Study On Melt-spinnability, Fiber Structure And Properties Of Poly(ethylene Terephthalate-co-ethylene 2,5- Furandicarboxylate) Copolyesters

2,5-furandicarboxylic acid?FDCA?has been obtained from renewable biomass resources on a large scale.Its structure and performance are similar to that of terephthalic acid?PTA?,and its synthesized poly?ethylene 2,5-furandicarboxylic??PEF?is similar to poly?ethylene terephthalate??PET?in terms of thermal and mechanical properties.Therefore,PEF is expected to replace petroleum-based PET.We conducted an earlier study on the fiber preparation of PEF and found that its spinnability is unstable;furthermore,having in consideration that currently FDCA is still expensive,one logical approach is to progressively replace PET with its furanic PEF homologue,that is,copolymerizing them to prepare poly?ethylene terephthalate-co-ethylene 2,5-furandicarboxylate?copolyesters?PEFT?.In this paper,the basic properties of a series of PEFT copolyesters were first characterized.And then,based on the sequence structure and composition,heat properties,crystallization and rheological behavior,the melt-spinnability were explored,and the optimum spinning conditions were determined.Finally,with variations in EF content,changes in fiber tensile strength,modulus,elongation at break,and shrinkage in boiling water were also studied,combined with the factors of crystallinity and orientational structure.The specific conclusions are as follows:?1?With the increase of EF content,the degree of damage to the symmetry and regularity of the copolyester molecular chains gradually increases.The cold crystallization T_ccc moves in the direction of high temperature,the melting point T_m moves in the direction of low temperature,and the initial thermal degradation temperature T_d,_5%increases first and then decreases.Among them,when the EF content exceeds 10%,due to the order of copolyester molecular chain has been disrupted too large,resulting in almost no crystallization,the copolyester has no melting point.When the EF content exceeds 8%,the initial decomposition of the copolyester temperature starts to fall below the PET.?2?PEFTs were non-Newtonian pseudoplastic fluid,and the non-Newtonian index n of PEFT-4 and PEFT-6 resins with high intrinsic viscosity[?]is smaller than that of other copolyesters,so their sensibility of shear rate increased as well.In the range of the shear rate in the tunnel,PEFT-4and PEFT-6 resins have lower viscous flow activation energy E than other copolyesters,and their has low sensitivity to temperature.The structural viscosity index??of the PEFT-4 and PEFT-6resins is higher than the remaining copolyesters at 260,270 and 280°C,indicating that their still has a high entanglement ratio.?3?The increase of crystallinity and degree of orientation in the crystal zone increases the tensile strength and modulus of the PEFT fibers,and decreases the elongation at break and boiling water shrinkage.However,the degree of crystallinity and orientation in the crystal zone affect the performance of the PEFT fibers differently.Among them,for the tensile strength,the degree of orientation in the grain zone has a greater influence on the tensile strength than the crystallinity in the PEFT as-spun fibers.For the tensile modulus in the PEFT fibers,the degree of crystallinity has a greater effect on the tensile modulus than the intermolecular force exerted by the EF unit.For the boiling water shrinkage,the effect of crystallinity on the shrinkage of boiling water is highest in the drawn fibers.