Biodegradation of flax fibers in the presence of silver nanoparticles

Biodegradation of flax fibers differing in the chemical composition, structure of cellulose, and content of concomitant natural impurities (pectin compounds, lignin, hemicellulose) was studied. The effect exerted on the biodegradation by silver nanoparticles immobilized in the fiber was evaluated.     

Biochemical and physicochemical treatment of flax fibers

Conditions were found for separating concomitant substances from cellulose in short flax fibers by treatment with surfactant and enzyme solutions. The chemical composition of the treated fibers was analyzed, and their structural organization was studied by IR Fourier spectroscopy.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1743–1746.Original Russian Text Copyright © 2004 by Shamolina, Bochek, Zabivalova, Vlasova, Volchek, Sinitsin.     

Single stage purification of flax,hemp, and milkweed stem and their physical and morphological properties

Agriculture biomass is an alternative possible solution for the extraction of cellulose, compared to the classical soft and hard wood. However, the valorization of cellulose is challenging for the researchers as it involves multiple steps. In the present study, the raw fibers of flax, hemp, and milkweed stem fibers were purified in single step using hydrogen peroxide in water. By this method authors successfully extracted the purified cellulose fibers without damaging the fiber length. The purified fibers were characterized to understand the thermal, functional, crystalline, and morphological properties by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FTIR results showed the effective removal of lignin and significant improvement in thermal stability was observed by TGA. Evidently, the SEM results showed significant improvement in the morphology compared to that of the raw fibers. XRD results showed that the treatment does not affect the crystallinity of the fibers.     

Bio-protected flax nanocomposites as basis for manufacturing of high-tech eco-products

Data on biodegradation of flax fibers of different chemical composition, structure of cellulose, and included natural impurities (pectic compounds, lignin, and hemicelluloses) are presented. The influence of silver nanoparticles immobilized in the fiber on biodegradation of the objects under study is evaluated. It is demonstrated that this effect depends on the concentration and size of nanoparticles in the polymer matrix.     

Wetting behavior of flax fibers as reinforcement for polypropylene

The wetting behavior of several flax (cellulose as reference) and polypropylene fibers is characterized by measuring the wetting rates (penetration velocities) of a series of liquids using the capillary rise technique. This present paper aims to provide a deeper understanding of the complex nature of natural fibers and their surface properties. The fiber surface tensions are estimated from plots of the normalized wetting rate as a function of the surface tension of the liquids assuming, in analogy to Zisman's method, that the maximum of the normalized wetting rate corresponds to the solid surface tension. The estimated surface tensions of the investigated flax fibers indicate that all the fibers are quite "hydrophobic." The method used to separate the fibers from the rest of the plants has a large influence on the estimated fiber surface tensions. In the case of polypropylene (PP) fibers, the estimated surface tension corresponds well with literature data. Grafting small amounts of maleic acid anhydrite (MAH) onto the PP surfaces will not affect the wetting behavior and, therefore, the surface tension, whereas grafting larger amounts (10 wt%) of MAH causes the polymer surface tension to increase significantly. Additional pH-dependent zeta-potential measurements show that even the "pure" PP-fibers contain acidic surface functions, possibly due to further processing at elevated temperatures (thermal degradation or other aging processes).     

Thermogravimetric measurement of amorphous cellulose content in flax fibre and flax pulp

Usually the raw material for flax pulp production is a blend which contains fibres and shives. In order to better understanding the structure of these materials and the effects of flax pulping, X-ray diffraction and thermogravimetry analysis under air atmosphere have been used. There was a significant effect of the fibre size on the composition, crystallinity, and thermal behaviour of the flax pulps. On the other hand, data obtained from thermogravimetric analysis have been modelled on the basis of two cellulose types characterized by different crystallinity levels, using kinetics equations based on the nucleation concept. As a result of these simulations, composition of the samples, pulp crystallinity and the proportion of amorphous cellulose are calculated.     

