11/09/2026
By Thomas Dugan

The Francis College of Engineering’s Department of Plastics Engineering invites you to attend a doctoral dissertation proposal defense by Hrushikesh Pujari, titled "Investigating Polymer-Additive Interactions: Implications for Degradation, Stabilization, and Process Monitoring."

Details

  • Date: Wednesday, Nov. 18, 2026
  • Time: 2 – 3:30 p.m.
  • Location: EITC 445

Committee members

  • Margaret Sobkowicz Kline, Ph.D., advisor, professor, Plastics Engineering, UMass Lowell
  • Wei Yan, Ph.D., associate professor, Civil and Environmental Engineering, UMass Lowell
  • Wan-Ting “Grace” Chen, Ph.D., associate professor, Plastics Engineering, UMass Lowell
  • Akshay Kokil, Ph.D., associate teaching professor, Plastics Engineering, UMass Lowell

Abstract

Polymer degradation and additive functionality play important roles in determining the stability, performance, and service life of polymeric materials. Exposure to ultraviolet radiation, oxygen, heat, and mechanical stress can cause transformations that alter polymer properties. Although these processes have been extensively studied, the mechanisms governing polymer degradation, the ways additives modify those processes, and the methods available for monitoring polymer-additive systems during processing remain incompletely understood.

This research examines the relationship among polymer degradation, additive functionality, and material response through three connected studies. The first investigates the photo-oxidative degradation of low-density polyethylene and linear low-density polyethylene under accelerated ultraviolet-A and ultraviolet-B exposure. Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, rheometry, tensile testing, and abrasion analysis are used to correlate chemical oxidation, structural evolution, viscoelastic changes, mechanical deterioration, and susceptibility to fragmentation.

The second study examines how organic stabilizers influence the photo-oxidative degradation of polyethylene terephthalate. Antioxidant formulations containing hindered phenol and phosphite additives are evaluated across different additive types, concentrations, and ultraviolet-exposure conditions. The work also examines the effectiveness of benzotriazole ultraviolet stabilizers, including UV-234, in mitigating ultraviolet-induced degradation in polyethylene terephthalate formulations. Comparisons with antioxidant-containing systems are used to evaluate how different classes of stabilizing additives influence degradation patterns and material performance.

The third study explores the use of in-line Raman spectroscopy for real-time characterization of titanium-dioxide-containing polymer systems during twin-screw extrusion. Raman spectroscopy is evaluated as a tool for monitoring additive concentration and composition during melt processing. Complementary characterization methods are used to validate the spectroscopic measurements and examine relationships among processing conditions, additive distribution, and mechanical properties.

By integrating studies of photo-oxidative degradation in polyethylene, additive-mediated stabilization in polyethylene terephthalate, and in-line characterization of inorganic additives during extrusion, this research develops a broader understanding of polymer degradation and additive functionality. The anticipated contributions include improved understanding of chemical and structural evolution, additive performance, and material properties, as well as the potential use of real-time spectroscopic techniques to monitor polymer-additive systems during processing.