its formulation ensures it will not react with or compromise the membrane, allowing you to create a fully compliant Class III membrane system where the bond breaker facilitates correct movement.
Q: Is this sealant truly paintable, and are there any special precautions needed for a perfect finish?
A: Yes, it is fully paintable once cured. The key is to allow the sealant to cure completely (typically 3mm per 24 hours). Because some solvent-based paints can react with flexible sealants, we always recommend conducting a small field test with your chosen coating to ensure perfect compatibility and prevent any crazing or tackiness.
Q: What is the main advantage of this MS Polymer technology over a standard polyurethane sealant?
A: The primary engineering advantage is its isocyanate-free chemistry, which enhances workplace safety. From a performance standpoint, MS Polymers typically offer superior UV resistance—meaning less yellowing and degradation—and broader substrate adhesion, often without needing a primer where a polyurethane would require one.
Q: Can I apply RLA Flex Pro MS in damp conditions?
A: The product is moisture-cured and can be applied to moist, non-porous surfaces. This is a significant advantage in unpredictable weather. However, you should not apply it to visibly wet surfaces or if rain is imminent, as this can affect the initial cure and tooling finish. For porous substrates, ensure they are dry to avoid trapped moisture causing issues.
Applications & Core Benefits
| Application / Use Case | Key Benefit | Primary Trades |
|---|---|---|
| Expansion & Construction Joints | High Movement Capability (400% Elongation) | Builders, Concreters, Remedial Contractors |
| Perimeter Sealing (Windows/Doors) | Excellent UV/Weather Resistance & Adhesion | Glaziers, Carpenters, Builders, Façade Installers |
| Waterproofing Bond Breaker | System Compatibility & Permanent Flexibility | Waterproofers, Tilers |
| Sealing Penetrations (Pipes/Ducts) | Acoustic Damping & Flexible Sealing | Plumbers, HVAC Technicians, Electricians, Builders |
| Sanitary & Kitchen Applications | Fungal Resistance & Non-Staining | Plumbers, Joiners, Tilers, Builders |
| Bonding Metals, Stone & Ceramics | High-Strength Adhesive Properties | Stonemasons, Metalworkers, Builders, Landscapers |
Applying RLA Flex Pro MS: Protocols & Best Practices
General Application Steps:- Preparation: Ensure the substrate is clean, sound, and prepared as per the Adhesion Guide. For correct joint design, install a tight-fitting backer rod to the required depth and use masking tape for neat edges. Avoid three-sided adhesion.
- Application: Apply between +5°C and +35°C. Cut nozzle to deliver the correct bead size. Using a professional sausage gun, apply the sealant into the joint, ensuring no air is trapped. Ensure sealant makes full contact with the joint sides.
- Tooling & Finishing: Within 30 minutes of application, tool the sealant surface with a spatula to create a smooth, concave profile. This ensures the sealant is pressed firmly against the substrates for maximum adhesion.
- Curing: Remove masking tape immediately after tooling. The sealant will skin in approximately 30 minutes (@23°C/50%RH) and cures at a rate of 3mm per 24 hours. Protect from water and abrasion during initial cure.
For Builders & Concreters: Sealing Pre-Cast Concrete Panel Joints
The Engineering Challenge: Pre-cast panel joints are subject to significant thermal expansion and contraction, requiring a sealant with high movement capability to prevent failure. Adhesion to concrete without extensive priming is critical for efficiency.
The System-Based Solution with RLA Flex Pro MS: RLA Flex Pro MS provides 400% elongation, easily handling the dynamic movement of large panels. It bonds directly to clean concrete, while its 3mm/24hr cure rate ensures a robust seal develops efficiently. Its service temperature range of -50°C to +120°C guarantees performance year-round.
Best Practice Note: For joints over 12mm wide, maintain a 2:1 width-to-depth ratio. Use an open-cell polyurethane backer rod to allow moisture to access the back of the joint, enabling a faster, more uniform cure.
For Glaziers & Carpenters: Perimeter Sealing of Window Frames
The Engineering Challenge: Creating a durable, weatherproof seal between dissimilar materials like anodised aluminium or PVC frames and masonry or timber surrounds. The seal must resist constant UV exposure without yellowing or cracking.
The System-Based Solution with RLA Flex Pro MS: FLEX-PRO MS excels with its primerless adhesion to both porous (brick, timber) and non-porous (aluminium, PVC) substrates. Its excellent UV stability ensures it won't break down, and its paintability allows for a clean, integrated finish that matches the facade.
Best Practice Note: For window frames, ensure a minimum joint width of 10mm. After application, tool the sealant to a concave profile to ensure positive water shedding and maximum adhesion to the sides of the joint.
Limitations & Safety
Product limitations and safety information
Limitations:
- Not suitable for structural glazing applications or permanent immersion in chlorinated or salt water (e.g., swimming pools).
- Do not apply to bituminous substrates, PE, PP, or PTFE plastics.
- Avoid application on cement-based substrates less than 28 days old.
- Do not use alcohol-containing solvents or soapy water as a tooling aid as this will inhibit the cure.
- Ensure old silicone sealant is completely removed from joints before application.
Safety & Handling:
- PPE: Always wear suitable chemical-resistant gloves (e.g., butyl rubber) and eye protection/goggles.
- Ventilation: Use in well-ventilated areas. If engineering controls are insufficient, use suitable respiratory protection.
- Handling: Avoid direct contact with skin and eyes. Wash hands thoroughly with soap and water after handling.
- First Aid: If in eyes, rinse with water for several minutes. If on skin, wash with soap and water. If irritation persists, seek medical attention. For advice, contact the Poisons Information Centre (Australia ph. 131 126).
RLA Flex Pro MS Adhesion & Preparation Guide
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Substrate preparation guidelines
- Concrete, Masonry, Brickwork, Stone: Ensure surface is sound, clean, and free of loose particles or laitance. Use a wire brush and oil-free compressed air to clean. Repair damaged areas first. Primer: Generally not required. For total immersion applications, use RLA PRIMER PU.
- Metals (Aluminium, Steel): Surface must be clean, dry, and free of rust, scale, or oxide films. Degrease with a suitable solvent like MEK or acetone. A preliminary adhesion test is recommended. Primer: Apply RLA UNIVERSAL PRIMER if required for critical applications.
- Glass, Ceramics: Substrate must be clean, dry, and free from all oil and grease. Primer: No primer required.
- Plastics (PVC, ABS, Polyamide): Clean surface to remove all processing oils and protective agents. A preliminary compatibility test is essential. Primer: No primer required. Note: Not suitable for PE, PP, or PTFE plastics.
- Timber & Wood: Ensure timber is dry, clean, and free from dust and oils. Primer: No primer required.
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