Page 44 - PR 2014 2016 10 Materials and Nanotechnology

320 Materials and Nanotechnology | Progress Report

Figure 52. Nanocarriers.

and further steps concern the assessment of is difficult by its insolubility due to very cross-
ex vivo and in vivo biodistribution of the de- linked structures. Besides, this tridimensional
veloped systems. structure shows a lot of problems for material
recovering and reprocessing. In spite of vari-
In addition to that, we are developing a tech- ous processes already developed and applied
nique for the capping of inorganic nanoparti- toward rubber recycling, the viability of these
cles of biomedical and clinical relevance with processes presents many challenges, either
crosslinked proteins, without the need of toxic technical or referring to material quality. The
reagents and solvents, to improve the bio- major effect of high energy photon, as gamma
availability, provide site specific delivery and rays in butyl and halogenated butyl rubbers is
possibly reduce allergenic reactions (Figure 52). the generation of free radicals, along chang-
es in mechanical properties. The addition of
Recovering/recycling of butyl and halogen atoms in the butyl rubber promotes
halobutyl rubbers compounds by ionizing a molecular rearrangement on the dehydro-
radiation halogenation of halobutyl rubber to form a

double bond in secondary and tertiary car-
Polymeric materials (plastics and rubbers) at- bon in bromobutyl and chlorobutyl rubbers,
tain a continuously and increasing proportion respectively, which facilitates the formation
of litter discarded in landfills; their impact in of cross-links when exposed to radiation high
environment are more and more concerning. energy. It was developed a controlled deg-
The implementation of new technologies to- radation process (de-vulcanization) in butyl
ward polymeric residues reduction, acceptable and halobutyl rubbers (chlorine and bromine),
under environmental viewpoint and at an in order to characterize their availability for
effective cost, proved to be a great problem, changing their properties. The rubber devul-
due to inhering complexities for polymers canized induced by high energy degradation
re-use. Ionizing radiation is capable to change was tested for reuse in the original formula-
structure and properties of polymeric materi- tion of the mixture of rubber and can replace
als; it is an expectation for problem solving of some parts of the pistine in the manufacture
polymeric residues management. Butyl and of final products. Butyl and halobutyl rubbers
halobutyl rubbers are used in a comprehen- compounds were subjected to gamma radia-
sive scale, in a great variety of applications tion, in air, at 5 kGy, 15 kGy, 25 kGy, 50 kGy,
such as tires spare-parts and various artifacts. 100 kGy, 150 kGy and 200 kGy, in a gamma
Rubbers are provided with a very low natural radiator, Co60. Mechanical essays of tension
decomposition, due to their chemical structure and elongation at break showed chain-scission
weather resistant and to enzymatic degrada- at doses up to 25 kGy; for doses higher than 50
tion and microorganisms. Rubber recovering kGy, it was observed an intense degradation.

Instituto de Pesquisas Energéticas e Nucleares