Enhanced Mechanical Properties and Functional Performances of Cationic Waterborne Polyurethanes Enabled by Different Natural Phenolic Acids

Abstract

Tailoring the performance of waterborne polyurethanes through composition control and structural optimization to meet the highly diversified modern demands is still one of the primary challenges faced by the polyurethane industry. Herein, various natural phenolic acids as neutralizers, for the first time, were applied for the preparation of castor oil-based cationic waterborne polyurethanes (CWPUs). The effects of these neutralizers on the microstructure (phase separation and hydrogen bond) and performance (mechanical properties, antibacterial activities, etc.) of the CWPUs were systematically investigated and compared with those of other commonly used neutralizers. The results indicate that apart from serving as neutralizers, phenolic acids also acted as antiplasticizing agents for the CWPU films by increasing the rigidity of the hard segment and hydrogen bond number. Also, the hydrophobic, rigid, conjugated structure of phenolic acids endowed the resulting CWPU films with excellent water resistance and UV protection. The introduction of phenolic acids also endowed the resulting polyurethane films with good antibacterial performance against both Gram-positive and Gram-negative bacteria. This study provides a novel and facile approach to tailor the performance of environmentally friendly cationic waterborne polyurethanes through natural phenolic acid neutralizers, along with eliminating long-standing issues of WPUs, such as irritating odor and air pollution.

Preparation and properties of green UV‐curable itaconic acid cross‐linked modified waterborne polyurethane coating

“…40 Compared with other WPU films modified by natural phenolic acid (14.1%) or click crosslinking (20%), the water absorption can reach 8.4%. 23,34…”

“…As the crosslinking density gradually increases, the segmental properties and chain mobility are reduced. 52 In short, compared with WPU modified by TEMPO-oxidized cellulose nanofibers, 8 Diselenide bonds and dual H-bonding, 32 Phenolic acid, 34 Soybean oil, 35 and Castor oil, 37 IHA crosslinking agent can improve the crosslinking density and stiffness of WPU coatings, so that the modified system has higher tensile strength and good elongation at break. The remaining test data of mechanical properties can refer to Table S2.…”

“…55 The increment of T g can be attributed to the increase of crosslinking density and intermolecular hydrogen bond in the polymer, which is much higher than that of WPU prepared from soybean oil, natural phenolic acid, and other biological raw materials. 2,34 The comparison results are shown in Figure S4. An increase in concentration of IHA in the WPU formulations directly leads to the increase in the crosslinking density in the WPU formulation, thus resulting in this thermal behavior.…”

“…In general, the UV-curable WPU coatings are based on hydroxyl (methyl) acrylate, 32 diethylene glycol diacrylate, 14 pentaerythritol triacrylate, 33 and other active monomers with multiple double bonds to polymerize free radicals under UV irradiation, 34,35 these coatings are still toxic and costly. Current studies are mainly focused on using a variety of biological materials for the synthesis of eco-friendly WPU, 36 such as vegetable oils completely or partly to replace polyol, 34 sustainability of biological material as small molecule chain extension agent. 37 However, these WPU coatings usually exhibit low intensity or prone to degradation on account of the introduction of a large number of biological materials and low degree of cross-linking.…”

Enhanced Water Resistance Performance of Castor Oil—Based Waterborne Polyurethane Modified by Methoxysilane Coupling Agents via Thiol-Ene Photo Click Reaction

“…In addition, broad glass-transition temperature of the samples endowed the films with a versatile shapememory effect. Zhang et al [18] prepared a serious of castor oil-based cationic waterborne polyurethanes and various natural phenolic acids as neutralizers. The results indicate that introduction of phenolic acids could endow polyurethane films with excellent water resistance and UV protection as well as good antibacterial performance.…”