03/23/2023
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a master's thesis defense by Brandon Italiano on “Preparation and Properties of Silver Nanowire Filled Conductive Thermoplastic Composites for Use in Melt Spun Fibers.”


Candidate Name: Brandon Italiano
Degree: Master’s
Defense Date: Monday, April 3, 2023
Time: 2 to 3:30 p.m.
Location: This will be an in-person defense in ETIC 445

Committee:

  • Advisor Stephen P. Johnston, Professor, Department of Plastics Engineering, UMass Lowell
  • Akshay Kokil, Assistant Professor, Department of Plastics Engineering, UMass Lowell
  • Jay Hoon Park, Professor, Assistant Professor, Department of Plastic Engineering, UMass Lowell

Brief Abstract:

Electrically conductive thermoplastic composites and fibers have been an area of significant interest for a variety of sectors. Both military applications such as signature management and environmental hazard protection, and commercial applications such as data transmission, sensors, and static discharge could be significantly impacted by advances in electrically conductive thermoplastic fibers. Conductive thermoplastic composites have significant advantages to intrinsically conductive polymers in terms of cost and processability, and compared to solid metal alternatives in terms of corrosion resistance, weight, and flexibility. The high aspect ratios and ultra-high conductivity of silver nanowires make them an attractive prospect for reaching high conductivity at low loading levels. However, there is a dearth of research regarding melt processed silver nanowire composites compared to other fillers.

In this thesis, the viability of melt compounding and melt spinning silver nanowires in a thermoplastic matrix was explored. Suspended silver nanowires were dispersed into a PA66 and PET matrix via a novel dispersion process followed by melt mixing. The dispersion process involved the deposition of layers of nanowires on thin thermoplastic films with subsequent solvent evaporation. These films were then stacked on top of each other, heated, and pressed together, resulting in significant dispersion prior to melt mixing. The effect of sonication of the suspended silver nanowires as well as residence time and screw speed during compounding were determined. Ideal loading levels were then identified by finding percolation thresholds. Finally, composites with loading levels above the percolation threshold were melt spun into fiber and characterized.

Sonication led to an increase in nanowire dispersion along with a small decrease in length. Melt processing resulted in significant reduction in nanowire length. Increased screw speeds led to larger reductions in average length along with increases in filler dispersion. Increased residence time had similar effects as increases in screw speed. Percolation thresholds of film samples were observed at 5% (wt.) for PA66 and 6% for PET. Conductivity at percolation was 8*10-3 S/cm for PA66 composites and 1*10-2 S/cm for PET composites. Melt spun fibers were found to have an electrical conductivity of <1.4*10-8 S/cm indicating a decline in conductivity associated with melt spinning of at least five orders of magnitude. Individual fibers were found to have resistances of >2.6*1014 Ω/meter length.

All interested students and faculty members are invited to attend the defense.