04/09/2021
By Sokny Long

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a doctoral dissertation defense by Orli Weizman on “Nanomaterials for Enhanced Performance in Electrical (CNT Yarns) and Barrier (Reduced Loss of UV stabilizers) Applications.”

Ph.D. Candidate: Orli Weizman
Defense Date: Friday, April 23, 2021
Time: 8 – 10 a.m. EST
Location: This will be a virtual defense via Zoom. Those interested in attending should contact Orli_Weizman@student.uml.edu and committee advisor Joey_Mead@uml.edu at least 24 hours prior to the defense to request access to the meeting.

Committee Chairs (Advisors):

  • Joey Mead, University Professor, Department of Plastics Engineering, University of Massachusetts Lowell
  • Hanna Dodiuk, Professor and Department Head, Department of Polymer Materials Engineering, Shenkar College - Engineering. Design. Art., Ramat Gan, Israel
  • Amos Ophir, Associate Professor, The Department of Polymer Materials Engineering, Shenkar College - Engineering. Design. Art., Ramat Gan, Israel
  • Samuel Kenig, Professor, The Department of Polymer Materials Engineering, Shenkar College - Engineering. Design. Art., Ramat Gan, Israel

Committee Members:

  • Julie Chen, Vice Chancellor for Research and Innovation, University of Massachusetts Lowell
  • Meg Sobkowicz-Kline, Associate Professor, Department of Plastics Engineering, University of Massachusetts Lowell

Brief Abstract:
Incorporating nanosized additives in polymer matrices presents unique opportunities to design a wide range of multifunctional polymer nanocomposites for various applications. In this work, two systems of nanocomposites were studied. The first deals with carbon nanotube yarns (CNTYs) for enhanced electrical conductivity, and the second with the nanosized particles (clays and silica) as means to reduce the migration and loss of organic additives (Ultraviolet stabilizer) in polyolefin films in a photo-oxidation and humid environment. The relationship between the compositions and the observed properties in these nanomaterial systems had been studied in this dissertation.

In part 1, an innovative approach to enhance the electrical conductivity of commercially available CNTYs has been investigated where tensile cyclic loading under ambient conditions improved the electrical conductivity of two types of CNTYs. It was found that that the electrical resistance of untreated-as-produced CNTYs was significantly reduced (by 80%) following cyclic loading, reaching the resistance level of high-cost super acid-treated CNTYs characterized by the environmentally unfriendly process. The enhancement of electrical conductivity was attributed to the gradual alignment and compaction of the CNT bundles, as demonstrated by electron microscopy. Simultaneously with the alignment, the stiffness of the CNTYs was increased without compromising their strength. The resultant electrical conductivity of the CNTYs, in addition to their low density, and high strength, could be used for conductive-reinforcing high-performance composites and advanced electronics. The cyclic (above 50 cycles) tensile stresses for enhanced electrical and mechanical properties were identified to be innovative and have been considered for a patent application and was published.

In part 2, the effect of nanosized additives (nanoclays and nanosilica) on delaying the migration of UV light stabilizers for linear low-density polyethylene (LLDPE) film was investigated long-term sustainability of films in a photo-oxidation/humid environments (In greenhouses and water reservoirs). The first section of part 2 dealt with developing a quantitative method to characterize the concentration of the protective additives (UV absorbers and UV stabilizers). The combination of Accelerated Solvent Extraction (ASE) coupled with UV Spectrophotometry was evidenced as a facile method to quantify the concentration of various protective additives. This section of the work was the basis of a written paper. The method allowed us to model the loss rate kinetics of the additives from the film before and after weathering exposure under accelerated conditions. The developed method was adapted to quantify the concentration of hindered amine light stabilized (HALS) additive in the neat and the nanocomposite LLDPE based films used in the second section of this part. In this section, the nanocomposite film containing nanosilica was effective in reducing HALS loss from the film under accelerated photo-oxidation and humid exposure, while nanocomposite film containing nanoclays was found to be ineffective in hindering the loss of the protective UV additives. The films' UV resistance was studied by following the appearance of the carbonyl groups on the film surface (characteristic of photodegradation) and the degradation of the mechanical properties. A good correlation between the UV stability and the HALS loss rate from the different films as a function of exposure time was established. A suggested mechanism was proposed. This section of the study was written in a third paper, that demonstrated that the proposed system has a commercial potential to extend agricultural films' service life.

All interested students and faculty members are invited to attend remotely.