Poly (Ethylene Terephthalate) Nanofibers Spun By Gas/Electrospinning

The new concept about fiber science and engineering has been developed with the development of nanofiber science. The research of nanometer science has focused on polymer nanofibers. The hygienical function to human by functional fabrics, such as fiber resistant to ultraviolet light, far infrared fiber and the fiber resistant to bacterium and deodorization, has already been approved, so there is great significance of the exploitation of the new materials and the new method to produce new materials. Using a series poly(ethylene terephthalate) with different molecular weight made by direct esterification, we obtained the PET nanofibers by gas/electrospinning. The distribution of fiber diameter was under 100nm mainly. At the same time, the process factors, which affect the distribution of the diameter and the morphology of the nanofibers were investigated in this article.The syntheses technology of PET is well known, the direct esterification technologically is simple. It is easy to obtain PET with different molecular weights by controlling the temperature, dosage of catalyzer, and other reaction condition. It was understood that the rheological properties of the PET solution depend on the characters of the solution such as temperature, molecular weight, concentration of polymer and shear rate. As well known, PET solution is the non-Newtonian fluid, its flow processes typical characters of non-Newtonian flow.For PET nanofibers spun by gas/electrospinning in this work, the optimal technical parameters were as follows: the voltage was 32kV, the distance between the spinneret and the collector was 23 cm, the volume rate of air flow was 1 0L/min, theconcentration of the spinning solution was 18%. The effects of the each processing parameter on the morphology and the diameter distribution of the nanofibers were investigated experimentally. The driven force of the spinning jet is increasing with the increase of the voltage. At the same time the gas flow is another added driven force. However, if the gas flow is too great, the jet is difficult to be produced in the stabilized form. The distance between the spinneret and the collector is another important processing parameter. When the distance is small, the volatilization of the solvent is insufficient, the jet splits to drops aggregated on the collector. As the result, there are many beads on the nanofibers. The concentration of polymer in spinning fluid is another remarkable factor to affect the process. If the concentration is too low, the solvent could not volatile timely and the solution drops also aggregate on the collector. When the concentration is too high, the fluidity is bad, what is disadvantage to spinning.Different collect methods may give different morphology and diameter distribution for nanofibers. Comparing the nanofibers spun by dry and wet spinning, we can know that the diameter distribution of the fiber spun by wet spinning is narrow than that spun by dry spinning. However, the morphology of the fiber spun by dry spinning is better than that by wet spinning. At the same time, the effect of different coagulant on morphology of PET nanofibers was investigated. Different coagulants have different polarity, so its interaction with the solvent is different. As the result, the diffusion rate of solvent in spinning fluid to the coagulant is different; the solidified rate of the fiber from the coagulant is different. It was understood that these effects would give the different morphology and diameter distribution of the nanofibers. It was known from the experimental results that the choice of mixture of water and ethanol as the coagulant is correct, the nanofibers collected in such a coagulant are the best. At last, the reasons to form the beads in nanofibers were analyzed.