Silicone V Polyurethane

Silicone Vs. Polyurethane Image

Silicone VS Polyurethane. Guideline to these Adhesive, Glues & Sealants.    

When it comes to selecting a silicone or polyurethane product the range seems virtually unlimited. Adhesives and sealants have become the go-to product from installing a new Colorbond® roof  through to truck fabrication and so much more. Understanding the differences and where to use them is important. Silicone is well known amongst most building tradies for kitchen applications through to roofing and plumbing work. Whilst polyurethane with its excellent flexibility after curing seems to be a favourite in steel fabrication like the motor body building sector from coach & bus manufacturing through to emergency vehicle fitouts. In broad terms, polyurethane has excellent resistance to being stretched and great ability to withstand vibration movement, silicone has good resistance to being stretched and poor ability to withstand vibration movement. For dynamic situations that are subject to vibration and or wear, polyurethane is the better option. 

In this blog we will dive into these ever so popular elastomer products and provide some guidance to their application. Before we begin, lets cover the all essentail question. How are you using these products? As an adhesive or a sealant! What is the difference between an adhesive and a sealant? An adhesive is a high strength product for the purpose of joining of two pieces of materials together. Whilst a sealant is a low strength caulk product that is perfect for filling and sealing gaps between different materials. This is the basic breakdown; however, you will find there are numerous adhesives that work well as a joint sealant and sometimes vice versa. Understanding your application and the results you are seeking is the most important consideration is selecting the right product.

Silicone or Polyurethane For My Project?

polyurethane caulking with a caulking gun

In the building and construction sector silicone is generally considered superior to polyurethane with some limitations. The big drawback with silicone however, is that it cannot be painted. You must use other caulking products when the application calls for painting. This blog article is a general guide to help you decide which type of caulk is best suited for your project.

When To Use Polyurethane. 

Use polyurethane when you are caulking a surface that is to be painted. Poly adheres to a wide range of surfaces with few limitations. Most manufacturer warranties last for five years but you can expect up to ten years if sunlight exposure and joint movement is minimal. Polyurethane is easier to clean up than silicone and takes about 24 hours to dry. Once dry, it is difficult to remove.

When To Use Silicone. 

Silicone adheres very well to numerous material whist being ideal for wet or exterior surfaces that don't need to be painted because it holds up well in sunlight and extreme temperatures. 

Silicone VS Polyurethane Overview Table.

Seal Flex (Polyurethane) Industrial Grade (Silicone)
Good Weather Resistance Great Weather Resistance
Tensile Strength: 1.6N Tensile Strength: 1.7N
Service Temperature: -30℃ — 90℃ Service Temperature: -62℃ — 177℃
Joint Movement: ±20% Joint Movement: ±25%
Excellent Abrasion Resistance Poor Abrasion Resistance
Tool Time: 10-15 minutes Tool Time: 3-5 minutes
Curing Time: 3mm/24hrs Curing Time: 2mm/24hrs
Shore A Hardness: 40±5 Shore A Hardness: 27
Elongation at break: >600% Elongation at break: >500%

Silicone and Polyurethane advantages and disadvantages.

Silicone and polyurethane have unique properties and applications. Choosing the right material depends on the specific requirements of the application.

Polyurethane Pros:

  • High strength & durability - can withstand heavy loads / impacts.
  • Good resistance to abrasion, chemicals, and oil.
  • Good flexibility maintaining its properties over a wide temperature range.
  • Can be painted and bondable with numerous materials.

Polyurethane Cons:

  • Poor temperature resistance can degrade at high temperatures.
  • Can release volatile organic compounds (VOCs) during curing.
  • Not suitable for medical applications due to toxicity concerns

  Silicone Pros: 

  • Excellent temperature resistance can withstand extreme heat and cold.
  • High flexibility, can maintain its properties over a wide temperature range.
  • Great electrical insulator can prevent electricity from passing.
  • Resistant to moisture, chemicals, and UV light.
  • Non-toxic, can be used in medical applications.

Silicones Cons:

  • Low tear resistance.
  • Not easily paintable. 
  • Can have a sticky or tacky surface.

What is the chemical differences between silicone and polyurethane?

Silicone is a synthetic polymer made up of silica, oxygen, carbon, and hydrogen atoms. The primary ingredient in silicone is silica — one of the most commonly occurring forms of sand. Polyurethane comes from a chemical reaction between a polyol resin and a poly-isocyanate which is a curing agent. The resin part can be modified with polyester, polyether or acrylic. Polyurethane is a synthetic chemical structure that is highly cross-linked with other chemicals.

What are some popular polyurethane brands? 

Here we list a few examples of the many different types of polyurethane sealants that are available in Australia. The specific type and brand of sealant you choose will depend on the application and the specific requirements of your project.

