Soudal Silirub LMN - Low Modulus Neutral Silicone

Health & Safety Recommendations

Read the packaging label and Safety Data Sheet before use and follow all site and local safety requirements. Keep the work area well ventilated throughout application and curing, particularly in bathrooms, kitchens, utility rooms, plant areas and other enclosed spaces where vapours can accumulate. Take normal labour hygiene into account, avoid prolonged skin contact, and wash hands thoroughly after use. If product gets into the eyes, rinse immediately with plenty of clean water and seek medical advice if irritation persists.

When working at height, around glazing, or near electrical services, ensure safe access equipment is in place and the area is protected from slips, trips and accidental contact. Keep the cartridge out of reach of children and store away from food preparation areas. Use masking tape to protect adjacent surfaces where necessary, and remove tape before the sealant skins to avoid tearing the bead.

Substrate Suitability

Soudal Silirub LMN is a low modulus, neutral cure silicone designed for sealing and weatherproofing joints on many common building substrates where movement accommodation is required. It adheres well to a wide range of typical construction materials when correctly prepared, including many metals, coated and painted surfaces, ceramic materials, masonry substrates and some plastics commonly used in building envelopes.

Silirub LMN is not suitable for PE, PP or PTFE (Teflon®), and it is not suitable for bituminous substrates. A preliminary adhesion and compatibility test is recommended on every surface, especially where substrates are unknown, newly coated, powder coated, factory finished, or where previous sealants, cleaning residues or release agents may be present.

For glazing related work, avoid direct contact with the secondary sealant of insulating glass units and avoid direct contact with PVB film in laminated glass. Where glazing system details are uncertain, carry out a compatibility check before proceeding and follow the glass manufacturer’s guidance.

Surface Preparation

All joint edges must be rigid, clean, dry and free from dust, grease, loose coatings and contamination. Remove old sealant fully where possible, and ensure any remaining residue is not acting as a bond breaker. On non-porous substrates, clean and degrease using Soudal Cleaner & Degreaser and allow it to flash off completely before applying Silirub LMN.

On porous substrates, prime where required using Soudal Primer 150 to support consistent adhesion, particularly in critical exterior joints or where the substrate is friable, dusty, very absorbent, or prone to surface chalking. Allow primer to dry as directed and keep the primed area clean before sealing. Mask both sides of the joint for a crisp finish, and ensure joint backing is in place where needed to control sealant depth and prevent three-sided adhesion.

Application Method

Cut the nozzle to suit the joint width, pierce the cartridge seal, and fit the cartridge into a suitable caulking gun. Apply Silirub LMN with steady, even pressure, keeping the nozzle angle consistent so the sealant is pushed into the joint rather than dragged across the surface. Work methodically and avoid entrapping air, particularly in deeper joints or where the joint line is irregular.

Tool the bead immediately after application, before skin formation begins, using a suitable profiling tool. A lightly soapy finishing solution can be used to improve toolability, but take care that the soapy solution does not contact the adhesion surfaces. If it contaminates the joint edges, adhesion loss can occur. For best control, dip only the finishing tool into the solution rather than spraying it over the joint, and avoid applying finishing solution in full sunlight where it can dry too quickly and mark the sealant.

Maintain good ventilation during application and keep the sealed joint protected from dust, water run-off and disturbance while it skins and cures. If a second reactive joint sealant is required in an adjacent area, ensure the first sealant has fully hardened before applying the next product.

Joint Dimensions

For reliable performance, form joints within the recommended working range. Minimum joint width is 5mm, maximum joint width is 30mm, and minimum joint depth is 5mm. As a general guide for sealing work, joint width should be approximately 2x joint depth, which supports the correct sealant geometry for movement capability and long-term durability.

Where joints are deeper or wider, use a suitable PE backer rod to control depth, prevent three-sided adhesion and help achieve the correct hourglass profile. Joint edges should be sound and stable, and any movement in loose trims, rattling panels or poorly fixed frames should be rectified before sealing.

Coverage

Coverage depends on joint width and depth, and on how consistently the bead is applied and tooled. For practical estimating, use the Platinum Chemicals Sealant Estimate Calculator to determine approximate metres per cartridge based on the joint dimensions being sealed.

Always allow a sensible margin for wastage on first-time applications, rough substrates, start-stops, and detailing around corners, penetrations and frame junctions.

