With the growing concern on the shortage of fossil resources and the environmental problems associated with their use, vegetable oils as renewable resources are important alternatives to fossil resources. Here, we used castor oil to synthesize 1-thioglycerol modified castor oil polyol with ultra-high hydroxyl value up to 463 mg KOH g −1 via a solvent-free thiol-olefin click reaction. The cross-linked polyurethanes were prepared from this polyol in a solvent-free and catalyst-free manner, and exhibited high tensile strength of ∼83 MPa and T g of ∼124 °C, much higher than other reported vegetable oil-based polyurethanes. Besides, the obtained polyurethanes exhibited excellent coating and optical properties , much better than the polyurethane from the unmodified castor oil. This work provides a green and high-efficient method of synthesizing vegetable oil-based polyol with ultra-high hydroxyl value to construct high-performance polyurethanes, which will expand the application of vegetable oil-based polymers.
A series of soybean oil-based polyols were synthesized via the reaction between epoxidized soybean oil and 1,3-propanediol, trimethylolpropane and xylitol, respectively. The aqueous polyurethanes were synthesized by prepared soybean oil-based polyols. The effect of hydroxyl value of soybean oil-based polyols on the mechanical, thermal, hydrophobic properties of the aqueous polyurethane films were also investigated. The results showed that the OH value of polyol increased, the T g of aqueous polyurethane films increased from 30.04 to 88.28 °C and the water contact angle of materials improved from 80.80° to 98.20°. Besides, water absorption reduced from 40.25% to 2.40%. Also, all samples were placed in the 1 wt% sodium hydroxide solution at 45 °C to test the degradation behaviors. After 24 h, the results demonstrated that aqueous polyurethane synthesized by the highest hydroxyl value(251.00mgKOH/g)polyol had the lowest degradation rate(7.10%). Finally, the mechanical properties and morphology of the aqueous polyurethane film after degradation were investigated, which proved that the hydroxyl value affected the mechanical properties and morphology of the aqueous polyurethane film after degradation.
Polyols are one of the dominant reactants in polyurethane (PU) synthesis. However, polyols from Sapium sebiferum oil prepared by epoxidation–hydroxylation have an inferiority of secondary alcohol groups and large non-functional branches. Their lower reactivity, which in turn limits the properties of the generated PU. In this study, the optimal reaction conditions for the synthesis of polyols with primary alcohol groups by lipase hydrolysis have been investigated by single factorial experiments and response surface methodology. The optimized conditions for lipase hydrolysis were identified as a molar ratio of 2.2 : 1, a reaction time of 11.2 h, and a temperature of 47.2 °C. The highest hydroxyl value of the obtained polyol with primary alcohol groups reached 211 mg KOH per g. Furthermore, a novel PU was successfully synthesized from the synthetic polyol and isophorone diisocyanate by an in situ polymerization method. The generated PU showed a glass transition temperature of 60.6 °C, an initial decomposition temperature of 307.2 °C, a tensile strength of 12.5 MPa, and a Young's modulus of 22.3 MPa. These good thermal and mechanical properties of the PU prepared from the modified polyol by lipase hydrolysis can be attributed to its greater number of chemical interactions and cross-linked networks.
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