Study On Polyurethaneurea Aqueous Dispersion And Its High Internal Phase Emulsion

For environmental and economic reasons, waterborne polyurethane (PU) aqueous dispersions have attracted increasing interest in recent years. However, the built-in hydrophilic segments in the macromolecular chain inevitably impart undesirable water-resistance performance to waterborne PU in industrial applications. In this dissertation, a series of stable polyurethaneurea (PUU) aqueous dispersions were prepared with C9-diol-based polyester polyol (POA) and/or fluoro Oligomer(Zonyl BA-N). The PUU films prepared with these aqueous dispersions showed excellent water-resistence performance and high tensile strength. Moreover, PUU nanoparticles in PUU aqueous dispersions were used to stabilize both water-in-oil (W/O) and oil-in-water (O/W) Pickering high internal phase emulsions (HIPE). Based on these two types of Pickering HIPEs, hydrophobic and hydrophilic open porous polymers (Poly-Pickering-HIPEs) with void wall functionalized by PUU were prepared respectively. This work enlarged research fields and applications of PUU, eliminated large quantity of surfactants used in the traditional HIPEs, and firstly prepared W/O and O/W Pickering HIPE with one type of particle. In addition, some vinyl ester resin (VER)-based Poly-Pickering-HIPEs was prepared using VER as the organic phase and exhibited high compressive strength and toughness. The main results were descripted as follows:1. A series of PUU aqueous dispersions were prepared with C9-diol-based polyester polyol (POA) and/or poly(neopentylene adipate) polyol (PNA). The high-temperature stability and freeze-thaw stability for all the aqueous dispersions are excellent. The PUU film prepared only with the POA exhibited the lowest water-absorbing amount, the highest tensile strength (51.3 MPa) and the best hydrolytic stability over all PUU films studied. The experimental results also showed a high degree of hydrogen bonding for urea groups, resulting in excellent water resistance performance and mechanical properties.2. A series of stable fluoro-containing PUU aqueous dispersions were prepared from POA and fluoro oligomer(Zonyl BA-N). The particle sizes of these aqueous dispersions were less sensitive to Zonyl BA-N content. The introduction of fluoroalcohol could increase the surface hydrophobicity of modified PUU films and the contact angle of water on the surface of these films increased from 88 to 113°. When Zonyl BA-N content was about 3%, the modified PUU films showed low water absorption and high tensile strength (44.3MPa). With the increase of fluoro oligomer content, the hardness and tensile strength of the modified PUU films decreased and elongation of the films increased resulting from the strong hydrogen bonding in urea carbonyl groups in the hard segments of PUU.3. With PUU aqueous dispersion as aqueous phase and mixture of styrene (St) and divinylbenzene (DVB) as the organic phase, temperature-dependent water-in-St/DVB Pickering HIPEs were prepared. And with these Pickering HIPEs as templates, the hydrophobic polymer Poly-Pickering-HIPEs with void wall surface functionalized by PUU was prepared. The measurements of near-infrared light backscattering showed that the upper limit of internal phase volume fraction of Pickering HIPEs stabilized solely by 1.0 wt% PUU nanoparticle was from 93.3 to 97 vol%. It is of interest to note that PUU particle layers adsorption at the water-oil interface and 3D network formed by PUU particles in organic phase played key roles in the stability of Pickering HIPEs. It was also found that Poly-Pickering-HIPEs morphology could be controlled by changing the Pickering HIPE aqueous phase volume fraction, polymerization temperature, as well as the crosslinker, electrolyte and PUU concentration.4. Using PUU aqueous dispersion as continuous phase, O/W Pickering HIPEs having dispersed phase volume fraction of up to 95% were prepared. It was found that the particles membrane made by adsorption of PUU nanoparticles at water-oil interface around the dispersed phase droplet, and prevented the coalescence between the neighboring dispersed droplets; in the same time, PUU nanoparticles formed a 3D network in continuous phase, which rose the continuous phase viscosity and enhanced Pickering HIPE stability. Furthermore, with acrylamide (AM) and N,N'-methylenebis acrylamide (MBAM) as monomer and crosslinker respectively, the open porous hydrophilic polymer-based Poly-Pickering-HIPEs were prepared. It was also found that the Poly-Pickering-HIPEs morphology could be effectively controlled by changing HIPE preparation conditions, such as aqueous phase volume fraction, as well as the concentrations of PUU, crosslinker and electrolyte.5. With vinyl ester oligomer (VEO) and styrene (or methyl methacrylate) mixture (VER) as the organic phase, W/O Pickering HIPEs were prepared with copolymer microspheres as sole stabilizer. Using the Pickering HIPEs as emulsion-templating, VER-based Poly-Pickering-HIPEs were prepared. Stability studies showed that the up limited internal phase volume fraction of this type of Pickering HIPEs was between 95 and 97 vol%; an appropriate increase in the VEO content is conducive to the stability of Pickering HIPE. Mechanical test showed that the Poly-Pickering-HIPEs had high compressive strength and toughness, and its Young's modulus increased with increasing the VEO content of the organic phase. SEM analysis showed that with increasing the aqueous phase volume fraction and/or decreasing the VEO content, the average void size of Poly-Pickering-HIPEs increased, and their void size distribution became broad.