The goal for tennis ball manufacturers has always been to manufacture tennis balls that will retain their original air pressure and bounce properties for as long as possible.
Wilson Double Core Tennis Balls
Recently, Wilson Sporting Goods introduced the Wilson Double Core tennis ball. The manufacturers claim that these balls retain their pressure and bounce for twice as long as conventional tennis balls.
Nanocomposite Coatings that Inhibit Air Permeation
The reason that these ball last twice as long is that the inner core of the balls coated with a nanocomposite coating that inhibits the permeation of air from the inside of the ball.
How the Coatings Work
The coating was developed by Inmat and utilises aligned vermiculite platelets to impede path of air from escaping. The vermiculite platelets have an aspect ratio of 10,000 to 1 and significantly increase the path/travel distance for the air.
Composition and Processing of the Coating
The patented coating known as Air D-Fense is mixed at low viscosity and hence low shear stress. This minimises the possibility of reducing the aspect ratio of the vermiculite platelets. The vermiculite is suspended in water, with the water taking up only 1% of the volume, meaning that the platelets must be aligned.
The patented coatings start with a latex polymer containing butyl microspheres, to which the vermiculite platelets are added. Addition levels up to 50% are used.
After application, the coatings dry, with the platelets still aligned, forming a barrier to air escape