Silicone adhesives and sealants - the ultimate guide.

Silicone Explained. 

Selecting the right silicone sealant or adhesive is not as straight forward as buying any product off the shelf. There are few silicone options for everything, as there are numerous different types with various degrees of strength, and characteristics. Silicone sealant & adhesives are highly flexible and have a great resistance to UV light and extreme temperatures. Silicone comes from silica which is a common mineral - glass, beach sand, granite, quartz etc are derived from silica. Silicone is typically heat-resistant and rubber-like, and found as a sealant, adhesive, lubricant, medical components, cookware and more. Today's blog is focused on silicone as a sealant and an adhesive rather than the other options. Popular as a caulk solution with a mould resistant additive, but can be engineered for structural adhesive applications involving glass, and high temperatures.  

Silicones have become the go-to-product in the building and construction sector. When it comes to bathrooms, roofing or kitchen renovations, sooner or later you will need a silicone product to caulk the joints and complete your work. They are ideal in preventing water ingress, minimise mould and can create a water tight or air tight environment in specific applications. An all-time favourite at Aerobolt is the Bostik® 6S range. 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. Clever Huh!

Silicone as an adhesive or a sealant.

How are you using silicone? Are you using it as a sealant to caulk a joint? Or as an adhesive to join two items? Before we dive into the world of silicones, lets cover this all-essentail question. 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. Bostik® V60 would be regarded as an adhesive that works really well on painted and or anodized aluminum & glass. Whilst a sealant or what we term joint sealant is a low strength caulking product that is perfect for filling and sealing gaps between different materials. The 6S range from Bostik® would be a silicone sealant perfect for caulking joints. 

polyurethane caulking with a caulking gun

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.

When and Where To Use Silicone. 

Silicone adheres to almost any material, it's ideal for a wide range of building applications including wet and or exterior surfaces because it holds up well in sunlight and extreme temperatures. 

Silicone For Sealing Around Plumbing Fixtures & More.

One of the common uses of silicone caulk is for sealing around plumbing fixtures such as bathtubs, showers, toilets, and sinks. It is also excellent for weatherproofing your house. Use it to seal around doors, windows, and utility cables coming in from outside, and you will be going a long way to minimising drafts. Sealing those openings can also help keep out rodents and vermin.

Silicone In Colder Temperatures.

man using silicone caulk to seal window in cold temperatures

Silicone is the best sealant to use in colder temperatures or cold application like the fabrication of cool rooms. Unlike polyurethane, the cold temperature do not not affect the application. In cold weather, polyurethane becomes hard to apply. Also, it will not make a permanent bond when the temperatures are too low. On the other hand, silicone caulk remains flexible.

Silicone After Application.

Once applied, silicone has a fairly long drying time, and it may produce unpleasant or potentially harmful fumes during its installation. Accordingly, you need to ensure the room is well-ventilated during use. It also needs to be protected from moisture for several days after application so that it can dry well. 

Silicone advantages and disadvantages.

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

  Silicone Pros: 

  • Excellent temperature resistance can withstand extreme heat and cold.
  • Flexibility, can maintain its properties over a wide temperature range.
  • Great electrical insulator that can prevent electricity from passing.
  • Facilitates thermal movement between different material types.
  • Resistant to moisture, chemicals, mould and UV light.

Silicones Cons:

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

Silicone Everday Applications.

Home repairs and maintenance – This is the most common use of silicone. Repairs to your gutters to fixing a leaking sink in the kitchen through to rejoining your shower screen to the tiles  and so much more. For the DIY guru or the professional tradie, silicone sealant or adhesive is a great go-to-product. 

Residentail & commercial construction is used as an adhesive glue and a joint sealant on numerous materials used in building construction as they are exposed to extreme weather conditions like sunlight, rain, or winds. It is also used to caulk gaps between the frames, windows and so much more. 

Adhesive and joint sealant for glass – due to its chemical composition, silicone can be used on any surface, be it glass, plastic, or metal, as it binds the surfaces strongly. It is the best among most others, as it is durable and long-lasting. It is prevalent in the glass sector to seal windows upon installation & other uses like aquariums’ edges and sides. Bostik V60 is very popular with exterior glass installations and internal fitouts with glass partition walls.

Appliances and Electronic devices – the ability to stick through extreme weather conditions have made silicone ideal for electrical insulation in the manufacture of appliances.  

Mechanical & Motor Body Fabrication - Suitable for form-in-place gaskets and plant maintenance. Also used in the fabrication of trucks and utility vehicles - electrical components like lights, blinkers, and sensors can be sealed with the help of this glue.

Where is silicone used?

Silicone can be found throughout our everyday lives, probably without even realising it. Here are some common uses of silicone. 

  • Medical devices – silicone is resistant to bacteria and therefore ideal for medical devices and components. These include defibrillators, heart pumps, catheters, CPAP maskes, tubes etc.
  • Construction – its stablity means you can use silicone in construction. It can bind together building materials such as concrete, plastics and glass.
  • Electronics – silicone is widely used in electronic devices. Perhaps the most notable is the smartphone. For example, silicone seals help prevent water damage and silicone cases protect the phone.
  • Aviation – Silicone adhesives seal critical parts of planes like doors, windows, fuel tanks and vents.
  • In the home – Products include water bottles, ice cube moulds, plastic gloves, silicone coated cookware and baby bottles. 

