Preparation And Properties Of Biobased Polyester Nanocomposites

In the present work, two kinds of bio-based polyesters with different stuctures andproperties were synthesized with itaconic acid (IA), succinic acid (SU), sebacic acid (SA) and1,3-propanediol (PDO), i.e. PPSe in glassy state and PPSS in rubbery state at ambienttemperature. Aiming to enhance the inherent poor mechanical properties of the bio-basedpolyesters, two kinds of reinforcement were incorporated into the polyesters to preparepolyester nanocomposites. We mainly studied the mechanical properties and shape memoryproperties of the composites.Zinc diacrylate (ZDA) was introduced to improve the mechanical properties of PPSe andPPSS. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction resultsindicated that ZDA restrained the crystallization of PPSe and decreased its melting point,while it had no effects on the crystallization and melting behaviors of PPSS. Thevulcanization curves of polyester/ZDA blends demonstrated ZDA could promote thecrosslinking of the two polyesters and thus improved their crosslinking density effectively.Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), andtransmission electron microscopy (TEM) results showed poly-ZDA particles disperseduniformly in the two polyester matrices. Stress-strain tests and dynamic mechanical analysis(DMA) results declared ZDA could improve the tensile stress and storage modulus of the twopolyesters at rubbery state significantly. Meanwhile, PPSe/ZDA composites maintained theexcellent shape memory properties of pure PPSe, showing high shape fixity (SF) and shaperecovery (SR).Graphene oxide (GO) modified with thiol (i.e. GS) was grafted onto the polyester chainsto enhance the mechanical properties of PPSS. The grafting reaction was initiated by heat orUV light separately. Thermo gravimetric analysis, Raman analysis, and EDS results indicatedthiol group was successfully grafted onto the lamellar structure of GO. Atomic forcemicroscopy (AFM) and SEM results displayed GS could disperse well in water as single layer.Fourier transform infrared spectroscopy (FTIR) experiments demonstrated GS was graftedonto the polyester chains successfully. The real GS content in PPSS/GS composites wascalculated by TGA results. DSC experiments were performed to research the effects of GS content on the crystallization and melting behaviors of the polyester composites. SEM andTEM results showed GS dispersed uniformly in PPSS matrix for two kinds of systems.Stress-strain tests declared GS could improve the tensile stress of both kinds of thecomposites effectively. DMA results showed the storage modulus of thermal-initiatedPPSS/GS composites was much higher than that of photo-initiated composites.