Silicone vs PU: What’s The Difference & Which Should You Use?

pipes

Silicone and polyurethane are two of the most popular products for manufacturing in the industry at the moment. From sealants to gaskets and o-rings, these materials find application across multiple industries. And, as you’d expect, many people tend to wonder about the comparisons between the two of them. 

In this article, we’ll dissect the polyurethane vs silicone debate to understand how they compare and operate. 

Silicone vs PU: Properties And Unique Selling Points

long caulk
long caulk

To begin on the silicone vs thermoplastic polyurethane debate, let’s take a look at both materials and how they came to be:

An Overview Of Silicone

Silicone is easily one of  the most popular synthetic compounds in the market at the moment. Made of silicon and different other elements, the compound is especially prominent for its flexibility in both properties and applications. 

Just as well, the formulation processes for silicone are flexible, meaning that the material essentially takes on different forms without stress. 

Primarily, silicone’s molecular structure consists of alternating oxygen and silicon atoms. This structure provides the material with its unique properties, so let’s take a look at what really makes it up: 

  • Silicon Atom (Si): As we explained earlier, silicon is the primary element that makes silicone possible. A naturally-occurring element, silicon is usually found in the crust of the Earth and is available in abundant quantities. With four valence electrons, the element easily forms bonds with others – a key component for why it easily forms silicone. 
  • Oxygen Atom (O): We all pretty much know about oxygen. Its job here is to form bonds with the silicon atoms, thus creating the foundation for the silicone polymer. This bond, known as the siloxane bond, is one of the most common in the natural environment.  
  • Carbon Atom (C): With carbon, you have atoms that are attached to the silicon in the deep molecules of this polymer. These atoms primarily provide the versatility and flexibility that the material needs – whether to work or form bonds with others.
  • Hydrogen Atom (H): Another critical component of the entire silicone form, hydrogen has a significant influence on the characteristics of the material. It especially improved stability and flexibility for silicone, ensuring that the compound is better suited for several of its applications. 

In general, the basic unit in a silicone polymer is the siloxane unit, which sees one silicon atom bond with two oxygen atoms. This unit can be linked in networks or chains, forming different silicone materials.

Some of these forms include: 

  • Linear Silicone Polymers: These polymers come with comparatively short chains of silicon-oxygen-silicon linkages. They are mostly used in making silicone lubricants, fluids, and other possible cosmetic products..
  • Cyclic Silicone Polymers: These polymers come in  ring-like structures – of course, also consisting of silicon and oxygen atoms. A great example of this are cyclomethicones, which are used in making cosmetic products.
  • Crosslinked Silicone Polymers: Also known as networked silicones, the crosslinked variants are derived by connecting cyclic or linear silicone polymers together. They are especially known for their optimal flexibility and heat resistance – making them especially ideal for use in making coatings, adhesives, and other industrial components.

Silicone’s Key Characteristics  

As part of the polyurethane caulk vs silicone debate, you should also be familiar with the material’s critical properties and characteristics. 

  • Heat Resistance: First off, the most important thing that strikes about silicone is the materia;’s impressive heat resistance. Thanks to the strength of the silicon-oxygen bonds, the material is able to withstand high temperatures. So, in applications where contact with heat is inevitable, silicone works well
  • Flexibility and Elasticity: The presence of organic groups attached to the silicon atoms also provides optimal flexibility, ensuring that the material is able to stretch without necessarily losing its shape.
  • Chemical Inertness: Besides all their benefits, silicones can be quite chemically inter. This means that they don’t react with many chemicals and are stable when applied in different environments. 
  • Water Repellency: If you need a material to work and repel water, silicone is there for you. Its molecular structure allows it to repel water, so it could even work in some aquatic scenarios.
  • Electrical Insulation: Silicone’s resistance to electrical conductivity makes it valuable in electronics and electrical applications.

Polyurethane: What Is It & Why Should You Care? 

