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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.

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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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Why Consider Cross-Linked Polyethylene Foam? A Primer on the Subject

Ever order a steak and find yourself overwhelmed by the choices? How do you want it done? Fries or baked potato? Butter and sour cream with the potato? It goes on and on. Well buying foam gets like that too, and unless you have a background in polymer chemistry some of the questions can be quite baffling.

One of the options foam fabricators throw at buyers is cross-linking. It's actually an important question as cross-linking has quite an effect on the properties of the foam. There are applications that might benefit from it while others won't. And should cross-linking be right for your application you may even be hit with another question: chemically cross-linked or irradiated?

To help you understand the questions, and decide if it's even something to consider, here's a primer on cross-linked polyethylene foam. It explains what the words mean and why you might want your next foam fabrication made from it. Individual sections address:

  • Understanding polyethylene
  • What is cross-linking?
  • Characteristics of XLPE foam
  • Benefits and applications

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Introducing Spunbond Materials

Spunbond materials are a subset of what's termed non-woven fabrics. That is, they are webs of material without the interlacing of threads produced by weaving on a loom. That means the fibers are randomly oriented and not interlocked, so a bonding process or medium is needed to fix them in place.

Non-woven fabrics are everywhere. Disposable wipes, diapers and pillow covers are just a few of the many uses around the home, but they're also used in agriculture, civil engineering and automobile interiors.

Why So Popular? 
Non-woven fabrics compete with wovens in two ways. First, they can be engineered to have practically any combination of properties needed. Tensile strength, absorption, and density are just of few of the characteristics polymer chemists are able to manipulate. In contrast, woven fabrics derive their properties mainly from the characteristics of the yarns employed.

Second, non-woven production processes are much faster than weaving. While a loom might turn out three to seven meters of woven material per hour, many non-woven processes could produce several hundred meters per hour. Naturally, this has an impact on cost.

Non-woven Production Processes 
Non-woven materials may be produced either from short lengths of fiber, (known as staple fibers,) or from continuous filament. Fibers can come from many sources, both natural and man-made, but filament is generally produced from polymers such as polypropylene, polyester and nylon.

A variety of methods are used to randomly orient fibers into a web before bond them together. One issue is that staple fibers must go through some kind of chopping process first. In contrast, spunbond materials, while lacking the randomness of fiber, are made directly from the polymer.

The Spunbond Process 
Polymer is melted and extruded through very fine holes, typically measuring 15 to 35 microns diameter. These thin continuous strands are made to spin as they solidify before landing on a moving conveyor or web of supporting material. The spinning randomizes the orientation of the strand as it lands and the conveyor motion ensures it forms a mat or web of material.

A bonding process, mechanical, chemical or thermal, joins the overlapping filament coils together, creating an engineered fabric. From polymer pellets to fabric web, it's an integrated process, and so highly cost-competitive.

Types of Spunbond Materials 

  • Polypropylene. This offers low density, good chemical and water resistance, and is readily formed as a breathable material. It works well in protective bags, sheets, pockets or pouches, is a good filter medium and absorbs oil well thanks to a porous structure. Spunbond polypropylene is also used for single-use gowns in the medical field.
  • Polyester. More expensive than polypropylene, this has higher tensile strength and better heat stability. It can be dyed or printed with conventional textile industry methods. Applications include fabric softener dryer sheets, automotive carpet backing and geotextiles.
  • Nylon. Has good tensile strength and tear resistance. Can absorb water but resists attack by alkalies and weak acids. Has good heat resistance and is air permeable. It's widely used as carpet underpad reinforcement, as quilt backing, and in automotive interiors.
  • Polyethylene. Similar to polypropylene, although with generally inferior properties, this is chemical and water resistant, and has good electrical insulation characteristics. A porous structure makes it a good oil absorber.
  • Polyurethane. This is an emerging material in spunbond form. Somewhat elastic, uses are anticipated in masks, diapers, medical tape, and also disposable clothing, thanks to textile-like properties.
  • Rayon. This creates non-wovens with textile-like properties like good drape and soft feel.
  • Bicomponent fibers. These consist of one polymer molded around a second, different, polymer. This enables a combination of properties such as the ability to take a dye combined with high strength.