Different Types Of Silicone Explained.  


Acetoxy Silicone Sealants .

They release acetic acid (which smells a little like vinegar) as they cure, and due to its fast curing time and rigidness when applied, it makes it one of the most commonly used sealants. On the downside, it generally has poor adhesion. 

Neutral (Neutral Alkoxy) Silicone Sealants .

A neutral silicone sealant releases alcohol as they cure, which results in them producing almost no smell. Compared to Acetoxy sealants, they have better adhesive properties for a greater range of materials. On the downside, they can be more expensive and are slower to cure, taking one to five days, depending on thickness, temperature, and humidity conditions.

Low Modulus Sealants. 

Stretchy but not the most hardwearing, these sealants offer better adhesion and offer more flexibility and durability. In general, low modulus sealants are preferred, especially in high moving joints such as window frames or expansion joints. These also work well with joint backer rods to ensure the sealant is applied at the depth intended.

High Modulus Sealants.

They are less stretchy but more hardwearing; they are recommended for sealing baths, showers, sinks, washbasins, kitchen worktops, and many other sanitary and internal applications.

What is the difference between neutral and acetic cure?

This terminology is commonly associated with silicones. Neutral cure means the silicone will release an alcoholic vapour as it cures. Normally these silicones will have better adhesive properties with a wider range of material and applications. A great all-rounder of a neutral cure silicone is Bostik’s Industrial Grade Silicone.  This product has superior adhesive properties, that works well with numerous materials and is Aerobolts number 1 silicone. Acetoxy silicones release an acidic vapour (smells like vinegar) as they cure. An example of this is Bostik® RTV 922, this is a high temperature industrial silicone.

What does low & high modulus mean?

Low modulus silicones have better elasticity, which means they can accommodate material movement better. An example of this would be the popular Bostik® 5CLM. Whilst high modulus means a more rigid silicone, an example of this is Bostik® V60. The V60 is a superior adhesive for painted and anodised aluminum and glass applications.

What are the main silicone adhesive & sealant applications? 

In Australia you will find a comprehensive offering of silicone options. Here are a few broad examples of silicone: 

RTV silicone. 

RTV silicone: This is a type of room-temperature vulcanizing (RTV) silicone that cures at room temperature and forms a flexible rubber-like material. It is commonly used in sealing and bonding applications, such as in automotive gaskets, electrical components, plant mainteance, and household appliances. RTV 926 is a high strength, rapid cure silicone.  

Silicone rubber.  

Silicone rubber: This is a type of silicone that is formulated to have high tensile strength, tear resistance, and elongation properties. It is commonly used in industrial and construction applications. Bostik RTV 922 is a silicone rubber that is ideal in automotive & industrial maintenance applications. Makes formed in-place gaskets for gear boxes, heating & refrigertion units.  

Silicone oil.

Silicone oil: This is a type of silicone that has a low viscosity and high thermal stability. It is commonly used as a lubricant, hydraulic fluid, or heat transfer fluid in various industries, such as automotive, aerospace, and manufacturing. WD-40® Specialist High Performance Silicone is a typical silicone oil based lubricant spray that works well on tools, rubber pipes, window seals, linkages, valves, locks, doors, plumbing fittings and belts. Molykote® 55M is another example of a silicone grease/oil and in this instance specifically for O-ring applications. 

Silicone sealant.

Silicone sealant: This is a type of silicone that is used to seal joints and gaps in construction and building applications. It is commonly used for sealing around windows, doors, and other building components to prevent air and water infiltration. Bostik® 6S range. 6s is a neutral cure silicone sealant, this means it will release a faint alcoholic vapour as it dries making it good for internal use.

Silicone adhesive.

Silicone adhesive: This is a type of silicone that is used to bond two surfaces together. It is commonly used in electronics, glass, medical devices, and automotive applications, where a strong and durable bond is required. Bostik® Industrial Grade is an example of a silicone adhesive. 

What are the most popular silicone brands? 

There are many different types and brands of silicone products available, 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 flexible silicone that is suitable for facade panelling and so much more. 

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 product 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 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. 

Bostik® V60: Superior adhesion to painted and anodized aluminum plus glass. V60 has excellent natural ageing stability. It will maintain its elastomeric joint sealant properties permanently, even under harsh conditions and temperature extremes. The thixotropic nature of this product ensures that it will not slump in typical construction joints with excellent UV stability & long life reliability

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 Summary. 

There is no single type of silicone that can be use for everything. There is a wide range of silicones available on the market, and all have different flexibility, durability, and resistance. So how do you know you are using the right one for the job? Silicone are normally categorised by what job it is suitable for, making choosing the right product very straightforward. Choosing the right silicone sealant or adhesive should not be difficult as numerous silicone products are sold with a heavy emphasis of their appliction. Silicone sealant and adhesives are highly flexible and have a great resistance to UV light and extreme temperatures. These products remain very flexible and are highly water-resistant. Aerobolt has a comprehensive range of adhesive and sealants + access to the entire Bostik range, feel free to chat with us on +61 2 9755 3747 for all your adhesive and joint requirements or contact us.

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