Fabrication of Microcrystalline and Powdered Cellulose from Short Flax Fiber and Flax Straw

Conditions of manufacture of microcrystalline cellulose from variously treated short flax fibers and of powdered cellulose from flax straw were examined. The effect of fats, waxes, and pectins contained in the fibers on the kinetics of hydrolysis of the polysaccharide was studied.     

Synthesis of cyanoethyl ethers of cellulose from flax fiber production waste

Conditions of preparation of cellulose cyanoethyl ethers with different degrees of substitution, based flax fiber production waste were examined. The chemical structure of the resulting cellulose ethers and variation of the structure of the cellulose materials during cyanoethylation were examined by IR-Fourier spectroscopy and X-ray diffraction analysis. The degree of substitution of cellulose ethers was examined in relation to cyanoethylation conditions and chemical composition of the initial cellulose materials.     

Cellulose nitrates from intermediate flax straw

Russian Chemical Bulletin - The results of studying the synthesis of cellulose nitrates from oilseed production residues (intermediate flax straw) and subsequent autoclaving of the obtained ethers...     

Structure and properties of flax vs. lyocell fiber-reinforced polylactide stereocomplex composites

Cellulose - A commonly used natural cellulose fiber (flax) and a regenerated cellulose fiber (Lyocell) were used at 20 wt% to reinforce polylactide stereocomplex (sc-PLA) composites. Composites...     

Recovery of wool from flax fibers using nitric acid

The principal possibility of preparing wool from cottonized flax fibers using nitric acid both in the course of cooking and in the bleaching step was studied. The influence of the nitric acid concentration and cooking time on the extent of flax delignification was examined.     

Sorption properties of plasma-modified flax fibers

Effect of plasma modification on the sorption properties of short flax fibers for Zn(II) ions was studied.     

Preparation of mixed cellulose ethers by the reaction of short flax fibers and cotton linter with monochloroacetamide

The conditions of preparation of mixed cellulose ethers containing carboxy and amino groups by the reaction of samples of short flax fiber and cotton linter with monochloroacetamide were examined. The influence of the amino groups of the mixed cellulose ethers on the rheological properties of their aqueous solutions was elucidated.     

Thermomechanical and crystallization behavior of polylactide-based flax fiber biocomposites

In this work, the rheological, thermal and mechanical properties of melt-compounded flax fiber-reinforced polylactide composites were investigated. The effect of compounding on fiber length and diameter, and the relationship between fiber content and the crystallization behavior of the biocomposites, at various temperatures, were also examined. After melt-compounding, fiber bundles initially present were, to a large extent, broken into individual fibers and the fiber length was decreased by 75 %, while the aspect ratio was decreased by nearly 50 %. The crystallization half-time was found to decrease with increasing flax fiber content, and showed a minimum value at 105 °C for all systems. The elastic modulus was increased by 50 % in the presence of 20 wt% flax fibers. The addition of maleic anhydride-grafted polylactide had a positive effect on the mechanical properties of the biocomposite. This system is particularly interesting in the context of sustainable development as it is entirely based on renewable resources and biodegradable.     

Property correlations for composites based on ethylene propylene diene rubber reinforced with flax fibers

EPDM composites filled with short flax fibers were prepared by melt blending procedure. The effects of fiber loading on the mechanical, thermal and water uptake characteristics were studied. The physico-mechanical, morphological thermal properties and water absorption behavior were discussed using tensile testing, differential scanning calorimetry, thermogravimetrical analysis and scanning electron microscopy. Scanning electron microscopy revealed that the flax fibers were well dispersed in the polymer matrix. The tensile strength and hardness of the composites were found to be improved at higher fiber loading. The water absorption pattern of EPDM/fiber composites at room temperature follows a Fickian behavior for composites with 10, 15 and 20 phr flax fiber.     

