Polyurethane Sealant - Difference Between Silicone & Polyurethane

What Is The Difference Between Silicone Sealant and Polyurethane Sealant

Polyurethane Sealant VS Silicone – Difference Between Silicone and Polyurethane Sealant

  • Posted by Direct Sealants in Sealants
  • January 8, 2018
  • No Comments

A sealant is a versatile material, whether it’s silicone sealant or polyurethane sealant.

Either way it forms an integral part of most people’s DIY toolkit.

If you’re interested in doing jobs around the house or you’re part-way through a renovation project.

Whether you’re planning to modernise a property or revamp the bathroom, here’s one thing we know.

It’s highly likely that in selecting the best sealant for the job, you’re given it some serious thought.

Which is no easy job.

There are various forms of sealant available, so which is the best option for you.

Here’s why it is so important to spend time weighing up the options.

Hopefully, this guide will provide the regarding the difference between silicone and polyurethane sealant.

A brief introduction to sealants

A sealant is a form of material, which is used to seal gaps and holes to make something airtight or watertight.

When you use sealant, you effectively form a seal, which prevents the movement of fluids and liquids.

Sealant is sometimes compared to caulking.

The main difference between building caulking and sealing is the flexibility of the seal.

Sealants tend to be made from much more flexible materials.

This makes them useful for areas and joints where a degree of contraction or expansion may occur.

They are not the same as adhesives, but it is possible to utilise sealants that have adhesive properties.

Sealants are used widely, and may come in handy for those working in the following industries:

  • construction
  • automotive
  • engineering
  • aerospace
  • marine

As well as those with an interest in DIY and property maintenance.

There are many different forms of sealant.

This guide will focus on silicone and polyurethane sealant.

Although these sealants have similarities, there are some significant differences.

Chemical difference between silicone and polyurethane

One of the principal differences between silicone and polyurethane sealants is the chemical composition.

Silicone is an inorganic substance, while polyurethane is organic.

The primary difference between organic and inorganic substances is the presence of carbon.

Organic compounds contain a carbon atom.

In most cases, a hydrogen atom is also present.

With an inorganic substance, it’s uncommon for either atom to be present.

Polyurethane is a polymer, which comprises of a series of organic atoms connected by carbamate.

Silicone is a unique material because it contains both inorganic and organic compounds.

These synthetic polymers comprise silicon and oxygen atoms, which are joined using C-Si bonds.

The makeup of the chain exposes the organic elements of the structure to external influences.

This is why silicone makes such a versatile sealant.

Silicone is commonly used in construction and the development of paint and food products.

The chemical makeup of both silicone and polyurethane sealant are important.

This is because the composition affects the breakdown of the materials.

When organic and inorganic substances are exposed to UV light from the sun, the way they react differs.

Inorganic materials are less responsive to UV rays than organic chemicals.

In the long-term, polyurethane, an organic material, will revert back to its natural state in response to UV exposure.

This affects both the lifespan and versatility of polyurethane sealant.

UV exposure & how sealants respond

Chemical composition is an essential consideration when choosing the type of sealant to use.

The type of compound will affect its response to UV exposure.

Organic chemicals change in response to UV exposure.

While inorganic substances are much more stable.

The main base polymer used in silicone sealant is a stable compound known as poly-dimethylsiloxane.

When silicone is exposed to UV light, the presence of inorganic compounds will prevent deterioration and disintegration.

The silica-oxygen (Si-O) bond found in silicone sealants is much more resistant to UV rays than the C-O bond present in polyurethane sealant.

The outcome is that silicone sealants are inherently stable and more robust in terms of weatherproofing.

It is possible to make polyurethane sealants more UV stable by adding chemicals that are designed to absorb UV light or increase UV resistance.

Bond It WG4 Weatherguard is a  good  UV and Ozone resistant and waterproof.

Lifespan of Silicone and Polyurethane Sealant

As you may have deduced from reading about the chemical composition and changeability of inorganic and organic compounds;

silicone sealants last longer than polyurethane sealants.