Curing Time

Silirub LMN cures by moisture reaction, so curing speed depends on temperature, humidity and joint geometry. While the sealant will skin relatively quickly under typical site conditions, deeper sections will take longer to cure through. Protect newly applied joints from early exposure to rain, wash-down water or cleaning, and avoid stressing the joint until curing has progressed sufficiently.

Be aware that a total absence of UV can cause colour change, and in dark rooms or acid environments white sealant can show slight yellowing. Where sunlight later reaches the joint, the colour typically returns closer to its original appearance.

Cleaning

Clean up during application is best carried out immediately. Before curing, wipe excess sealant from tools and non-porous surfaces using Soudal Swipex Wipes. Keep cloths clean and change them regularly to avoid smearing silicone residues across the surface.

Once cured, Silirub LMN can only be removed mechanically. For cured residue removal and clean-up support, use Soudal Silicone Remover Gel or Soudal Sealant Remover Spray in line with their labels, and test first on sensitive finishes. Do not use aggressive solvents on plastics or coated surfaces without checking compatibility.

Limitations

Silirub LMN is not paintable, so it should not be specified where a paint finish across the joint is required. It must not be used in applications where continuous water immersion is possible. Do not use on natural stone such as marble or granite where staining can occur, use Silirub MA or Fix ALL Flexi in those situations.

Do not use on polycarbonate, use Silirub PC instead. Silirub LMN is not suitable for bonding aquariums, Silirub AQ should be used for that type of application. Avoid direct contact with the secondary seal of insulating glass units and avoid direct contact with PVB film in laminated glass.

Avoid contact with bitumen, tar or other plasticiser-releasing materials such as EPDM, neoprene and butyl, as this can cause discolouration and loss of adhesion. Where EPDM sealing is required, use Silirub EPDM. Do not apply when rain or frost is imminent during the curing period, and do not seal onto damp, dusty, unstable or contaminated edges.

Other Information

Silirub LMN conforms to LEED requirements relating to low-emitting materials for adhesives and sealants, including SCAQMD Rule 1168 and USGBC LEED 2009 Credit 4.1 criteria, supporting use on projects where VOC control and indoor air quality targets are relevant. As with all sealants, final performance depends on correct joint design, correct preparation and correct application, so always test adhesion where substrates are unfamiliar or where coatings, cleaners or previous sealants may affect bonding.

Once opened, cartridges have a limited shelf life and should be resealed and stored correctly if not fully used. Store in accordance with the packaging guidance, protect from extreme temperatures, and keep cartridges sealed until required to maintain consistent extrudability and curing behaviour.

Q) What is Soudal Silirub LMN and what is it designed to do?

A) Soudal Silirub LMN is a low modulus, neutral cure silicone sealant designed for professional glazing and high movement building joints where long term weather sealing matters. It is thick bodied for controlled gunning and clean tooling, and it skins very quickly, typically around 7 minutes, which helps reduce dust pick-up on busy sites. Once cured it remains permanently elastic and is rated for joint movement up to ±25%, making it suitable for perimeter seals and exposed junctions that expand and contract through temperature cycling. It is MEKO free, highly resistant to UV and ageing, and performs across extreme service temperatures from -60°C to +150°C.

Q) Where would you typically use Soudal Silirub LMN on a building?

A) Soudal Silirub LMN is typically used on exterior perimeter sealing and high movement connection joints where long term water and air sealing is required. Common examples include sealing around window and door frames, façade junctions, curtain walling interfaces, roofline details, and compatible joints in building services where vibration and thermal cycling occur. Because it is low modulus, it accommodates movement with less stress on the joint edges, which helps reduce the risk of edge tearing and de-bonding over time. It is also a good choice for maintenance sealing where you need strong weather resistance, fast skinning, and a neat professional bead that stays elastic in service.

Q) Is Soudal Silirub LMN suitable for interior sealing as well as exterior work?

A) Yes, Soudal Silirub LMN can be used internally and externally, provided the joint design and substrate selection are appropriate. Internally, it is useful where you need a durable, permanently elastic silicone seal that tolerates movement and remains stable over time, such as around frames, service penetrations, and junctions that experience vibration or thermal change. Externally, it excels on exposed joints because it is highly resistant to UV, rain and ageing, and it stays flexible in extreme temperatures. The key is to ensure the joint is correctly sized, edges are clean and stable, and the detail avoids known compatibility risks near insulating glass edge seals and laminated glass interlayers.

