ERSA Pro Stringer Magazine 5 - 2019 prostringer 5-2019 - web | Page 14

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PEEK STRINGS
Playing Characteristics of PEEK Polymer
Strings
By Steve Crandall
Vice President, Sales & Marketing
Ashaway Racket Strings
For the past few years, Ashaway has been marketing several lines of string utilizing the “ZX”
designation. As it has always been one of my pet peeves when marketers tout a new technology
in ads, but don’t really say anything substantive about it, I will try to rectify that here, so far as ZX
goes.
For those adept at polymer science PEEK is a high temperature, engineering grade polymer
known as polyetheretherketone. According to the online encyclopedia, Wikipedia, "Polyketones
are a family of high-performance thermoplastic polymers. The highly polar ketone groups in the
polymer backbone of these materials gives rise to a strong attraction between polymer chains,
which increases the material's melting point. Such materials also tend to resist solvents and have
good mechanical properties."
In layman's terms, this means that PEEK materials have several physical properties of interest to
manufacturers. Specifi cally, PEEK monofi laments and fi bers are very tough and durable, and have
excellent abrasion resistance, particularly under extreme conditions. The material's melting point
is 633ºF (334ºC), which is very high for plastic. Its maximum continuous service temperature is
500ºF (260ºC), and short-term service can be up to 570ºF (300ºC). By contrast, PET, polyester,
the material typically used for soda bottles and monofi lament tennis string, loses strength rapidly
as temperatures reach 200°F. Even much vaunted aramid fi bers begin to lose strength around
450°F. So PEEK is hot stuff !
In terms of abrasion resistance, PEEK also off ers good performance. In tests measuring "thread
on thread" abrasion conducted at room temperature, PEEK multifi laments outlasted aramid fi bers
by a factor of approximately 5.5. PEEK also has very low moisture uptake at 0.1%, which means
you don't need to worry about your racquet string performance in hot and humid conditions. This is
why PEEK strings have become so popular in locales closer to the equator.
But perhaps the most interesting application for PEEK—other than racquet strings, of course—is
in musical instrument strings. A number of manufacturers now off er PEEK-based violin, guitar, and
other musical strings. PEEK monofi lament provides a subtle but appreciably fuller tone than other
synthetic string materials such as nylon. It also holds tension, so it stays in tune much longer on
a guitar or violin than other conventional music strings. So when tennis players say they love the
way their PEEK strings sound and how long they play, they have good reason.
In racquet strings, PEEK off ers low dynamic stiff ness that allows it to deform and recover more
completely than other synthetic materials. It can also be made to have exceptionally low creep un-
der continuous tension, allowing racquet strings to maintain tension and playability longer. And as
noted previously, the manufacturers continue to improve and "tweak" the material, making it even
better for string applications. Recent advances have produced PEEK fi laments that are even fi ner
and stronger than before.
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ERSA PRO STRINGER // ISSUE 5-2019