Study On Preparation, Structures And Properties Of β-cyclodextrin/Polyurethane Composites

Polyurethane is a kind of block copolymer which contains soft and hard segments. Softsegments are formed by polyhydric alcohols and hard segments are formed by isocyanates andchain extender agents. Because of the special structures of polyurethane, there are many excellentproperties of polyurethane, such as toughness, abrasive resistance, low temperature resistance，excellent elasticity and resilience etc. Now, polyurethane has been widely used in many industrialareas, for example, coatings, adhesives, textile finishing agents, spandex etc. Based on thedispersion medium, polyurethane is divided into two types. One is solvent polyurethane and theother type is waterborne polyurethane. Compared with the properties of these two kinds ofpolyurethane, the common properties include abrasive resistance, fatigue durability, toughness andothers are well. Although there are many superior performances of polyurethane, someweaknesses still exist. When traditional solvent polyurethane is used in some special areas, themechanical, antistatic, dyeing ability or other properties need a deeper modification. Comparedwith traditional solvent polyurethane, the mechanical and heat-resistance properties of waterbornepolyurethane are insufficient. To get the requirements of use standard, polyurethane needs adeeper physical or chemistry modification.In this research, we made use of β-cyclodextrin which was easily available in the nature tomodify the properties of solvent polyurethane and waterborne polyurethane. In the structure ofβ-cyclodextrin, there is one lipophilic central cavity and the outside of cavity is hydrophilic. Toimprove the dispersion of β-cyclodextrin in the matrix of waterborne polyurethane,β-cyclodextrin/polyethylene glycol inclusion complexes were prepared by physical blending andhydrophilic polyethylene glycol was introduced into the complexes. The characterization ofcomplexes indicated that: β-cyclodextrin which was modified by polyethylene shows good watersolubility and particle size of assembly decreased. In the system of β-cyclodextrin/polyethylene glycol inclusion complexes, polyethylene glycol changed the crystal structure decreased thecrystalline of β-cyclodextrin. Then β-cyclodextrin/polyethylene glycol inclusion complexes wereadded into waterborne polyurethane emulsion and waterborne polyurethane/β-cyclodextrin/polyethylene glycol composites were prepared. Composites were characterized and indicated:β-cyclodextrin/polyethylene glycol inclusion complexes didn’t affect the storage stability ofwaterborne polyurethane emulsion. There were good compatibility betweenβ-cyclodextrin/polyethylene glycol inclusion complexes and waterborne polyurethane and bettermechanical properties of composites than pristine waterborne polyurethane when the weightcontent of complex was less than4%. Characterization also demonstrated the interaction betweenβ-cyclodextrin/polyethylene glycol inclusion complexes and waterborne polyurethane matrix wasintermolecular hydrogen bonding and complexes increased the physical cross linked points ofwaterborne polyurethane. Besides, the addition of β-cyclodextrin/polyethylene glycol inclusioncomplexes improved the heat resistance of waterborne polyurethane.For further study of β-cyclodextrin in solvent polyurethane (spandex spinning dope),polytetramethylene ether glycol was also used to modify β-cyclodextrin and β-cyclodextrin/polytetrahydrofuran inclusion complexes were prepared. Then, complexes were added into solventspandex spinning dope and polyurethane/β-cyclodextrin/polytetrahydrofuran composites wereprepared by physical blending. Result of characterization indicated that: there was goodcompatibility between β-cyclodextrin and solvent polyurethane matrix. Mechanical propertiesreached the best when the content of β-cyclodextrin/polytetrahydrofuran inclusion complex was4%. β-Cyclodextrin modified by polytetramethylene ether glycol could increase the hydrogenbonding interaction, heat resistance, moisture absorbance, water vapor permeability and dyingability of solvent polyurethane.