PEEK is Just Another Plastic (so is polyester, and nylon – aka. “synthetic gut”)

PEEK is a high temperature, engineering grade polymer (aka. plastic) 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.”

Let’s Rewind for a Second

Ever since Babolat invented gut strings in 1875, that is what the sport has used and continues to use today! As you would expect, natural gut is a very expensive string to manufacture as it uses the intestinal lining of the cow. Natural gut was your ONLY option to use in a tennis racquet up until the 1960s when plastics (aka. nylon, aka. “synthetic gut”) were invented. However, even when nylons became the defacto strings for the mass public many top professionals still prefer to use natural gut because of its power and comfort.

Now that manufacturers had a new synthetic material to work with, they began to try and mimic the properties of natural gut. Multifilaments had come the closest but were still quite stiff in comparison due to the fact that they are still essentially made of nylon, just hundreds or thousands of fibers of it. And in most recent years, multifilaments have been abandoned due to the high cost of manufacturing and the rise in popularity of polyester monofilaments (since the late 1990s) and their higher profit margins. Some of the most popular strings today are polyester and co-poly strings. Most polyester and co-poly strings are solid monofilaments: a single filament extrusion with varied profiles and surface textures. These strings are not sensitive to moisture and do provide good abrasion resistance, which explains their “durability.” But their drawbacks are: they go dead after a few hours, they transfer more vibrations to the arm and they are much stiffer in comparison to natural gut. In many cases polyester strings are on the highest end of stiffness when compared to the market and especially when compared to natural gut. 

I Love Charts

The chart below shows comparative data of several strings, including the best selling polyester string. The numbers should give you an idea of the differences in the stiffness of strings and how that impact affects your joints. 

Look at the stiffness numbers. By comparison, the stiffness of PEEK is the closest to natural gut of any synthetic string material. That’s why we call it a “manmade polymer equivalent to natural gut.” This means it absorbs impact force more like gut.

Many of you probably use what Rafeal Nadal uses: Babolat RPM Blast. Not only that but you’ve probably been advised to use even the same gauge (thickness) of string that he uses: 15L (which is VERY thick). Now look at the stiffness of that string. It is almost 3x that of natural gut AND it stretches far less! No wonder why so many people get arm issues from using this string. Not only is it the stiffest, it has ZERO give (the least stretch), thus transferring all that impact directly to your arm! 

In layman’s terms

Lewis Hamilton (he’s a Formula 1 driver) drives on Pirelli slicks (tires). That doesn’t mean you should. In fact, it would be dangerous to put those tires on your car. Plus they don’t even last for more than 50 miles. Polyester strings are like racing tires.

PEEK has the highest melting point

PEEK monofilaments and fibers are very tough and durable, and have excellent abrasion resistance because the material’s melting point is at an extremely high 633ºF (334ºC)! By contrast polyester melts at 500ºF (260ºC) and nylon melts at an even lower temperature of 428ºF (220ºC). 

The best comparison I can think of is diamonds on glass. Diamonds are harder that glass so it will scratch glass. Likewise, glass is harder than plastic so it will scratch plastic. Think of PEEK as the diamond of tennis strings.  

In racquet strings, PEEK offers low dynamic stiffness that allows it to deform and recover more completely than other synthetic materials. It can also be made to have exceptionally low creep under 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 filaments that are even finer and stronger than before.

In Conclusion

This string is designed for players seeking both gut-like playability and superior durability in a solid monofilament string, as well as players using it in hybrid stringing patterns. Like natural gut, PEEK is softer than any other synthetic material thus reducing impact shock. And like polyester, its smooth characteristic but higher melting temperature means that other strings will be sliding on top of PEEK, not the other way around. Thus generating BETTER spin. ZERO polyester, 100% performance