Offering footwear manufacturers high durability and improved processing, the Huntsman Polyurethanes’ Footwear team is launching the AVALON ABX range of thermoplastic polyurethane (TPU). This new series of high performance TPU/rubber compounds is available in a variety of hardnesses, from 60 Shore A to 90 Shore A, responding to the demand for soft applications in casual and athletic shoes as well as harder sole types for cleated sports plates.

Manufacturers are also set to benefit from improved processing in terms of faster cycle times, lower mould clamping requirements and enhanced production robustness. Durability of the AVALON ABX range is achieved through excellent abrasion and hydrolysis resistance. It has a rubber-like smell and tactile feel. Together with improved adhesion to polyurethane midsoles, the new range also offers enhanced dimensional stability. This enables footwear producers to formulate separate parts of the sole which can then be placed back in the mould, making the technology ideal for dual density applications as well as for inserts, heels, top-pieces, kippers and over-moulded designs.

Craig Roberts, marketing manager, Huntsman Polyurethanes’ Footwear team, says: ‘The launch of AVALON ABX reflects our continual drive to identify and create innovative, tailor-made solutions that enable customers to benefit from footwear technologies that expand their business potential and provide processing efficiency.’

* Based on a newly-developed polyester system using the high performance SUPRASEC 2904 pre-polymer, Huntsman Polyurethanes’ Footwear team has worked in partnership with Gusbi Off.Mecc.Spa, the Italy-based machine manufacturer, to create a new PU system specifically for its machine, which utilises the NEWFLEX technology. Meeting the specifications of EN-344 and tested by the PFI testing institute in Germany, the new polyester system provides a rapid demould time and extended cream time to enhance productivity for footwear producers. Together with the NEWFLEX technology, the new PU system minimises screwlife and defects to improve the outsole’s aesthetics and physical properties, providing outstanding performance for safety shoes.

The same pre-polymer can be used for the midsole and the outsole, enabling manufacturers to meet the necessary requirements for safety boot midsoles while optimising the production process. With the same rapid demould, the technology also allows for densities below 0.35, making it suitable for casual shoes.

NEWFLEX technology requires the PU system to be cast into an open mould. The PU reaction starts with a certain degree of polymerisation before a second mould clamping pressure is applied, resulting in a reduced number of air bubbles and voids in the outsole and the ability to produce enhanced transparency compared with standard moulding technology. An anti-static version of the technology is also available for safety shoes.

Craig Roberts, marketing manager, Huntsman Polyurethanes’ Footwear team, says: ‘Working together with Gusbi, we have been able to optimise the technology to achieve a more efficient process while improving product quality to offer footwear producers an innovative technology, enabling them to penetrate new business sectors.’

* A new high performance sockliner system from Huntsman Polyurethanes’ Footwear team is being unveiled at Simac 2004. The polyether polyurethane system, based on SUPRASEC 2444 technology, allows insole producers to achieve different characteristics in the final foam from just a single, versatile chemical system. This means that the specific demands of manufacturers’ customers can be met without the need for numerous individual formulations, resulting in significant cost and time saving.

Different types of footwear require different levels of performance from a sockliner; a casual shoe may require a soft foam with a high level of comfort, whereas for a sports shoe, low weight with good support and compression set resistance may be more important. With SUPRASEC 2444 technology, these different requirements can be met in a simple, cost-effective way. By varying either the amount of material poured into the mould or the mixing proportions of the two liquid components, the hardness or density of the sockliner can be varied over a wide range. Keeping the density low and varying the mix ratio enables the producer to create a range of hardnesses at the same weight. Adjusting the weight of the material in the mould can then be used to vary the hardness and level of compressive support further. The system can be processed on most types of conventional polyurethane moulding equipment.

Processing robustness and a high degree of dimensional stability allow products to be produced with densities as low as 0.25g/cm3 over a range of hardnesses from 30-50 Asker C. Rapid demould times of less than 2.5 minutes can be achieved and the polyether-based technology ensures easy handling and flow in the mould, enabling very thin components to be moulded if required. The resulting products have a soft latex feel, exceptional tear strength, low compression set and the comfort characteristics associated with a high performance material. SUPRASEC 2444 systems are inherently resistant to bacterial and hydrolytic attack, important factors in the moist environment inside a shoe, ensuring the integrity of the sockliner during wear.

‘This new technology delivers enormous production benefits to footwear manufacturers. Its versatility means that one single technology can cater for a host of different application requirements, while maintaining properties which are essential to durable footwear solutions’, says Craig Roberts, marketing manager, Huntsman Polyurethanes’ Footwear team.