SAE industrial felt, or technical felt, is nonwoven wool felt used in technical applications. There are two methods of manufacturing industrial felt: wet felting or dry needle punch felting.
Technical felts are produced in a variety of thicknesses, densities, and compositions to meet a wide range of needs. The SAE, formerly known as the Society of Automotive Engineers, mandates the standards of measurements applied to nonwoven wool felts used in:
At Bouckaert, we custom manufacture our SAE industrial felt using the needle punch method. Before discussing the differences between manufacturing methods, here are the characteristics of SAE felts and nonwoven wool felts in general.
Characteristics of Industrial Wool Felt
Felt is a versatile fabric explicitly engineered for high-pressure applications in specialized industries. With the natural benefits of using wool fiber (click here for our previous post on wool felt usages), here are some of the advantages to using industrial wool felt:
Maintains its physical properties as it wears
Highly absorbent and moisture-wicking (will seal out lubricants and oil)
Sound and vibration dampening
Does not ravel or fray
Resistant to wear and tear
Acts as a filtration system (gas and oil applications)
Excellent padding for moving parts in machinery
Natural fire-retardant properties
Industrial applications such as these require high levels of aversion to abrasion, oil and grease absorption, and wear and tear. To ensure the best application results, SAE felts are classified by their density, wool content, and durability.
Density: Each grade of SAE felt ranges from hardest to most pliable, the main differing characteristic between felt grades. The thickness of pressed wool felt is controlled by the amount of pressure or needling applied during the manufacturing process. The denser the felt, the better it will retain its shape against the physical environment.
Wool content: Each grade of SAE felt is (usually) a combination of raw wool fibers and polyester fiber but additional materials such as cotton, rayon/viscose, synthetic, or plant fibers can be used instead. These “filler” materials are added to create a particular characteristic to the final product that can not be achieved by wool and/or polyester alone.
Durability: During the manufacturing process, the more pressure/needling applied (we will get into this in the next segment), the denser the felt will be. Durability relies, in part, on the amount of densification.
To note, the color of SAE industrial felts will vary. Since the wool used is natural and undyed, there is no way to control color consistency from lot to lot. There are also strict tolerance requirements based on wool content and density combined. The shape of wool can change naturally (depending on temperature) or manually (from cutting the material); density and wool content need to be adjusted to consider tolerance issues.
The Differences in Manufacturing
Wet Felting VS Dry Needle Punch Felting
All technical felts are produced under the same specs; the difference lies in the manufacturing process. Despite these “technical” differences, both processes in making SAE grade felt start the same way.
The wool fiber is first cleaned and blended with any additional synthetic materials before the carding process. The carding machine disentangles and mixes the fibers together to create a uniform web, aligning the individual fibers into a singular direction. Several of these webs are layered in alternating directions on a machine called a cross-lapper to build-up to the weight of the desired finished felt. This layered material will be much thicker (and less dense) than the finished product as it has not been densified yet. This material is referred to as a batt.
The wet felting manufacturing process is known as the more “traditional” way of producing nonwoven felts. It uses heat, moisture, and pressure to mat and densify the fiber together.
The batts are wetted with hot water and fed into a plate hardener. The plate hardener applies vibrational pressure to the wetted material using rollers to help the fibers interlock together. The hot water, added acid, and pressure eventually cause the batts to shrink down in size, creating the densely matted fibers of a pressed felt.
The wet felt is left with a sulfuric acid residue that is then neutralized in tanks filled with sodium chloride (soda ash) and warm water solution. Once the felt is neutralized, it goes through a refulling machine to smooth out any irregularities on the surface. The felt must then be dried either in a dryer or oven or hung and stretched in a drying room.
Needle Punch Method (Dry Needle Felting)
Here at BIT, we manufacture our SAE grade felts using the needle punch method. Needle punched SAE felt is marked with an “N” for “needled in the official designation (example F-7N). Here’s the difference in manufacturing:
As the name suggests, dry needle punch felting eliminates the use of moisture. Instead, the batts enter a needle loom; a precise machine that uses thousands of barbed needles mounted on a needle board to pierce the layered webs of fiber. The repeated punching of the needles entangles the fibers together to create the thick, dense felt.
Depending on the desired density, some needle punched SAE felts will then go through a heated press to further densify the material. Read more in-depth on the needle punch method here.
So Why Use Needle Punched Felt Vs A Pressed Felt for your SAE Needs?
