Polyurethane Mold Rubber vs Silicone Mold Rubber: What Variables Determine Which To Choose?

There is no doubt to the fact that rubber is one of the most versatile materials in the world. The material helps across different manufacturing processes, providing a safe and reliable way to make molds and build different components. 

However, when looking to create the best flexible molds, most manufacturers are faced with the option of choosing between polyurethane mold rubber and silicone mold rubber. In this article, we’ll shed light on this comparison and help you to understand which of these might be better for your use across different product manufacturing stages.

Polyurethane Mold Rubber vs Silicone Mold Rubber: What Are They?

Understanding Polyurethane Mold Rubber 

Polyurethane mold rubber is a synthetic rubber material that has become especially popular in casting and mold making applications. Known to many as PU rubber or polyurethane rubber, the material is especially prominent for its operational versatility and ability to stand the test of time. 

With polyurethane mold rubber, you have a rubber variant with considerable hardness as well as an ability to perform at a high level. It is tough and strong, while also resisting abrasion and allowing you to reproduce metals with the finest details available. 

Just as well, combinations between polyurethane and other materials can easily be achieved to get rubber variants. Whether it’s wax polyurethane or some other mix, the materia easily works well with other components, giving you the perfect baseline for miniature silicone molds. 

Polyurethane mold rubber comes with different formulations and properties. So, if you’re to make a choice, you want to make sure that its properties are in line with your molding and casting requirements. Examine your project needs when selecting the right type of PU rubber, and make sure that you can achieve high-quality results from molding and making your cast.

Key Properties Of Polyurethane Mold Rubber: 

Overall, it’s pretty easy for you to check the following characteristics when choosing polyurethane mold rubber: 

  • Optimal Flexibility and Elasticity: This rubber variant offers an impressive level of elasticity that allows it to work for different functions. When you’re looking to create a mold with complex details, it easily conforms to what you need. 
  • Operational Durability: You also get a considerable amount of wear and tear resistance from polyurethane. This means that it works quite well as a flexible casting material that easily works with different castings without degrading or suffering any loss to its form. 
  • Dimensional Stability: Even after applying considerable pressure to it, you can count on PU rubber to maintain its dimensions and shape. Over time, this means you get to enjoy consistency and repeatability in the moldings as well as the material. Even better, you don’t need to make any adjustments.
  • Chemical Resistance: Another prominent feature of PU rubber is that it generally resists a broad range of chemicals. This expands its application scope considerably. 
  • Ease of Use: And, for manufacturers looking for a tool that they can work with, PU rubber is a solid option. Mixing and pouring the material is as easy as it gets, so both beginners and expert mold makers will be able to work with it.

Exploring Silicone Mold Rubber 

Silicone rubber is one of the most popular products on the planet. The stretchy material is used in both home and industrial applications, and it has pretty much become a staple in modern life. 

Thanks to its stretchy and elastic nature, silicone has also become a major material for rubber manufacturing and mold casting. These silicone molds and casts can be used in different industries as well, expanding their functionality significantly. 

Interestingly, silicone mold rubber is an artificial rubber variant with a chemical makeup that incorporates different polymers and elastomers. As a synthetic polymer, silicone mold rubber works in different casting and molding applications. 

Key Properties Of Silicone Mold Rubber

To function effectively, silicone mold rubber conforms to some of the following characteristics: 

  • Flexibility and Elasticity: Silicone mold rubber also provides impressive levels of elasticity and flexibility. Anyone looking to create intricate details and undercuts will be able to do so without stress. 
  • High-Temperature Resistance: Inherently, silicone rubber does quite well to resist high temperatures. As such, you can rest assured about the material’s ability to work in casting projects that require elevated curing temperatures. 
  • Release Properties: You also get impressive release properties when you work with silicone mold rubber. As such, castings made with the material can be taken out of the mold without the need for any release agents. 
  • Non-reactivity: If your molding task will require additional materials, then you can count on silicone mold rubber to work perfectly. The material is known for its ability to work well with other materials, and as such, you can make easy combinations without worrying about the right fit. 

