Synthesis And Properties Of Polyesters Based On 2,5-furandicarboxylic Acid

With development of world economy, the excessive consumption of resources increased shortage of petrochemical, developing the non-petrolum based material to substitute petrochemical products is an effective way to solve the problem of excessive consumption of resources. Biomass resources is widespread and renewable, the future of material development will be focused on bio-based products. A series of FDCA-based polyesters were prepared by using transesteration melt polycondensation and low temperature solution polymerization respectively from biomass monomer 2,5-furandicarboxylic acid (FDCA) and the second monomers, such as ethylene glycol (EG), 1,3-propylene glycol (PDO) and 1,4-butylene glycol (BDO). The molecule structures were characterized by fourier transform infrared (FTIR), nuclear magnetic resonance (1H-NMR), and intrinsic viscosity were measured by ubbelohde viscometer. It was studied the influence of polycondensation time and polycondensation temperature on transesterification polycondensation, and the influence of polycondensation time, polymerization temperature and amount of solvent on the solution polycondensation.The properties of these polyesters were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis(TGA) and X-ray diffraction (XRD). DSC results showed that glass transition temperature of FDCA-based polyesters were close to that of correspond TPA-based polyester, but melting point temperature of FDCA-based polyester were 50~70℃lower than that of TPA-based one. FDCA-based polyesters were thermally stable up to 330℃with only a few decomposition, PEF got the best stability, followed by PTF, the last is PBF. Their themal decomposition tempertures are very similar to corresponded TPA-based polyester. Crystallization rates of FDCA-based polyesters were improved with increase of the number of methylene, the sequence of crystallization rate: PBF>PTF>PEF.The isothemral cryrstallization results showed that its crystallization behavior has good relationship with the Avrami equation. In the range of 116~132℃, crystallization rate constant k decreases as the temperature increasing,and half-cryrstallization time t1/2 increases. The Avrmai index n values are lie in between 2.09~2.53, which are independent on the changes of temperature. During the melting process after isothermal crystallization, double melting peaks were appeared. The main peak corresponds to crystal that formed during isothermal crystallization process, the other one is the instability crystalline and recrystallization during the melting process. With the crystallization temperature increasing, recrystal melting peak moved to higher temperature obviously, but the primary crystal melting peak didn't move besides with narrower and sharper shape. According to the theory of Hoffman-weeks, thermodynamic equilibrium melting point Tm0 of PBF was calculated to be 173℃. Temperature is most sensitive factor to the crystallization behavior. With degree of supercooling△T increasing, t1/2 was shorten and crystallization rate constant k was increased. High undercooling will accelerate the formation of crystallization.