The Pros and Cons of Needle Punched SAE Felt Vs Pressed SAE Felt
The use of chemicals in wet pressed felts gives the advantage of creating a smoother finish that allows the material to hold its shape better as it wears. The upside for needle punched felt is its economical and eco-friendly benefits; eliminating the use of harsh elements makes a cleaner production line that is more cost and time effective.
For exceptional sound insulation, needle punched felt is the go-to choice for acoustic paneling needs. But if there is one thing to remember when choosing between a wet felt or a needle punch felt, it is that both are produced under the same specs mandated by the SAE. The performance of needle punch felt is not compromised because of its manufacturing process.
Want to know how BIT can add value to your business by providing custom manufactured SAE grade industrial felts? Get in touch today!
One of the hottest trends in office furniture and interior design is the rise of polyester (PET) acoustic panels. The use of these panels is growing significantly in markets such as construction, retrofits of existing offices, and other commercial and public spaces.
Over the past 3 years, polyester acoustic panels have seen a massive upsurge in demand. This is due, primarily, to their flexibility in color, form, and ease of use when compared to traditional fiberglass acoustic panels. Fiberglass panels can cause irritation and air contamination due to the chemicals they sometimes contain in their binders.
The industry has quickly adopted these panels whether being used as desk dividers, light fixtures, hanging sound baffles, wall-mounted art, or any number of other uses. But what exactly are polyester acoustic panels? How are they made? What should you look for in a quality product or a vendor? We answer all of these questions and more.
How are polyester acoustic panels made?
To understand the challenges that arise on the quality front, you first have to understand how polyester acoustic panels are made.
1. Define the desired outcome
The process to create a finished acoustical panel starts with determining what characteristics we want the finished panel to have. We can affect acoustical curves (NRC), stiffness, surface texture, or color by changing the fiber material or size, product density or thickness, or manufacturing processing of our finished panels. Each variable lets us dial in the ideal finished characteristics. Our standard Poly-Sonic panels are comprised of recycled polyester fiber and special lower melting point polyester fiber.
2. Manufacture the needle punch felt
Next, we start the manufacturing process. Every polyester acoustic panel starts out life as a nonwoven, needle punch felt. This felt is similar to the felt kids make craft projects out of, but much thicker and denser!
We begin by taking raw fiber and turning it into a “web”. We then build density and surface characteristics by adding batts and needling the material together. The repeated needling that the felt receives is one of the keys to creating a stiff panel while maintaining a super smooth-surfaced panel. From this process, we create a “master roll” of felt. For a more detailed description of how needle punch felt is made, check out this link.
The felt moves to the heat-setting machinery following the creation of the master roll. This could be a mold for 3d shaped panels or some form of flat pressing system. This process changes the material from a roll of flexible felt to a stiff polyester acoustic panel.
When heat hits the polyester fibers, they melt and flow like a liquid thermo-plastic. Fibers like these are specially designed to have a low melt point. As this material cools, it turns back into plastic but is now spread throughout the felt, attached to all the fiber around it, and (with the assistance of the needling) creates the stiffness of the finished acoustic panel.
The heat-setting process is one of the most difficult to perfect. This is because the material will shrink three-dimensionally while being heated. And any imperfections in needling will create very obvious surface defects.
The final manufacturing step is to cut the panels to their final dimensions or shape. Most architects and interior designers need tolerances of +/- 1/8th of an inch. Some elaborate designs require tighter than +/-1/16th of an inch. This would normally favor a die-cutting process but in many cases, the variety of shapes and rectangular dimensions needed would make this cost-prohibitive. Only with extremely precise cutting tools such as CNC machinery using oscillating blades, lasers, or waterjet cutting can near-perfect acoustical panels be cut every time.
What quality attributes should you look for when assessing polyester acoustic panels?
There are several factors to consider when determining whether a polyester acoustic panel is of top quality.
Is the first panel just like all the others and, also as important, is each individual polyester acoustic panel consistent within itself?
One of the key giveaways of an inconsistent process is that one panel does not look like the next. When dealing with large-scale projects, even minor consistency problems can stand out when looking from panel to panel or from one section of a panel to another. Unfortunately, due to the nature of the panel manufacturing process, it is impossible for panels to be exactly identical, but the closer they are, the better.
