Study On The Synthesis And Properties Of Polyester-based Polyurethane Emulsion

Several types of the isocyanates and the polyols are selected, with the addition of the chain extender-dimethylol propionic acid (DMPA), to synthesize series of polyutethane (PU) emulsions according to the internal emulsion method. The isocyanates used in the process include toluene diisocyanate (TDI) and 1,6? hexamethylene diisocyanate(HDI) and the poiyols include polyethylene adipate glycol . polybutanediol adipate glycol ... polyneopentylene adipate glycol polyhexamethylene adipate glycol and poly caprolactone glycol. The relationship between the stability of the PU emulsions with the particle size of emulsion is investigated with transmission electron microscopy (TEM). With the aid of the differential scanning calorimetry (DSC), The relationship between the low-temperature properties of emulsion cast film with its structure is studied. The crystallization behavior of the polyester-based PU emulsion cast film is analyzed by X-ray diffraction. The rule of the hydrolysis resistance properties of film is showed by means of infrared spectroscopy (IR) and the comparison of the mechanical properties and the solvent-resistance before and after its hydrolysis. The results showed that the stability of the PU emulsion is controlled by the content of the chain extender- DMPA. With the increase of the content of DMPA, the average particle size is decreased and the stability of the PU emulsion is increased. The PU emulsion cast films prepared from polyneopentylene adipate glycol- polyhexamethylene adipate glycol and polycaprolactone glycol exhibit a good hydrolysis resistance, which conforms to the long-chain atom law and Turpin's bix experience rule? The emulsion cast films prepared from polyneopentylene adipate glycol has no crystalinity lower tensile strength higher elongation at break low glass temperature(Tgs = -21.45℃), better low-temperature property and worse solvent resistance. The higher tensile strength( 2OMpa) and better solvent resistance of emulsion cast films prepared from polyhexamethylene adipate glycol is partly due to the crystalmity of its soft segment. A good comprehensive tensile properties appears on the emulsion cast films prepared from polycaprolactone glycol with tensile strength of about 1OMpa, lowest (Tgs = -46.63 ℃) and best solvent resistance.