I'm a beginner—can I use polyester strings?

Try these steps in order

1. Record how many times you play each week, the length of a session, and when the current strings were installed. Separate strings that break in the center, strings whose feel changes before they break, and strings for which you have no replacement history; that shows whether durability is truly the need. With your reference racquet, play a 5-minute service-line mini-rally, then hit 20 baseline balls, 10 change-of-direction balls, and 10 serves. Record whether extra effort is required for depth and whether the ball goes long with your normal swing.
2. If the current setup already meets the goal, confirm it first with a fresh string from the same family. Comparing old nylon with new polyester confounds material and age, so establish a fresh reference setup first. If a reason to test poly remains, show the current racquet, gauge, and reference tension to a stringer and choose only one relatively less-stiff polyester candidate or one hybrid of polyester and a softer material. Avoid arbitrary settings outside the recommended range.
3. Keep the first playtest within 30 minutes and use the same drill. Record net clearance, balls landing inside the baseline, impact feel on off-center contact, and whether you have to shorten the swing unnaturally. Judge the distribution of 20 balls hit at normal pace rather than one hard shot. Keep a usage log in the racquet bag and note changes in response, string movement, and notching after each session. Adopt the setup only if it repeatedly reduces the target problem without sacrificing comfort or depth; otherwise return to the reference material.