Preparation And Characterization Of Thermosets Derived From Tri(2-Cardanylethyl) Citrate

The utilization of renewable resources as raw materials in bio-based thermosetting resins is one of the hottest topics in the field of thermosetting resin industry. The investigation of biobased materials is crucial to a sustainable society. However, it is still challenging to obtain biobased thermosetting resins with both high material properties and high bio-based contents. Therefore, it is of great scientific and practical significance to develop bio-based high performance thermosetting resins without sacrificing bio-based contents.In this dissertation, a novel bio-based unsaturated resin, tri(2-cardanylethyl) citrate, was prepared the transesterification reaction between renewable triethyl citrate(TEC) and 2-cardanyl ethanol(Cardolite 2020). Then a three-armed, soybean oil-liked epoxy resin(ET3) was synthesized through a conventional epoxidization procedure. The unsaturated and epoxy oligomers were fully characterized using Fourier transform infrared spectroscopy(FT-IR), proton nuclear magnetic resonance spectroscopy(1H-NMR), and gel permeation chromatography(GPC). Thermosets based on ET3 were formulated using anhydrides as the curatives. Thermosets based on a benchmark bio-based epoxy resin, epoxidized soybean oil(ESBO), were also included as the references. The thermal and mechanical properties of the thermosets were characterized by means of thermal gravimetric analysis(TGA), dynamic mechanical thermal analysis(DMA) and tensile test. The effects of the curative structures and anhydride to epoxy ratios on the properties of the thermosets were also studied. The results showed that thermosets based on ET3 possessed both high material properties and high biobased contents.In the second part, two of six-armed cardanol-based unsaturated oligomers(T6) were synthesized by reaction of tri(2-cardanylethyl) citrate and diisocyanates(hexamethylene diisocyanate, isophorone diisocyanate). After epoxidation, two six-armed epoxy resins, ET6 H and ET6 I, were obtained. The structures of the resins were confirmed by 1HNMR, FTIR and GPC. Thermosets based ET6 were prepared using anhydrides as the curatives. The thermal and mechanical properties of the thermosets were characterized by TGA, DMA and tensile testing. The effects of the structures of the epoxy oligomers on the properties of the thermosets were also studied. The results revealed that the thermal and mechanical properties of ET6-based thermosets were higher than those of ET3-based ones.In the third part, highly functional bio-based methacrylate oligomers were synthesized via the reaction between methacrylic acid and ET3; then, biobased thermosets were produced from free-radical curing of these methacrylates using styrene(St) as a reactive diluent. Thermosets of methacrylated epoxidized soybean oil(MESO) were also prepared as the references. The thermal and mechanical properties of the thermosets were characterized by TGA, DMA and tensile testing. The effects of methacrylate functionality and styrene contents on the properties of the thermosets were also studied. MET3-based thermosets showed better material properties in comparison with MESO-based ones.