Aligned Deposition of Polyurethane Fiber Arrays In Single and Multiple Layers

In this study, polyurethane (PU)fibers were manufactured using our recently reported Spinneret based Tunable Engineering Parameter (STEP) technique. Mixture of N-Methyl-2-pyrrolidone(NMP) and Tetrahydrofuran(THF) was chosen as solvent for PU fiber deposition. Initially the volume ratio of NMP/THF was set at 6:4 and beaded fibers were obtained at 24% wt of PU. With further increase in PU concentration, beads were observed to gradually stretch along fiber axis and finally smooth fibers (diameter ranges from 400nm to 800nm) were obtained at 39% wt. Solvent effect on PU fiber morphology was investigated by varying the NMP/THF. Eight different ratios (volume ratio of NMP/THF= 1/9,2/8,3/7,4/6,5/5,6/4,7/3,8/2 respectively) with PU dissolved at 30% wt., were investigated to determine PU spinnability. PU fibers exhibited ultimate elongation up to 453.5%, which makes it possible to make braids of few PU fibers: PU fiber braids were made with two and three fibers respectively. The braiding angle was controlled by the number of twists added to the braids. Bio-scaffolds of polyurethane fibers were fabricated through continuous deposition of PU fiber arrays and the fiber spacing can be well controlled through STEP technique. Stress-strain analysis demonstrate typical sigmoidal shape characteristic of elastomeric materials. Current ongoing efforts are devoted towards embedding multi wall carbon nanotubes in polyurethane fibers and understanding the reinforcement mechanisms and polymer molecular arrangements under high elongation.