Preparation of organosilicon-synergized, internally cross-linked waterborne polyurethane and its performance optimization in BOPP film printing

Abstract

To develop high-performance waterborne ink binders for bi-oriented polypropylene (BOPP) film printing, a series of aqueous polyurethane (APWPU) dispersions were synthesized via trimethylolpropane (TMP)-mediated internal cross-linking, in combination with organosilicon modifications using 3-aminopropyltriethoxysilane (APTES) and bis-hydroxypolydimethylsiloxane (PDMS-OH). An orthogonal experimental design (L₉(3⁴)) was employed to systematically evaluate the synergistic interactions and statistical significance of these modifiers. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle measurements indicated that the introduction of APTES and PDMS, along with increased TMP content, resulted in larger dispersion particle sizes (up to 100 nm) and reduced transparency. The organosilicon components significantly reduced surface tension and enhanced interfacial adhesion to the BOPP film. The hybrid cross-linking network simultaneously reduced water absorption and surface free energy, improved the water contact angle, and achieved balanced mechanical properties with a tensile strength of 11.98 MPa, elongation at break of 465.36 %, and enhanced thermal stability. Orthogonal ANOVA revealed that APTES significantly affected water absorption (p = 0.012) and elongation at break (p = 0.005), while PDMS-OH primarily influenced elongation at break (p = 0.024) and adhesion energy (p = 0.039). An optimal formulation, APWPU-6 (TMP 1.5 wt%/APTES 3 wt%/PDMS-OH 7 wt%), was identified based on the experimental results.