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Too many polys

Q: I was reading one of your playtest reports the other day, and it said that the string was a “polyamide.” The playtest made the string sound interesting — especially the comfort rating — but I don’t want to recommend a poly to my customers and risk causing arm problems. Are polys really that good these days?

A: Usually when people talk about “poly” strings, they are referring either to polyester or poly ether ether strings. These “polys” have gained a reputation of exacerbating arm problems, but the polyamide you’re asking about is a different animal.

The confusion about “poly” strings is understandable because most strings are some form of poly. Poly is short for polymer, which is any substance that has a large number of similar units (also called monomers) bonded together in long chains. The only string that is not a poly is natural gut.

The polyamide string you read about is a nylon string. Nylon is one of the most important members of the polyamide family. Another member of the polyamide family is aramid (AKA Kevlar), which has two different monomers that alternate over and over. If you compare a piece of nylon string with a piece of aramid string, though, you probably won’t detect much similarity, despite the family relationship between the two.

There are other polys that feel closer to nylon than aramid does, despite differences in chemical ingredients. Chief among these is polyolefin — which is a bunch of olefin molecules chained together. There are also copolymers — polymers made by the reaction of two different monomers — that seem identical to nylon, even though they contain two different sets of “similar units” instead of just one, as in simple nylons.

Another example of two strings that you might erroneously think of as comparable in playing qualities based on their chemical make-up are Zyex strings, which are poly ether ether ketone, and the Luxilon line of strings, which are based on poly-ether-ether. Zyex strings are much more similar to a nylon, while Luxilon strings are superficially similar to strings made of polyester.

With few exceptions, polyesters and poly ether ethers are used to make monofilament strings that feel very stiff and wiry when you take them out of the package.

As you can see, seemingly tiny changes at the molecular level can in some cases result in huge changes in the final product, while in other cases strings with seemingly much different chemical make-ups can perform similarly. This underscores the importance of experimenting with as many different string types and constructions as you can — the chemical details don’t mean anything compared to how a string works in the racquet.

From the November 2007 issue
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