Levich Institute Seminar Announcement, 05/17/2005

Tuesday, 05/17/2005
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Dr. David Goldwasser
Polymers Research and Development
Nike IHM, Inc.

"Development of an Environmentally Friendly version of Nike's Air Technology"


The pneumatic element in Nike's air technology, which was licensed from its inventor Marion F. Rudy (USP 4,183,156 etc), consisted of a pressurized bladder made from a thermoplastic polyurethane elastomer that was inflated with a perfluorinated gas at pressures ranging from 10 to about 30 psig depending on design. Bladders were fabricated by welding sheet or lay flat tubing or by extrusion blow molding. The bladders lost almost no pressure over an interval measured in years because perfluorinated gases had essentially zero permeability through the TPUs used. The bags gained pressure over time because atmospheric gases diffused into the pressurized bladder that compensated for pressures losses resulting from bladder creep during shoe manufacture. Perfluorinated gases are inert, non-toxic, and have no effect on the ozone layer. They are long lasting greenhouse gases and have been subjected to increasingly tighter regulation, and have been banned in some European countries.

Nike undertook to find an environmentally friendly, permanently pressurized cushioning technology. We were not to identify an acceptable replacement gas or a monolithic elastomeric membrane or coating that could be used to manufacture bladders at acceptable cost. Suitable bladders formerly made from flat sheet can be made from multilayer sheet as described in USP 5,713,141 etc. The sheet consists of a thin EVOH barrier layer contained within a multilayer extrusion in which the primary components of the other layers are polyurethane elastomer and regrind. Bladders that were formerly made from lay flat tubing or by extrusion blow molding which had been employed in visible applications could be made from multilayer sheet in which the EVOH layer is subdivided into a number of layers on the order of a micron in thickness by twin sheet thermoforming as described in USP 6,082,025 etc. These products required development of extrusion processes that were significantly more complex than those used by Nike in the past and twin sheet thermoforming as well as development of more complex methods of testing the performance of parts. We will cease using perfluorinated gas in our air bladders by the end of 2005.



Thermoplastic Polyurethanes and other thermoplastic elastomers , rheology, structure property relationships