Emerging Applications 
Development of spunbond manufacturing processes is continuing, with new forms of material entering the market and new applications being found. Spunbond foam offers superior handling characteristics with lower weight and increased softness. Today, we are able to laminate adhesive to spunbond materials to film, foam, and other materials as well as die cut, water jet cut, slit, and kiss cut this material in a number of application settings. The cost-effective spunbond process facilitates engineering of specific performance characteristics such as strength, water and chemical resistance, and feel. New spunbond materials are emerging constantly, and improved manufacturing methods are enabling yet more applications. Already spunbond polypropylene is seen as an alternative to polyurethane foam, and other applications are sure to follow. If you are interested in learning more about Spunbond Fabrics, give us a call and we would be happy to help you learn more. 

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The Advantages of Low Permeability Foam

When choosing materials for projects, one of the larger concerns becomes balancing performance and cost. There is no sense in paying more for capabilities that you do not need. Low permeability foams are ideal for many projects that involve low pressure gasketing. They can keep out dust, vapor and gases. And, they cost less than other projects that may be overengineered for your purposes. By giving you the qualities you need at a manageable price, you can keep costs in check, leading to better margins all around.

How is Permeability Measured?

When creating a foam material, you can decide whether it is appropriate for your specific needs through water seal testing. To test, a U-shaped sample that is 100 mm thick is cut. The sample is compressed between two acrylic plates until it reaches half the original thickness. One hundred milimeters of water is then poured into the U. To pass our tests, the water must stay at that 100 mm level for 24 hours.

Where can you use Low Permeability Foam?

Low permeability foam can offer air or water sealing in a number of environments. It's available in sheets, rolls and bun stock and can be laminated to a wide range of pressure sensitive adhesives. Some of the places where low permeability foam is the ideal material:

  • Weather-stripping in buildings and vehicles.
  • Gaskets in HVAC, automotive and electronics.
  • Vapor seals in appliances and data processing equipment.
  • Packaging in areas where you need cushioning and a high level of shape retention.

Low permeability foam is available both as an open cell, low compression foam and as highly water resistant Superseal foam. All of these grades are available with a biocide and come in rolls, bun stock or sheets that range from .0125 inches to 2 inches thick.

Why Choose Low Permeability Foam?

Low perm foam has characteristics that make it an appealing option in a large range of applications. It's a highly adaptable material, giving you the flexibility to create exactly the part that you need. In an application such as automobile manufacturing, you have a large variation in the distance between the blower and the wall. But, for effective gasketing, you need a material that is highly resistant the the passage of air. Low permeability foam can be compressed to different degrees to fit into the area, while providing the sealing that is needed.

It costs less than products that may be more than you need for the application at hand, allowing you to bring in projects at a budget that allows greater profitability. Some of the benefits of this material include:

  • High resistance to abrasion and wear
  • Excellent shape retention
  • The ability to be laminated to several different pressure sensitive adhesives
  • Properties that give you controlled cushioning
  • Easily die cut
  • Light weight
  • Controlled permeability; this allows you to decide just how breathable your gasket or other part is made
  • Resistance to water leakage
  • Manufactured with out the use of damaging chlorofluorocarbons

We can make parts that are customized to your very needs and specifications. Our experts have years of experience choosing the right materials to give you the best performance possible. Contact us to discuss your needs and which items are the best fit your for application.

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All About Pressure Sensitive Adhesive

Foam is a fantastic cushioning material, used in industries from automotive to medical for providing comfort and protection. It's not the easiest material to work with though. Cutting accurate, high-quality shapes takes specialized equipment and more than a little skill, while securing it in place can be even more of a challenge. Conventional fasteners can pull through, especially with low density foams, and adhesives applied as a bead tend to run into the open cells, reducing flexibility rather than bonding to adjacent material--many times, the psa is used as a temporary fastener until a mechanical fastener can be put in place.

In many cases the solution is to laminate an adhesive onto the foam. Merryweather offers an adhesive lamination service which makes foam fabrications easier to handle and put in-place. Adhesives come in many forms; the type that works best with foam is known as "Pressure Sensitive Adhesive" (PSA). These come in many forms with the most popular being two sided (also known in the industry as double coated adhesive) with a carrier membrane (typically a paper, film, foil or cloth) or a transfer adhesive which peels directly off the release liner when it is removed to adhere the foam to the substrate. Double coated adhesives add stability to the foam so that it cannot be stretched out of shape. They can also be used to prevent plasticizer migration. Since transfer tapes do not have a carrier, the adhesive is extensible and more conformable, and sometimes at a cost savings.

