Study On Waterborne Polyurethane (WPU) Based On Modified Tung Oil Via Interesterification

Waterborne polyurethane (WPU) is a binary polyurethane system which replaces solvents with water as a dispersion medium. Compared with solvent-based polyurethane, the WPU is non-organic solvents, nonflammable, easy to operate, easy to clean adhesive residue and no-harm to the environment. With the growing awareness of environmental protection and improvement of environmental regulations, solvent-based polyurethane will gradually be replaced by WPU.With the growing shortage of oil resources, it is of great significance if plant oils which have the advantages of renewable, biodegradable and non-toxic can be incorporated into polyurethane to combine the excellent properties from both plant oil and polyurethane, because this is consistent with resource conservation and environmental protection requirements. The plant oil-based polyurethane will be a new class of environment-friendly polymer materials with the unique chain and phase structures. Tung oil is the only plant oil with three conjugated double bonds and has many unique properties. The Tung oil-based polyurethane is expected to have excellent overall performance.In this research, Tung oil is modified by trimethylolpropane to make it hydroxylated through transesterification. The hydroxylated Tung oil with two hydroxyl groups is then introduced into WPU, leading to a new type of WPU with excellent properties. The structure of Tung oil-based polyol was identified as expected by FTIR and MS. The results of hydroxyl value and iodine value of Tung oil-based polyol show that the products retain the conjugated double bonds of Tung oil. In order to study the influence of hard segment contents, modified Tung oil contents, modified method of Tung oil and charging order, the dynamic mechanical properties, infrared spectroscopy, particle size and Zeta potential of WPU were obtained. The results show that:the properties of emulsion and water absorption of the WPU with different hard segment contents are mainly determined by the DMPA content. The storage modulus of polyurethane film increases and the microphase separation becomes complete with the increase of hard segment contents; the relationship between modified Tung oil content and the properties of the WPU is very complex. It is decided by the location and content of modified Tung oil that is incorporated into the WPU. Overall, the miscibility between soft and hard segments increases with the increase of modified Tung oil content. At the same time, the storage modulus of polyurethane film increases; compared with the WPU that is modified by the ammonolysis product of Tung oil, the WPU that is modified by the alcoholysate of Tung oil has smaller average size and higher Zeta potential, so the system is more stable. Its film has greater water absorption, storage modulus and loss modulus and better strength and impact resistance. The phase separation is imperfect; compared with the WPU that is prepared by the one-step, the WPU that is prepared by the two-step has larger average size and lower Zeta potential. Its film has greater water absorption, storage modulus and loss modulus and better strength and impact resistance. The phase separation is complete. In addition, the H-bonding interaction of it is very obvious.