Preparation and properties of a novel low crystallinity cross-linked network waterborne polyurethane for water-based ink

A novel linear and cross-linked network polyurethane dispersion (LWPUD and CWPUD) being blue transparent, low acid number and low crystallinity were prepared using the pre-polymerization and chain-extending reaction synthetic method. The properties of LWPUD and LWPUF(linear WPU film) with different 2,2-dimethylolpropionic acid (DMPA) contents were examined by fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM) and dynamic light scattering technique (DLS), X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA). The particle size of CWPUD, the water resistance and the mechanical property of cross-linked WPU film (CWPUF) with different TMP contents were investigated. The results showed that with increasing DMPA content in polyurethane chain, the particles of LWPUD became more uniform and regular, and the glass transition temperature of LWPUF decreased, while its thermal stability increased. With increasing the TMP content in polyurethane chain, the particle size of CWPUD and the water resistance and the tensile strength of CWPUF increased, while the elongation at break of CWPUF decreased. By adding water-based colorant, wetting agent, adhesion promoter and deionized water into LWPUD and CWPUD, a novel water-based ink with low crystallinity was obtained. The adhesion, water resistance and anti-adhesion of the cross-linked network water-based ink were better than those of the linear water-based ink in application on polyethylene terephthalate (PET) substrate.