Properties of Flax Cellulose Solutions in Tertiary Amine N-Oxides and of Films Thereof

The solubility of flax fibers differing in the degree of purity in triethylamine N-oxide monohydrate was studied. The size and amount of the associates in equiconcentrated solutions were estimated from the turbidity spectra. Rheological properties of solutions of cotton and flax cellulose were compared. Hydrated cellulose films were obtained from solutions, and their physicomechanical properties were studied. The films were characterized by IR spectroscopy.     

Rheological,morphological and mechanical properties of flax fiber polypropylene composites: influence of compatibilizers

In this work, the rheological, mechanical and morphological properties of flax fiber polypropylene composites were investigated. The effect of incorporating a polypropylene grafted acrylic acid or a polypropylene grafted maleic anhydride on these properties has been studied as well. According to scanning electron microscopic observations and tensile tests, the addition of a compatibilizer improved the interfacial adhesion between the flax fibers and the polymer matrix. The tensile modulus of composite containing 30 wt% flax fibers was improved by 200 % and the tensile strength improved by 60 % in comparison with the neat PP. Plasticizing effect of the compatibilizers as a result of their lower melt flow index was also shown to decrease the rheological properties of the composites, even though the effect was not pronounced on the mechanical properties.     

Synthesis of Carboxymethyl Cellulose Based on Short Fibers and Lignified Part of Flax Pedicels (Boon)

The conditions under which carboxymethyl ethers of cellulose with various degrees of substitution can be prepared from wastes formed in production of flax fibers were studied. The structure of the cellulose ethers synthesized was studied by IR Fourier spectroscopy and physicochemical methods.     

Improved hygrothermal durability of flax/polypropylene composites after chemical treatments through a hybrid approach

There are growing research interests in flax fibers due to their renewable ‘green’ origin and high strength. However, these natural fibers easily absorb moisture and have poor adhesion with polymer matrix leading to low interfacial strength for the composites. A hybrid chemical treatment technique combining alkali (sodium hydroxide) and silane treatments is adopted in the current study to modify flax fibers for improved performances of flax/polypropylene composites. Changes in chemical composition, microstructure, wettability, surface morphology, crystallinity and tensile properties of single flax fiber before and after chemical treatments were comprehensively characterized using techniques including SEM, FTIR, AFM, XRD, micro-fiber tester, etc. It was found that hemicellulose and lignin at the fiber surface were removed due to alkali treatment, which helped to reduce moisture absorption of the composites. Alkali-treated flax fibers were later subjected to silane treatment, which helped to improve the compatibility between flax fiber and polypropylene matrix. After alkali-silane hybrid chemical treatment, moisture absorption of the composites was further decreased. At the same time, the interfacial bonding strength between flax and polypropylene is significantly enhanced. All these results validate the great advantage of the hybrid chemical treatment approach for flax/polypropylene composites, which has the potential to promote the application of chemical treatment techniques in the plant fiber composite industry.

Graphic abstract

     

Characterization of alkali treated flax fibres by means of FT Raman spectroscopy and environmental scanning electron microscopy

Flax fibres grown under well managed conditions were submitted to NaOH chemical treatments, so called Mercerization. The extent of the polymorphic transformation of cellulose I into cellulose II taking place within the crystalline domains of the fibre cellulose was dependent on the alkali concentration. FT Raman spectroscopy turned out to represent an ideal tool for detecting the polymorphic transformation of the cellulosic fine structure of the flax fibres in vivo. In addition to the differences of the FT Raman spectra in the frequency range below 1500 cm(-1), second derivatives of the spectra in the range of the CH stretching vibrations could also be used to distinguish the two polymorphic modifications. The intensity ratio R of the stretching modes v(s)COC and v(as)COC represents a spectral parameter characterising the molecular structure of the flax fibres. As a supplementary tool, Environmental scanning electron microscopy (ESEM) was used to visualize the microstructural fibre properties dependent on the alkali concentrations during the Mercerization.