Aerobolt® Seal Flex:  Seal-Flex is a high quality general purpose polyurethane (PU) adhesive and joint sealant that works well in numerous industrial and construction applications. Seal-Flex cures fast to form a permanent durable flexible seal that can absorb vibration and is paintable. This is Aerobolt's #1 general adhesive & sealant. If you are looking for a structural adhesive with good load carrying capacity you should consider Bond Flex or Bond Flex Plus.

Bostik® Seal N Flex: Bostik Seal N Flex is a another polyurethane joint sealant that is popular in Australia. It is designed for use in a variety of applications, including construction, and automotive, It is known for its flexibility and ability to withstand extreme temperatures and weather conditions.

Tremco® Vulkem: Tremco Vulkem is a polyurethane sealant that is often used in roofing and waterproofing applications. It is designed to provide a durable, long-lasting seal that can withstand exposure to harsh weather conditions and UV radiation. 

3M® Marine Adhesive Sealant: 3M Marine Adhesive Sealant is a polyurethane sealant that is specifically designed for use in marine environments. It is waterproof, weather-resistant, and able to withstand exposure to saltwater and other corrosive substances. 

Soudal® Fix All®: Soudal Fix All is a multi-purpose polyurethane sealant that can be used in a wide variety of applications. It is known for its high bonding strength, fast curing time, and ability to seal gaps and cracks in a variety of materials.

What are some popular silicone brands?  

There are many different types and brands of silicone sealants available in Australia, each with their own specific features and applications. Here are a few examples: 

Bostik® Industrial Grade Silicone; Industrial Grade silicone has great adhesive properties for numerous construction surfaces including glass, aluminium, timber, brick, masonry & more. Industrial Grade Silicone is a general-purpose adhesive and joint sealant that is permanently flexible after curing. 

Selleys® All Clear: Selleys All Clear is a popular brand of silicone sealant that is designed for use in a wide range of applications, including bathrooms, kitchens, and other wet areas. It is known for its flexibility, waterproofing ability, and resistance to mildew and mold growth. 

Bostik® 5CLM; Bostik 5CLM® is a high performance construction silicone that is ideal for high joint movement. It cures by absorption of atmospheric moisture to form a flexible and durable elastomeric sealant. A neutral cure flexible silicone that is suitable for many natural stones and facade panelling. 

Dowsil® 732: Dowsil 732 is a versatile silicone sealant that is used in a variety of applications, including construction, electrical, and automotive. It is known for its high strength, durability, and resistance to temperature extremes. 

Bostik® Roof and Gutter: Bostik Roof and Gutter is a silicone adhesive sealant that is specifically designed for use in roofing and guttering applications. It is known for its excellent adhesion to a wide range of materials, including metal, concrete, and tile.

Geocel® Trade Mate: Geocel Trade Mate is a multi-purpose silicone sealant that can be used in a variety of applications, including construction, plumbing, and electrical work. It is known for its high strength, flexibility, and resistance to weathering and UV radiation. 

Bostik® 6S;6s is a neutral cure silicone, this means it will release a faint alcoholic vapour as it dries making it good for internal use. Bostik 6S is a single component sealant that cures to become a flexible and durable elastomeric seal and available in a wide range of colours to match or compliment its surrounds. Key features include (1) Contains a fungicide to resist mould. (2) Provides excellent adhesion properties to powder coated steel and glass. (3) And will not slump in typical joints.

Tremco® Proglaze: Tremco Proglaze is a silicone sealant that is specifically designed for use in curtain wall and façade systems. It is known for its excellent adhesion to glass, metal, and other materials, as well as its resistance to UV radiation and weathering. 

These are just a few examples of the many different types of silicone sealants that are available in Australia. The specific type and brand of sealant you choose will depend on the application and the specific requirements of your project. 

Silicone Verses Polyurethane Summary. 

In a nutshell, choosing between silicone and polyurethane depends on your specific situation. Silicone is ideal for applications that require high-temperature and weather resistance without painting. Polyurethane is better for applications that require high strength, durability, and resistance to abrasion and chemicals. Aerobolt has a comprehensive range of silicones, polyurethanes and other types of adhesives like our MS Polymer range. We can assist with selection and application so feel free to chat by calling 02 9755 3747 or contact us. 

Silicone Sealants.

With the exception of being unpaintable, silicone sealants are an excellent all-around sealant choice. These products remain very flexible and are highly water-resistant. They’re also less prone to shrinking than most other sealants, and they stick to almost any material. The main downside to these sealants is that they’re expensive, but they’re some of the most useful for creating water and air barriers. 

Polyurethane sealants.

For a tough sealant that adheres to nearly everything, a polyurethane-based sealant could be the best bet. These sealants create strong bonds between materials and seal joints to prevent fluids and other substances from passing through. They’re also abrasion resistant and provide more flexibility than many other sealant types. Polyurethane sealants come in tinted hues like gray, black, or white for matching or complimenting its surrounds.

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