Processes of molecular modification of polymers irradiated with ion beam.

Author(s)

Adriana de Oliveira Delgado

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2012-01-31

Examining board members

Marcia de Almeida Rizzutto; Marcia Carvalho de Abreu Fantini; Raphael Liguori Neto; Ademar Benévolo Lugão; Elidiane Cipriano Rangel

• Advisor: Marcia de Almeida Rizzutto

Abstract

Nowadays the demand for materials with improved properties for application in different elds of science and technology is constant. Ion beam irradiation is a usual and important tool of modication of materials and polymer irradiation, in particular, has given new perspectives of use for these modied materials. Hence, the aim of this work is the identication of the processes of modication of polymers irradiated with high energy ion beams and how they occur. In this investigation, samples of polytetrauorethylene (PTFE) and poly-ether etherketone (PEEK) were irradiated at the Unilac accelerator at GSI Helmholtzzentrum for Schwerionenforschung GmbH, at Darmstadt, Germany, with C, Xe, Au and U beams with energy between 3.6 and 11.4 MeV/u. The samples were irradiated at room and cryogenic (20-40 K) temperature. The sample analyses were performed through: Residual Gas Analysis (RGA), UV-Vis Absorption Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and X Ray Diraction (XRD). Under irradiation, the main processes of modication of PTFE were the chain scissioning and the formation of CF3 terminal and side group. Besides that, cross-linking and new unsaturated structures were also observed, evidenced by the formation of terminal and internal double bonds. CF3 and CF were the main degassed fragments that were observed. During irradiation of PEEK, a great amount of hydrogen gas was liberated as a consequence of the scission in the aromatics rings. Some rearrangement reactions occurred and gave rise to formation of the following groups: alkyne, esther, uorenon and alcohol. Moreover, the process of carbonization in the sample caused an increase in the polymer conductivity. When irradiated under cryo-temperature some recombination processes became more dicult and most of the volatile fragments remained frozen in the polymers. Some degradation models proposed to explain damage effects after thermal and electron beam exposure were sucessfully extended to the obtained results in the case of irradiation with swift heavy ions. (AU)