Q) What makes Silirub LMN “low modulus” and why does that matter?

A) Low modulus means Soudal Silirub LMN is formulated to remain softer and more elastic, so it can stretch and recover without placing excessive stress on the adhesion line. In real terms, this matters most on perimeter and façade joints where materials move at different rates, such as aluminium or uPVC frames against masonry, or metal flashings against rigid cladding. A higher modulus sealant can pull at the joint edges during movement, increasing the risk of tearing or edge de-bonding over time. With a ±25% movement capability and strong elastic recovery, Silirub LMN is designed to handle repeated movement while staying watertight and visually consistent.

Q) Which substrates does Soudal Silirub LMN generally stick to without primer?

A) Soudal Silirub LMN offers primerless adhesion on many common construction materials, including glass, masonry substrates, metals, wood and selected plastics. In everyday use that means it often performs well on anodised aluminium, stainless steel, coated metals, painted timber, and sound mineral backgrounds when they are correctly prepared. Primerless does not mean preparation-free, so joint edges still need to be rigid, clean, dry and free from dust, grease and release agents. Because coatings and plastics vary widely, a small adhesion and compatibility test is always sensible, especially on powder coated metals, painted finishes, and unknown plastics. For critical exterior joints, improved reliability may still require Soudal Primer 150.

Q) When should you use Soudal Primer 150 with Silirub LMN?

A) Use Soudal Primer 150 with Soudal Silirub LMN when the substrate is porous, inconsistent, friable, dusty, very absorbent, or where the joint is particularly critical and exposed. Typical examples include chalky masonry, weak cementitious repairs, marginal timber edges, and mineral backgrounds where surface suction can vary and reduce reliable wetting. Primer helps stabilise the surface and supports more consistent adhesion, which reduces the chance of local edge lift and patchy bonding over time. Apply Soudal Primer 150 neatly only on the bonding faces, allow it to dry as directed, and keep the primed area clean before sealing. Even when primer is used, correct joint design and backing remain essential.

Q) What is the best way to clean surfaces before applying Soudal Silirub LMN?

A) For non-porous substrates, clean and degrease the joint edges using Soudal Cleaner & Degreaser, then wipe dry with a clean, lint-free cloth before applying Soudal Silirub LMN. This step is important because invisible oils, polish, release agents and handling marks are common causes of silicone adhesion failure. On porous substrates, remove dust, laitance, loose paint and friable material back to a sound edge, then consider Soudal Primer 150 if the surface is weak or inconsistent. Always remove old sealant fully where possible, because residual silicone often acts as a bond breaker. A small compatibility test is recommended on coated surfaces, plastics, and any unknown substrate.

Q) How do you apply Soudal Silirub LMN for a neat, continuous bead?

A) Cut the nozzle to suit the joint width, pierce the cartridge seal, and use a suitable caulking gun to apply Soudal Silirub LMN in a steady, continuous pass. Keep the nozzle in contact with the joint and aim to push the sealant into the cavity rather than dragging it across the surface, as this helps avoid air pockets. Maintain consistent pressure so the bead profile stays even, especially at corners, mitres and terminations where weak spots often occur. Work in manageable lengths so you can tool before skin formation, which is typically around 7 minutes. If a crisp line matters, mask both sides of the joint and remove tape immediately after tooling.

Q) How quickly does Silirub LMN skin and why is fast skinning useful?

A) Soudal Silirub LMN typically forms a surface skin in around 7 minutes, which is very fast for a professional neutral cure silicone. Fast skinning is useful because it reduces the time the bead is vulnerable to dust pick-up, light debris, and accidental contact, which helps keep the finish cleaner on active construction sites and glazing workshops. It also supports quicker finishing sequences, provided you plan the work so tooling happens promptly. The key is to apply and tool in short, controlled runs rather than gunning an entire elevation in one go. Fast skinning does not mean instant cure, so joints still need appropriate time to cure through before being heavily exposed or stressed.

Q) What is the recommended joint size for Soudal Silirub LMN?