Polyurethane Mold Rubber vs Silicone Mold Rubber: General Advantages & Disadvantages of Each Rubber

A plumber applies silicone sealant to the joining of ceramic tiles in the bathroom

So, too give you a clear understanding of the benefits of both, let’s look into what you could get from both: 

 

Property Silicone Mold Rubber  Polyurethane Mold Rubber 
Cost-Efficiency  Upfront, it can be more expensive. But, the costs can be more advantageous in the long term due to mold longevity.  Usually more cost-effective for high-volume production. 
Medical Simulation Perfect for overall medical applications – from training models to simulations and more.  Works for medical simulation, but you might run into longevity challenges.
Special Effects Commonly used in special effects and film production for durability and detail reproduction. Suitable for special effects, especially when wear resistance is required.
Food Grade Functionality Perfect for food grade applications, as long as you use the ideal material grade.  Not necessarily the right fit for food contact. 
Operational Longevity  Renowned for its long-lasting build and its ability to easily hold its own when pulled through multiple castings. Can generally handle frequent use, but you might not be able to get the same lifespan as you get with silicone.
Release Properties Release properties are good, so it most likely won’t need any additional release agents.  You might need additional release agents when working with these mold rubbers. 
Chemical Compatibility Works well with a broad range of casting materials  The material’s compatibility will most likely change in terms of formulations; so be careful when considering chemical resistance. 
Intricate Shapes Perfect when you need to capture intricate details and work with delicate surfaces. And even better, you don’t damage the original object.  Also great for complex shapes – as well as intricate details and deep undercuts. 
Durability  Lasts quite long and will be able to withstand several castings without experiencing any significant wear. Offers impressive levels of durability and wear resistance, and is especially adept at high-volume casting. 
Wear Resistance Wear resistance here doesn’t necessarily compare favorably with polyurethane molds.. Optimal wear resistance across the board. So, it works well for abrasive casting materials.
Temperature Resistance High-temperature resistance, suitable for casting materials requiring elevated curing temperatures. Limited high-temperature resistance in some formulations.

Polyurethane Mold Rubber vs Silicone Mold Rubber: Which Is More Expensive?

At the end of the day, everyone wants to save money when choosing the right material for casting rubber parts. As such, it’s understandable that you might be looking for which of the materials will help you to save as much money as possible. 

Generally, there is no custom cost profile for these materials. Instead, you can generally look into a few considerations when choosing which to get from a pricing perspective:  

Polyurethane Mold Rubber:

  • Variability in Pricing: In most cases, the amount of money you pay for polyurethane mold rubber will vary based on the product formulation itself. Some polyurethane rubbers are designed to properly fit into specialized applications, and this means that access to them will be more challenging. To get these formulations, you’d need to pay more money. 
  • Quantity Discounts: You might also be able to get discounts when you make purchases of polyurethane mold rubber in larger quantities. Many suppliers offer bulk discounts to users, making the per-unit cost more manageable for larger projects. 
  • Specialized Formulations: Polyurethane mold rubbers come in different variations – each with its own specific applications. For those that require high-temperature casting and industrial applications, you’d find that they tend to be more expensive as they offer more advanced properties. 
  • Ease of Use: While polyurethane mold rubber is generally easy to use, you can find variations that require a few more accessories and additives for pouring and mixing. As such, these requirements tend to have a much broader effect on overall cost.

Silicone Mold Rubber:

  • Standard Formulations: Like the polyurethane counterparts, silicone mold rubbers also tend to come in different formulations. The standard variants are competitively priced, so if you’re looking to save money on your rubber moulds, then they might be the perfect choice for you.
  • Food-Grade Options: If you need to make a mold for a product that will be edible,. Then food-grade silicone easily works. The material is perfect for things like silicone teethers, medical implants, and much more. However, due to their specialized application, these molds tend to come at a higher price point. 
  • Longevity and Reusability: The silicone mold rubbers that work best for long will undoubtedly cost more. However, this shouldn’t discourage you – thanks to the material’s longevity, you will be able to save costs across the board.

At the end of the day, the decision of whether silicone or polyurethane mold rubber will be more expensive will depend on these factors. At Legenday, we provide detailed price quotes for out mold products, allowing you to make necessary assessments and to come to proper conclusions before going forward. 

Just as well, you can rest assured that our rubber mold products are of the highest quality. So, overtime, you get to save money. 

Polyurethane Mold Rubber vs Silicone Mold Rubber: Which Is Easier To Use? 

When it comes to ease of use, both polyurethane and silicone rubber molds also come with their pros and cons. And if you’re looking to get a flexible molding material, you definitely want to make sure that you have something that is easy to use and which won’t be so challenging to work with.

So, how do the two compare across the board? 

Polyurethane Mold Rubber:

  • Mixing: For polyurethane mold rubber, you usually get to mix two major components – a polyurethane base and a curing agent. Generally, ease of mixing will vary based on the product you’re working with. However, as long as you’re able to achieve precise ratios for the components, you shouldn’t have an issue going forward.
  • Pot Life: The pot life for polyurethane rubbers is usually limited. This means that you only have a small window of time to mix and pour the material before you start to see curing. 
  • Release Agents: The polyurethane mold rubber can require the use of a smooth on mold release agent to cut out the chances of sticking. This is especially true if you’d be making different castings.
  • Venting: There are cases where polyurethane molds will need additional venting to enable air escape during casting. By doing this, you can prevent the formation of air bubbles in the final cast that you get. 

