Advanced Quality Control in the Leather Industry: Thermography and Emerging Techniques

The leather industry is one of the symbols of Made in Italy, and it is fundamental to the country's economy and tradition. Italy is the biggest producer of leather in Europe, with known tanning districts located in Tuscany, Veneto, Campania, and Lombardy. Italian leather is renowned worldwide for its high quality, handcrafted, and eco-friendly nature; therefore, the existence of flaws in leather products is a critical issue that must be solved and corrected. Nevertheless, defect identification remains a substantial challenge, both economically and environmentally. This thesis has been elaborated in cooperation with the SOLARIS project, part of the wider MICS (Made in Italy Circular and Sustainable) program whose purpose is to create innovative and sustainable solutions for the manufacturing sector in Italy. This research particularly examines the manufacturing process regarding potential defects, along with the application of thermography as a non-destructive test (NDT) aimed at improving leather quality control, along with the Hot Disk method in the evaluation of thermal properties. In the leather sector, traditional quality control consists of a combination of human observation and destructive tests. Unfortunately, these methods tend to be tedious and inaccurate. Thermographic analysis, instead, allows for rapid and contactless detection of surface and internal anomalies by evaluating temperature distribution, without destroying the products. The Hot Disk method further complements this approach by measuring thermal conductivity and diffusivity, offering deeper insights into material uniformity. A part of the thesis is dedicated to a case study, in collaboration with SOLARIS project, which applied thermography and temperature measurements to leather samples with and without defects. The study focused on identifying specific flaws such as grain detachment, coating separation, stains, and creases, correlating them with their thermal behavior. Additionally, laser tests were integrated to compare thermal cycles and to activate their surface for specific treatments, giving more evidence for the thermographic analysis and presenting another angle of view in connection with defect identification. The results demonstrate the effectiveness of thermography as a real-time defect identification method. This allows manufacturers to find hidden defects without changing or destroying the material. Combined with the Hot Disk method and laser tests, this approach offers a more sustainable and efficient alternative to traditional quality control methods. This thesis highlights the practical applications of thermography in the leather sector by improving defect detection and optimizing quality control. It demonstrates its potential to reduce waste, improve resource efficiency, and support a more sustainable and competitive industry.