Polyurethane vs Silicone
Silicone and polyurethane are common types of materials used to produce many products and components. While both materials may be used to create similar objects, the physical properties and environmental conditions in an application will ultimately dictate the appropriate material for your product design. In this post, we will uncover the differences between silicone and polyurethane to streamline your material decisions.
What is Silicone?
Silicone, also known as polysiloxane, is a rubbery elastomeric material made of carbon, hydrogen, oxygen, and silicon. Like polyurethane, most silicone is a thermosetting material that can essentially take on any shape or form, depending on the viscosity and manufacturing process. When designing with silicone, there are typically three types of materials available, such as Liquid Silicone Rubber (LSR), High Consistency Rubber (HCR), or Room Temperature Vulcanizing (RTV). Each material option features a different set of physical properties and molding techniques to accommodate various design needs. Specific chemical additives can be incorporated in silicone during its raw, liquid state to achieve a range of properties, including tear strength, temperature, electrically conductive, and flame resistance. Silicone is available in hardness levels between 10 to 90 Shore A.
What is Polyurethane?
Polyurethane is formed through the chemical reaction between a polyol and diisocyanate. Unlike silicone, polyurethane can be soft and flexible as a cushion to something as hard and rigid as metal. Thermoset polyurethanes, in particular, can be chemically engineered into a solid or foam and portray a wide range of physical properties and surface finishes through either a cast molding or Reaction Injection Molding (RIM) process. Cast molding with thermoset polyurethane can offer a significant amount of customization to meet specific design and performance requirements, while RIM combines the superior properties of thermoset polyurethanes with the adaptability of injection molding techniques. Because of this, there is almost an endless range of material options and design flexibility to meet exact requirements. Polyurethane is available in three hardness scales, including Shore A, D, and 00. For more information about hardness and how its measured, click here.
Differences Between Silicone & Polyurethane
Despite making similar products, silicone and polyurethanes differ significantly. As an example, the table below breaks down these variations to help discern between these two sought-after materials:
|Commonly injection, cast, or compression molded||Commonly cast or Reaction Injection Molded (RIM)|
|Foam is often considered a specialty material, due to high costs & processing difficulties||Can be engineered into many types of solid and foam materials|
|Hardness levels typically range in Shore A scale||Hardness levels can range between Shore A, D, 00 scales|
|Able to withstand temperatures between -65°F up to 500°F||Able to withstand temperatures between -80°F up to 300°F|
|Exhibits high resistance to extreme temperatures, but often displays low tensile strength, abrasion resistance, & wear and tear properties||Exhibits high abrasion resistance, tensile strength, & extended wear and tear properties. Physical properties can be customized to meet specific performance requirements|
|Material costs are significantly higher, especially for foam||Offers a more economical setup for small & large runs|
Which Material Should You Choose?
Silicone and polyurethane can fit into a wide range of products and components, depending on your application and performance requirements. However, polyurethanes can produce stronger, more robust products with an almost endless range of physical properties and small to large, complex geometries. For this reason, this adaptable material is often considered for applications, such as military & defense, medical devices, and paper & media handling to name a few. Silicone, on the other hand, is typically best for products that must withstand high resistance to extreme temperatures. For instance, silicone can often be found in consumer and medical products, such as baby goods, baking or cooking supplies, and tubing or hoses, depending on the type of silicone. When evaluating silicone vs polyurethane, it is important to consider the key physical properties required for improved performance.
If you are seeking material assistance for your product design idea, complete our design tool, here, or download our Durethane datasheet below to explore the superior properties available.