TPU nanocomposites with good adhesive strength and water resistance for thermal sublimation transfer printing

Abstract

Thermoplastic polyurethane (TPU) is widely used as a hot-melt adhesive in various applications, particularly in fabric heat transfer printing. Among the commonly used heat transfer inks, direct-to-film (DTF) ink and sublimation ink are most prevalent. However, DTF ink exhibits poor affinity for natural fabrics such as cotton, and sublimation ink lacks white pigment. Additionally, the inherent transparency of TPU limits its application in heat transfer printing on dark fabrics. To address these limitations, this study employs nano titanium dioxide (TiO₂) to color TPU, enhancing its opacity and enabling its use on dark fabrics. Furthermore, by incorporating triglycidyl isocyanurate (TGIC), a crosslinking reaction is induced in the TPU/TiO₂ composite, facilitating its application on both dark fabrics and natural fibers like cotton. The resulting TPU-based nanocomposite demonstrates excellent adhesion strength and water resistance. When the TiO₂ content reaches 10 % (designated as TT10), the composite exhibits a high whiteness index, indicative of strong opacity. The addition of 1 % TGIC further crosslinks the TPU/TiO₂ composite, maintaining its strong opacity while enhancing adhesion strength and water resistance. Notably, the adhesive strength of the composite surpasses that of pure TPU, and its water resistance improves as well. This TPU-based nanocomposite shows promise for heat transfer printing applications on dark fabrics and natural materials such as cotton.