Page 16 - PR 2014 2016 03 Applications of Ionizing Radiations

58 Application of Ionizing Radiations | Progress Report

tics. The main types of light stabilizers are: after irradiation. In conclusion, the radiation is
UV absorbers, quenchers and free radicals acting in the clay incorporated in the polymer
scavengers. In addition to the conventional and changing their properties.
organic additives, some inorganic additives
were obtained recently with the development Effect of ionizing radiation in polyurethane
of nanotechnology. This study evaluates the catheters coatings with silver nanoparticles
different additive systems (HALS, NPCC, nZnO
and nTiO ), applied 0.25 % (in weight) in LLDPE. The present work aimed to study the use of
2
The samples were mixed by high rotation ho- ionizing radiation for coating of silver nanopar-
mogenizer and extrusion. Later, the samples ticles on central polyurethane catheters (FIG.
were molded by injection and aged in QUV-B 24), providing reduction of infections associ-
simulating 6 months of exposure to weather. ated with contamination of catheters intro-
Tests of FTIR and tensile strength comparing duced into the bloodstream (FIG. 24). Fourier
to the non-aged samples were carried out in transform infrared spectroscopy (FTIR) en-
order to evaluate the performance of several abled the identification of functional groups
additive systems concerning the degradation in the structure of macromolecules, such as
behavior of linear low density polyethylene. polyether urethane. A study of the thermal
behavior of central venous catheters before
Radiation effects in the crystal polystyrene and after irradiation was performed in order
composite with clays to characterize the polymeric material of these

catheters. The DSC and TG were employed to
The changes in the mechanical and thermal observe the changes material properties before
properties of the materials have been investi- and after degradation. The DSC curve at the
gated by several authors after being irradiated. constant heating and cooling rate allowed
In this sense, the polymer nanocomposites the characterization of thermal properties,
consist of a class of materials formed with such as Tm and Tg of copolymers, as well as
inorganic nanometer dimensions, such as clay highlighting the main thermal events. Silver
and other minerals, dispersed in a polymeric nanoparticles have physical, chemical and
matrix. Indeed, there is a great technological biological properties only when compared to
interest in the study of polymeric nanocom- metal on a macroscopic scale, and they have
posites due to their excellent properties and been used in the medical field because of its
ability to control the characteristics of those remarkable antimicrobial activity. Titanium
systems to reach application requirements. In dioxide nanoparticles obtained by the sol
this work, polystyrene (PS) crystal composite gel method were used as the coating cath-
with 3 % of organically modified clay – Choc- eters for subsequent impregnation of silver
olate – were irradiated with radiation doses of nanoparticles with ionizing radiation at 25
300, 450 and 600 kGy in an electron accelera- kGy. A Raman spectrometry was used to iden-
tor. The results demonstrated that irradiation tify the polymorph of titanium oxide, rutile.
PS with clay presented a reduction in tensile In trials with (ICP OES), amounts of titanium
strength compared with pure PS. Furthermore, and silver coated catheters in titanium oxide
the Izod impact strength also had a reduction and silver were evaluated. The comparative
in samples of PS with clay compared to pure assessment conducted between the catheters
PS and TGA analysis indicate a tendency to before and after irradiation by FTIR, Raman
decrease the thermal stability of the material and DSC enabled the use of ionizing radiation

Instituto de Pesquisas Energéticas e Nucleares