Polyurethane elastomers are typically considered excellent electrical insulators. However, there are applications that require polyurethane to be a non-insulator to avoid electrical charge accumulation and the potential for discharge. These situations can be detrimental to part performance and longevity as well as create a dangerous environment – so it is imperative that the right material with the correct conductivity be utilized in these applications. Fortunately, polyurethane can be customized to avoid the risks associated with static buildup and electrical charge discharge – a property known static dissipative.
What is Electrostatic Discharge?
It will first be helpful to better understand a few concepts related to conductivity, electrical charges, and static dissipative polyurethane.
Electrostatic Discharge occurs when two electrically charged materials come in contact. An everyday example of electrostatic discharge is the shock you receive from the static electricity generated when you walk across a rug and touch a metal object, or repeatedly rub a balloon across your head to make your hair stand up. While these examples are mild and have negligible impacts on our bodies, some electrostatic discharge events can have severe impacts on part performance with costly consequences. If not grounded properly, electrostatic discharge in manufacturing or industrial settings can cause significant damage to a product or even create a safety hazard.
One of the best ways to avoid the concerns associated with electrostatic discharge is to prevent the static buildup from occurring in the first place. When designing a part for an application that may be susceptible to electrical charge buildup, it is crucial to identify a way for the static charge to be safety grounded. This can be accomplished by selecting a material with the right level of conductivity. Plastics for example are insulators and often generate static buildup, but static dissipative polyurethane is an excellent material to avoid the risks associated with electrostatic discharge.
The conductivity of a material is related to its resistivity. Resistivity is measured in ohms and represents how electrical current moves through a material. For example, a low resistivity indicates a material that readily allows electric current; in other words, the material has a high conductivity. When it comes to static conductive materials, there are 4 main categories:
- Conductive: materials are materials that have a surface resistance of 1 x 105 ohms/square or less.
- Static Dissipative: materials have a surface resistance of more than 1 x 105 ohms/square but not greater than 1 x 109 ohms/square.
- Anti-Static or Resistive: materials have a surface resistance of more than 1 x 109 ohms/square but less than 1 x 1012 ohms/square.
- Insulative: materials have a surface resistance of greater than 1 x 1012 ohms/square.
How to Achieve Static Dissipative Polyurethane
There are a variety of methods to achieve a static conductive material. As noted below, carbon nanotubes are the additive PSI Urethanes relies on for our static dissipative polyurethane formulations.
- Metal salts: this creates a top surface that attracts moisture which makes the top surface good, but the interior of the part may not be as conductive.
- Carbon Black & Carbon Fiber: both materials require high loading of the filler and can leave marks. The anti-static properties can have hot and cold spots throughout the part. The conductivity of carbon black and carbon fiber additives sometimes changes over time, making this option less effective over the life cycle of the part.
- Cataphor: a reactive chemical that is limited in what formulations and durometers it can produce. In addition, it also lowers the physical properties of the urethane.
- Carbon Nanotubes: a non-reactive material that does not change the physical properties of polyurethane, nor does it mark materials it comes into contact with. It should also be noted that in most cases, there is an improvement in physical and mechanical properties. Very small amounts are needed and conductivity is uniform throughout the part, even if it abrades. This is the process that PSI Urethanes integrates into our formulations.
Would your application require a static dissipative polyurethane formulation?
Contact the professionals at PSI to learn more about our custom urethane solutions including static dissipative properties.
PSI’s Custom Static Dissipative Polyurethane
There are many industries that have to properly manage the potential for electrostatic discharge such as mining, electronics, robotics, high speed manufacturing, automotive, and material storage and handling. Each of these sectors has applications that benefit from custom formulations of static dissipative polyurethane.
Creating a custom formula, such as static dissipative polyurethane, can oftentimes be tricky. There are many factors that will impact the performance, durability, and ultimately, the lifespan of your part or product. It is important that OEMs understand that not all urethane manufacturers offer the same solutions and expertise in custom polyurethane formulations.
At PSI Urethanes, our team specializes in custom polyurethane products. Our in-house engineering and technical assistance staff help you create custom urethane products that meet your application needs and solve your problems. We are experts in custom polyurethane formulation and we offer customers strategic guidance to identify the optimal formula needed.
To define your custom formulation needs, the first and most important step, is gaining a full understanding of the application in which the part will be used. This usually involves detailed designs, an understanding of the product environment and much more. A robust product design that incorporates the right materials is key to preventing electrostatic discharge problems. OEMs must identify where the static is being created and how to safely bring the generated static buildup to ground – one solution being static dissipative polyurethane.
Once the full picture of the application has been realized, OEMs can turn to experts in urethane formulation for guidance and to help identify the optimal formula needed. At PSI, we encourage our customers to leverage our expertise, tapping into our years of know-how and expertise as well as experience with a variety of products and industries. We collaborate with our customers during the design and development process to create the strongest, toughest and most durable custom urethane product to meet their needs – as well as the most cost-effective formulation to achieve their goals.
About PSI Urethanes
Since 1966, through our own independent research and activity in the Polyurethane Manufacturers Association, PSI Urethanes has stayed on the leading edge of urethane technology – including developing advances in new materials, comprehensive designs, and processing technologies. Today we are among the most respected and trusted suppliers of custom urethane products.
We operate from our 45,000-square-foot manufacturing facility in Austin, Texas, which houses an extensive stock of polyurethane products. Our fully equipped manufacturing facility includes a versatile range of processing machinery, which allows us to work on unique, one-of-a-kind projects, as well as high volume components. Our in-house engineering, tooling, and custom mold shop, produces custom and stock production orders with exceptionally fast turn-around times. From conception to prototyping, to final production runs, our technical representatives and design engineers will work closely with your staff to meet your critical tolerances and specifications. You are guaranteed to receive experienced, professional, and personalized service from the first contact through your on-time delivery, with complete confidentiality and dedication to protecting your good name.