From Castor Oil‐Based Multifunctional Polyols to Waterborne Polyurethanes: Synthesis and Properties

A novel castor oil‐based multifunctional polyol (CM) is fabricated through mild thiol‐ene photo induced reactions using castor oil (CO) and 1‐thioglycerol (MPD) as building blocks. The effect of the reaction time, molar ratio of thiol to carbon–carbon double bond, and the loadings of photo‐initiator are optimized. The resulting CM is combined with CO and employed as cross‐linkers to prepare castor oil‐based water‐borne polyurethane emulsion with desirable mechanical properties and water resistance. Owing to the incorporation of CM cross‐linker with high hydroxyl value of 371 mg KOH/g (which is 2.27 times higher than that of the CO), the prepared castor oil‐based waterborne polyurethane (CMWPU) possesses compacted 3D network structure with high cross‐linking degree, leading to improved glass transition temperature (45 °C), tensile strength (10.8 MPa), water contact angle (87.4°), and decreased water absorption rate (16.12%) with 20% CM additions. Overall, this work illustrates the feasibility of introducing bio renewable CM combined with CO to develop castor oil‐based WPU employing a sustainable development strategy.