Resumo em Inglês:

Abstract Cellulose nanocrystals (CNC) and nanofibrils (CNF) were obtained by acid hydrolyzis and mechanical treatment, respectively, of cellulosic fibers from paper. Additionally, surface modification was performed for CNC by neutralization (NaOH) and oxidation (TEMPO). The thermal stability, surface properties and rheological behavior of these nanomaterials were compared. A clear difference in CNC surface was found upon neutralization and oxidation treatments, leading to distinct thermal behaviors. Optical and rheological properties were found to be predominantly by the particles size, being strongly affected by inertial effects.

Resumo em Inglês:

Abstract Glass fibre (GF), nanoclay (NC) and hybrid composites compatibilised with maleic anhydride polypropylene (MAPP) were prepared by extrusion and injection moulding. The fourier transform infra-red spectra revealed the characteristic absorption peaks of MAPP in the compatibilised GF and NC composites. A decrement in the peak intensity of X-ray diffraction patterns of NC composite was obtained as the MAPP content increased indicating a partial exfoliation of NC. The thermogravimetric analysis showed that the incorporation of MAPP into hybrid composites reduced the thermal stability of the material. The dynamic mechanical analysis showed an increase in the storage modulus in the hybrid composites with lower content of MAPP due to the enhancement in the interfacial adhesion between the GF, NC and PP matrix.

Resumo em Inglês:

Abstract Fuel Cells based in polymers are an alternative for the conventional energetic matrices. However, materials currently available still present disadvantages to overcome. Membranes of polycarbonate (PC)/sulfonated polycarbonate (PCs) blend/sepiolite nanocomposites have previously been studied by the authors, resulting in good mechanical properties and promising properties of vapor transmission and ionic migration resistance. However, their production in large scale is still a challenge. The aim of this work was the development further the formulation and processing of the previously studied material. Films of PC/PCs blends (50/50 wt%) with different content of sepiolite clay, with and without chemical modification, have been prepared in an extruder and evaluated by FTIR, XRD, DSC, TGA, DMA, tension strength and water vapor transmission (WVT). Even after two processing steps, the blend-based nanocomposites keep good thermal and mechanical properties. However, changes in WVT were observed with respect to data obtained in previous studies.

Resumo em Inglês:

Abstract This study dealt with the fabrication and analysis of poly(lactic acid) (PLA) mediated chitosan nanocomposite. Such a novel nanobiocomposite may get future applications in drug delivery, and nanofinising of textile and polymer surfaces. Herein, this nanocomposite has been considered as an antibacterial finishing agent for a hydrophobic textile fabric like polyester. The prepared nanocomposite was characterized for zeta size and morphology, and subsequently applied on a woven polyester fabric though a coross linker. The treated polyester fabric was analyzed for textile functional characteristics as well asantibacterial activity. The spectral and optical properties demonstrated that the nanocomposite developed exhibited spherical morphologies with a mean nano particle size of ca. 88 nm. The treated fabric projected satisfactory antibacterial and fair fabric attributes. Hence, the nanofinished polyester fabric is a potential biocompatible candidate as medical and antibacterial textiles in addition to be used in antibacterial water filtration and materials packing.

Resumo em Inglês:

Abstract The objective of this work was to compare the barrier and mechanical properties and shrinkability of coextruded films chlorine-free, with high barrier chlorine multilayer films traditionally used to preserve fresh beef. Four 9-layer barrier-shrink films containing PET, ethylene ionomers, polyamide PA66/6 modified with amorphous PA, 32 or 44 mol% EVOH and PE were produced in a commercial scale triple bubble co-extrusion line. Seal strength, puncture resistance, oxygen and water vapor permeability and film shrink were measured for the four films and compared to the EVA/PVDC/PE film properties. The results obtained under controlled laboratory conditions show that films made with one layer of EVOH 32 mol% of ethylene encapsulated between two layers of PA66/6 modified with amorphous PA have gas barrier properties and puncture resistance better than a typical EVA/PVDC/PE, seal strength and shrinkability comparable to this film and therefore have potential to preserve fresh beef.

Resumo em Inglês:

Abstract The preparation and characterization of magnetic microspheres based on gelatin for use in drug delivery systems are reported. Sugars were employed as crosslinking agents and type A gelatin and type B gelatin were compared to prepare microspheres by water-in-oil emulsion. The influence of gelatin and sucrose concentration, temperature and stirring speed on microbeads’ characteristics was studied. The gelatin concentration and stirring speed were the parameters directly associated with the particle sizes. We found no relevant difference between the use of type A and type B gelatin. In addition, the gelatin crosslinking study revealed that sucrose is not a crosslinking agent but fructose can crosslink the protein chains when the reaction medium has pH 9. The size of the microspheres varied from 5 to 60 μm as measured by optical microscopic images. Doxorubicin adsorption and release were successfully performed using the microspheres crosslinked with fructose under the action of an external magnetic field. It was observed that the microspheres absorbed 69% of the doxorubicin that was in solution. After 24 h, about 45% of the DOX was displaced from microspheres to saline medium in the free form in the solution.

