NCJ Number
206376
Journal
Journal of Forensic Sciences Volume: 49 Issue: 3 Dated: May 2004 Pages: 505-510
Date Published
May 2004
Length
6 pages
Annotation
This study subjected nine types of polymers in various forms to thermogravimetric analysis (TGA) in order to determine the potential of TGA as a tool for determining different species of polymers.
Abstract
The qualitative identification of polymers by typical methods, such as Fourier transform infrared spectroscopy (FTIR) or mass spectrometry (MS) can be especially difficult due to the inclusion of dirt, glass, char, and other foreign particles in samples taken from scenes of high destruction, such as fires or explosions. TGA has long been an accepted analysis method for polymers in industry. Its advantages in a forensic setting are as follows: the required sample size is relatively small, and very little sample preparation is required. The current study tested TGA's performance in analyzing the following polymers in various forms: chlorinated polyvinyl chloride (CPVC), polyvinyl chloride (PVC), low-density polyethylene (LDPE), nylon, polypropylene, polystyrene, tygon, nitrile, and natural latex. This paper describes sample preparation, calibration of the instrumentation, and TGA parameters. The analyses produced excellent discriminating results even when samples were contaminated with silicates, organics, moisture, and char. The analysis techniques used were designed for a typical forensic analysis, such as analysis of blast fragments and arson debris. The techniques used yielded satisfactory results even when sample sizes were less than five milligrams. The primary disadvantage of TGA is its destruction of a portion of the collected evidence. Samples are reduced to a carbon char, with the eluted gases being either dissipated into the atmosphere or passed on to another instrument. 6 figures, 1 table, and 8 references