The distribution of colors in a panel is one of the first things to stand out. Many panels have a “heathered” look to them. This comes from blending two or more colors of fiber together. Do you see clumps color? Or is everything evenly spread out?
Another one of the most noticeable attributes comes when comparing the thickness of different panels. When placing panels next to each other on a wall or in a line of desk dividers, check to see if the panels are of different thicknesses.
The thickness of each acoustic panel is one of the major drivers of its acoustical absorption capability. Thicker is better!
Many applications for acoustic panels, such as desk dividers, require very stiff panels. Make sure to check if the panels stiff enough for your use. Is each panel consistently stiff? This could be from one corner to another or from one surface side to another.
Many manufacturers struggle with getting enough heat all the way through the panels to fully activate the low-melt fiber. This is especially true on thicker panels. Often, an inferior panel will have a softer center and two harder surface faces when you look at the panel from the side. When this happens, the panels tend to not hold mounting bolts or hardware as well and also tend to collapse and bend easily when held from only one side. This usually destroys the panel by creating unwanted wrinkles on the surface.
Acoustic Certifications (ASTM C423)
Polyester acoustic panels have many uses, but as the name implies, “acoustic” tends to be the key attribute for many applications. All panels should have an NRC value, and most “standard” specifications will.
Where this gets tricky is when comparing panels from different vendors that look the same but have vastly different ASTM C423 results. Logic says that the higher number is better, right? Well, not quite…
There are different variations of the ASTM C423 test. These range from “A” mount where the acoustic panel is placed directly against a cement floor (and will have a lower NRC number) to “E Mount” where the panel is suspended several inches in the air (and the NRC number will be higher). It isn’t wrong for a vendor to use “E” mount test data, but make sure you compare apples to apples when comparing!
As a secondary note for ASTM C423 testing that produces an NRC value, keep in mind that NRC is an average of performance at different frequencies. If you have specific acoustical profiles or sound frequencies that you need to target, then make sure you look at the charts to compare performance at your specific frequency.
The acoustical curve of BIT’s Poly-Sonic 45 (9mm thick) acoustical panel using ASTM 423 A-mount. Note the different absorption coefficients at different frequencies. NRC: 0.30
Flame and Smoke Certifications (ASTM E84)
The ASTM E84 certification uses a combination of a flame spread and smoke generation test. It is one of the most important certifications for applications that are considered “building materials”. Depending on your application, you may not require this certification, but most suppliers will have their acoustic panels tested to this specification.
There are several results possible all resulting from the flame spread portion of the test. The generally accepted standard is “Class A” and, if your application requires this test then be sure to look for this.
One word of caution here, not all ASTM E84 tests or testing labs are equal. Many of our customers are wary of using unknown foreign laboratory results for good reason. We have heard some horror stories about vendor-provided laboratory results looking good but when independently tested their panels fail miserably.
Due to the moral values and legal penalties involved in failing this test, most of our customers will conduct their own testing using a US certified lab. We recommend that you do the same if you do not personally know the lab that conducted the testing.
What to look for in a vendor
Now that we have reviewed the critical parts of a quality panel, it is easier to identify what to look for (and what we strive to be!) in a vendor as well. For many customers, being able to provide a consistent, high-quality panel is paramount and all-encompassing. Other normal vendor characteristics to inquire about are minimum order quantities, lead times, and, of course, price. However, there are a few other factors to consider that not every PET acoustic panel vendor can provide.
First is the ability to customize. The market is becoming flooded with 9mm thick panels that look, feel, and perform pretty similarly. But your company might require a distinct acoustical performance curve, custom color options, or different thicknesses. Finding a supplier who can work with you to provide the exact product you need isn’t always needed, but be sure to review your requirements and make sure the company you are working with can handle them.
Another often overlooked aspect of vendor capability is someone you can build a relationship with. Maybe you are in a bind and need an order shipped early. Or you are stuck with a whole truckload of panels after a customer backed out of a deal. Is your vendor willing to take them back no questions asked? Finding a company that you can work with is often worth paying a bit more when they save you headaches down the road!
Bouckaert Industrial Textiles tries to meet all of our customer’s needs from minimum order quantities, to lead time, to price, to customization and relationship. Our Poly-Sonic polyester acoustic panels are designed and manufactured entirely in the USA.
Have questions or want to learn more about us? Contact us today!
