The Preparation And Characterization Of Waterborne Hyperbranched Polyurethane

The energy-saving and environment-friendly materials with the propertiesof harmless, high safety factors and easily degradable have become a hot issuein recent years in order to solve increasingly serious environmental problems.Waterborne materials which are low cost, environmental and nonflammablethrough replacing the organic solvent by water have become popular in manymarkets. Waterborne polyurethanes (WPUs) have gained increasing interest in aboard range of application owing to their excellent elasticity, abrasion resistance,viscosity control and non-toxicity. Absence of anomalous linkages (branching,crosslinking) which make the traditional linear PUs have poor water resistance,thermal behavior and mechanical properties which are inferior to that ofsolvent-based polyurethanes. Crosslinking-modification as a high-efficiencymethod to improve the properties of WPUs has drew a lot of attentions and themost robust way to improve the mechanical properties of PUs is the chemicalbonding of PU chain with functionalized hyperbranched polymers (HB) throughcrosslinking. Because of the HB owing the highly branched, three-dimensionalspherical structure and high functionality, it makes possess unique and differentproperties, such as low viscosity, high solubility and low entanglement degree. A small amount of HB architecture is sufficient for manifold the performanceand application of WPUs. In this work, a series of waterborne hyperbranchedpolyurethane (WHBPU) were synthesized by endcapping the hyperbranchedester and the synthetic process, fundamental properties and the application valueof production were also studied and discussed.The objective of this work is to synthesize the nonionic waterbornehyperbranched polyurethane (WHBPU) with the unsaturated double bonds at theterminal through the modification of hyperbranched polyesters (HBPs). Theproducts are incorporated with the hydrophilic monomers and acrylicfunctionality by modifying some of the hydroxyl groups of hyperbanchedpolyester(HBPs) with the prepolymers which are formed by the reaction ofdiisocyanate and monomers containing the ending hydroxyl groups such asisophorone diisocyanate (IPDI), Methoxypolyethylene glycols(MPEG-1000)and Hydroxyethyl methacrylate (HEMA), respectively. The MPEG segmentcould enhance the polymer dispersible in aqueous mediums and unsaturatedacrylic groups are able to form the crosslinking network with the other carbondouble bond. So the synthetic products could be used in the area of the additiveor coating raw materials. The structure and molecular weight of the synthesizedWHBPU was characterized by FT-IR,1H-NMR and GPC (Gel PermeationChromatography).The dispersibility and average particle sizes were determined by UV-visspectrum and laser light scattering, respectively. The variation tendency of viscosity was measured by rotational rheometer. The crystallization morphologyof the WHBPU polymers was investigated using X-ray diffraction andpolarizing optical microscopy. The phase transition behaviors and morphologyof the WHBPU were investigated using differential scanning calorimetry (DSC)and thermo-gravimetric analysis (TGA). Those properties of WHBPU polymerscan help us understand the relationship between the molecular structure andfeatures.The WHBPU oligomers were dissolved in water and measured by UV-visspectrums analyzer. The spectral shapes of the oligomers are very similar toeach other and the absorption maxima are observed at around220nm. Theseresults showed that the WHBPU can be cured under UV irradiation withphotoinitiator Api-180(percent of weight is4%). To compare the performance ofWHBPU films, stability of emulsion, hardness, gel content, water resistance andfilm flatness ware measured in order to choose the best candidate to coatingresin. Furthermore, the factors which affected the coating property werediscussed.At last, the WHBPU oligomer with biodegradable and biocompatibleamphiphilic star copolymers acted as a unimolecular reverse micelle in CHCl3toestimate the loading-capacity ability of WHBPU.The results as follow:The WHBPU was obtained through─NCO functional group react with the─OH. The molecular weight of hyperbanched oligomers is lower but consistent with theoretically predicted molecular weight and the observed values ofmolecular weight distribution are in reasonable agreements. This indicated thosesynthesized WHBPU have ideal structures.The WHBPU are well water dispersible and the dispersibility is governedby the hydrophilicity of the chains. The average particle sizes of aqueousdispersions were increasing with the increase of MPEG contents exceptWHBPU-8:4. This is due to the change of dispersion morphology. Therheological measurement showed WHBPU display a non-newtonian behavior.The crystallinity was the same with MPEG and the crystalline degree increasedwith the increase of MPEG contents. The DSC showed that the WHBPU possessthe glass transition temperature and melting temperature with the temperaturerising. The TGA results confirmed that these films had good thermal propertiesand the decomposition process consisted of two stages: first step for hardsegment (urethane groups) and second step for soft segment (ester and etherchain segments).The films of WHBPU-4:8have the best comprehensive performance to bethe coating raw material. The films performance was corresponding to thedegree of cure and crosslink density.The water soluble dyes, methylene blue (MB), were successfullytransported from water to the insoluble chloroform phase by the core-shellWHBPU, indicating the great potential of the micelles as nano-carries. Themaximum percent of removing MB can reach90%which was determined by proportion of hydrophilic and hydrophobic segments. The property of WHBPUmay be useful in the field of coating color protection, drug-loading, the dyeremoval, water treatment and so on.