Ageing of fibre-laden aqueous foams

Fibre-laden liquid foams are used in the production process of novel non-woven fibrous materials, employed for example for thermal or acoustic insulation. Here we present an experimental investigation of the stability of such foams. We find that on a time-scale of a few minutes the presence of fibres does not alter the drainage properties of the foam. On a longer time-scale fibres slow down drainage, mainly due to their slowing down of coarsening. The drying of our aged samples leads to a fibre network with a fibre concentration profile that appears to be determined by gravity. Our experiments were performed using fibre concentrations of a few percent, as relevant also to the foam-laid forming of paper, where aqueous foam instead of water is used as a carrier medium for fibres.     

Characterization of sugar palm (Arenga pinnata) fibres

The aim of this study was to characterize tensile and thermal properties of sugar palm (Arenga pinnata) fibres obtained from different heights (1, 3, 5, 7, 9, 11, 13, and 15?m) of sugar palm tree. This study has confirmed that in a mature sugar palm tree, degradation was occurred and altered the properties of its fibre. Fibres obtained at the area of live (green) palm frond were found to have a better tensile properties as a result of its optimum chemical composition especially cellulose, hemicelluloses and lignin. For the fibre obtained from the upper part of sugar palm tree, it shows slightly decreasing trend in tensile properties compared to mature fibres. It is due to the fibres are juvenile where their cell walls are progressively built up thus give slightly lower properties than matured fibres. For the fibre obtained from the area of dead palm frond, the fibres are considered to be degraded biologically. It is believed that polymeric chains in microfibrils were broken and their cellulose content was decreased which demonstrated inferior properties (tensile strength, modulus, elongation at break and toughness). The use of such fibre for application as reinforcing fibre in composite is not recommended since the strength of the fibre and composite will be reduced. There were four phases of decomposition of the fibres where the sequence of decomposition started with decomposition of moisture, followed by hemicelluloses, then cellulose and next is lignin while the ash was the last component left. The thermal degradation of these components were found in ranges of 45?C123, 210?C300, 300?C400, 160?C900 and 1723?°C, respectively. Thermogravimetric analysis and derivative thermogravimetric analysis curves showed that the fibre of 1?m showed higher thermal stability than the fibres of 3?C15?m. The different thermal stability for each fibre was due to different chemical compositions especially when the fibre containing high ash content which result in higher thermal stability.     

Thermal decomposition of asbestos-containing materials

Asbestos is the common name applied to a group of natural, fibrous silicate minerals, which were once one of the most popular raw materials to be used in building materials. Asbestos was mainly used for the production of assortment asbestos–cement products. Today it is generally known that asbestos belongs to the group of hazardous materials and shows carcinogenic activity. In Poland, asbestos-containing materials are stored in special landfills. This is not the final solution to the asbestos problem because the fibrous structure of asbestos is still maintained. Therefore, methods based on recycling must be found which will be able to destroy asbestos’ dangerous fibrous structure. One of these methods may be thermal decomposition, where chemically combined water is released from the asbestos materials during heating. This leads to changes in the crystal structure and to the formation of new mineral phases. The aim of the preliminary research presented in this study was to determine the thermal behaviour as well as the structural and phase transformations of asbestos–cement materials during heating to high temperature. In the present study, three different types of asbestos-containing materials from Poland were examined. Differential thermal analysis, thermogravimetry with evolved gas analysis, X-ray diffraction, infrared spectroscopy and scanning electron microscopy were used to study the thermal decomposition of asbestos–cement samples. It was found that there were no significant differences between the type of asbestos–cement samples used—their thermal decomposition takes place in a similar way.     

Supercritical Carbon Dioxide Isolation of Cellulose Nanofibre and Enhancement Properties in Biopolymer Composites

