Performance evaluation of ultrasonic assisted leather bonding for improved durability and sustainability

Leather products are typically manufactured using adhesive bonding and stitching methods. These methods pose challenges such as reduced flexibility owing to thick seams, aesthetic surface defects, higher production time, energy and chemicals consumption during the manufacturing processes. To address these limitations, this study investigates ultrasonic assisted adhesive free bonding as a sustainable alternative for joining chrome tanned leather. The objective was to evaluate the influence of welding time (WT), delay time (DT) and holding time (HT) on the tensile performance of bonded leather and to establish an optimum process window using a Taguchi L₉ experimental design. The bonding experiments were conducted on 1 mm thick leather, and the bonded joints were characterized through tensile testing and SEM/EDS analyses to assess their mechanical performance and interfacial bonding characteristics. The results showed that WT was the most influential process parameter governing joint strength. The highest experimental tensile strength of 2.1175 MPa was obtained at WT = 0.4 s, DT = 0.6 s and HT = 0.2 s while the Taguchi optimization predicted an optimum tensile strength of 1.709 MPa at WT = 0.4 s, DT = 0.2 s, and HT = 0.4 s. The SEM observations revealed dense fiber interlocking and interfacial consolidation in high-strength joints. EDS analysis confirmed adhesive-free bond formation without significant compositional changes at the weld interface. The proposed approach offers a promising sustainable joining solution for leather products used in footwear, fashion accessories, automotive interiors, furniture and emerging wearable applications.