Research On The Modification And Application Of Multi-functional Waterborne Polyurethane Acrylate

A research on the modification and application of multi-functional waterborne polyurethane acrylate （WPUA） was made with the intention to break the bottlenecks of waterborne UV coatings in their development and application. A series of linear and branched WPUA products with increased functionalities of polymer molecules were synthesized, in order to overcome the shortcomings of films in rigidity, strength and the resistance to water and solvent. Subsequently, to meet the requirments for special performances and technologies, two novel nano-composite coatings, MWPUA/SiO₂ and MWPUA/CB, were developed; moreover, a high-solid-content and water-dispersible system （HSWPUA） with polymer as the continous phase was originally obtained. Finally, bio-inspired by the high-efficient light-harvesting and energy-transferring mechanisms of plants, thioxanthone/amine photoinitiator was synthesized in bionic way and the photoinitiating efficiency was optimized to explore a new technical way of improving the UV curing efficiency of deep layers in colored coating. Briefly, the major work and results we made and got are as follows:After modifying the soft and hard segments and addressing the problems of linear product about the functional structure and performance regulation, diamine used before was replaced by polyamine compounds, which were then centered on to connect prepolymer branched chains that were terminal-capped by acrylate. Thus the functional groups got increased with the increase of terminal number, making the reaction effective and complete even under the effect of high space hindrance and the influence of complex factors, and a series of novel WPUA products with increased functionalities were obtained. Systemic research was made on the effect and influence of average functionality on the properties and structures of polymer and, based on it, the functionalities and combination properties were modified to primarily overcome the shortcomings of traditional WPUA in rigidity, strength and the resistance to water and solvent.Surface modification was conducted to nano SiO₂ by introducing coupling agents having UV curable groups, and chemical bonds were established between nano CB and MWPUA polymer by means of grafting. In this way, nano particles in MWPUA/SiO₂ and MWPUA/CB got dispersed uniformly and stably, MWPUA/SiO₂ obtained strengthened abrasive resistance and adhesive power, and MWPUA/CB got greatly improved UV curing performance, favorable for the special demand of applied wood floor coatings and black coatings.To meet the higher requirments of WPUA dispersion for more complicated equipments and technologies, a new concept of“high-solid-content and water-dispersable polyurethane acrylate”was proposed, and HSWPUA/acetone, HSWPUA/ethanol/acetone and HSWPUA/acrylate complexes were actually prepared. The obtained samples have solid contents over 70%. Such product, combining the technologies of high-solid-content, UV curing and water dispersion, can be accomodated to different coating methods with satisfactory combination properties like viscosity, adhesive power and water dispersion stability.Bio-inspired by the high-efficient light-harvesting and energy-transferring mechanisms of plants, bionic investigation was made into thioxanthone/amine, a photoinitiator having similar light-harvesting and energy transferring processes. Through designing proper bridges and imitating protein supramolecular systems, the formerly separate photosensitive cells and photoinitiating cells were integrated into the same macromolecule or polymer. Based on the comparison with the structure and mechanism of plant photosystem, systemic research was made on how the arrangement, composite structure, energy transferr and electron-transfer affect the photoinitiating efficiency, and meaningful results were got primarily.