The physical properties, such as the fibre dimension and crystallinity, of cellulose nanofibre (CNF) are significant to its functional reinforcement ability in composites. This study used supercritical carbon dioxide as a fibre bundle defibrillation pretreatment for the isolation of CNF from bamboo, in order to enhance its physical properties. The isolated CNF was characterised through zeta potential, TEM, XRD, and FT-IR analysis. Commercial CNF was used as a reference to evaluate the effectiveness of the method. The physical, mechanical, thermal, and wettability properties of the bamboo and commercial CNF-reinforced PLA/chitin were also analysed. The TEM and FT-IR results showed the successful isolation of CNF from bamboo using this method, with good colloidal stability shown by the zeta potential results. The properties of the isolated bamboo CNF were similar to the commercial type. However, the fibre diameter distribution and the crystallinity index significantly differed between the bamboo and the commercial CNF. The bamboo CNF had a smaller fibre size and a higher crystallinity index than the commercial CNF. The results from the CNF-reinforced biocomposite showed that the physical, mechanical, thermal, and wettability properties were significantly different due to the variations in their fibre sizes and crystallinity indices. The properties of bamboo CNF biocomposites were significantly better than those of commercial CNF biocomposites. This indicates that the physical properties (fibre size and crystallinity) of an isolated CNF significantly affect its reinforcement ability in biocomposites. The physical properties of isolated CNFs are partly dependent on their source and production method, among other factors. These composites can be used for various industrial applications, including packaging.     

Analysis of glass fiber reinforced cement composites and their thermal and hygric material parameters

Methods of thermal analysis are employed in a study of the high-temperature properties of three different types of glass fiber reinforced cement composites together with the measurements of their thermal and hygric parameters. First, basic TG and DTG measurements are carried out to get the first insight into the high-temperature behavior of the analyzed materials. Then, mercury porosimetry and scanning electron microscopy of specimens subjected to the temperatures of 600 and 800°C are performed and compared to the reference specimens not exposed to any thermal load. Finally, measurements of thermal and hygric parameters of the studied materials are done and matched with the results of the material characterization experiments. Three main effects are found to influence the thermal and hygric properties of the analyzed materials. The first is the decomposition of the cement matrix, which is clearly a negative factor. The second is the positive effect of the presence of fibers that could partially keep the cement matrix together even after significant decomposition of cement hydration products. The third important factor affecting the thermal and hygric properties is the composition of the particular materials. The application of vermiculite aggregates instead of sand is found to be clearly positive because of its porous character leading to the bulk density decrease without worsening the other properties. Also, wollastonite aggregates are a better choice than sand because of its fibrous character that could partially magnify the effect of fiber reinforcement. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modeling liquid porosimetry in modeled and imaged 3-D fibrous microstructures

In this paper, an analysis to distinguish the geometric and porosimetric pore size distributions of a fibrous material is presented. The work is based on simulating the intrusion of nonwetting fluid in a series of 3-D fibrous microstructures obtained from 3-D image reconstruction or virtual geometries mathematically generated according to the properties of the media. We start our study by computing the pore size distribution of two typical hydroentangled nonwoven materials and present a theoretical model for their geometric pore size distributions based on Poisson line network model of the fibrous media. It is shown that the probability density function of the geometric pore size distribution can be approximated by a two-parametric Gamma distribution. We also study connectivity of the pore space in fibrous media by computing and comparing the accessible and allowed pore volumes in the form access function graphs. It is shown that the so-called ink-bottle effect can significantly influence the fluid intrusion in a porous material. The pore space connectivity of a homogeneous fibrous media is observed to be a function of thickness, solid volume fraction (SVF), and fiber diameter. It is shown that increasing the materials' thickness or SVF, while other properties are kept constant, reduces the pore space connectivity. On the other hand, increasing the fiber diameter enhances the connectivity of the pores if all other parameters are fixed. Moreover, modeling layered fibrous microstructures; it is shown that the access function graphs can be used to detect the location of the bottle neck pores in a layered/composite porous material.     

Use of wollastonite in a thermoplastic elastomer composition

Thermoplastic elastomer compositions (TPEs) based on wollastonite-filled SEBS/PP/oil blends were prepared and characterized. The development of new TPEs with improved mechanical strength may broaden their applications, especially for soft goods. Wollastonite is a natural filler that combines high thermal stability with low health hazard in comparison to other fibrous inorganic fillers. Morphological, thermal and mechanical properties of the composite materials were studied by transmission electron microscopy (TEM), thermogravimetry (TGA), tensile tests and dynamic mechanical analysis (DMA). The results indicate that the filler was mainly distributed as nanoparticles in the PS domains, improving the mechanical resistance of the materials even at low concentration (2 phr).     

Why do we observe significant differences between measured and ‘back-calculated’ properties of natural fibres?

The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘back-calculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule-of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.     

