Preparation,Structure And Properties Of Ultra High Molecular Weight Poly(Ethylene Oxide)fiber

Owing to the simple molecular structure,good water solubility,complexing capability and biocompatibility,polyethylene oxide(PEO)has attracted much attention and has a wide range of applications.At the same time,PEO fibers have great potential for the application of biomedical materials.However,PEO fibers,prepared via conventional electrospinning,melt-spinning,solid-state extrusion and solution spinning,show poor strength due to limited molecular weight of raw materials(<10⁶).This strongly hinders their application.Gel-spinning is an effective method to prepare high performance fibers using flexible chain polymers.Given the unique polymerization method,PEO with viscosity average molecular weight of>10⁷,i.e,ultra-high molecular weight poly(ethylene oxide)(UHMWPEO),can be produced.Most importantly,the theoretical tenacity of the UHMWPEO fibers produced by the gel-spinning method can reach about 20 GPa while the maximum tenacity of that fibers reported in literatures is only 0.66±0.04GPa.In this study,factors affecting the degradation of UHMWPEO were investigated aiming to solve the serious problem of degradation.After evaluating the effect of a series of solvents,N,N-dimethyl-formamide(DMF)was determined as the most suitable spinning solvent to prepare the UHMWPEO fibers so far.Then,the gel-spinning process of UHMWPEO/DMF was studied,and the UHMWPEO fiber was prepared through solution extrusion,solvent extraction and hot drawing processes.Finally,the effects of spinning dope concentration and nozzle draft ratio on the mechanical properties of the fibers were also examined.The specific research conclusions are as follows:(1)The degradation rate of UHMWPEO was reduced by removing oxygen from the solutions and choosing polar solvents such as H₂O,DMSO and DMF.Rheological tests showed that UHMWPEO formed gel structure in DMF and toluene(TL).According to the above results,DMF was selected as the most suitable solvent for the gel-spinning of UHMWPEO.(2)UHMWPEO with viscosity average molecular weight of 5×10⁶ was used to prepare precursor fibers,and the crystallization,orientation,molecular weight and tensile properties of precursor fibers were also studied.The results showed that the crystallinity and orientation degree of the precursor fibers increased with increasing spinning dope concentration and nozzle draft ratio.Compared to the viscosity average molecular weight of the raw material,the retention rate of the molecular weight of the precursor fibers exceeds 60%.Besides,the tenacity of the precursor fibers increased with increasing nozzle draft ratio while their elongation at break decreased.(3)The influence of the hot drawing process on the structure and properties of the precursor fibers was investigated.The results showed the tenacity of the precursor fibers was significantly improved by increasing the draw ratio during the hot drawing process.In particular,the tenacity of the drawn fibers reached up to 7.46±0.12c N/dtex(0.90±0.01 GPa)when the maximum draw ratio was up to 16,which is about 36%higher than the highest value reported in literatures.The increase in tensile strength was mainly due to increased crystallinity and orientation degree(which increase linearly with draw ratio)during drawing.