Kevin M. Kit and Sudhakar
Jagannathan
Department of Material Science and Engineering
University of Tennessee, Knoxville
The Fiber Society Annual Fall Technical Meeting, October, 2002, Natick, MA
Abstract
A polymer blend, a combination of two or more polymers developed for superior properties to suit specific applications, is produced by mixing the individual polymers in melt phase or by casting from a common solvent. The desired properties of the blend are obtained only when the two parent polymers are completely miscible. However most of the polymers commercially used for making polymer blends are not compatible with each other in solid and liquid state.
Electrospinning is a process by which fibers with diameters as small as 10 nanometers are produced when a polymer solution is accelerated from a capillary towards a grounded target by an electric field. When two different polymers are spun from a common solvent using this method, a nano-size fiber of the blend results whose final morphology is determined by the processing conditions and the properties of individual polymers. Hence this method is suitable to produce a homogenous phase for almost any polymer pair that is melt immiscible but soluble in a common solvent.
This process has been used to spin nylon 6, nylon 66 fibers and their blends from a solution of formic acid and poly(ethyleneterepthalate) from triflouroacetic acid. The solution concentration of the polymer and the composition of the individual polymers are varied and its effect on the structure, morphology and properties are studied using scanning electron microscopy, x-ray diffraction and dynamic mechanical analysis. We find that the polarity and viscosity are correlated with the formation of bead defects in the fibers of polystyrene and polycarbonate produce beads in the fibers. The nylon, having higher polarity, yields fibers of smaller diameters without any beads. The solution concentration has been found to strongly affect the fiber size, with 5% solution of nylon 66 produced fibers as small as 15nm, which increases to size greater than 100nm as the concentration is increased to 20%. On the other hand, the variation in target distance and applied voltage does not have much effect on the dimensions of the fibers. The mass throughput of the fiber, however, is found to be a function of spinning voltage.
The orientation of
the as spun and wound nylon and polyethylene fibers and its effects on the
morphology and mechanical properties of the spun blends will also be presented.