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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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All About Foam Convolution

Foam Convoluting is a process through which the surface of a piece of foam is customized to fit the requirements of a particular application. If a piece of foam in a hospital bed, for example, a unique pattern can be designed to allow for both levels of full body support and long-lasting comfort when compared to other options.

The Benefits of Foam Convolution
Foam Convoluting is a maximum yield process. Customizations to the foam are made specifically to provide the highest possible value given what a piece of foam will eventually be used for. If you use foam convolution to design a new piece of bedding, for example, the foam is customized in a way that will allow for things like:

  • Enhanced levels of air circulation.
  • Maximum support.
  • Increased comfort while still maintaining the desired level of support, and more.

It is for these reasons that flexible foam fabrication is often used across a wide range of industries, including in both bedding and healthcare, to create things like:

  • Acoustic applications, like use as sound treatment for a recording studio, thanks to their sound absorption properties.
  • Privacy panels that are more durable, more attractive and more versatile than concrete alternatives.
  • Office applications like ergonomic furniture, which creates a more comfortable environment for employees to maintain productive without sacrificing their health or stamina.
  • Insulation designed to eliminate drafts in a building, thus keeping cool air in during the summer and warm air in during the winter, increasing the energy efficiency of the whole building and decreasing utility bills at the same time.

Foam convolution is also often used in applications like sound management, acoustic treatment and similar products in an audio recording or other entertainment environment. Depending on the pattern being used, foam convolution can absorb mid and low range sound frequencies much better than alternative options.

The Materials Used in Foam Convolution
During this process, foam can be custom fabricated in one of four ways depending on the intended goal:

  • By pattern
  • By the total size of the pattern being worked with
  • By the depth of each intended cut that will be made
  • The spacing between multiple patterns that all come together to form a single piece.

In addition to the foam itself, a number of important materials are used during the foam convolution process. A specially designed divider is often used to slice a larger piece of foam down the middle, while at the same time also creating the specific pattern that will be present on the final product. A series of rollers move a piece of foam across the divider, allowing for the process to be largely automated after all of the initial design work has taken place.

By and large, foam convolution is one of the single best ways to achieve the results that you're after for a particular application. The products of foam convolution play an important role in the lives of millions of people on a daily basis - from acoustical engineers to patients in hospitals to people just trying to get a good night's sleep - and the process in general is something definitely worth celebrating. Questions about Foam Convoluting or other machine processes? Give us a call--we're happy to help!

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Seven Surprising uses for Reticulated Foam

Ever unloaded the dishwasher and found the spoons or knives didn't come clean because they were stuck together? Well imagine that happening with surgical instruments. Placing instruments in bags made from open-cell foam is one way healthcare professionals avoid this. Steam reaches the surfaces but foam keeps them from touching.

Open-cell is another term for reticulated foam. One way of visualizing reticulated foam is to picture a mass of bubbles, then think how they'd look if the wall between each bubble was removed. Effectively, you'd have a three dimensional mesh where every cell is open to its neighbor. Cell size and density are controllable during manufacture. Density is specified in terms of pores per linear inch (ppi) and is controllable from 4 to 100 ppi. (A larger number means smaller pores.)

This results in some interesting and useful properties. Reticulated foam is compressible, yet springs back when the load is released. It's lint-free, porous, and at under two pounds per cubic foot, lightweight. As a result, it's used in a very wide range of applications. Here are some that may surprise you.

  1. Blood filtration and oxygenation. Heart-lung machines put oxygen back into blood, but tend to create bubbles. Passing the blood through a felted reticulated foam breaks these up, making it safe to return to the body.
  2. Air filtering. From automobile cabin air filters to nebulizers, there's a long list of air filtration applications. Even small lawnmower engines use reticulated foam to prevent dust and grit from being sucked in.
  3. Filtering molten metal. In casting, as metal is poured into a die it's important to remove impurities. Reticulated foam wouldn't withstand the heat; instead it's dipped into a ceramic slurry which dries to leave a more durable, heat-resistant mesh.
  4. Stabilizing fluid in tanks. Gasoline in an empty tank will slosh about, but fill that tank with reticulated foam and the gasoline moves slower. The foam can also help dissipate static, reducing the risk of fire if the tank ruptures. (Ink jet printer cartridges are a similar reservoir-type application.)
  5. EKG pads. Electrical conductivity between skin and electrode pads is improved with a specially formulated gel, but applying this adds a rather messy step. Reticulated foam EKG pads are pre-impregnated with the gel, saving time on prep and clean-up.
  6. Sound absorption. Reticulated foam makes an excellent windshield for microphones. Sound still penetrates but wind buffeting is absorbed, eliminating most background noise.
  7. Surgical instrument sterilization. Discussed before, reticulated foam: allows steam to penetrate, stops instruments touching, and avoids lint carryover.

Is your application next?

Reticulated foam is surprisingly versatile. With an open cellular structure it can filter or stabilize fluids, so finds application in areas ranging from motorsport to healthcare. If you're interested in learning how this lightweight material could benefit you, contact Merryweather today.

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