Polyurethane is another versatile polymer that is made of repeating units. The difference in silicone vs polyurethane, however, is that the units here are linked by urethane groups.

In polyurethane, you have a plastic product that can be adjusted to exhibit different properties. And, this flexibility means that it can work in different applications and industries.   

To begin with, polyurethane is formed through a reaction between two types of compounds: 

  • Polyols: Compounds that come with different hydroxyl groups. You typically have diols (compounds with just two hydroxyl groups) or triols (three hydroxyl groups). In general, these polyols offer the backbone for the general polymer chain. 
  • Isocyanates: Essentially, compounds with different isocyanate groups – mostly diisocyanates. Their job is to react with the hydroxyl groups, forming the urethane linkages and, by extension, the polymer itself. 

This bond – known as the polyurethane reaction or polymerization – sees the formation of urethane linkages, which eventually creates the polymer chains that make up the polyurethane material itself. 

Another line of convergence in the silicone vs polyurethane caulk debate is the fact that both materials come in different types and forms. Like silicone, you can find polyurethane in different forms, each varying based on their characteristics and properties. Some of these include:

  • Flexible Foam: With flexible foam, you have a polyurethane type that usually comes in upholstered furniture. It is soft and can provide impressive cushioning. 
  • Rigid Foam: Known for its impressive thermal insulation properties, rigid foam polyurethane is great for insulation in buildings – as well as packaging and refrigeration. 
  • Coatings and Adhesives: As you can imagine, coatings made of polyurethane help to provide protection against external elements. On the flip side, the material’s adhesives provide impressive bonding with other materials. 
  • Elastomers: Polyurethane elastomers operate like faux rubber. For polyurethane vs silicone rubber, you get a material that provides properties like resilience and flexibility and which is used to make wheels, seals, and more.
  • Thermoplastic Polyurethane (TPU): While elastomers mimic the properties of rubber, TPU emulates the properties of plastic. It can be melted and molded, and it works in applications such as consumer good manufacturing and footwear making. 
  • Integral Skin Foam: Mostly, this polyurethane form comes with a dense outer layer that covers a softer inner layer. It provides a comfortable grip, and thus is perfect for making automotive parts.

Each of these types comes with its specific characteristics, and they can essentially be decided based on your choice of isocyanates and polyols. At Legenday, we can help provide whatever polyurethane form you’re looking for. 

Key Material Properties

Next, let’s take a quick look at the overall features of polyurethane and why many manufacturers use it in their processes. 

  • Durability: Polyurethane is especially known for its strength and ability to rest any form of abrasion. In applications where wear and tear are likely, you want this material with you.
  • Flexibility: While this property will depend considerably on the formulation, you should know that it is possible to engineer polyurethanes to be both flexible and soft or stiff and rigid. 
  • Chemical Resistance: Several polyurethane variants exhibit optimal resistance to chemicals, oils, and solvents.
  • Versatility: With an impressive ability to be customized based on your specific requirements, it’s no wonder that polyurethane is used across different industries.
  • Insulation: This is especially prominent in rigid polyurethane foam, which offers impressive thermal insulation. As such, the material is especially energy-efficient.

Silicone vs PU: Differences In Characteristics

sealant

Now, let’s get to the major silicone vs polyurethane debate. Should you get a PU sealant? Who wins in the polyurethane vs silicone tubing argument? 

Material Composition

As we explained earlier, silicone’s primary composition is silicon – with the addition of hydrogen, carbon, and oxygen atoms being arranged in a repeating pattern that incorporates organic groups. 

As for polyurethane, the material is formed based on the chemical reaction that exists between polyols and isocyanates – thus resulting in a polymer chain with urethane linkages.

Heat Resistance

For silicone, you get impressive heat resistance as well as an ability to easily withstand high temperatures without undergoing any form of material degradation. Polyurethane does the same, but that will be based mostly on the formulation. Rigid polyurethanes especially do well to resist heat, while others might not. 

