04/05/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation defense by Christopher G. Souza on: “Coextrusion and Melt Spinning of Nylon 6,6 Fibers Flame Retarded with Blends of Polyphosphonate in Polyeste.r”

Candidate Name: Christopher G. Souza
Degree: Doctoral
Defense Date: Wednesday, April 10, 2024
Time: 2 to 3:30 p.m.
Location: This will be an in-person defense held in Southwick 240 and will also be streamed via MS Teams.

Commitee:

  • Advisor: Stephen P. Johnston, Ph.D, Professor, Plastics Engineering, University of Massachusetts Lowell
  • Akshay Kokil, Ph.D, Assistant Teaching Professor, Department of Plastics Engineering, University of Massachusetts Lowell
  • Jay Park, Ph.D, Assistant Professor, Department of Plastics Engineering, University of Massachusetts Lowell
  • Margaret Sobkowicz-Kline, Ph.D , Professor, Plastics Engineering, University of Massachusetts Lowell

Brief Abstract:
Nylons are commonly used in melt spinning for the production of apparel but have proven difficult to flame retard due to environmental and health concerns, in addition to adverse reactions that occur during melt processing. An organophosphorus flame retardant, polyphosphonate, has been incorporated into nylon 6,6 melt spun fibers using coextrusion and melt blending to circumvent these issues. First, the reactivity between nylon 6,6 and polyphosphonates has been examined via melt compounding, chemistry experiments with similar small molecules, and nuclear magnetic resonance spectroscopy. Subsequently, blends of polyphosphonate and polyester were examined to study how blend morphology was affected by blend ratios and processing conditions. A 40/60 blend ratio and optimized processing temperatures were shown to sufficiently inhibit the adverse reactions between nylon 6,6 and polyphosphonate during coextrusion and melt spinning, while maximizing the flame-retardant loading level owing to the evolution of the blend’s morphology. Third, a series of 2D axisymmetric simulations were carried out to investigate flow behavior in the bi-component melt spinning die as temperature, flow rate, and skin/core ratio were adjusted. The process window was then validated through extensive melt spinning trials and successful bi-component FR fibers were characterized.