Typically, a polyurethane sealant will produce effects that last between 5 and 10 years.

While a silicone joint could last more than 20 years.

The difference boils down to the fact that silicone sealants won’t break down as a result of UV exposure.

Another consideration to factor in is temperature.

Just as UV exposure can alter organic chemicals, changes in temperature can also affect the performance of sealants.

If you have a joint, which is subjected to changes in temperature, this can result in contraction or expansion.

In this case, silicone sealants are almost always the best choice, as they are more flexible.

Essential considerations

Whether it is for those looking to do;

  • work to their homes
  • professionals who use sealants on a regular basis

The quality of work is important, but economics may also play a role.

As a homeowner, you probably don’t want to be paying out for an overhaul every 5-10 years.

The lifespan will affect how much you spend.

But it also impacts the duration of warranties offered by manufacturers.

Typically, a manufacturer will offer a 5 year warranty for polyurethane sealant.

For silicone sealants a warranty of up to 20 years is typical.

It’s always worth doing your homework, reading up on different manufacturers and products .

This allows you to compare prices and warranties before you make any decisions.

The choices you make may depend on your budget and how long you want the results to last.

If you’re planning to move in the near future, you may prefer to spend less.

In some cases, it is possible to transfer a warranty from a previous homeowner to the new owner.

Price difference between Silicone and Polyurethane Sealant

For many people, cost is a factor when it comes to choosing which type of sealant to use.

There are two main issues to consider when you’re weighing up the options of silicone and polyurethane sealants.

Firstly, the cost of the material.

Silicone is significantly more expensive than polyurethane.

The initial outlay may be double if you opt for silicone.

The second factor to think about is labour costs.

If you plan to do the work yourself, choosing polyurethane may seem like an economical choice.

However, keep in mind how much time you’ll have to devote to the cause over the coming years.

If you’re going to pay somebody to do the work for you, consider:

  • the cost of one course of silicone sealant
  • compared to two, three, or even four rounds of polyurethane sealant.

In the long-term, silicone may represent better value for money even though the initial cost could be significantly higher.

Moving from one sealant to another

If you’ve bought a house or you’re making some changes at home, you may be thinking about the option of moving from one type of sealant to another.

It is possible to swap polyurethane sealant for silicone sealant, but this can be an extensive job.

This is due to the fact that it’s essential to ensure that all the previous sealant is removed before placing the new sealant.

If there are traces of polyurethane remaining underneath a silicone seal, for example, this could cause the seal to disintegrate.

If you do plan to replace polyurethane sealant with silicone sealant, it’s wise to seek expert advice to make sure that the job is done properly.

The cost of removing or repairing a failed seal is usually much higher than the fee charged to replace polyurethane sealant with silicone sealant.

Which type of sealant is best for which job?

Generally speaking, silicone sealants are more versatile and flexible than polyurethane sealants and they work better in most environments.

The inorganic composition means that silicone is resistant to UV rays, making it a better option than polyurethane sealant, which will eventually revert back to its natural form.

Silicone is compatible with many different materials, including glass, metal and tile, but it doesn’t bond well to wood.

Polyurethane is often a better option for wood, as it dries hard.

This drying process means that it is possible to seal wood, but it does make the job more difficult.

As the sealant hardens, it’s much more difficult to apply.

Sealants are used widely in many industries.

If you’re thinking of embarking on a DIY job or you’re in the midst of planning a renovation or carrying out a revamp.

It’s worth doing some research when it comes to selecting the type of sealant to use.

There are lots of different types of sealants, and silicone and polyurethane are among the most popular choices.

Both offer advantages and disadvantages.

The flexibility, longevity and versatility of silicone sealants often make them the best option.

The initial cost is usually significantly higher.

The results will last a lot longer.

Therefore, this may represent a better, more cost-effective option in the long-term.


Weigh up the pros and cons.

Consider the job you’re undertaking and bear your budget in mind.

Hopefully, this guide will help you to make the right decision.

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