Synthesis And Application Of Unsaturated Polyesters Derived From Itaconic Acid

Due to the increasing concern about the depletion of fossil reserves, greenhouse gas emission, and other environmental problems, there is an increasing interest in the utilization of bio-based feedstock in both industry and academia. At present, majority of polymers are derived from non-renewable resources and account for approximately 7% of oil and gas annual consumption in the world. The conversion of biomass to useful polymers or composites has considerable economical and environmental value. With the rapid development of bio-based materials, more and more natural resources, such as vegetable oil, starch, soy protein and cellulose have been used as the renewable feedstock to produce polymeric materials. Up to now, a large quantity of polymers derived from renewable resource or natural polymers, such as starch, cellulose, polylactic acid(PLA) and poly(hydroxyl alkanoates)(PHA), have been commercialized. However, compared with the achieved progress on bio-based thermoplastics, the research on bio-based thermosetting resins, especially the thermosetting resins with high glass transition temperature(higher than 100°C) and comparable mechanical properties with petroleum-based counterparts are very limited. Considering the concept of bio-based materials and their development tendency, the thermosetting resins derived from bio-mass, especially the high-performance ones, should also have a bright future.In this work, the following research work has been done.1. In the first part, three bio-based unsaturated polyesters were synthesized from itaconic acid and different diols(ethylene glycol(EG), 1,4-butanediol(BDO) and 1,6-hexandiol(HDO)). Their chemical structures were confirmed by FT-IR, 1H-NMR and acid value as well as hydroxyl value. Waterborne UV curable coatings based on these polyesters were manufactured and their mechanical properties, thermal stability and coating properties including pencil hardness, flexibility, adhesion, water resistance and solvent resistance were investigated. Results showed that the UV-cured polyester coatings exhibited high hardness(3H), good water resistance and solvent resistance(>250).2. In the second part, in order to improve the adhesion of the coatings which was prepared in the first part, a series of bio-based unsaturated polyesters was synthesized by melt polycondensation of itaconic acid with 1,4-butanediol and glycerol. Their chemical structures were confirmed by FT-IR, 1H-NMR, acid and hydroxyl values. Waterborne UV curable dispersion coatings based on these polyesters and acrylated epoxidized soybean oil(AESO) were formulated. The average particle size and their stability before curing as well as the coating properties after curing, including adhesion, flexibility, pencil hardness and solvent resistance, were investigated. Results demonstrated that the glycerol segment in the polyesters together with AESO led to the excellent coating properties in terms of highest grade of adhesion(5B), 0T flexibility, pencil hardness of 5H and excellent solvent resistance(no appearance change after 250 double rubs with ethanol and acetone).3. In the third part, a series of bio-based polyesters which were prepared in previous work were applied to copolymerize with acrylated epoxidized soybean oil(AESO). Thermal and mechanical properties of the resulting thermosets were investigated by differential scanning calorimetry(DSC), tensile testing and dynamic mechanical analysis(DMA). Their coating properties on tinplate and glass plate were also studied. Results showed that the tensile strength, modulus, glass transition temperatures and bio-based content of the AESO-based thermosetting resins were significantly improved after the introduction of the synthesized polyesters. In addition, the modified AESO systems could be well coated on the surface of tinplate and glass plate and good coating properties such as hardness, flexibility, adhesion, solvent resistance and water absorption were demonstrated.