Abstract
Nowadays, waterborne polyurethanes (WPUs) prepared from renewable resources has attracted more and more attention. However, due to its structure, the prepared films easily swells in water and greatly affects the application range of WPUs. Therefore, solving the problem of water resistance is a way to improve the application range of WPUs. In this study, a series of WPU dispersions were prepared using castor oil as the bio-based polyol. Besides, the thiol-ene photo click reaction was carried out on the WPU films for silane modification. The effect of the silane modification on the chemical structures of the WPU dispersions and the properties of the WPU films was investigated and discussed. The results revealed that the WPU dispersions had a smaller particle size and potential, showing excellent stability. In addition, the modified WPU films showed highly water resistance which 72 h water absorption could be reduced to 1.94% and the contact angle was up to 99.34°. Moreover, the modified WPU films also exhibited excellent solvent resistance (in acid and salt solution) and thermal stability. This study can provide a new way to improve the water-resistance, hydrophobicity, and thermal stability of bio-based waterborne polyurethane for potential application in painting, adhesives and inks.
Highlights
Polyurethanes (PUs) are an important class of polymers and exhibit an exceptionally versatile range of properties and applications in coatings, adhesives, sealants, elastomers, and foams
The WPU Dispersions (WPUDs) were synthesized with dimethylol propionic acid (DMPA) and a variable ratio between the OH groups in castor oil, the NCO groups in IPDI, and the OH groups in the emulsifier (1:1.7:0.69; 1:2:0.99) with solid content with 10 wt% were obtained after removal of the Methyl ethyl ketone (MEK) by rotary evaporation [5]
The two WPUDs have a small particle size ranging from 180–200 nm and WPUDs prepared with emulsifier hydroxyl molar ratio of 0.69 is larger than those prepared with emulsifier hydroxyl molar ratio of 0.99
Summary
Polyurethanes (PUs) are an important class of polymers and exhibit an exceptionally versatile range of properties and applications in coatings, adhesives, sealants, elastomers, and foams. Zhang et al [16] obtained a series of castor oil-based waterborne polyurethanes as hair styling agent. It showed that these samples exhibited good hair-styling performance, and even better than commercial hair spray product. Zhang et al [17] reported development of a multifunctional castor-oil-based waterborne polyurethane with high strength using controlled amounts of dithiodiphenylamine. 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. Water can enter the polymer network to swell the films, limiting its practical application [19,20,21]
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