Silicone V Polyurethane

Silicone vs. Polyurethane: A Comprehensive Guide to Adhesives and Sealants When it comes to choosing between silicone and polyurethane products, the options may seem endless. Both adhesives and sealants are widely used in various industries, from installing a new Colorbond® roof to fabricating trucks and beyond. Understanding the differences between these materials and knowing where to apply them is crucial. Silicone is a household name among builders, used for everything from kitchen installations to plumbing and roofing. Meanwhile, polyurethane, with its impressive flexibility once cured, is a favorite in steel fabrication sectors such as coach and bus manufacturing or emergency vehicle customization. Generally speaking, polyurethane excels in resisting stretching and handling vibration movements effectively, whereas silicone has moderate resistance to stretching and struggles with vibration resistance. For dynamic situations involving vibration or wear, polyurethane tends to be the better choice. In this post, we’ll delve deeper into these popular elastomer products and offer some guidance on their applications. Before diving in, let’s address a fundamental question: Are you using these products as adhesives or sealants? An adhesive is a high-strength product meant to join two materials together, while a sealant is a lower-strength caulk that fills and seals gaps between different materials. While this is the basic distinction, some adhesives function well as sealants and vice versa. Understanding your project requirements and desired outcomes is key to selecting the right product. ### Silicone or Polyurethane for Your Project? In the construction field, silicone is often seen as superior to polyurethane, though it does have limitations. One major drawback of silicone is that it cannot be painted. When painting is required, other sealants must be used instead. This article aims to help you decide which type of sealant is best suited for your project. #### When to Use Polyurethane Choose polyurethane when you need a surface that will eventually be painted. It adheres well to a wide range of surfaces with minimal limitations. Most manufacturers offer warranties lasting five years, but with minimal sunlight exposure and joint movement, you might expect up to ten years of durability. Polyurethane is easier to clean up than silicone and takes around 24 hours to dry. Once cured, it becomes difficult to remove. #### When to Use Silicone Silicone adheres effectively to many materials and is ideal for wet or exterior surfaces that don’t require painting. It performs well under sunlight and extreme temperatures. ### Silicone vs. Polyurethane Overview Table | Feature | Seal Flex (Polyurethane) | Industrial Grade (Silicone) | |-------------------------|----------------------------------|---------------------------------| | Weather Resistance | Good | Great | | Tensile Strength | 1.6N | 1.7N | | Service Temperature | -30°C to 90°C | -62°C to 177°C | | Joint Movement | ±20% | ±25% | | Abrasion Resistance | Excellent | Poor | | Tool Time | 10-15 minutes | 3-5 minutes | | Curing Time | 3mm/24 hours | 2mm/24 hours | | Shore A Hardness | 40±5 | 27 | | Elongation at Break | >600% | >500% | ### Advantages and Disadvantages of Silicone and Polyurethane Both silicone and polyurethane have distinct properties and applications. Selecting the right material depends on the specific needs of your project. #### Polyurethane Pros: - High strength and durability, capable of withstanding heavy loads and impacts. - Good resistance to abrasion, chemicals, and oil. - Excellent flexibility, maintaining properties across a wide temperature range. - Paintable and bondable with multiple materials. #### Polyurethane Cons: - Poor temperature resistance, degrading at high temperatures. - Releases volatile organic compounds (VOCs) during curing. - Not suitable for medical applications due to toxicity concerns. #### Silicone Pros: - Exceptional temperature resistance, withstanding extreme heat and cold. - High flexibility, maintaining properties over a wide temperature range. - Great electrical insulation, preventing electricity flow. - Resistant to moisture, chemicals, and UV light. - Non-toxic, suitable for medical applications. #### Silicone Cons: - Low tear resistance. - Difficult to paint. - Can have a sticky or tacky surface. ### Chemical Differences Between Silicone and Polyurethane Silicone is a synthetic polymer composed of silica, oxygen, carbon, and hydrogen atoms. Its main ingredient is silica, one of the most common forms of sand. Polyurethane is formed from a chemical reaction between a polyol resin and a poly-isocyanate, which acts as a curing agent. The resin part can be modified with polyester, polyether, or acrylic, creating a highly cross-linked chemical structure. ### Popular Polyurethane Brands Australia offers a variety of polyurethane sealants. The exact type and brand you choose depend on the application and project requirements. - **Aerobolt Seal Flex**: A premium polyurethane adhesive and sealant ideal for industrial and construction projects. It cures quickly to form a durable, flexible seal that absorbs vibration and is paintable. Consider Bond Flex or Bond Flex Plus for structural adhesives with strong load-bearing capabilities. - **Bostik Seal N Flex**: A versatile polyurethane sealant used in construction and automotive industries. Known for its flexibility and ability to endure extreme temperatures and weather conditions. - **Tremco Vulkem**: Often used in roofing and waterproofing, this sealant provides a long-lasting, durable seal against harsh weather and UV radiation. - **3M Marine Adhesive Sealant**: Specifically designed for marine environments, it is waterproof, weather-resistant, and resistant to saltwater and corrosive substances. - **Soudal Fix All**: A multipurpose polyurethane sealant effective in sealing gaps and cracks in various materials. ### Popular Silicone Brands Several silicone sealants are available in Australia, each suited to specific tasks. - **Bostik Industrial Grade Silicone**: Ideal for construction surfaces like glass, aluminum, wood, brick, and masonry. It remains flexible after curing and serves as both an adhesive and sealant. - **Selleys All Clear**: Suitable for bathrooms, kitchens, and other wet areas, known for its flexibility, waterproofing, and resistance to mildew and mold. - **Bostik 5CLM**: A high-performance silicone for high joint movement, curing by absorbing atmospheric moisture to form a flexible and durable seal. Neutral-cure, making it suitable for natural stone and facade panels. - **Dowsil 732**: Used in construction, electrical, and automotive applications, it’s known for its strength, durability, and resistance to temperature extremes. - **Bostik Roof and Gutter**: Designed for roofing and guttering, offering excellent adhesion to metal, concrete, and tiles. - **Geocel Trade Mate**: A multipurpose silicone sealant for construction, plumbing, and electrical work, known for its strength, flexibility, and UV resistance. - **Bostik 6S**: A neutral-cure silicone with fungicide to resist mold, providing excellent adhesion to powder-coated steel and glass. It doesn’t slump in typical joints. - **Tremco Proglaze**: Specifically for curtain walls and facades, known for its adhesion to glass and metal and resistance to UV and weathering. ### Conclusion Ultimately, the decision between silicone and polyurethane hinges on your specific scenario. Silicone is perfect for high-temperature and weather-resistant applications without painting, while polyurethane excels in strength, durability, and resistance to abrasion and chemicals. Aerobolt offers a wide range of silicones, polyurethanes, and other adhesives like our MS Polymer range. For assistance with selection and application, feel free to reach out at 02 9755 3747 or contact us. © 2024 Aerobolt Australia Pty Ltd. All rights reserved.

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