Silicone Mold Rubber:

  • Mixing: Unlike polyurethane old rubber, silicone flower molds consist of a single-component material that won’t need to be mixed with catalysts. So, you don’t need to bother about precision in ratio measurements and can insead focus on simplifying the overall mixing process.
  • Pot Life: Silicone mold rubber offers a more extended pot life than polyurethane. As such, you get greater flexibility in pouring – especially if you’re working with larger molds.
  • Release Agents: While you could add release agents to silicone mold rubber, it isn’t a necessity. The material already exhibits high levels of inherent release properties, so you can work without any release agents if you choose. 
  • Venting: One of the benefits of silicone molds is that they can conveniently capture intricate details without any venting requirements. This makes for a much easier mold-making process across the board. 

All in all, most users tend to find silicone mold rubbers easier to use. Whether you’re a beginner or you’re working on projects that require less accurate mixing, this material does quite well across the board. All you have to do is make sure that you can optimize the properties of the rubber, and you’re good to go.

Polyurethane Mold Rubber vs Silicone Mold Rubber: Durability Comparison

Durability is one factor that you absolutely want to consider when selecting a mold option. At the end of the day, everyone wants to save money. So, whether you choose polyurethane molds for concrete or silicone molds for jewelry, you want something that will easily be able to stand the test of time and which won’t break or budge. 

So, how do polyurethane silicone molds compare in this regard? 

Polyurethane Mold Rubber Durability:

  • Wear Resistance: In terms of wear resistance, polyurethane mold rubber is quite solid. It easily holds its own when put through different castings, and it doesn’t experience any loss of detail when considering the mold.
  • Tear Strength: High tear strength is another reason why you might want to select polyurethane rubber. You can use it to mold different objects with undercuts and intricate shapes, making it a very reliable manufacturing option overall. 
  • Abrasion Resistance: Polyurethane molds don’t have a problem with keeping their form even when they go through abrasive conditions. For extended periods, they don’t show any form of degradation. 
  • Impact Resistance: Some variants of polyurethane mold rubbers can withstand impact as well. So, if you need to create a mold that will be subject to extended physical handling and stress, then you could consider this material as well. 
  • Chemical Compatibility: Your formulation of polyurethane mold rubber can be made compatible with different casting materials. However, you want to keep in mind that your choice of formulation will be important here if you hope to optimize long-term chemical resistance. 
  • Temperature Resistance: Sadly, the same resilience that polyurethane molds have to chemicals doesn’t necessarily extend to the temperature front. In most cases, you’d find formulations that don’t necessarily work for casting materials that require elevated curing temperatures.

Silicone Mold Rubber Durability:

  • Longevity: The biggest pro that silicone mold rubber has going for it will have to be the longevity that you get. The material is capable of withstanding several castings over an extended period, all without showing much signs of degradation. 
  • Tear Resistance: Typically, silicone rubber molds have impressive levels of tear resistance. This means that the molds will be able to hold on to their structural integrity when physical stress is impressed upon them.
  • Abrasion Resistance: Some types of silicone mold rubbers tend to be durable. However, compared to polyurethane formulations, they might not necessarily exhibit the same levels of abrasion resistance. 
  • Chemical Compatibility: You can count on silicone mold rubber to operate with a broad range of casting materials. It also resists chemicals, although you want to be careful with the formulation you select as not every one works with all chemicals.
  • Temperature Resistance: In terms of temperature resistance, you don’t have anything to worry about as far as silicone molds are concerned. The molds are perfectly capable of withstanding the heat generated during curing, so feel free to apply this process as you see fit.  
  • UV Resistance: Another added benefit of silicone mold rubber is its resistance to the sun’s ultraviolet rays. The material is perfect for outdoor functionalities, and it can come in contact with the sun’s rays without experiencing any significant degradation. 

Polyurethane Mold Rubber vs Silicone Mold Rubber: What Are They Best Used For?

Both polyurethane and silicone mold rubber have unique properties that make them ideal for different applications. As such, your choice will depend on your application requirements.