A) For best performance, form joints within the typical working range for Soudal Silirub LMN. Minimum joint width is 5mm, maximum joint width is 30mm, and minimum joint depth is 5mm. A practical rule for durable movement joints is joint width being around 2x joint depth, which supports the correct bead geometry for movement and stress distribution. Where joints are deeper, use a suitable PE backer rod to control depth and prevent three-sided adhesion, which can restrict movement and increase stress at the bond line. Joint edges should be rigid and stable, and any loose trims or moving components should be fixed properly before sealing.

Q) How long does Soudal Silirub LMN take to cure and when is it safe to expose it?

A) Soudal Silirub LMN cures by a moisture reaction, so cure time depends on temperature, humidity, ventilation and joint geometry. While it skins quickly, deeper sections take longer to cure through, so avoid stressing the joint or exposing it to heavy wash-down, aggressive cleaning, or wind-driven rain until curing has progressed sufficiently. In cool, dry, low-airflow conditions, curing will be slower, especially in deeper joints. Good ventilation helps cure development, particularly in sheltered recesses and internal junctions. If the sealed joint is part of a weather-critical detail, plan the work so the bead is protected during early curing. Always avoid applying when rain or frost is imminent during curing.

Q) Can Soudal Silirub LMN handle extreme temperatures and UV exposure?

A) Yes, Soudal Silirub LMN is designed for demanding external exposure. Once cured, it remains functional across a wide service temperature range from -60°C to +150°C, which is useful where joints experience cold starts, direct sun exposure, and rapid thermal cycling on metal and glass interfaces. It is also highly resistant to UV, rain, and ageing, which helps maintain elasticity and sealing performance on exposed elevations and roofline details. This durability is one of the main reasons to choose a premium silicone rather than an acrylic or lower grade sealant for external junctions. For reliable results, make sure joint edges are properly cleaned and the joint is correctly backed and tooled.

Q) What colours does Silirub LMN come in and how do you choose the right one?

A) Soudal Silirub LMN is available in a broad colour range including Brilliant White, Clear, Brown, Black, Grey and Anthracite Grey (RAL7016). Colour choice is usually driven by the frame or façade finish, the visibility of the joint, and whether you want the seal to blend in or create a defined shadow line. For modern window frames and cladding details, Anthracite Grey (RAL7016) is often chosen to match common powder coated aluminium and uPVC tones. Clear is useful where the joint line should be visually minimal, but it can still show surface imperfections if tooling is poor. Always test a small bead where appearance is critical, as adjacent colours and lighting can change perception.

Q) Is Soudal Silirub LMN suitable for sealing around double glazed units?

A) Soudal Silirub LMN can be suitable for many perimeter sealing tasks around frames and glazing details, but compatibility limitations must be respected. It is not suitable for direct contact with the secondary sealant of insulating glass units, which is part of the IGU edge seal system. It is also not suitable for direct contact with PVB films used in laminated glass. These restrictions are important because direct contact can create compatibility risks within the glazing system. If your joint design brings silicone close to IGU edge seals or laminated interlayers, the glazing detail must prevent direct contact and you should carry out a system suitability check. Where details are uncertain, do not guess, confirm the glazing build-up and separation before sealing.

Q) Can you use Soudal Silirub LMN on plastics and metal trims?

A) Soudal Silirub LMN adheres well to many metals and selected plastics, which makes it useful for trims, frames and façade components. It typically performs well on anodised aluminium, stainless steel, and many coated metals when cleaned properly with Soudal Cleaner & Degreaser. Plastics are more variable, so compatibility testing is important, especially on unknown plastics or factory finished profiles. Do not use it on PE, PP, or PTFE (Teflon®), as adhesion is unreliable. Also avoid polycarbonate, where Silirub PC should be used instead. If the plastic is solvent-sensitive or has a release coating, adhesion can be unpredictable, so a simple test bead and peel check after curing is a sensible safety step.

Q) Can Soudal Silirub LMN be painted over after it cures?

A) No, Soudal Silirub LMN is a silicone sealant and is not paintable in the way acrylic sealants are. If you paint over it, paint usually fails to adhere properly or it cracks and flakes as the silicone flexes. For joints that must be painted, you would normally specify a paintable sealant system rather than silicone. Silirub LMN is best chosen where the sealant line will remain exposed and colour matched using the available range such as Brilliant White, Grey or Anthracite Grey (RAL7016). If the joint sits in a paint line and you need a paint finish, address that at specification stage rather than hoping paint will bond to cured silicone later.