Resumo em Inglês:

Abstract A polymeric adsorbent based on sodium alginate (SAG) grafted with polyacrylamide (PAM) (SAG- g-PAM) was synthesized using an ultrasound-assisted method. The addition polymerization was carried out with ammonium persulfate as the initiator, at different acrylamide (AM) concentrations. The SAG-g-PAM copolymers were evaluated by FTIR and 13C NMR spectroscopies, thermogravimetric analysis, grafting efficiency (%GE) and intrinsic viscosity in NaCl solution at 25 °C. Graft copolymers could be obtained in reaction lasting until 10 min by using ultrasound energy with grafting efficiency above 75%. The decolorization efficiency and adsorption capacity of the SAG- g-PAM copolymers were investigated in the adsorption of methylene blue (MB). The dye adsorption was pH dependent, and adsorption capacity (69.13 mg/g) maxima was at pH 10. All the graft copolymers have shown the same decolorization efficiency (99%), and the best one for MB removing is the SAG-g-PAM6 (%GE = 75%), since lower acrylamide content is required in the synthesis.

Resumo em Inglês:

Abstract This study presents the preparation and characterization of composite materials using Plastic Waste from Hydrapulper (PWH) from paper industries extruded with sugar cane fiber residues from ethanol industries. The factorial design showed that composite material with 40% of sugar cane fiber, pressed with 5 ton was the optimized condition. The main findings attested that the composite is resistant up to 250 °C and its hardness is increased compared to the raw PWH. The material presented woodsy aspect although water absorption has increased. So, this study offers a good alternative for the use of plastic waste generated as a by-product of recycled paper industry as well as a destination to the sugar cane bagasse.

Resumo em Inglês:

Abstract Recently, the physical and chemical effects of ultrasound in polymeric materials synthesis have attracted great attention. This work presents the synthesis of novel polymeric materials by polymerization of isophorone diisocyanate with different polyols. Polymers were synthesized by step miniemulsion polymerizations, using ultrasound bath and thermostatic bath. The effects of ultrasound, temperature and polyol type were evaluated by Fourier transform infrared spectroscopy, gel permeation chromatography, dynamic light scattering and titrimetry. Polymerization under ultrasound bath showed that different reaction temperatures in the range between 50 °C and 80 °C directly influence the molecular weight of the polymers, urea/urethane formation and increase of diisocyanate consumption rate. In addition, different polyols used in polymerizations in miniemulsion had a significant effect on the characteristics of the resulting poly(urea-urethane) nanoparticles. Finally, ultrasound assisted polymerizations showed a faster diisocyanate consumption rate, but did not lead to enhanced molecular weights.

Resumo em Inglês:

Abstract Compounds of poly(3-hydroxybutyrate) (PHB) and titanium dioxide (TiO2) with filler content between 1% and 10% were prepared in a laboratory internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/TiO2 compounds was investigated by differential scanning calorimetry (DSC). Melt and cold crystallization rates rise with increasing cooling/heating rates. A higher cooling rate translates to a lower melt crystallization temperature, while a higher heating rate results in a higher cold crystallization temperature. TiO2 promotes melt crystallization of PHB, behaving as a nucleant agent. The total crystallinity developed after melt and cold crystallization decreases for low levels of TiO2, i.e. 2% per weight, and is almost independent of the heating/cooling rate. The melting temperatures and rates are minimally affected by both the heating rate and filler content. The results suggest that the desired PHB microstructure can be controlled by filler content and adjusted heating/cooling rate.

Resumo em Inglês:

Abstract The effect of molecular weights and hydrolysis degrees (HD) of polyvinyl alcohol (PVA) on thermal and mechanical properties and crystallinity of polylactic acid (PLA)/PVA blends was investigated. Blends were prepared by the melt blending method using PLA/PVA ratios: 80/20, 90/10 and 97/3 wt. %. A single glass transition temperatures was observed for all PLA/PVA blends, suggesting the formation of binary compatible blends at concentration range studied. Thermogravimetric analysis results showed a better thermal stability for PLA/PVA blends containing PVA of higher Mw and HD. According to mechanical properties, low quantities of PVA (3 wt. %) do not affect the tensile strength of blends (irrespective of Mw and HD). However, as the PVA content increases, tensile strength tends to lower values, especially for blends with 20 wt.% of PVA, with 98% of HD.

Resumo em Inglês:

Abstract A sulfated polysaccharide fraction from the red alga Gracilaria intermedia (PLS) was obtained by papain digestion (60 °C, 30 min). The extract was subjected to colorimetry and turbidimetry analysis, Fourier transform infrared (FTIR) spectroscopy, 1H, 13 C and 2D 1H COSY nuclear magnetic resonance (NMR) and gas chromatography/mass spectrometry analysis. Antioxidant activity tests were performed (chelation of ferrous ion, total antioxidant capacity, and scavenging of DPPH radicals); significant activity of the extract indicated that these polysaccharides may be used as non-synthetic antioxidants. The rheological behavior of aqueous polysaccharide solutions was studied at 25 ± 1 °C using steady-shear and dynamic oscillatory measurements. All the solutions analyzed showed pseudoplastic behavior and potential to act as a thickening agent, as proved through a preliminary comparison with a commercial product used for this application.