Balls for "Jeu de paume" (palm game)

Sirris helped a plastic injector to develop balls for players, while the official supplier had disappeared with its specifications and formulations.

Jeu de paume is an ancient sport, the direct ancestor of pelota, Frisian handball, tennis and more generally all racket sports. This game is still played in Belgium, especially in Hainaut.

Sadly for the players, the main manufacturer of the balls disappeared from the market. A manufacturer of other ball types is supplying a substitution product but the quality of these new balls is less good because they rapidly lose their rebound properties and have to be changed too often.

Serviplast, the plastics injector in Bastogne, was asked to produce new balls with properties similar to those for jeu de paume. The firm came to Sirris to develop solid non-porous balls in a material and with a process compatible with its machinery.

What ought to be "easy" in principle, actually isn't, especially as no information and precise specifications are available and that only a few new balls can be used for reference. The specifications include many points:

  • injectable ball of around 50 mm
  • weight identical to the initial ball
  • similar rebound
  • identical touch and feel

The project consisted in:

  • identifying the polymer of the existing balls
  • assessing the importance of the porosities on the final properties
  • selecting several elastomer thermoplastics capable of reproducing the properties of the existing balls; a TPE with high damping properties was identified
  • producing some compounds
  • studying and producing a test mould
  • injecting the pilot run of balls in various mixtures and conditions to qualify the selected materials and the process

Several compounds were produced at Sirris to arrive at a mixture having all these characteristics. Several elastomer thermoplastics were tested and blended in various proportions with a foaming agent and with a heavy mineral filler to obtain the tricky combination of wanted effects.

The final result is very close to the original balls.

Using the formulation identified by Sirris, Serviplast had the mixture produced by a compounder and will next inject batches of balls in a new mould made by its tooling department and thus supply the jeu de paume enthusiasts.