Effect of molecular weight of liquid polysulfide on water and organic solvent resistances of waterborne polyurethane/polysulfide copolymer

In the present work, polyester waterborne polysulfide-based polyurethane (WSPU) films were successfully synthesized from liquid polysulfide(PSF), poly(butylene adipate) (PBA) and isophorone diisocyanate (IPDI). The effect of PSF molecular weight on the chemical structures, mechanical and thermal properties of the resultant films were investigated by Fourier transform infrared (FTIR) spectroscopy, tensile test and Thermogravimetric analyzer (TGA). As the molecular weight of PSF increased, microphase separation was enhanced to some extent, resulting into an enhanced mechanical behavior and thermal stability. Meanwhile, with the increase in molecular weight of PSF, water resistance investigated by means of water uptake and mechanical behavior analysis was enhanced in general. Chemical resistance to organic solvents was also improved. When the molecular weight of PSF was about 5000, the water uptake and solvent swelling decreased to 2.83% and 95.1% respectively. The excellent performance may suggest a broader application in the surface material areas for WSPU films.