Center for Composite Materials - University of Delaware

Research Summary

Electrospinning: Nano-Fiber Production and Analysis for Electroactive Composites

Authors: David Wilson, Cedric Jacob (PhD Candidate), Erik Thostenson (PhD)

INTRODUCTION

• Primary Goal: To create nano-structure customized electroactive actuators and sensors for application in smart composites
• Polyvinylidene fluoride (PVDF) is a ferroelectric polymer – it has both piezo and pyro electric properties
• Electrospinning allows customization of the nanostructure, as well as inclusion of composite filler materials and phase control

ELECTROSPINNING

During electrospinning a polymer solution is subjected to high strength electric field causing the fluid particles to flow from injector needle to collector plate.
The process:
1. PVDF dissolved in solution
2. Solution pumped to electrostatically charged injection needle
3. Electric charge draws fluid towards collector plate
4. Instability causes spinning – fiber elongation and reduction in diameter

ELECTROSPINNING SETUP

PROCESS VARIABLES

• Correlate system parameters with output properties
• This allows for the selection of a microstructure and being able to “dial-in” the appropriate system parameters
• Generate parametric surface plots from resulting data

NANO-FIBER PRODUCTION

• Electrospinning results in the production of a thin film of randomly oriented fibers
• Co-electrospinning (multiple jets and polymer solutions) results in two intermingled phases.
• Second phase is marked with fluorescein dye
• Degree of phase overlap can be tuned to produce different micro-scale geometries

MORPHOLOGY CONTROL

• Scanning electron microscopy (SEM) is used to image the nano-fibers and study their morphology
• Different variables bring about different fiber types
• Environmental conditions (e.g. Humidity)
• Process conditions (e.g. Solvent Strength)
• Environment is maintained under 3% relative humidity and STP.
• The lower percent solution fibers (>13%) re-dissolve after spinning due to larger amounts of DMF in solution. Surface tension effects can be seen on images.
• Higher concentrations (> 18%) yield the best quality fibers, with little to no re-dissolving due to full evaporation of DMF

FUTURE WORK

Carbon Nanotube Integration:
• Carbon nanotubes can be embedded into the electrospun fibers which allows for maximum loading without reaching electrical conductivity

Improvement in collector plate solvent evaporation should improve fiber morphology at low concentrations

CONCLUSIONS

• Electrospinning allows for the control of nano and micro structure in polymer composites
• PVDF is used as an electroactive polymer with applications in smart composites
• Current research studies the effect of using CNT reinforcement to alter electrical properties, the use of a heat bulb to protect samples from re-dissolving after spinning, and the building of a drum to replace the collector plates

ACKNOWLEDGEMENTS

Nanotechnology in Undergraduate Education (NUE)
• This research is supported by the National Science Foundation under Grant No. (1138182), Dr. Mary Poats, Program Director.
Science and Engineering Scholars Program
• University of Delaware Office of Undergraduate Research and Experiential Learning

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