Preparation And Chain Extension Of Poly(et Hylene 2,5-furandicarboxylate)

There is an increasing worldwide concern about the research of bio-based materials from renewable biomass resources in recent years. Bio-based polyester had achieved a big process due to its advantages at ecology protection. A kind of polyester with furan ring could be prepared form 2,5-furandicarboxylic acid(FDCA) and dihydric alcohol, which has a similar property with polyester synthsised from terephthalic acid(PTA). Melt polycondensation(direct esterification, interesterification) as a kind of efficiency and economic method had been widely used in the synthesis of polyester. However, since the poor thermostability of furan ring, the synthesized FDCA based polyester via melt polycondensaion possesses deep colour and low molecular weight. So the preparation of high molecular weight FDCA based polyester has a significance meaning to expand its application field.In this paper, poly(ethylene 2,5-furandicarboxylate)(PEF) and poly(propylene 2,5-furandicarboxylate)(PTF) based on FDCA, ethylene glycol(EG) and propylene glycol(PDO) were synthesized via direct esterification. In order to obtain the appropriate condition for synthesis FDCA based polyester, the mole ratio of monomers and polycondension time were discussed. A high molecular weight of PEF and PTF were prepared by chain extension reaction based on the synthesized PEF and PTF. The influence of temperature and time of chain extendsion on the [η] were inverstigated. A serious of techniques were used to studied the structure and properties of FDCA based polyester.The research on the PEF showed that the intrinsic viscosity [η] and polycondension rate of PEF all reached to the maximum value as the EG/FDCA ratio equal to 1.8. High EG/FDCA ratio is benefit for esterification and polycondensation reaction. However, the excess EG leaded to some vice reactions and reduced the polycondension reaction rate and [η] DSC results show that the Tm and crystallization capacity of PEF decreased with the increasing EG/FDCA ratio and polycondensaion time. PEF showed lower crystallinity Xc when cooling from melts with high cooling rate.The research on the PTF showed that the [η] and polycondension rate of PTF all reached to the maximum value as the PDO/FDCA ratio equal to 1.4. Excess PDO reduced the degree of polycondension of PTF. PDO showed low reactivity compared with EG when react with FDCA due to the side methyl in PDO molecule. The side methyl and mpurities in PDO also decreased the thermostability of PTF. DSC and WAXD analysises showed that the crystallization capacity of PTF is poor due to the oxidization degradation and the side methyl in PDO molecule.The research on the extension of PEF and PTF showed that: The appropriate condition for chain extension of FDCA based polyester were under melt state and nitrogen atmosphere. The appropriate chain extension time of PEF and PTF was 30 min and 60 min respectively. The appropriate chain extension temperature was 230 °C and 200 °C respectively. The appropriate NCO/OH ratio for extension of PEF and PTF were 3 and 2 respectively. Tg, Tm, ΔHm and Xc of extended PEF were reduced due to the introduction of TDI. However, the crystallization capacity of PTF was improved after chain extension. The thermostability of PEF was improved after chain extended, but the chain extension had no influence on its thermostability of PTF.