Aparecido Junior de Menezes

Polyethylene cellulose nanofibrils nanocomposites

This paper investigates the use of an aqueous dispersion of polyethylene copolymer with a relatively high content of acrylic acid as a compatibilizer and as an alternative medium to obtain polyethylene CNF nanocomposites. The CNF content was varied from 1 to 90wt% and the appearance, optical, thermal, mechanical and rheological properties, as well the morphology of the films were evaluated. The PE/CNF films are transparent up to 20wt% of NFC indicating a good dispersion of CNF, but a poor distribution, with PE-rich and CNF-rich regions observed by SEM. Improved mechanical properties were achieved, with a 100% and 15,900% increase in the Youngs modulus with 1wt% and 90wt% NFC, respectively. The rheological behavior indicated good melt processability. According to these results, aqueous polyolefin dispersions seem to be a promising, easy and relatively fast route for obtaining cellulose/polyolefins nanocomposites with low to high contents of cellulose nanofibrils.

Characterization of Cellulose Nanocrystals Grafted with Organic Acid Chloride of Different Sizes

In the work presented in this article surface chemical modifi cation was applied to ramie cellulose nanocrystals by grafting organic acid chlorides presenting different lengths of the aliphatic chain. The objective of this surface chemical treatment was to enhance the nonpolar nature of the grafted nanocrystals and improve their dispersibility in a nonpolar polymeric matrix. The occurrence of the chemical modifi cation was evaluated by Fourier transform infrared (FTIR) spectroscopy, the degree of crystallinity by X-ray diffraction, and the morphology by scanning electron microscopy with fi eld emission gun (FEG-SEM) and atomic force microscopy (AFM). The morphology and crystallinity provided by different experimental methods were carefully compared.

Correlation among volumetric conductivity, electrical threshold field and compensation plots by oxidation induction time on LDPE/CB composites

The thermodynamic compensation effect plot derived from Eyring rate process theory was applied to the thermal and UV ageing of LDPE/Carbon Black composites containing commercial carbon black (CB) and carbon black surface oxidized with nitric acid. Correlations were tested among compensation effect, electrical threshold field and volumetric electrical conductivity. Compensation plots from OIT measurements correlate with thermal and UV ageing effect on activation ΔS and ΔH values, giving a good linear correlation for all samples studied. The relative changes in dc conductivity and electrical threshold field are consistent with the OIT compensation plot, demonstrating that this analysis can be used to monitor LDPE/CB composite degradation under thermal or UV ageing. It can also be used to evaluate, quite accurately, the effect of oxidizing the surface of the CB on the electrical properties (dc conductivity and electrical threshold field) of the LDPE/CB composites.

Characterization of biosurfactant from yeast using residual soybean oil under acidic conditions and their use in metal removal processes

This study aimed at the production of biosurfactants from yeasts under acidic conditions using residual soybean oil as a carbon source, as well as the biosurfactant produced in the solubilization of metals in sewage sludge. The yeast Meyerozyma guilliermondii was considered the best producer in both pH 4.0 and 2.0; therefore, the product obtained by this yeast was characterized by Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (NMR) spectroscopy. Moreover, it was applied in metal removal assays in anaerobic sewage sludge. The spectra obtained in FT-IR suggested that M. guilliermondiis biosurfactant had a similar structure to glycolipids from the sophorolipid class, and it was confirmed by 1H NMR spectroscopy. In the bioleaching assays, the application of biosurfactant (2%) produced by M. guilliermondii with pH adjusted to 2.0 was able to solubilize 15.9% of cadmium from the sewage sludge.

Caracterização morfológica de nanocristais de celulose por microscopia de força atômica

O isolamento de nanocristais de celulose (CNCs) de fibras vegetais e uma alternativa promissora para sua aplicacao como reforco em matrizes polimericas. A caracterizacao dos CNCs e fundamental para a confiabilidade da tecnica, alem de determinar as aplicacoes possiveis a partir de cada tipo de fibra. A partir da tecnica de microscopia de forca atomica, um estudo da morfologia e distribuicao dos CNCs de semente de manga, vagem de algaroba, pseudocaule da bananeira e fibra do mesocarpo de dende foi realizado neste trabalho. Os CNCs foram obtidos via reacao hidrolitica com acido sulfurico em concentracoes que variaram de acordo com a fonte da fibra. Os resultados obtidos revelaram dimensoes variando de 300 a 500 nm em comprimento e 4 a 16 nm em diâmetro. A apresentacao morfologica em forma de agulha demonstrou que o isolamento das fibras de celulose em CNCs foi efetiva. A razao de aspecto associada a formacao cilindrica em agulha dos CNCs isolados evidenciou o alto potencial das fontes de dende e de vagem de algaroba para o reforco de bionanocompositos.