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Merryweather Foam Blog

Since 1948, we have been industry leaders in fabricating unique, foam components for customers in the medical, sound absorption, automotive, and unique packaging industries. At Merryweather Foam, we pride ourselves on our ability to combine experience, innovation, and excellent customer service. We have the knowledge, manpower & equipment to help you get the job done. Visit our website to see our fabrication portfolio as well as our capabilities.

Should you be using PORON® Urethane Foams?

Also available in Medical Grades

When budgets get squeezed the selection and purchase of every component, spare part or piece of material is scrutinized carefully. Many times engineers and maintenance technicians have little choice but to go with the least expensive, despite knowing it's likely to fail prematurely. That in turn leads to unplanned downtime and additional repair work, the costs of which can quickly negate the initial savings realized.

Gaskets and sealing materials are a good illustration. In many applications a better quality foam material will last longer and reduce overall costs, yet it's difficult to convince management of this.

PORON® Urethane foam is an excellent example. Properties like superior uniformity and compression set resistance result in much longer life and potentially lower overall costs. Making the case for using PORON® hinges on understanding the differences between it and other foams, and the benefits that result.

Introduction to PORON® Urethane Foams
PORON®is the name of a family of urethane foams produced by Rogers Corporation. They use a proprietary process plus special additives to control bubble formation during the foaming reaction. This results in an open cell structure with small pores of very consistent size that are distributed evenly throughout the foam. In contrast, the pores in other foams have a far more random nature.

The benefit of uniform pore size and distribution is predictable properties and performance. Two pieces of the same grade of PORON® will display the same characteristics, (within limits, naturally,) regardless of when each was made. In fact it would be fair to call PORON® an engineered foam.

Performance Characterization
The piece-to-piece consistency of PORON® lets Rogers Corporation publish a broad array of test and measurement data. In addition to the density numbers put out by almost all foam manufacturers, Rogers provide ASTM test results along with other material properties.

In select applications it's important to know parameters like thermal conductivity, dielectric constant and surface and volume resistivity. More generally, users of flexible foam fabrications want to know about elasticity and recovery. Merryweather can provide detailed performance information for every grade of PORON® on request, but the numbers below for PORON® 4701 (a firmer grade,) should give a general appreciation.

  • Density: 15 – 30 lb/ft3
  • 25% Compression force deflection: 8 – 60 psi
  • Shore "A" durometer hardness: 18 – 55
  • Max compression set: 10%

In less technical terms, PORON® is quite soft and resists taking a compression set. In other words, it's good material for many gasket applications.

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PORON: When Fire is a Possibility

Many types of foam burn rapidly. Some even drip burning material on to the surface below, helping a fire spread rapidly. However, there are foams formulated to provide high levels of fire resistance. Whenever possible these should be used near potential sources of ignition.

The fire-resistance of foam for use in appliances, enclosures and equipment is measured by testing to procedures set out in the UL94 standard. (Note: this does NOT address foam used in upholstery or building construction.) Flammability (the ease with which a material burns,) is shown by a UL94 rating, such as the UL94 V-0 indication carried by PORON® 4701-V0-M.

Foam Flammability
Anything composed of carbon and hydrogen will burn if conditions are right, and that means having oxygen and an ignition source. All foams are formed from these elements and oxygen is always present in the atmosphere, so to start a fire all that's needed is an ignition source. This could be provided by an electrical spark, such as when motors or relays produce arcing. High temperatures, as caused by friction between moving parts or electrical current flowing through wiring are others possible causes.

UL94 flammability ratings
The UL organization is an independent global testing organization dedicated to improving safety. Founded in 1894 as "Underwriters Electrical Bureau" it started out by testing noncombustible insulation material and grew to become first "Underwriters Laboratories" and now just UL.

