Influence of halloysite nanotubes on physical and mechanical properties of cellulose fibres reinforced vinyl ester composites

Natural fibres are generally added to polymer matrix composites to produce materials with the desirable mechanical properties of higher specific strength and higher specific modulus while at the same time to maintain a low density and low cost. The physical and mechanical properties of polymer composites can be enhanced through the addition of nanofillers such as halloysite nanotubes. This article describes the fabrication of vinyl ester eco-composites and eco-nanocomposites and characterizes these samples in terms of water absorption, mechanical and thermal properties. Weight gain test and Fourier transform infrared analysis indicated that 5% halloysite nanotube addition gave favourable reduction in the water absorption and increased the fibre–matrix adhesion leading to improved strength properties in the eco-nanocomposites. However, halloysite nanotube addition resulted in reduced toughness but improved thermal stability

Piassava fibers (Attalea funifera): NMR spectroscopy of their lignin

Lignin of piassava (Attalea funifera) was analyzed by H-1- and C-13-NMR spectroscopy. The HGS-nature of this lignin was confirmed but p-coumarate units are also present in the lignin. Methoxyl and phenolic hydroxyl contents per phenylpropanic unit were determined by H-1- NMR spectroscopy to be 0.57 and 0.68, respectively and are in agreement with wet chemistry methods. A small extent of lignin condensation (35%) was explained by the high content of cinnamyl alcohol structures, evidenced by C-13-NMR-DEPT. An extended C-9-formula for the piassava lignin was established to be (C9.00H2.25H3.73O0.89)-H-ar-O-al(OH)(0.69)(ph)(OH)(0.86)(al)(OCH3)(0.57).11549149

Piassava fibers. (Attalea funifera) .1. Chemical analysis, extraction and reactivity of its lignin

Piassava fibers have approximately 14% humidity and contain 0.8% ash, 0.7% extractives, 45.0% Klason lignin and 28.6% cellulose, with a total of 54.4% holocellulose. Microanalysis (54.5% C; 5.84%; 0.52% N) shows a higher carbon content than normally found in plant materials. Total hydroxyl groups are 14.0% of the material. The content of methoxyl groups (4.8% or 10.7% of the lignin) and phenolic hydroxyl groups (3.5% or 7.8% of the lignin) are in the expected range. The calculated C-9 formula for the lignin is C9H5.35O0.92 (OHphen)(0.72)(OCH3)(0.51). The average molecular weight for the dioxane/HCl extracted lignin is in the range of 3,500 dalton and that for the NaOH lignin is 1,100 dalton, but their FTIR spectra are similar. Using an alkaline (pH 10) dioxane/water (1:1 v:v) mixture and pressure (6 MPa), 46% of the piassava can be solubilized in 15 min at 250 degrees. After 30 min at 280 degrees, 88% of the piassava is converted to give a heavy oil with 56% yield. At 200 degrees and 10 Pa, 71% of this oil can be distilled. The distillate was analyzed by GC/MS and five phenols were identified in good individual yields.29670571

Atomic force microscopy (AFM) investigation of Langmuir-Blodgett (LB) films of sugar cane bagasse lignin

The morphological features of Langmuir-Blodgett (LB) films of pure lignin extracted from sugar cane bagasse and composites of lignin and cadmium stearate have been investigated using atomic force microscopy (AFM). Results indicated that despite the non-amphiphilic nature of lignin and associated relatively poor stability and transferability of the lignin monolayer, the surface of the film is smooth at the micron level and comparable to that of LB films from typical amphiphilic compounds. Distinct domain structures from lignin and cadmium stearate could be visualized in the composite LB film even in one monolayer thick LB films. The mean surface roughness increases with increasing numbers of layers.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.541556

Surface morphology and molecular organization of lignins in Langmuir-Blodgett films

Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate molecular organization in Langmuir-Blodgett (LB) films of two kinds of lignins. The lignins were extracted from sugar cane bagasse using distinct extraction processes and are referred to here as ethanol lignin (EL) and saccharification lignin (SAC). AFM images show that LB films from EL have a flat surface in comparison with those from SAC. For the latter, ellipsoidal aggregates are seen oriented perpendicularly to the substrate. This result is confirmed by a combination of transmission and reflection FTIR measurements, which also point to lignin aggregates preferentially oriented perpendicularly to the substrate. For LB films from EL, on the other hand, aggregates are preferentially oriented parallel to the substrate, again consistent with the flat surface observed in AFM data. The vibrational spectroscopy data for cast films from both lignins show random molecular organization, as one should expect

Cellulose/iron oxide hybrids as multifunctional pigments in thermoplastic starch based materials

Cellulose/iron oxide hybrids were prepared by the controlled hydrolysis of FeC2O4 in the presence of vegetable and bacterial cellulose fibres as substrates. By varying the relative amount of FeC2O4 and NaOH, either hematite or magnetic iron oxides were grown at the cellulose fibres surfaces. This chemical strategy was used for the production of a number of materials, whose coloristic properties associated to their reinforcement role allowed their use as new hybrid pigments for thermoplastic starch (TPS) based products. The TPS reinforced materials were characterized by several techniques in order to evaluate: the morphology and the compatibility between the matrix and the fillers; the mechanical reinforcement effect of the cellulose/iron oxide pigments on TPS and the coloristic properties of the composites. All materials showed good dispersion and strong adhesion for the cellulose/iron oxide nanocomposites in the TPS matrix thus resulting in improved mechanical properties

Investigation of the effects of starch on the physical and biological properties of polyacrylamide (PAAm)/starch nanofibers

Abstract Here, we report the development of a new polyacrylamide (PAAm)/starch nanofibers’ blend system and highlight its potential as substrate for efficient enzyme immobilization. PAAm was synthesized and blended with starch. The final blend was then electrospun into nanofibers. The response surface methodology was used to analyze the parameters that control nanofiber’s diameter. Electrospun mat was then modified either by cross-linking or phytase immobilization using silane coupling agent and glutaraldehyde chemistry. Physico-chemical properties of blends were investigated using spectroscopic and thermal studies. The evaluation of immobilized enzyme kinetics on both pure and the starch blended PAAm nanofibers was performed using Michaelis–Menten kinetic curves. Fourier transform infrared spectroscopy results along with differential scanning and X-ray diffraction confirmed that blending was successfully accomplished. TGA analysis also demonstrated that the presence of starch enhances the thermal degradability of PAAm nanofibers. Finally, it was shown that addition of starch to PAAm increases the efficacies of enzyme loading and, therefore, significantly enhances the activity as well as kinetics of the immobilized enzyme on electrospun blend mats