Generally, polyurethane mold rubber provides a broad range of functionalities that allow it to work. You can consider it for the following situations: 

  • High-Volume Reproduction: The biggest functionality benefit for polyurethane mold rubber is its use in high-volume productions. For massive volumes, the rubber variant is more than perfect. 
  • Wear Resistance: Polyurethane molds are also perfect for applications where you have abrasive casting materials. From working with neoprene resins to concrete and more, the material’s ability to maintain its shape is critical.
  • Complex Shapes and Undercuts: If you need to mold objects with complex shapes, then you can count on polyurethane mold rubber to work out. The material exhibits impressive tear strength, so it works well for intricate designs. 
  • Cost-Effective Production: If your project requires a considerable number of castings, you can find that polyurethane molds offer a more cost-efficient option.
  • Industrial and Architectural Elements: Most industrial applications tend to use this material as well to create molds. 
  • Prototyping: You can also find polyurethane being used to create molds of models and prototypes for different products. 

Silicone Mold Rubber:

  • Food-Grade Applications: Food grade silicone has become especially popular for several functions. And when it comes to the mold, you also find silicone molds being used to create kitchen utensils and some food items.
  • High Temperature Casting: For applications that involve casting materials at elevated curing temperatures, silicone mold rubber is also ideal. 
  • Intricate and Delicate Objects: One of the biggest benefits of silicone is its ability to conform to even the most intricate details. Even better, you don’t have to cause any damage to the original object. 
  • Medical Simulation: When creating simulations of items and devices that are applied in the medical space, silicone mold rubber is an ideal choice. This extends to dental and orthopedic functionalities as well. 

At the end of the day, both options come with their strengths and weaknesses. However, the choice for you will depend on the intricacies of your project and its parameters.  

Silicone rubber molds work better when you want optimal longevity and to work with intricate details. However, polyurethane rubber molds work better if you have a project that needs high-volume production and wear-resistant applications. 

By clearly understanding your project parameters and what you’re looking to achieve, you can optimize the results of your process. 

Expert Tips for Successful Mold-Making

Now that you understand the option to choose when making your mold, you should also keep some important mold creation tips in mind as you set out to conduct this process. Regardless of the option you choose, here are a few tips you want to maintain: 

Prepare Your Workspace:

Ensure that your workplace is clean and properly organized. Factors such as ventilation and tool selection should be prioritized here, so you can enjoy a more seamless mold-making process.

Properly Prepare the Original Object:

Make sure to clean the original object thoroughly. This way, you can take our dirt and dust and ensure that the mold quality is optimized as much as possible. If you find any delicate surfaces, you can make use of a sealer or release agent to clear it. 

This will be especially important if you hope to create custom silicone molds. You can check out the polyurethane sealant vs silicone to learn more about the differences between the two.

Build a Mold Box or Containment Structure:

We recommend building a mold box or a containment structure around your object to help create a more defined shape and size. Just as well, ensure that the box is strong enough and won’t leak – this way, you prevent any rubber from leaking.

Measure and Mix Mold Rubber Accurately:

Considering that the molds won’t be used on their own, you want to focus on making sure that all rubber components are in the right proportions. From the curing agent to the base and more, ensure that all components are in the right order. 

Eliminate Air Bubbles:

The presence of air bubbles will significantly affect your mold quality. So, see to it that they are minimized as much as possible – if not completely eradicated. 

To do this, ensure a thorough mix of the old rubber. You can also make use of a vacuum chamber to achieve the right bubble elimination effect.

Pour Mold Rubber Carefully:

While pouring the mixed mold rubber over your prepared object, do so in a slow, paced manner. This allows you to prevent any air entrapment and will also cut down on the presence of air bubbles. 

Allow Sufficient Cure Time:

Manufacturer recommendations should be followed in terms of curing time and temperatures. Just as well, see to it that the mold is entirely cured before you go on to the casting process. 

Demold Carefully:

As you start to demold the cured mold from the original object, be careful with the process. The last thing you want to do is to damage the object or the mold. If the need arises, you can get a mold release and use it between both halves. 

Proper Mold Storage

You should store the molds in a cool, dry place without access to direct sunlight. Temperature control should be prioritized, and you should also keep molds clean and free of dust. 

Safety First:

You should always focus on safety when conducting the molding process. Wear personal protective equipment (PPE) as recommended by your manufacturer and focus on all safety precautions that are related to the process and the specific mold rubber and casting materials. 

Conclusion

When conducting rubber mold creation and manipulation, selecting the right material option can easily be the key to success for you. Fortunately, you have two impressive options in polyurethane and silicone mold rubber. 

Choosing the right one will generally require a consideration of your requirements. We’ve outlined how each option compares above, so feel free to see which works for you. Even better, you can reach out to us at Legenday to help provide your high-quality materials – or for a consultation if you need one. 

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