Before we begin to talk about multi-durometer parts, it is essential that we take time to first discuss what a durometer is. A durometer is an instrument that is used to test and measure the hardness of various materials, including polymers, elastomers, and rubbers. The higher the number on the scale, the greater resistance the product has to indentation. Therefore, the harder you need a material to be, the higher the number should be on the durometer. Lower numbers on the scale indicate less resistance, and therefore, a softer material.

The entire name of the scale is actually the Shore® durometer scale, named after inventor Albert F. Shore in the 1920s. Eventually, the initial Shore durometer scale that he invented, evolved into multiple durometer scales. The A, D and OO durometer scales are the most commonly used ones in the measuring of plastics, silicone, and rubber parts.

When you require urethane products with varying degrees of hardness, ESCO Plastics can provide multi-durometer custom castings that are suitable for a wide variety of manufacturing applications. To speak with an ESCO Plastics representative about urethane multi-durometer parts, our production capabilities, or to place an order, please call us toll-free at 1-800-223-4144, locally at 281-443-3710, send us an email, or submit our online contact form. We’d love to hear from you!

In order to measure the hardness of a material, durometer scales take a measurement of the depth of an indentation caused by an applied force on a standardized foot presser. The depth of the indentation is dependant on several factors, including the hardness of the material, its viscoelastic properties, the shape of the presser foot, and the duration of the test. Viscoelastic properties simply refers to materials that exhibit both viscous and elastic characteristics when undergoing stress.

A measurement of 0 indicates the maximum possible indentation of a material, and a measurement of 100 indicates that almost no indentation is possible as the material has a very high resistance. To give you an idea of where certain products rank on the hardness scale — a gel shoe insole would receive a measurement of 30 on the Shore OO scale, a rubber band would come in at just over 60 on this scale, but at a 20 on the Shore A. A tire tread is close to 100 on the Shore OO, a 70 on the Shore A, and a 10 on the Shore D, and a hard hat is an 80 on the Shore D scale.

Urethane parts can be poured with both hard and soft segments on the same part. These parts reap the benefits of both segments. The different hardnesses of the materials bond together without the need for screws or other fasteners, making them superior in terms of strength and durability. Some parts require a soft segment to seal in an application, while a harder segment provides the structural support that is needed. Multi-durometer parts perform well in these applications.

Now that we have looked at some of the reasons for different scales and varying degrees of hardnesses in materials, let’s look at why an accurate durometric measurement of your product is important. When you consider the examples we provided, you can begin to understand that choosing the right hardness is crucial to the overall success of your product. If you were to create a tire tread that had the softness of a gel insole, it would not be able to support the weight of the vehicle on which it was placed. On the other hand, if a tire tread were created with the hardness of a hard hat, it would never afford the smooth and comfortable ride that everyone wants.

Durometric measurement is also important for helping to make sure that your product will be able to withstand the different stressors that may come from the different environments in which it will be used. For example, friction is usually one of the most important factors to take into consideration in drive applications. In this situation, you would want to make sure that you have selected a durometer that is able to adequately drive the parts it comes into contact with. Too soft, and it will become deformed over a period of time. Too hard, and it will put unnecessary stress on other parts. Choosing the right durometric measurement is pivotal to the success of your product. Don’t hesitate to contact ESCO Plastics today if you need assistance with determining the right durometric measurement for your processes.

What Each Scale Indicates


Since each durometric scale measures essentially the same thing, you might be wondering why there are different scales. Each Shore durometer scale measures the varying levels of hardness of different materials, but they are each designed to precisely measure materials within a certain range. The scales are fine-tuned to either measure incredibly soft products, incredibly hard products, or a wide range of products between these two extremes.

Each scale has a differently shaped presser foot as well as a specific spring force. The Shore OO scale measures extremely soft materials such as a gel shoe insole. The Shore A scales measures a much wider range of hardness in materials, including mouse pads, smartwatch bands, and leather belts. The Shore D scale measures extremely hard rubbers, semi-rigid plastics, and rigid plastics such as shopping cart wheels, toy blocks, and PVC pipes.

Polyurethane and cast urethane products are manufactured in such a wide variety of hardnesses, that it is important to be able to accurately measure each one for the application in which it will be used. When urethane products need to have the benefits of both soft and hard characteristics, a multi-durometer part is the best way to go. Multi-durometer parts often do away with the need for metal backing or support plates. A simple change away from these expensive metal backing plates reduces costs, improves delivery, and removes the corrosiveness of the metal. Improve your application’s performance by utilizing the versatility of this multi-durometer process. Call ESCO Plastics today and let us know what we can do for you.

