Lightweight and Comfortable Sole Systems

Lightweight and Comfortable Sole Systems The feet are the most important parts of the human skeleton, bearing body weight throughout a lifetime and therefore subject to constant stress. Feet must be able to support body weight and withstand the forces that come into contact with the ground during functions such as walking, running and stopping. Foot comfort is connected to the contact pressure between the sole of the foot and the ground. High pressure values, particularly at the ground-foot interface, may cause blood flow obstruction, pain or the emergence of various pathological disorders. To increase foot comfort, materials must be used that reduce contact pressure in the risk areas on the sole of the foot during load bearing. Polyurethane systems are the most common materials encountered in this application. The lightweight printing of products in shoe sole and slipper systems is achieved through the low mold density feature. However, low density products generally require more open cells than high density products, which causes problems in dimensional stability after final application and results in lower strength test values compared to high density products. This article demonstrates that high strength and comfort values can be obtained from low density products using the new generation systems developed by Kobe Polyurethane. We provide a solution to the dimensional stability problem that poses a risk in low density products through our newly developed Kobester polyester product. With the new system polyester, the desired saturation has been achieved in soft products. While these new system combinations provide comfort, lightness and high impact resistance, they also ensure long-term durability. While the reaction profiles of these new systems match the reaction profile of standard sportswear and slipper systems, shorter mold opening time provides convenience and maximum production capacity efficiency. With the use of appropriate paint and mold release agents, it delivers excellent surface performance even at low mold temperatures.

Kobe Polyurethane Shoe Systems

In the Kobecat 120-Kobester LB1732-Kobenat Z002 system, developed for low density and low hardness sports sole production, the hardness value is 50-60 shA and the mold density can be printed as 320-420 kg/m³ depending on the model.   [caption id="attachment_141525" align="aligncenter"] Figure 1. Kobe Polyurethane Sole System[/caption] In slipper and sole systems, mechanical tests are conducted to examine material behavior. The most important of these tests are flex resistance and tensile tests. In the developed base system, both flex resistance and tensile test results exceed standard products. In the Kobecat 120/Kobester LB1732/Kobenat Z002 system developed for sports soles, test conditions were made more stringent, with the flex test showing more than 150,000 steps at 0°C. In the tensile test, maximum load carrying capacity and percent elongation at break were determined.   [caption id="attachment_141527" align="aligncenter"] Figure 2. Flex Test[/caption] The work comprises three stages. First, laboratory synthesis and application studies are conducted together with design; in the second stage, test castings and testing with the low pressure machine are performed in-house; in the final stage, tests of products resulting from customer trials and customer production runs are carried out. The results of these three-tier verification tests are shown in the table below.   [caption id="attachment_141531" align="aligncenter"] Table 1[/caption]

Kobe Polyurethane Slippers System

In the Kobecat 118-Kobester LB1732-Kobenat X001 system developed for low density and low hardness slipper sole production, the hardness value is 55-65 shA and the mold density can be printed as 220-250 kg/m³ depending on the model. [caption id="attachment_141532" align="aligncenter"] Figure 3. Kobe Polyurethane Slipper System[/caption] Although flex resistance expectations in slipper systems are low, the developed Kobecat 118/Kobester LB1732/Kobenat X001 system exhibits more than 40,000 steps of flex performance. Competitor products tested under the same conditions showed values between 10,000-30,000 steps. [caption id="attachment_141533" align="aligncenter"] Table 2[/caption]     Gülhan Sarıgöl R&D Engineer Kobe Polyurethane