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Neues Lichtschutzsystem für TPU in Sport- und Freizeitanwendungen

von Cinzia Tartarini, Karl-Heinz Hornbach, Dr. Kerstin Schrinner

Thermoplastic polyurethanes are prone to degradation both during processing and enduse, as a result of the combined effects of thermal-oxidative and UV light exposure. During manufacture, antioxidants are effective at preventing free-radical induced oxidation, and maintaining low color. Thermoplastic polyurethanes based on aromatic isocyanates are generally characterised by poor light stability. Light colored and transparent TPUs used in Sports and Leisure applications therefore have to be stabilised against discolouration.

Thermoplastic polyurethane makes it possible in the fields of sport and casual footwear to manufacture so called lightweights with high grade quality characteristics for very specific requirements. The chosen raw materials determine reactivity, functionality and molecular weight – all important factors which have a direct bearing on the final properties. In this way, the finished material (e.g. shoe sole) can be made rigid or flexible, highly elastic or with good shock absorbing properties, and with varying degrees of thermal stability and abrasion resistance. Finally, factors such as ageing resistance, light stability and behaviour in different media, and more complex properties like grip and flex-crack resistance are important characteristics for the targeted applications.

Stabilising systems currently used for thermoplastic polyurethane generally consist of UV absorbers, hindered amine light stabilisers and antioxidants. The focus of this paper will be the improvement of initial colour and light stability of aromatic based Thermoplastic polyurethanes. A new solid light stabiliser system will be introduced and application data will be discussed.