Q) What are the main limitations and “do not use” cases for Silirub LMN?

A) Soudal Silirub LMN should not be used on PE, PP, PTFE (Teflon®), or bituminous substrates, as reliable adhesion is unlikely. It is also not suitable on polycarbonate, use Silirub PC instead. Avoid natural stone such as marble and granite because staining can occur, and do not use it in applications involving continuous water immersion. For EPDM and other plasticiser-releasing materials, avoid direct contact because discolouration and adhesion issues can occur, and use Silirub EPDM where EPDM sealing is required. For glazing systems, do not allow direct contact with IGU secondary seals or PVB interlayers in laminated glass. If a joint is structural, do not treat Silirub LMN as a structural glazing adhesive.

Q) How do you tool Soudal Silirub LMN without ruining adhesion at the edges?

A) Tool Soudal Silirub LMN immediately after gunning, before it skins, using a suitable profiling tool to compact the sealant against both joint sides and create a smooth, weather-shedding profile. A lightly soapy finishing solution can improve tool glide, but take care that the solution does not contaminate the adhesion surfaces. If soapy water reaches the joint edges, local adhesion loss can occur and the bead can lift at the margins. The safest approach is dipping only the finishing tool into the solution rather than spraying it over the joint. Remove masking tape straight after tooling while the sealant is still workable. Avoid tooling in full sun where finishing aids can dry too quickly and mark the surface.

Q) How do you clean up Silirub LMN during application and after it cures?

A) Clean-up is easiest while Soudal Silirub LMN is uncured. Remove smears from tools and non-porous surfaces using Soudal Swipex Wipes as you go, and change wipes regularly to avoid spreading silicone residue. Once the sealant has cured, it cannot be dissolved and must be removed mechanically. For cured residue and assistance with removal, use Soudal Silicone Remover Gel or Soudal Sealant Remover Spray in line with their labels, and test first on sensitive coatings and plastics. If old silicone is being replaced, remove it thoroughly because residual silicone often prevents new silicone bonding properly. Proper masking is also a practical prevention step, especially on visible frame finishes and glazing lines.

Q) Why can white silicone sometimes yellow, and does that apply to Silirub LMN?

A) With Soudal Silirub LMN, colour stability is generally good, but like many silicones, some colour effects can occur depending on environment. A total absence of UV can cause colour change, and in dark or acidic environments a white sealant can show slight yellowing. Where sunlight later reaches the joint, the colour typically returns closer to its original appearance. This is usually an aesthetic issue rather than a performance failure. To reduce the risk, keep joints clean, avoid exposure to harsh chemicals during early curing, and choose a colour that suits the environment if you expect the joint to sit in a consistently dark zone. If appearance is critical, test a small area first and review after curing.

Q) What are the most common causes of adhesion failure with Silirub LMN, and how do you avoid them?

A) Most adhesion failures with Soudal Silirub LMN come down to contamination, weak surface layers, poor joint design, or incorrect material selection. Grease, dust, polish, release agents, and old silicone residue can all prevent proper wetting and bonding, which is why Soudal Cleaner & Degreaser and thorough residue removal matter. Friable porous edges can fail within the substrate rather than at the sealant, so stabilising with Soudal Primer 150 can improve reliability on borderline backgrounds. Three-sided adhesion and overly deep joints increase stress and can cause edge tearing, so use a PE backer rod and correct geometry. Finally, avoid known incompatibilities such as IGU secondary seals, PVB interlayers, polycarbonate, and bituminous substrates. A small test bead remains the simplest safeguard.

Q) How should Soudal Silirub LMN be stored, and what should you do with a part-used cartridge?

A) Store Soudal Silirub LMN cartridges sealed, upright where possible, and protected from extreme temperatures. Good storage helps maintain consistent extrudability and predictable curing behaviour. Once a cartridge is opened, it has a limited practical shelf life because moisture in the air begins curing the product at the nozzle and tip. If you need to pause mid-job, reseal the nozzle tightly and keep the cartridge in a cool, dry place, but expect to remove a cured plug from the nozzle before reuse. For best results on professional work, use opened cartridges promptly and avoid carrying part-used cartridges between jobs where storage conditions vary. Always check the product is gunning smoothly before starting a visible joint run.

Technical Data Sheet

Declaration of Performance (DoP)

Safety Data Sheet