Establishing the bleeding and diffusion of chromophores from lining/upper fabrics in shoes to MidSole in sneakers – a case study

Abstract

‘Chemical’ migration, in particular bleeding, in the footwear industry is an issue that has not been well understood. In this work, a specific case problem is investigated concerning the occurrence of black-colored staining in the polyurethane (PU) midsole after production of the shoes and storage in a warehouse for about 4–6 wk. Considering the qualitative nature of the standard tests employed in the footwear industry (like SATRA TM340 and TM 343), here, (chemical) methodologies are designed to understand and identify the source of chromophore(s), how they are transferred to PU, and their diffusion kinetics. In this process, different chosen temperatures and relative humidity conditions are employed to evaluate their influence on the transfer and diffusion of chromophores from the lining/upper fabrics. Preparative chromatography and high-resolution mass spectroscopy have enabled the identification of the responsible chromophores for the coloration of the shoe sole. This work provides a fundamental base for understanding a significant issue in the footwear industry.

Keywords:

• migration
• pigments
• chromophores
• staining
• shoe sole
• polyurethane
• SATRA

Acknowledgements

The experiments and analysis shown in this work were performed at the School of Material Science and Engineering, Nanyang Technological University Singapore. The authors appreciate the help provided by various technicians during this work. Thanks are also due to Mr Artem Kashtanov and Mr Ye Kai who have contributed to the discussions relating to testing according to SATRA TM343.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data avilabilty statement

Research data are not shared.

Notes

1 Deals with the qualitative determination of possibility of a material to lose color in wear resulting in staining of a material in contact.

2 Deals with the determination of the bleeding of color, if any, from one material (like fabric or leather) to another (for example, polymer sole) when placed in intimate contact.

3 Though TDI also behaved similar to toluene, it was not selected as it could have unforeseen reactions with PU.

Additional information

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.