Research On Formation And Adjustment Of Fibrous Membrane In Melt Electrospinning

As a branch of electrospinning, melt electrospinning has become one of the importantmeans to make ultra-fine fibers. Because there’s no need to use solvent, it has certainadvantages compared to solution electrospinning. Theoretically, any kind of polymer whosemelt temperature is higher than its decomposition temperature can be used in meltelectrospinning. The whole process and the products are nontoxic, which give it broadapplication potential in the fields such as filtration, protection, biology, medicine, etc.At present, research on melt electrospinning is not quite deep. On the basis of previousresearch work, this paper focused on two important physical fields during spinningprocess—electric field and temperature field of the spinning space. The self-made meltelectrospinning device was modified to realize the effective adjustment of the two fields.Ultra-fine fibers whose diameter ranged from dozens of nanometers to several micrometerswith self-bonds between each other were prepared through experiments. And the impactmechanism of the two fields on the spinning process was analyzed and discussed.For the research on electric field, different ways of loading high voltage were applied.Different jet motion and deposition features were recorded, compared and analyzed when thepositive pole of the high voltage was connected to the spinneret and receiver respectively. Themechanism behind was discussed according to the distribution and dynamic change of theelectric field. Another way to change the electric field is to use two high voltage powersupplies, one of which outputs positive voltage and the other negative voltage. The positiveone was connected to the spinneret and the negative one to the receiver. The potentialdifference was adjusted to the same with the voltage loaded when only one positive voltagewas connected to the spinneret. Then the two kinds of electric fields were compared in orderto analyze the regulating mechanism of electric field on fiber formation process. Theexperiment results indicate that under the same potential difference, using two suppliers helpsto form and keep more compact electric field, which leads to thinner fibers and more compactfibrous membrane.For the study on space temperature field, three kinds of spinning raw materials wereadopted--polylactic acid (PLA), polycaprolactone (PCL) and their mixture (PLA/PCL) madeby melting and stirring. The ambient temperature was set at different values during spinningprocesses in order to observe and analyze the influence of it on the melt electrospinningprocess and fibers’ properties. The experimental results indicate that the change of theambient temperature field could adjust the fibers’ diameter and morphology effectively. Aproperly-set ambient temperature would not only help to thin the fibers but also to createself-bonds between fibers to some extent, which is good for the dimensional stability andmechanical property of the membrane. Meanwhile, fibers diameters are varied due to thedynamic change of the temperature field. Different polymers show different sensibility andadaptation to the temperature field. As for the mixture, the impact of the temperature field onits spinning process is between that of the two pure polymers, and would be mainly decidedby the polymer which takes more proportion in the mixture. Experiments using PLA/PCL mixture with different mixing ratios show that more PCL the mixture contains, greater impactit would get from the ambient temperature field, more self-bonds would be got betweenfibers.