Nanocompositos de poli(3-hidroxibutirato-co-3-hidroxivalerato) e nanotubos de carbono / Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) carbon nanotubes nanocomposites

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

11/06/2010

RESUMO

This work has evaluated the effect of addition of multi walled carbon nanotubes (NTC) in the thermal and mechanical properties, morphology and hydrophobicity of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), the PHBV. The addition of carbon nanotubes could result in an improvement of PHBV properties, a natural polyester that due to its biodegradability and biocompatibility has an important application potential. Thus, nanocomposites of PHBV/NTC were produced by solution mixing, and then solvent casting. In the production of PHBV/NTC, we have evaluated the use of ultrasonic bath, ultrasonic processor and the functionalization of NTC by oxidation reactions, in the NTC dispersion in the PHBV matrix. First, we have performed the NTC characterization and functionalization by two methods: oxidation with nitric acid (HNO3) and oxidation with hydrogen peroxide (H2O2), at different reaction times. After oxidation, NTC (abbreviated as NTCOOH) were characterized for the presence of functional groups on their surface and the damage of their structure. The NTCOOH obtained from oxidation with HNO3 showed a higher thermal stability compared to those obtained in the H2O2 oxidation. The amorphous carbon production varied with the oxidation time to HNO3 and remained constant for H2O2. There was no significant difference in the quantification of hydroxyl, carbonyl and carboxyl groups on the surface of NTCOOH. The oxidation with HNO3 3 mol L for 12 hours was more suitable for the production of nanocomposites PHBV/NTCOOH. Subsequently, nanocompósitos of PHBV/NTC and PHBV/NTCOOH were produced using ultrasonic bath with 0.05 % (m/m) of NTC and NTCOOH, respectively. The DSC analysis showed that the NTC and NTCOOH act as nucleating agents and that the PHBV/NTC and PHBV/NTCOOH have the same thermal behavior. The SEM micrographs showed a good interfacial adhesion between the NTC and NTCOOH with PHBV matrix, and the formation of smaller agglomerates in the case of PHBV/NTCOOH indicated that oxidation of NTC improved their dispersion in the PHBV matrix. Finally, nanocomposites PHBV/NTC with 0.05, 0.50, 1.00, 1.50 and 2.00 % (m/m) of NTC and PHBV/NTCOOH with 2.00 % (w/w) were produced using ultrasonic processor for the NTC dispersion. It was found that the nucleating effect of NTC was proportional to increase of its concentration in the PHBV/NTC and the small increase observed in the thermal stability (~7°C) did not depended on the concentration of NTC. The use of ultrasonic processor greatly improved the dispersion of NTC in the nanocomposites and the hydrophobicity of the PHBV/NTC increases with increasing concentration of NTC. The nanocomposite of PHBV/NTC 1.50 % (w/w) showed the best results in tensile test, with 48 % increase in elastic modulus of, 49 % in maximum tensile strength and smaller decrease on elongation (37 %) compared to the pure PHBV. These improvements were not observed for PHBV/NTC 2.00 % (m/m) but were observed for PHBV/NTCOOH 2.00 % (m/m), indicating that oxidation of NTC allowed to obtain better mechanical properties for higher concentrations of NTC. A very important result in this work was the low adherence to blood clots (low thrombogenicity) verified for the PHBV/NTC 2.00 % (w/w), which extends the application of these nanocomposites in the medical field.

ASSUNTO(S)

nanocompósitos nanotubos de carbono biomateriais biopolimero nanocomposites carbon nanotubes biomaterials biopolymer

ACESSO AO ARTIGO

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