German polymer manufacturer Covestro and Brazilian footwear manufacturer Calçados Beira Rio are working on a range of concept shoes designed to offer a more sustainable footwear solution.
The companies have now presented two examples of how alternative raw materials can be used to recast shoe designs in a more sustainable mould.
The shoes - one, a dressy, high-heeled pump, the other a casual tie-shoe - serve as an illustration of what is possible in the quest for more sustainable solutions, said the companies.
Both feature Covestro products derived from alternative raw materials such as CO2, biomass and plastic waste. The company is increasingly exploring the use of such raw materials to reduce its dependence on fossil materials and increase the sustainability of the value chain.
One of Covestro’s best-known developments in this area is its CO2 cardyon technology. This includes the company’s CO2-based polyols, that are used, among others, to produce polyurethane foams, although new applications are continuously being developed. According to Covestro, its CO₂ technology has now developed into a platform technology that contributes to resource conservation and circular economy and to reducing the ecological footprint of its materials.
The CO2 replaces some of the traditional fossil raw materials previously used, without impacting any of the properties of the foam, which, in this case, is used as the base in the upper and inner lining of both shoe designs.
The outer soles of the shoes are made from two different types of thermoplastic polyurethane. One type is also based on cardyon; in the other, 60 percent of the carbon content is derived from biomass.
In addition, the heels of the pumps contain recycled Makrolon. Water-based adhesives and polyurethane coatings eliminate the need for solvent-based products, improving conditions during production as well.
Covestro’s cardyon product is currently also being used in applications such as the ECO foams from the Slovenian footwear supplier Plama-pur, The foams are characterised by durability and a high compression hardness, which not only gives them better physical properties than fossil-based foams but, importantly, better elasticity and a finer cell structure.
The CO₂-based precursor is also found in concept sneakers designed by Chinese shoe designer Axis Liu, in the form of a thin, translucent film made of the thermoplastic polyurethane Desmopan 37385A, which matches the color and structure of the upper material. It is applied to the upper by hot stamping and features good scratch and abrasion resistance.