Self-Cross-Linkable Anionic Waterborne Polyurethane–Silanol Dispersions from Cottonseed-Oil-Based Phosphorylated Polyol as Ionic Soft Segment

Phosphorylated polyols (phospols) derived from cottonseed oil (CSO) were employed to synthesize novel, DMPA- (dimethylol propanoic acid-) free, catalyst-free, waterborne polyurethane dispersions (PUDs). Three different phospols bearing both hydroxyl and ionizable phosphoryl groups were synthesized through the ring-opening hydrolysis of epoxidized cottonseed oil (ECSO) in the presence of ortho-phosphoric acid. The phospols were characterized by 1H NMR spectroscopy, FTIR spectroscopy, and gel permeation chromatography. Three phospols (phospol-P5, -P10, and -P15) having hydroxyl numbers of 130, 160, and 180 mg of KOH/g, respectively, were used as internal emulsifiers in waterborne PUDs with isophorone diisocyanate and 3-aminopropyltriethoxysilane (APTES). All three PU dispersions showed excellent storage stabilities (>6 months), and the average particle sizes of the PUDs ranged from 30 to 68 nm. The cured films were characterized by FTIR (ATR) and solid-state 29Si NMR analyses. The hydrophobicities of the films were measured by the contact angle technique, and their anticorrosive properties were studied by the polarization technique. The films of the phospol-P5-based dispersion exhibited the highest tensile strength, thermal stability, Tg value, and contact angle and the best anticorrosive properties. All of the experimental results revealed that both the hydroxyl contents of the phospols and the extents of siloxane cross-linking played important roles in determining the thermomechanical properties, hydrophobicities, and anticorrosive properties of the corresponding PUD films.