The Effect of Aging on the Mechanical and Thermal Properties of Thermoset Polyvinyl Toluene

Open Access
Author:
Berman, Arielle Elise
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Zoubeida Ounaies, Thesis Supervisor
  • Jacqueline Antonia O'Connor, Honors Advisor
Keywords:
  • Polyvinyl Toluene
  • Thermoset
  • Design of Experiments (DOE)
  • Crosslink
Abstract:
The illegal importation of special shielded nuclear materials (SSNM) is a serious national security concern, as these materials could be weaponized if they fall into the wrong hands. Solid scintillating organic detectors, which are usually made of scintillating hydrocarbon plastics, may be used to prevent the smuggling of these materials into the United States. In order to fabricate the polymer-glass composite detectors, lithium GS20 glass shards are suspended in thermoset polyvinyl toluene (PVT), which has a molecular structure of [CH2CH(C6H4CH3)]n. The composite scintillates, or emits light, when subjected to gamma rays and neutrons resulting from the active interrogation of the SSNM. Through the process of Pulse Shape Discrimination (PSD), one can detect the difference between fast neutrons, thermal neutrons, and gammas. However, time, temperature, and applied loads are all factors that could negatively affect the detector’s mechanical stability and performance. As a result, this thesis seeks to quantify and compare the effect of thermal degradation, also known as aging, on PVT. The research approach includes processing and synthesizing polyvinyl toluene, curing and polishing the samples, performing mechanical as well as thermal testing, and finally statistically analyzing the results. The modulus of elasticity, percent elongation, stress and strain at fracture, and glass transition temperature (Tg) are the properties of interest. A Design of Experiments (DOE) methodology is used to systematically test the polymer specimens, which are made based on ASTM D638 Standard dogbone-shaped mold using a predetermined curing technique. In order to establish limits for the temperature and time of operation needed to maintain the mechanical integrity of the detectors, statistical calculations are performed on the collected data. Such information will assist in improving future PVT-based detectors, therefore contributing to the progress towards making this country safer by eliminating illegally trafficked special nuclear material.