Flexibility and Durability

Elastic and durable, silicone is perfect for applications that will require it to move constantly. Polyurethane, on the other hand, offers a broad range of flexibility and durability options.

Chemical Resistance

Both materials resist exposure to pils, chemicals, solvents, and more. However, like the heat resistance metric, this tends to vary for polyurethane based on the formulation you have. 

Biocompatibility

With medical-grade silicone, you have a material that is easily compatible with human tissue. Polyurethane offers the same benefit, although it will need to be specially treated first.

Electrical Insulation

Both materials are quite good when it comes to electrical insulation. So, they can be used in electronic applications across the board.

Hardness Range

Generally, readings on hardness for materials are done on the Shore durometer scale. For silicone, hardness levels tend to range from very soft (which is indicated by a Shore A 50 reading) to relatively firm (indicated by a Shore A 70 reading or higher).

On the other hand, the hardness ranges for polyurethane move from extremely soft (a reading of Shore A 20 or lower) to moderately hard (around Shore A 90 or higher).

Water Repellency

You can find silicone easily repelling water. However, while polyurethane does this too, its ability will generally depend on the formulation.

Processing Complexity

When the time for processing comes, you’ll find that silicone can be a bit of a challenge to work with. This is why anyone looking to process the material would have to do so with proper expertise and the right tools.

Processing complexity for polyurethane tends to vary since you have different material formulations to choose from. 

Environmental Impact

A major point of distinction in the silicone vs polyurethane debate is the environmental impact. While silicone is generally environmentally stable with a low propensity of degradation, the same can’t necessarily be said about polyurethane. Some formulations of the latter aren’t so biodegradable, and they can raise environmental concerns in the long run.

At the end of the day, both products offer their upsides and downsides. Your choice here will depend on your application and the specific requirements you have for the material. At Legenday, we put all of this into consideration when making materials, and we can provide consultations to help you make more informed decisions. 

Silicone vs PU: Differences in Applications

caulk

In general, silicone and PU can be used in different industries. They are both versatile, with distinct properties that make them perfect for a broad range of applications. And, the choice between them will usually depend on factors such as environmental conditions and the needs of your specific application. 

Nevertheless, there are some distinctions in the general application for both materials:

Medical and Healthcare

In the healthcare space, silicone is used to make implants and devices – a direct consequence of the material’s biocompatibility. On the flip side, polyurethane is much better for making medical tubes, wound dressings, and other implants.  

Electronics

Silicone comes with impressive electrical insulation properties, which make it perfect for making electrical components. Just as well, you can see it being used for electrical connectors, cable coatings, insulators, and more.

Construction and Architecture

With silicone sealants, you can incorporate sealing gaps and weatherproofing features for buildings. Just as well, coatings made of the polymer can offer impressive water resistance in building materials.

Automotive

Silicone can be applied in developing seals, gaskets, and hoses. With its heat resistance and flexibility, the polymer offers high quality across the board. Just as well, you can find silicone fluids and greases that are being used as lubricants.

Cookware and Bakeware

Generally, the silicone material doesn’t stick. This, combined with its heat-resistant properties, makes the polymer perfect for making kitchen products like oven mitts and spatulas. So, next time you find a non-stick frying pan, it was most likely made using silicone. 

Cosmetics and Personal Care

Ingredients that are offshoots and by-products of silicone can be found in skincare products. Here, they optimize spreadability and extend their non-toxic properties to the feel on the skin.

Aerospace

Planes and helicopters need high-quality thermal insulants, seals, and more. Thanks to silicone’s long-term durability, the materials help in the development of these components.

Applications of Polyurethane:

Foams

Regardless of the variant, polyurethane foams work in the development of insulation pads. These find application in making furniture, seats for cars, and more.

Coatings and Adhesives

With polyurethane coatings, you also get sufficient protection for surfaces that can be used in industrial floors, paints, and more. 

Elastomers

With their ability to mimic rubber, polyurethane elastomers find use in wheels, gaskets, and other industrial components that need durability and flexibility.

