Synthesis And Properties Of Acrylic Modified Waterborne Polyurethane

In this experiment, water-borne polyurethane (PU) was synthesized from polypropylene glycol (PPG)-GE220, isophonone diisocyanate (IPDI), dimethylol propionic acid (DMPA), using dibutyltin dilautrate as activator. The reaction mixture was reacted for serveral hours at a temperature of about 85 C until the NCO content reached the theoretical value, and cooled to 60 C to obtain a urethane prepolymer. Or at the end of reaction HEA were added and reacted for 2 hours at the temperature of below 60 C to avoid the C=C polymerizing with each other. The polyurethane prepolymers were prepared by the two methods above. The prepolymers were dispersed into distilled water dissolved with chain extender and neutralizer under agitating, and the polyurethane dispersions (PU and PU') were obtained. The more of the dosage of HEA, the thicker of polyurethane dispersion was.With DMPA increasing, PU dispersion was a milky unstable system with deposit turned to water-soluble steady system, but the water or solvent resistance of PU and modified PU emulsion film were very poor if the dosage of DMPA was so much, to ensure the stability of PU ,the less DMPA the better performance of PU. With the NCO/OH (R) value increasing, the PU emulsion film tured from pastiness to impasiness.Particle size and distribution of PU and the modified PU emulsion was detected by laser scatter particle analyzer. The result indicated: the emulsion particle size of PU modified with PA by blending was increased unremarkable and the particle distribution was wide; the emulsion particle size of PUA by emulsion co-polymerization was increased remarkable and the distribution was narrow. With the dosage of HEA increasing, the emulsion particle size of PUA was increased litter and litter. The increscent degree of the particle size and the distribution of PU modified with acrylic indicated the compatibility and blending degree of hard segmentin PU and PA segment. So the compatibility and blending degree of hard segment in PU and PA segment in PUA1 or PUA10 was higher than others.PU and modified PU dispersion was dried on polyetrafluoroethylene board at a temperature of 30 C for a week and emulsion films about 1mm thickness were obtained. Transparence, water and solvent resistance, thermal stability, FTIR spectra and scanner electron microscope (SEM) spectra were detected, respectively. The result indicated: the emulsion film of PU modified with acrylic by emulsioncopolymerization was transparent. The films by graft copolymerization modification were as transparent as PU or PA. The film by emulsion copolymerization was transparent but it was a yellow film. The film by blending with PU and PA was translucent. The water and solvent resistance of PUA1 prepared by emulsion copolymerization with acrylate monomer and PU chain extended by hydrazine hydrate acted as seeded emulsion was the best of all the sample, and the thermal stability was also good. The thermal agravic about 90% temperature was about 405 C. It was higher about 25 C than the PU emulsion film. The surface of the emulsion copolymerization modification was slippery and emulsion particle cannot be observed in the films. The water and solvent resistance of the emulsion film prepared by graft copolymerization was changed with the dosage of HEA increasing. The water and solvent resistance was changed from preferable to poor then to preferable too. The thermal stability of PUA10 was higher than PU' and the thermal agravic about 90% temperature was about 400 C. It was higher 30 C than PU'. The emulsion particle in the graft copolymerization film was stacked close, but the water and solvent was poorer than PUA1.