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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 15 (2010) pp 430-434

Spectroscopic Analysis of Polyethylenes

Ernesto Davidson*,† Jacobo Reyes-Romero, Delfín Moronta, Gema González§, Othman Falcón**

†Escuela Básica, Facultad de Ingeniería, Universidad Central de Venezuela. Los Chaguaramos, Caracas 1041 A, Venezuela,; ‡Escuela de Física, Facultad de Ciencias, UCV, Caracas, Venezuela; §Escuela de Física, Facultad de Ciencias, UCV, Caracas, Venezuela, e IVIC, Laboratorio de Ciencia de los Materiales, Departamento de Ingeniería III, Altos de Pipe, Edo Miranda Venezuela; **Escuela de Ingeniería Mecánica, Facultad de Ingeniería, UCV. Los Chaguaramos, Caracas
Received March 24, 2010. Accepted June 17, 2010.

Published: 22 December 2010

Abstract. In this laboratory experiment shows the connection among the structure and properties of virgin and recycled high density polyethylenes (v-HDPE and r-HDPE) and medical grade polyethylene (UHMWPE-Gur1050),as a result of changes arising for effect from external factor (mainly during the manufacturing and reprocesses). These changes could induce the possible occurrence of free radicals. This research was carried out for students of undergraduate chemical and science of materials of Central University of Venezuela (UCV) and Jose Maria Vargas University (UJMV). We used the spectroscopic analysis of Fourier transform infrared (FTIR), near and visible ultraviolet(visible UV) and electron paramagnetic resonance (EPR). It provides undergraduate engineering students with a clear understanding of the structure of polymers, enabling them to establish correlation with their properties, which is very important for both their academic and professional life. The analysis of the nature of free radicals was determined both in a qualitative as well as in a quantitative through laboratory exercises, using each one of the above mentioned spectroscopy. Spectroscopic analysis for the polyethylenes showed allyl and carbonyl groups presence. In addition, r-HDPE oxidants groups, we observed more intensity in the pristine ones of v-HDPE and UHMWPE. We concluded that v-HDPE and UHMWPE manufacturing process, and r-HDPE re-processed, lead to free radical formation of carbonyl, in both samples v-HDPE and UHMWPE. In the other hand, the thermo-mechanical of r-HDPE, leads to highest free radicals formation, and promotes degradation process in this polyolefin in comparison to the pristine ones (v-HDPE and UHMWPE-Gur-1050).

Key Words: Laboratories and Demonstrations; organic chemistry; polymer chemistry; spectroscopic; fourier transformed infrared; ultraviolet; electronic paramagnetic resonance; free radicals

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