Novel Waterborne UV-Curable Hyperbranched Polyurethane Acrylate/Silica with Good Printability and Rheological Properties Applicable to Flexographic Ink

Novel waterborne UV-curable hyperbranched polyurethane acrylate/silica (HBWPUA/SiO₂) nanocomposites were prepared by a three-step procedure and sol–gel method. ¹H NMR and ¹³C NMR results indicate that HBWPU is successfully synthesized. Surface tension and contact angle tests both demonstrate the good wettability of the nanocomposites. Besides, the kinetics of photopolymerization of HBWPUA/SiO₂ films were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy, which reveals that the modified SiO₂ could accelerate the curing speed of HBWPUA coatings. Thermal gravity analysis indicates that the HBWPUA/SiO₂ hybrid films have a better thermal stability than the pure HBWPUA cured films. Furthermore, the hybrid films show enhanced pencil hardness, abrasion resistance, and adhesion. On the basis of the above, HBWPUA/SiO₂ nanocomposites were finally applied to waterborne UV-curing flexographic printing ink, which is printed on poly­(ethylene terephthalate) and glass. The nanocomposite presents good rheological behavior because the ink has a lower <i>Z</i>₀, a higher <i>Z</i>_∞, and the viscosity rebuild time is 375 s. Three colors (red, yellow, and blue) of ink were used to test its printing quality, the curing time was below 30 s, and the adhesion was excellent without being stripped. All of the inks show good water resistance and abrasion resistance. Moreover, the red and blue inks possess better solid densities than the value of 1.07 of yellow ink, and are 1.83 and 1.84, respectively. The current study suggests that the process has promise in applications of food packages

Layer-by-Layer Assembly of Polysaccharide Films with Self-Healing and Antifogging Properties for Food Packaging Applications

Self-healable, transparent, and antifogging polysaccharide films composed of acrylamide-modified chitosan (AMCS) and alginate aldehyde (ADA) were fabricated via layer-by-layer (LBL) assembly. The Schiff base linkage formed between amino groups of AMCS and aldehyde groups of ADA was used to construct the films. Fourier transform infrared spectroscopy and X-ray photoelectron spectra revealed that the films were cross-linked through Schiff base bonds. Ultraviolet–visible spectroscopy and field emission scanning electron microscope characterizations demonstrated that the films exhibited linear growth during the LBL process. The films showed a repetitive self-healing property, and the repeated damage-healing of the films was thickness-dependent. The films can heal the scratches that penetrated to the underlying substrates. Besides the excellent self-healing property, the films showed an antifogging property due to the hydrophilic nature of the two polysaccharides. The antifogging ability of the film was thickness-dependent. Also, the films could regain their transmittance and fog-resistant property after mechanical abrasion due to their self-healing capability. These self-healable and fog-resistant polymeric films have potential applications in food packaging