Synthesis and Properties of Repeatable Bio-Based Thermosetting Polyurethane Resins
Thermosetting polyurethane resin has some problems such as non-repeatable processing,which greatly reduces the service life of material and causes waste of resources.In this paper,using hydroxylmethylated lignin(Lig-OH)prepared by hydrothermal method as bio-based soft segment,isophorone diisocyanate(IPDI)as hard segment,trimethylol propane(TMP)as cross-linked chain extender,4,4'-diaminodiphenyl disulfide(4-SO)as secondary chain extender,and 4-methylumbellione(4-MU)as bio-based end sealing agent,the biodegradable thermosetting polyurethane resin(LPU)was successfully prepared.Its structure was characterized by Fourier infrared spectroscopy,its self-healing properties were studied by optical microscope and 3D profiler,and its mechanical properties and repeatability were studied by tensile and repeated machining test.The results show that LPU-5(TMP 18 mmol)has the best mechanical properties,with the tensile strength up to 18.92 MPa,elongation at break up to 709.82％.After total incision repair,the tensile strength and elongation at break can reach 16.90 MPa,630.32％respectively,and the repair efficiency is up to 89％after full-cut repair.After the spline is completely cut and repaired,the resin can be crushed and reprocessed into a complete polyurethane film,which has excellent repeatability.And it can realize the dual repair function under heating and ultraviolet light,in which LPU-2 can complete the scratch repair at 75 ℃ for 10 min.
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