What is needle punch felt? When most people think of textiles, they think of products like shirts, jeans, and blankets. But the world of fabric goes far beyond clothing and blankets. Textiles are used to make everything from the seatbelts in your car to acoustic panels or desk dividers in your office to the blue medical PPE masks that everyone has become used to in 2020.
Most of the fabrics you encounter each day are woven or knit (think of those warm blankets your grandma knitted for you as a kid). Even most of your shirts are made this way except they use much thinner fibers. If you look closely at the clothes you are wearing, then you will likely see a very small grid pattern.
But a large portion of the fabric that we encounter every day is made using “nonwovens”. As the name suggests, nonwoven felt is made by joining fibers through methods other than weaving such as by using needle entanglement, heat, moisture, or pressure to hold the fibers together.
One of the most well-known types of nonwoven is children’s craft felt. Remember that colorful fabric you used to make your art projects? That is made using a nonwoven construction technique called “cross-lapped needle punch” or more simply “needle punch.”
Needle punching is one of the methods used for making a nonwoven felt. This involves taking loose fibers and “needling” them together using a needle loom full of barbed needles to force the fiber to push through and entangle itself. It is also one of the types of nonwoven that Bouckaert Industrial Textiles specializes in producing.
What Applications is Needle Punch Felt Used For?
Beyond craft felt, needle punch felt has many uses, often in highly technical applications. Some of the most common uses are:
Acoustic panels and baffles
Equestrian saddle pads
Office and desk dividers
Padding for vehicle sun visors
Molded automobile headliners and trunk liners
High-performance thermal insulation
Synthetic soil growing media
How Is Needle Punch Felt Made?
The process for making needle punched felt begins with determining the final use for the felt and what properties it needs. Depending on whether the goal is to create a thermal “heat shield” or under carpet padding or filtering COVID19 particles out of a house filtration system, will create very different needs for how an engineer will create a product.
For any type of nonwoven, including needle punch felt, this process starts with fiber selection. Different fibers have different characteristics that provide different traits that can help with different requirements and can potentially be combined in different percentages to create even more capabilities in the finished felt.
Once the desired fibers have been chosen, other specifications such as weight per sq yard, thickness, surface texture, and many other factors must be determined to achieve the optimal product for the end-user.
Once all of the design engineering has been determined, the construction of the felt starts with large bales of loose fiber. These fibers can be synthetic like polyester, nylon, acrylic, rayon, or fiberglass, or they can be organic like wool, cotton, or alpaca.
These bales of fiber must then go into machines called bale breakers. These machines break the compact bale of fibers apart so that they are easier to process.
Many felts involve mixing different types of fiber together in order to get the desired outcome. This is done by carefully weighing the fiber that goes from the bale breakers into the next step of the process, blending and carding to achieve the correct % of the blend.
The breaking up and mixing of fiber is done at carding. Carding works by feeding loose beds of fiber into large wired rollers. This wire works to separate each strand of fiber, mix and blend the components together and orient the fiber in a single direction.
The fiber exits the carding machine in the form of a web. This webbing is similar to the fake spider webs you see around Halloween time and resembles the consistency of cotton candy. It is the first time the fiber looks like a fabric but, just like cotton candy, this material has very little strength to it.
This webbing is laid onto a conveyor belt which carries the web to a cross-lapper. The lapper folds each thin layer of webbing over itself which provides weight and thickness to the finished felt. The number of layers depends on the target thickness and weight of the finished product.
After the lapper, the layers of webbing will enter the needle loom. This is where needle punch felt gets its name.
A needle loom is a precise machine that uses barbed needles mounted on a needle board to pierce the layered web of fiber. The needle boards punch the fibers at a rate of 600-2,000 punches per minute. This repeated punching of needles entangles the fibers together which creates a strong bond. Needle looms can be “in-line” or “off-line.”
This is the end of the felt-making process for some felts. But others go on to receive different finishing treatments such as additional needling or adding more layers of felt to build density, heat treating, calendaring, singeing, and laminating. Some felts also get combined into composite layers with other felt, foam, rubber, or other materials. Here is a quick video of an “off-line” needle loom that is further entangling (or densifying) a piece of felt.
Whether creating an automotive heat shield, an acoustic panel, an industrial felt for gasketing, or any other needle punch nonwoven. Bouckaert Industrial Textiles is here to help you engineer the best product to meet your needs. If you think that a nonwoven felt might be the right choice for your application or have any other questions, then contact us today!