Footwear

You can find polyurethane being used to produce shoe soles and midsoles. Once more, this is a benefit of the material’s durability and cushioning properties. 

Automotive Components

Polyurethane is used in automotive parts such as bumpers, seats, and suspension components due to its impact resistance and flexibility.

Textiles

Polyurethane coatings tend to be incorporated in textiles to optimize durability and water resistance. From upholstery to clothing and footwear, this functionality is quite broad.

Silicone vs PU: Material Pros and Cons

materials

Now that we understand some of the lines of divergence in the polyurethane vs silicone adhesive comparison, let’s look at where both materials shine and where they could do better. 

So, what are the advantages and disadvantages of polyurethane vs silicone sealants?

Silicone Pros

  • Heat Resistance: The biggest benefit you stand to get from silicone is the fact that the material easily withstands high temperatures without any form of degradation or deformation. Thanks to this property, silicone easily operates in environments where temperatures can be elevated and you can count on it
  • Flexibility: Silicone materials are also known for their impressive elasticity across the board. For manufacturers, this means that you can shape and mold them into different forms. And, for applications that require constant movement, these materials easily take the prize.
  • Durability: Despite being flexible, silicone easily holds its own against different environmental factors, including UV radiation, moisture, and chemicals. With this impressive durability level, the material ensures that whatever you make with it will easily last long. 
  • Electrical Insulation: Silicone is an excellent electrical insulator, making it suitable for electrical and electronic components where insulation is crucial.
  • Biocompatibility: Silicone is biocompatible. This means that it interacts well with the tissues in the human body. When you consider  polyurethane implants vs silicone, this material just might be the perfect fit. 
  • Non-Toxic: Another point to silicone’s overall safety is the fact that the material isn’t toxic. So, it works well in different applications and environments.
  • Water Repellency: Silicone is considered hydrophobic, meaning that it repels water.You already get a polyurethane sealant waterproof option, and the good news is that this is also available with silicone materials. This means that you can get better customization – especially after you conduct a thorough assessment of your needs. 
  • Broad Hardness Range: Part of the customization benefits you enjoy with silicone also extend to hardness. Based on your requirements, you can get a silicone polymer that is either hard or soft. 

Silicone Cons

  • Cost: First and foremost, silicone tends to be expensive compared to many other materials. This isn’t surprising since you get a great deal of benefits from the polymer. Nevertheless, the investment in this material is quite considerable. 
  • Limited Bonding: Although the polymer bonds well to itself and other silicone-based materials, you might not find it easy bonding silicone with other materials. To do this, you’d most likely need special adhesives or put the polymer through additional surface treatment. 
  • Limited Abrasion Resistance: In some silicone variants, you might witness limited resistance to abrasion and mechanical wear. All in all, this could affect the variants’ suitability for applications that come with high friction levels. 
  • Low Tensile Strength: Compared to a few other materials, silicone doesn’t necessarily have a hgh tensile strength. 
  • Processing Challenges: The processing of silicone materials can be more complex than other plastics, requiring specialized equipment and techniques.
  • Poor Conductivity: Silicone doesn’t do well when it comes to conducting electricity or heat.

Polyurethane Pros 

  • Operational Versatility: The most prominent benefit of polyurethane is its ability to be formulated and exhibit a broad range of properties. Whether you want it flexible or rigid, the material is available across the board.
  • Durability: Tough and with an ability to resist abrasion, polyurethane is perfect for use in high-wear environments and applications. 
  • Flexibility: While this will depend on the formulation, polyurethane can offer excellent flexibility and elasticity. In applications that require deformation or movement, the material is more than ideal.
  • Chemical Resistance: Some polyurethane formulations also do well to resist materials like solvents and chemicals. Once more, this improves their range of applications considerably.
  • Insulation: The rigid polyurethane foam does well to insulate a material from temperatures. When used in applications like making fridges, it can go a long way to improve energy efficiency. 
  • Adhesion: A major line of distinction in the polyurethane vs silicone adhesive debate is the fact that polyurethane does quite well when it comes to bonding with other materials. From fabrics to metals and plastics, this material does quite well to bond. 
  • Customizability: Any polyurethane format can easily be adjusted to meet your requirements. So, whatever needs you have, you can essentially create a material that matches it with polyurethane. 
  • Reduced Noise and Vibration: Polyurethane comes with a pristine ability to soak in shock and reduce vibrations. As such, it is a good cushion component and sound dampener. 

