Another area of concern is the evolution of grommets/stringing systems over the last decade (e.g., both the grommets in the frame and the string tubes through the racquet handle). These innovations have generally mandated the use of thicker and stronger strings to achieve adequate string life. Thicker strong strings help to address the string breakage problem, but often at the expense of playability and overall string performance.
So what's a manufacturer to do? Our job is to make strings people want to use, not tell them they have to use strings they don't want. If these new racquet designs improve performance, we need to make strings that perform as well as they do. We've had some success beefing up the jackets, or wear layers, on our strings, and with changing the core construction packages. But the one solution we've found more effective than any other was one we actually happened on by accident: transferring the use of PEEK polymers from the central core to the wear layer.
PEEK polymers like Zyex® have a number of properties that lend themselves to racquet string, including exceptional elasticity, or dynamic stiffness, which increases power and absorbs impact shock; the ability to hold tension, which increases the playing life of string; low coefficient of friction, which increases the ability to generate spin; and more. But another key attribute of PEEK is its abrasion resistance. In tests measuring "thread on thread" abrasion conducted at room temperature, PEEK multifilaments outlasted aramid fibers by a factor of approximately 5.5. In fact, one of the original applications for PEEK was as aerospace insulation designed to protect electrical wiring from abrasion damage.
We had been thinking of abrasion resistance in terms of string on string wear, but the increased string stress caused by these new racquet designs clicked on the light bulb in our heads. If Zyex insulation could protect wire, we thought, why not string? So we got to tinkering in the lab and what we've come up with is an entirely new surface element of Zyex filaments in the jacket of the string that increases their overall durability in these new racquets, and especially enhances loop strength to reduce frame breakage. Being made of Zyex, it also optimizes power and improves tension holding. In short, an excellent way to make string for newer designed racquetball racquets.
Zyex® is a trademark of Zyex Ltd