When deciding on the level of performance that you need from the products used in your application, it is important to consider some of the benefits of multi-durometer parts. Polyurethane products have many amazing qualities that make them far superior to rubber, metal, and even plastic products. When it comes to a range of hardnesses, no other material surpasses molded urethane products. It is precisely this broad range of hardnesses that make it such a great candidate for combining the properties at both ends of the scale of to create a multi-durometer part. We can create the parts you need that will have the softness to seal in an application while retaining the hardness needed to provide the appropriate structural support.

Coupled with the property of hardness is the benefit of a high load-bearing capacity. When it comes to tension and compression, polyurethane products have proven to have a high capacity. These products may undergo an overall change in their shape under the pressure of a heavy load, but maintain their ability to return to their original shape once the pressure of the load is removed. In fact, the material indicates very little compression has set in when it is designed accurately for a specific application.

Strong Resistance


While there are certain non-polyurethane products available that are great performers, their durability is challenged when exposed to certain elements or environments. When you consider the applications in which your product will be used, there are a number of factors that should be considered to help you determine the part that you need manufactured. For example, if the product will be in an environment where it will experience severe wear from either abrasion or impact, then only a molded urethane product can provide the resilience and resistance you need. In processes where there will be high stress on a product that may put it at risk of tearing or breaking down, a polyurethane product will provide the qualities of high tear resistance and high tensile properties that you want.

Polyurethane products also exhibit incredible resistance properties when exposed to materials such as water, oil, and grease. When you take the resistance properties of urethane products and then combine a softer elastomer with a harder one, you get an abundance of benefits, as your product now offers the flexibility of a soft material with the strength of a hard material. If you are not sure which multi-durometer product is best for your applications, then be sure to call ESCO Plastics today and let one of our trained specialists help you determine what is best for your needs.

Excellent Resilience

Urethane products have not only strong qualities of resistance, but also great resilience properties which make them excellent performers. Whether your products will be used in environments where they will be exposed to harsh environmental conditions or a variety of chemicals, you can rest easy knowing that your multi-durometer polyurethane products will withstand even the harshest settings.

In environments where mold, mildew, and fungus occur frequently and would begin to degrade even the strongest metals, rubbers, and plastics, molded urethane products will exhibit a true resilience. Their chemical composition is precisely what makes them inhospitable surfaces for these types of growth, and therefore an excellent choice for products manufactured or used in tropical environments. Due to the high humidity of tropical environments, it is also important that your components have effective electrical insulating properties.

In terms of actual resilience, you would be hard-pressed to find a better-performing product than polyurethanes. Resilience is the elastic energy that a given material can absorb and then release once the load-bearing weight is removed. While rubber is generally considered a resilient product, polyurethane products far exceed even their capabilities. Molded urethane products can withstand more loads than rubber due to the unique combination of their hardness and flexibility.

You may need polyurethane products that be used in applications where they will need to absorb repeated shock or vibration. Their ability to absorb the energy from shocks and vibrations coupled with their ability to quickly return to their original shape are part of what make these products such excellent performers.

Polyurethane elastomers (PU) are part of the polyurethane group and are capable of being casted. Elastomers are found in a variety of products, from hoses and cables to adhesives and clothing. Because elastomers are part of the polyurethane family of products, they retain the great qualities that polyurethane itself possesses. Elastomers have a high resistance to the following environmental and performance factors:

  • Abrasion and Friction
  • Wear and Tear
  • Water
  • Oil
  • Grease
  • Chemicals

In addition to these areas of resistance, elastomers are also resilient in environments with drastic temperature changes and are ideal for use in humid climates, as they will not promote mold, mildew, or fungal growth.

Versatility and Customizability

Polyurethane has a versatility that is unmatched by any other product. It can be custom-tailored to match parts that you currently use so that you will not have to miss a day of production waiting on a replacement part. You work in a fast-paced industry, so when you need a replacement, you need it now, and ESCO Plastics can help you with that. No matter what you need, we are able to execute your solutions quickly. We can work with you to meet the custom specifications needed for your application.

Multi-durometer parts can also be used to help repair or replace coatings on your tools so that they will return to their original level of durability. Whether you need rolls, brushes, rings, tubes, nozzles, clamps, seals, or any other component, polyurethane is the perfect choice to meet all of your production needs. You can send an existing component to us so that we can create a model which you approve before the entire run of the product is begun.

At ESCO Plastics, we take great pride in our work and our clients’ satisfaction. No matter what application or environment your products will be placed in, we know that you will glad you chose to order multi-durometer polyurethane products from us.