Investigation of Adhesion in Multi-Material TPE Systems Using T-Peel Tests and Taguchi-Based Parameter Optimization

Abstract

Multi-material pellet extrusion additive manufacturing (PEX-AM) can integrate ultrasoft thermoplastic elastomers (TPEs) that are impractical as filaments. However, the reliability of the interfacial adhesion remains unknown. This study aims to quantify and optimize adhesion in ultrasoft (TPE30-00) and soft (TPE45A) TPE systems manufactured via PEX-AM. FT-IR and thermal analyses are conducted to identify material and define stable processing windows. The processing windows of 195°C–225°C (TPE30-00) and 195°C–245°C (TPE45A) are chosen accordingly. Interfacial performance is assessed using a modified ISO 11339 T-peel geometry. Furthermore, a design of experiments (DoE) with a Taguchi L9 orthogonal array evaluates the main effects of head temperature/flow couples and raster angles for both materials. Mean peel resistance ranges from 273 to 881 N/m. The dominant factor is the TPE30-00 head temperature/flow setting, followed by the raster angle of the TPE45A. The DoE increases the optimum peel resistance to 964.8 N/m and shifts failure toward cohesive fibrillation of the TPE30-00 interlayer rather than premature interfacial debonding. Durability is tested by displacement-controlled cyclic shear (Δδ = 10 mm, 2 Hz) to 10⁶ cycles. Dynamic modulus remains essentially stable, with changes lower than 4%, while the secant modulus decreases, consistent with viscoelastic/preloaded relaxation rather than interfacial degradation.