Study On Waterborne Polyurethane Modified By Methyl Methacrylate

With strengthening of environmental protection awareness, environment-friendly waterborne polyurethane (WPU) has drawn more and more attention. However, with the presence of hydrophilic ionic groups in the backbone of polymer, WPUs suffer from some drawbacks, including the inferior mechanical properties (hardness, strength or elasticity) and reduced chemical resistance from water or other organic agents. To overcome those limitations, WPUs are usually modified with acrylics, aiming to combine the advantages of both polymeric components in a synergistic way to meet the variety of end-use requirements.In this paper,a series of methyl methacrylate modified waterborne polyurethanes were prepared. The effects of polyols structure on morphology of latex particles, the structure and performance of the films ware studied. The elastomeric properties of waterborne polyurethane were tailored by incorporation of polymethyl methacrylate.Heterogeneous structure and mechanical properties of WPUA films varied with changing content of PMMA. Furthermore, the relationship between micro-separated structure and mechanical properties was investigated comprehensively.Waterborne polyurethane dispersions (WPU) derived from polycarbonate diol(PCDL), polyester diol (PBA) and polyether glycol (PPG) were synthesized.Subsequently, methyl methacrylate monomers were introduced in WPU to form waterborne polyurethane-acrylic (WPUA) via in situ polymerization. Transmission electron microscopy (TEM), zetasizer, and rotating viscometer were employed to characterize the morphology, particle size, and shear viscosity of WPUA emulsions,respectively. The structures, chemical resistance, mechanical properties, physical aging behaviors, and thermostability of WPUA films were also studied by ATR-FTIR, water absorption measurement and immersion test, electromechanical universal testing machine, UV-Vis spectroscopy, and TGA. The variation of polyols composition and structure has a significant influence on the morphology and structure of WPUA emulsion particles and the properties of films. The distinct core-shell structure was achieved in the latexes of PCDL-based WPUA emulsion, which film exhibits excellent mechanical properties and aging-resistant performance.A series of aliphatic polycarbonate (PCDL) based waterborne polyurethane and polymethyl methacrylate hybrid dispersions (WPUA) were prepared via a two-step procedure. The heterogeneous structure of hybrid dispersions was investigated, showing that the dispersed particles possess a nano-sized core-shell morphology. The hydrogen-bond interactions in hard domains are weakened by incorporation of PMMA component. The nanostructural heterogeneity in the dried films was determined by using MDSC, AFM, SAXS, DMA and linear rheology techniques. The tensile strength and strain-hardening modulus increase and the elongation at break decreases with increasing PMMA content. Plastic deformation of PMMA domains in WPUA only results in a loss in recoverable elasticity at low strains. With an optimized content of PMMA, the WPUA2 sample shows sharp yielding behavior while maintaining high extensibility and good recoverable elasticity at large strains. The improvement in elastomeric properties and other physical properties by incorporating PMMA component can expand the applications of waterborne PUs as environment-friendly thermoplastic elastomers.