Composite Islands In A Sea
Nonwoven fabric developed at NCSU may provide lightweight, less expensive, stronger alternative to woven military tent fabrics.
Janet Bealer Rodie, Assistant Editor
The research is directed by Behnam Pourdeyhimi, Ph.D., the college’s associate dean for industry research and extension, William A. Klopman Distinguished Professor and director, Nonwovens Cooperative Research Center (NCRC). According to Pourdeyhimi, the project evolved from one of NCRC’s core research programs, and funding for this particular application comes from the US Air Force.
The optical micrograph above left shows the spunbond fabric surface after jet-dyeing. The cross section of Islands-In-A-Sea (above right) shows 36 nylon islands in a sea of polyethylene.
The spunbond, thermally bonded fabric uses Melbourne, Fla.-based Hills Inc.’s Islands-In-A-Sea bicomponent fiber technology. In the fabrics developed thus far, the sea, or matrix, is polyethylene, which has a low melting point and therefore is weaker. The islands are nylon fibrils, which have a higher melting point and so are stronger. Other possible sea polymers include polypropylene and copolyester, and the islands also could be polyester.
Pourdeyhimi explained the fabric’s dynamics as they relate to the thermal bonding: “By using this composite fiber where the matrix melts and the islands do not, the islands crisscross through the bond area without getting damaged, so the matrix really acts as the glue that holds the stronger elements together.
In a tear or a tensile process, when you apply stress to these fibers, the matrix transfers the stress to the islands, and since they have not been damaged in the bonding process, they can take a lot more stress. As you begin to really tear the fabric, the islands begin to separate and peel away from the matrix and bunch together, very similarly to gauze.” The result, he said, is “a 5-ounce fabric that has more than 40 pounds of tear strength — and the structure is not even optimized yet. This fabric can have tensile strength as high as 300 to 400 pounds.”
A more flexible but equally strong version of the fabric is lightly hydroentangled before being thermally bonded.
Two 5-ounce fabrics laminated together make a fabric that is stronger than the 20-plus-ounce coated woven polyester fabric the military is now using for its tents. Pourdeyhimi hopes eventually to reduce the weight by half again without compromising the strength.
For tents, the first version of the fabric would have an extruded rubberized coating to make it impermeable. The second would be saturated with a resin such as polyurethane and would be more permeable, making it suitable for artificial leather, furnishings and automotive applications.
For more information about this fabric development, contact Behnam Pourdeyhimi, Ph.D., (919) 515-1822, firstname.lastname@example.org.