FELT 101: Everything you always wanted to know about Felt. If you still need additional information, email Durofelt@att.net and we will be happy to help you. Or call us Monday thru Friday @ 501-225-2838 between 8:00 am - 5:30 pm Central time where a human being answers the phones.
Wool is an animal fiber that forms a protective covering of sheep. Raw wool, obtained from shearing sheep, is cleaned to remove debris and vegetable matter. Natural wool AKA 100% wool AKA Compressed Wool felt is made of fibers that are physically interlocked and consolidated by mechanical work, chemical action and moisture without the use of weaving, knitting, stitching, thermal bonding or adhesives.
Raw wool fibers of 22 to 28 micron diameter are used to make felt. If blended felt is required, raw wool is mixed with man made fibers as based on required ratio.
Process of making felt: Wool fibers are opened and separated by the use of an Opner machine that has spikes and wires to untangle wool locks. Then a Carding machine with revolving rollers in opposite direction and wired surface acts as a comb to comb wool fibers.
Milling process: involves interlocking wool fibers with moisture which allows wool fibers to swell up, become bulky and remain steady. During this process, rubbing action is generated which helps these wool fibers to interlock. This action is similar to rubbing a knitted woolen sweater in soapy water and then trying to remove the knitting thread which is difficult. The same rubbing action is done by the Milling Machine.
Wool fibers are placed on the table and depending on thickness and density required for specific orders, additional layers of wool fibers are added. Then continuous pressure and steam is applied to make the felt material. This process is similar to the process of making cotton candy. The felt sheets are then run through electrically heated rollers to make sure thickness is even. After that felt products are manufactured from these felt sheets.
Compressed Wool Felt AKA Engineering Felt is available in sheets and rolls. Technical Felt AKA Industrial Felt is available in sheets only. Both felts are available in various qualities, thickness and density.
Carbon felt is the highest grade of felt. Raw wool goes thru additional steps to remove every spec of debris before felt sheets are manufactured. Carbon felt products are used for precision polishing where even a minute scratch can make a difference. For eg., parts made for replacement knee surgery, hip replacement, etc., have to fit in a patient precisely so the patient is comfortable and can be mobile. This is the main reason items made from Carbon felt are more expensive.
The porous cells of wool enhance its suction capability which in turn helps in transmission of liquids. These liquids when slowly released allow the felt to also act as an efficient medium of lubrication AKA Felt Wicking.
Dry and wet filtration of suspended particles in air and gas is also due to porous structure of felt. Characteristics like elasticity and resistance to wear help wool felt to be used as "Pressure Pads" in steel service centers during slitting and shearing operations. It also acts as "coolant wiper" thus serving a dual purpose of an industry.
Resilience is an inherent characteristic of sheep wool fiber which results in a good sealing agent. This can prevent leakage of dust, noise, heat, cold, etc.
Air trapped in porous cells of felt also makes it an excellent insulation material. High porous structure makes felt a bad conductor of sound waves.
Felt can withstand maximum temperature 100 degree C OR 212 degree F. Anything higher will burn the felt and turn it into charcoal.
Density = Mass divided by Volume. Density is calculated as grams per sq. cm. These densities are accepted worldwide.
Common densities for felt material are Soft (0.20 gm/c3 - F-10), Medium (0.26 gm/c3 - F-5) and Hard (0.36 gm/c3 - F-1). Other densities such as F-55, F-60, etc., generally are used for gaskets, seals and O-rings because wool content is between 70% - 75% mixed in with polyester, cotton, etc.
High Density Felt materials are manufactured in same densities as used in Felt Buffing Wheels and Felt Polishing Bobs. These densities are High Density Soft (0.50 gm/c3), High Density Medium (0.60 gm/c3), High Density Hard (0.70 gm/c3) and High Density Rock Hard (0.80 gm/c3). That means High Density Hard (0.70 gm/c3) is approx. 85% denser than Hard density (0.36 gm/c3 - F-1). Using a science equation, the molecule of each wool fiber is very tightly packed making the material very dense. High Density Felt materials are used to make razor strops, are used for sharpening knives and to punch out felt cores to use under Timpani mallets.
Felt is a very versatile and unique product so if you can imagine it, you can use it.
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