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Selecting Foam for Sealing and Gasket Applications

Fabricated Gaskets
​Gaskets come in a boundless array of shapes, sizes and materials, but they all do the same job. Gaskets exist to seal gaps. It might be the gap between two pipe flanges, the gap around an electrical cabinet, or even the gap between two pieces of ducting in an a/c system, but the gasket's job is always the same: fill that gap.

Flexible foam fabrications are often a good choice for gasket material. There are many different types of foam but most are lightweight, can be cut into various shapes, and may be purchased pre-laminated with pressure sensitive adhesive (PSA) for ease of installation. Most importantly, most foams compress readily and do an excellent job of sealing out, (or keeping in,) fluids, gases, dusts and other contaminants.

For a fabricated foam gasket to perform as needed it must be matched to the application. That demands a good appreciation of the following:

  • How gaskets work
  • Typical gasket applications
  • Key performance characteristics
  • Environmental factors
  • Media
  • Foam gasketing materials available from Merryweather.

How Gaskets Work
If surfaces like pipe flanges and cabinet doors could be made perfectly flat there would be no gaps for fluid to leak through. In the real world though, surfaces are far from flat. Sheet metal panels inevitably have undulations that cause varying gaps as a door is closed and pipe flanges have machining marks that create leak paths. And even if the surfaces were smooth, alignment tolerances would still create gaps of varying widths.

A gasket is a piece of compressible material fitted between two surfaces that will be clamped together. It's job is to prevent leaks from or through the joint. Being soft, it squashes down more where the gap is smaller while remaining thicker for wider spaces. Its softness also lets it flow into small indentations on the two surfaces, blocking even microscopic leak paths.
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Our Rogers Preferred Convertor Status - What It Means to You

We are proud to be a Rogers Corporation Preferred Converter

At Merryweather Foam, we are proud of the relationships we build with our customers and suppliers. We understand companies still do business with people, and we are proud of our knowledgeable and friendly team. Sometimes the results of these relationships are relatively invisible. Other times they result in tangible achievements.

Near the bottom of the Merryweather Foam website's home page, you'll see a series of logos and certifications. We are pleased to have earned the right to display these logos and are happy to share what they can mean to you, our customers and potential customers. One of those is a logo that designates Merryweather Foam as a Rogers Preferred Converter.

Who is the Rogers Corporation?

Rogers Corporation is one of the oldest material manufacturers in the United States. Founded in 1832, its roots are in paperboard manufacturing. Since then, Rogers has successfully evolved and adapted their products, technologies, and manufacturing presence to meet the demands of current and emerging markets. Among many other products, Rogers produces advanced foams for cushioning and protective sealing. Rogers is noted for their reliability, efficiency and performance.

What is the Benefit of Being a "Preferred Converter"?

By achieving Preferred Converter status of Rogers Corporation, Merryweather Foam can provide our customers quicker access to Rogers products at more affordable pricing. This allows us exceptional access to desired Rogers products like PORON® Urethane and BISCO® Silicone materials which are used in gaskets and sealing, impact and energy absorption and heat shielding. This positively impacts our customers using quality Rogers products by providing them with better access at the best pricing available.

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Advanced Cushioning & Gasketing with PORON® Urethanes

PORON® Urethane foams from Rogers Corporation offer high performance solutions that help solve a variety of industry problems. Serving a range of markets, from mobile communications to automotive to more general industrial needs, PORON® Urethane foams exceed performance expectations from one use to the next. Whether sealing against dust, managing vibrations, or providing impact protection, PORON® Urethanes can help.


With an impressive catalog of options, Rogers' PORON® Urethane foams are available in a wide range of thickness options. In addition to performance within an application, PORON® Urethane materials are also easy to fabricate. And while features such as excellent compression set resistance, low outgassing, and good chemical resistance are important, Rogers' materials provide peace of mind. With proprietary technology and a thorough understanding of the markets they serve, Rogers engineers its materials with the end use in mind. But with materials of this quality, "end" is not a word they use very often. Visit our materials page for more information on PORON® or please contact us and we would be happy to help you.

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