Specifying a PSA lamination is a good first step towards simplifying foam assembly, but it's not enough. Adhesives have many different properties and the relative importance of each depends on the application. A deeper understanding of PSA's helps with selecting the best adhesive for any given application.

What is a PSA?
Some adhesives need a chemical reaction to create a bond, others use heat or exposure to UV light. In the case of a PSA the activation method is pressure. Bringing adhesive-coated surfaces together with just light pressure is enough to create a bond. (In chemical terms, the adhesive "wets" the surface, allowing a bond to form.) Increasing the pressure doesn't automatically increase the strength of the bond, although it may do so if it increases the area "wetted" by the adhesive.

Tack, Peel and Shear: The Key Adhesive Properties
Tack indicates the initial bond strength. In the lab it's usually measured by the "loop" test. A loop of adhesive-coated tape is briefly brought into contact with a surface. The force needed to separate tape and surface is the tack strength.

A high tack number shows a bond forms quickly. This can be a problem if it might be necessary to separate and reposition two surfaces, which is why "Post-It" notes have low tack. Conversely, shipping labels are secured with a high tack adhesive, which is why repositioning them is never a good idea!

As a measure of the force needed to separate two adhesive-bonded surfaces, peel indicates bond strength. It's determined by pulling the two surfaces in opposing directions, but only after the bond has had time to build strength.

Shear is measured by applying a force parallel to the bonded surfaces. It's really an indicator of bond durability.

Specification sheets for adhesives typically list all three of these parameters, usually with a note about the test procedures followed. Most often, these are ASTM standards, although Pressure Sensitive Tape Council (PSTC) testing methods are sometimes used. However, since both temperature and humidity are factors in the bond, both organizations standardize temperature and humidity during testing.

PSA Types
PSA's consist of an adhesive, mixed with an elastomeric base material and a tackifier. The tackifier, as the word suggests, increases the initial tack, while the adhesive creates the actual bond, (which may take time to build.) Forming the foundation of the PSA, the elastomer provides properties like flexibility and temperature range.

Three elastomer chemistries are used in PSA's: rubber, acrylate and silicone. Rubber is the least expensive and provides good peel and shear strength plus a high level of flexibility. Rubber-based adhesives tend to yellow over time and lack strength at elevated temperatures.

Acrylates Acrylics stand up well to UV and solvent attack and will work over a temperature range of -45 to 121 degrees Celsius (C). Their downsides are poor creep resistance and a higher price.They also require a 72 hour dwell time to build up to their full bond strength.

More expensive still, silicone-based PSA's have a broader temperature range, (-73 to 260 degrees C,) and good resistance to chemical and solvent attack.

PSA Selection
While relative importance depends on what the application needs, these points should always be considered:

  • Need for repositioning or removal – this would indicate use of a low-tack PSA.
  • Lowest temperature expected – PSA's can lose flexibility at low temperatures.
  • Highest temperature expected – elevated temperatures reduce shear strength.
  • Humidity – moisture-laden atmospheres will significantly reduce the bond strength achieved.
  • Vibration – especially if combined with high temperatures, as this can lead to premature shear failure.
  • Presence of chemicals and/or solvents – these will attack many PSA's, especially those using rubber elastomers.
  • Substrates being bonded together are very important in determining the type of PSA needed

Typical Applications and Benefits

Applying PSA to cut foam shapes simplifies assembly operations and results in higher quality products. An appropriate level of tack lets workers position foam pieces before securing them in place. Fasteners are eliminated, saving money as well as space in stores and at assembly. Perhaps most importantly, with the right PSA for the application, foam pieces will stay in place for the life of the product, avoiding warranty problems and improving quality. Whether the application is automotive interior trim, under-hood sound deadening or cushioning, acoustic control, packaging, transit cases, medical or something else, pre-laminating a PSA onto foam results in a better product.

Pick up the Phone

PSA's come in many different forms and matching properties to the application is essential. Start that discussion today by calling or emailing a product specialist at Merryweather Foam.

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