Synthesis and adhesion property of waterborne polyurethanes with different ionic group contents

Bio-Based Waterborne Polyurethane Coatings with High Transparency, Antismudge and Anticorrosive Properties

Green and environment-friendly preparation are of the utmost relevance to the development of transparent antismudge coatings. To prepare a waterborne polyurethane (WPU) coating with antismudge property, it is challenging to balance the stability of dispersion and the antismudge property of coating. Herein, we prepare a transparent bio-based WPU coating grafted with a minor proportion of poly(dimethylsiloxane) (WPU-g-PDMS) using renewable castor oil, monocarbinol-terminated PDMS, hexamethylene diisocyanate trimer, and 2,2-bis(hydroxymethyl)propionic acid as raw materials. Effects of the dosage of monocarbinol-terminated PDMS, the curing temperature, and the curing time on the antismudge performance were studied. Results showed that rigorous stirring (3000 rpm) is necessary to obtain a stable WPU-g-PDMS dispersion with a storage time longer than 6 months. A high curing temperature (>160 °C) and a period of curing time (>1 h) are indispensable to obtain the excellent antismudge property because they would facilitate the grafted low-surface-tension PDMS chains to migrate from the interior to the coating surface. The facts that simulated contaminated liquids such as water, HCl solution, NaOH solution, artificial blood, and tissue fluid could slide off easily and cleanly, and marker ink lined on the coating surface could shrink, indicated that the WPU-g-PDMS coating has good antismudge properties, which could be self-compensated shortly after deterioration. Due to the high cross-linking degree caused by multifunctional polyol and isocyanate, the WPU-g-PDMS coating has high hardness and good anticorrosive performance. The antismudge functionalization and waterborne technology of bio-based polyurethane coatings proposed in this work could be a promising contribution to the green and sustainable development of functional coatings. This kind of WPU-g-PDMS coating is expected to protect and decorate electronic screens, vehicles, and buildings, especially endoscopes.

Structure–Properties Relationship in Waterborne Poly(Urethane-Urea)s Synthesized with Dimethylolpropionic Acid (DMPA) Internal Emulsifier Added before, during and after Prepolymer Formation

Dimethylolpropionic acid (DMPA) internal emulsifier has been added before, during and after prepolymer formation in the synthesis of waterborne poly(urethane-urea)s (PUDs) and their structure–properties relationships have been assessed. PUDs were characterized by pH, viscosity and particle size measurements, and the structure of the poly(urethane-urea) (PU) films was assessed by infra-red spectroscopy, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis, plate–plate rheology and dynamic mechanical thermal analysis. The adhesion properties of the PUDs were measured by cross-hatch adhesion and T-peel test. The lowest pH value and the highest mean particle size were found in the PUD made by adding DMPA after prepolymer formation, all PUDs showed relatively ample mono-modal particle size distributions. The highest viscosity and noticeable shear thinning were obtained in the PUD made by adding DMPA during prepolymer formation. Depending on the stage of addition of DMPA, the length of the prepolymer varied and the PU films showed different degree of micro-phase separation. Because the shortest prepolymer was formed in the PU made with DMPA added before prepolymer, this PU film showed the lowest storage moduli and early melting indicating higher degree of micro-phase separation. The highest storage modulus, later melting, higher temperature and lower modulus at the cross between the storage and loss moduli corresponded to the PU made by adding DMPA after prepolymer formation, because the longer prepolymer produced during synthesis. The lowest thermal stability corresponded to the PU made by adding DMPA during prepolymer formation and the structures of all PU films were dominated by the soft domains, the main structural differences derived from the hard domains. Whereas DMPA-isophorone diisocyanate (IPDI) urethane and urea hard domains were created in the PU film made by adding DMPA during prepolymer formation, the other PU films showed DMPA-IPDI, polyester-IPDI and two different DMPA-IPDI-polyester hard domains. Finally, the adhesion properties of the PUDs and PU coatings were excellent and they were not influenced by the structural differences caused by adding DMPA in different stages of the synthesis.

Spraying Preparation of Eco-Friendly Superhydrophobic Coatings with Ultralow Water Adhesion for Effective Anticorrosion and Antipollution

Sustainability, eco-efficiency, and green chemistry guide the development of new materials in various fields. Herein, we designed and fabricated bio-based superhydrophobic coatings by means of a facile spraying synthesized method. The as-prepared superhydrophobic coatings exhibited high water repellency with higher water contact angle being up to 156.9 ± 2.7° and a lower sliding angle of only 4.3 ± 0.6°. Also, the water adhesion on the superhydrophobic coatings was as low as 11 μN, which was far less than that (346 μN) of the normal polyurethane surfaces. The superhydrophobic properties still retained high stability under the conditions of soaking in acid solution (pH = 1) and alkaline solution (pH = 13). Meanwhile, the as-prepared bio-based superhydrophobic coatings were verified for effective corrosion and pollution protection ability. The electrochemical measurements showed excellent corrosion resistance with a higher corrosion voltage of -204.7 mV and lower corrosion current of 1.494 × 10^-5 A/cm². The corrosion protection efficiency reached a value of 95.2%, and meantime, the superhydrophobic coatings displayed higher antipollution performance without any stains when they were removed from the polluted liquids. On this basis, the underlying physical-chemical mechanisms clearly revealed that the surface micro-nanostructures could capture the continuous and stable air layer to segregate the corrosion and pollution media.

Carbon nanotube/polyurethane films with high transparency, low sheet resistance and strong adhesion for antistatic application

Carbon nanotube/poly(urethane) films for antistatic application with high transparency, low sheet resistance and strong adhesion were obtained by optimizing the ratio of SWCNT to WPU.