Polyurethane Cons:

  • Cost: Like silicone, you should also expect to pay considerable sums if you hope to get high-quality polyurethane. So, when comparing silicone vs PU foam or polyurethane vs silicone for concrete, be sure you’re able to get your money’s worth.
  • Environmental Concerns: We already pointed out the use of isocyanates in some polyurethane formulations. For these formulations, it is important to consider the possible environmental risks that abound in the production process. And, be sure to conduct proper disposal and handling.
  • Degradation in Sunlight: When they come in contact with the sun’s UV rays, some polyurethane materials could degrade. This puts a major limit on their possible outdoor applications, although the use of coatings and additives could improve this. 
  • Not Biodegradable: Polyurethane is not biodegradable. Once again, this is why you want to make sure you dispose of it properly – especially if it’s used to make single-use products.
  • Processing Complexity: Compared to most other materials, the processing of polyurethane can be more complicated. 
  • Potential VOC Emissions: You also need to consider the fact that some polyurethane products could release volatile organic compounds (VOCs) both during and after the production process. This impacts air quality and can be a hazard on its own. 
  • Temperature Sensitivity: All of the material’s properties listed above can easily be influenced by changes in ambient temperature. And, as you can imagine, they will have effects on the material’s long-term performance. 

Conclusion 

Everyone is faced with the choice of silicone vs polyurethane. And, we always recommend that you make your decision based on what you’re trying to achieve and the product you want to make.

At Legenday, we’ll be here to provide high-quality material options based on your choices. Just as well, feel free to contact us if you need a consultation or counsel on manufacturing processes. Reach out to us, and let’s see how we can be of help to you.

Frequently Asked Questions 

  • Is Silicone cheaper than PU? 

There is no uniform answer to this as the cost estimates for both materials usually vary based on the  suppliers. So, the first thing you need to do is get a price quote before you make a decision. 

Just as well, we recommend that you exercise patience in this regard. Keep in mind that the fact that a material is cheaper than the other doesn’t necessarily mean that it is the right choice for you. So, before anything else, we recommend that you prioritize overall quality. As long as the material meets your needs, you shouldn’t have much of a problem. 

  • How is silicone made? 

Different manufacturers make their silicone polymers using different methods. However, the general process usually incorporates steps such as the production of silane, material polymerization, and much more. 

At Legenday, we make use of only the best production processes, ensuring that you get a high-quality polymer that is able to meet your needs. 

  • Which material lasts longer – silicone or PU?

If longevity is your biggest priority, then you might get better service from silicone. With the material being inorganic, its production process leaves space for additives that can help increase its overall shelf life.

  • Is PU eco-friendly? 

Compared to silicone, PU isn’t so eco-friendly. The material is capable of releasing isocyanates and VOCs, all of which can impact air quality and generally have a negative effect on the environment. Nevertheless, modifications can be made to the material to improve its effects on the environment. 

In terms of application, however, there isn’t much to worry about from an environmental point of view.

  • Can silicone be applied over polyurethane?

If the need arises, you can apply heat treatment to polyurethane before coating it with a silicone-rubber material. From there, you can apply the silicone-rubber at room temperature once the eating process is complete.

  • Silicone vs polyurethane sealants: Which one should you choose?

At the end of the day, this depends primarily on what you’re looking to achieve. Silicone and polyurethane provide different benefits and demerits, and you will need to be more careful with your selection. 

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