PREDICTION OF PREDOMINANT MECHANISMS IN THE SEPARATION OF SECONDARY DISPERSIONS IN A FIBROUS BED

The different drop capture mechanisms for secondary dispersions in fibrous beds are reviewed. A quantitative analysis showed that interception and sedimentation are the predominant mechanisms in fibrous bed coalescers. The selection of operating parameters, e.g. velocity, fibre size and drop size depends upon these mechanisms. A 3 cm deep fibrous bed of glass wool, with a fibre diameter of 25 pm, was found to capture more than 80% of the dispersed phase from an inlet secondary dispersion of 15 Mm drop size. Almost 70% of these drops were captured due to the interception mechanism.     

Environmental effects on fibre reinforced polymeric composites: Evolving reasons and remarks on interfacial strength and stability

The interface between fibre and matrix of fibrous polymeric composites is most critical and decisive in maintaining sustainability, durability and also reliability of this potential material, but unfortunately a comprehensive conclusion is yet to meet the label of confidence for the engineering viability. Fiber reinforced polymer (FRP) composites are being accepted and also utilized as better and reliable alternative materials for repairing and/or replacing conventional materials, starting from tiny objects to mega structure in various engineering applications. The promise and potential of these materials are sometimes threatened in speedy replacement of conventional materials because of their inhomogeneities and inherent susceptibility to degradation due to moist and thermal environments. Environmental conditioning is traditionally believed to be a physical phenomenon but present literature has revealed that the interdiffusion between fiber and polymer matrix resin comprises of physical, chemical, mechanical, physico-chemical and mechano-chemical phenomena. The failure and fracture behavior at ambient conditions itself is a complex phenomenon till at present. The service conditions which are mostly hygrothermal in nature, along with a variation of applied loads make the mechanical behavior nearly unpredictable, far off from conclusions in evaluating the short term as well as long term durability and reliability of FRPs. It is essential to accurately simulate the initial and subsequent evolution process of this kind of damage phenomena, in order to explore the full potential of the mechanical properties of composite laminates. The present review has emphasized the need of complying scattered as well as limited literature on this front, and has focused on creating the urgency to highlight the importance of judicious uses of these materials with minimum safety factors with an aim to achieving lighter weight in enhancing specific properties.     

Kapok/cotton fabric–polypropylene composites

Kapok/cotton fabric has been used as reinforcement for conventional polypropylene and maleic anhydride grafted polypropylene resins. Treating the reinforcement with acetic anhydride and sodium hydroxide has modified the fabric (fibres). Thermal and mechanical properties of the composites were investigated. Results show that fibre modification gives a significant improvement to the thermal properties of the plant fibres, whereas tests on the mechanical properties of the composites showed poor tensile strength. Mercerisation and weathering were found to impart toughness to the materials, with acetylation showing slightly less rigidity compared to other treatments on either the fibre or composites. The modified polypropylene improved the tensile modulus and had the least toughness of the kapok/cotton reinforced composites. MAiPP reinforced with the plant fibres gave better flexural strength and the same flexural modulus at lower fibre content compared with glass fibre reinforced MAiPP.     

Surface phenomena at polymers

Polymers with advanced properties can be achieved among other measures by reinforcing with fibrous materials, by polymer blending and surface modification. Using the surface treatment of PP-EPDM injection moulding specimens (washing, flaming, plasma-treatment) an overview on progress in surface analytics is given. It is shown that XPS, contact angle and zeta-potential measurements give corresponding results concerning the composition of the surface region. Additional to the kind of interaction forces at interfaces the mechanical properties of reinforced polymers are governed by sorption layers and electrical phenomena at interfaces. Corresponding results were obtained at chalk filled PE-HD and glass fibre reinforced polyamide.     

Thermal,spectral, magnetic and biologic characterization of new Ni(II), Cu(II) and Zn(II) complexes with a hexaazamacrocyclic ligand bearing ketopyridine moieties

Five types of fibrous assemblies, namely, polyester, wool, cashmere, kapok, and goose down, were tested for their heat-insulating properties in the natural state using the apparatus developed by the authors. The influences of bulk density, fiber type, fiber arrangements, and compression on the heat-insulating properties of the fibrous assemblies was examined systematically. The results show that kapok assembly with low bulk density, goose down assembly with high bulk density and the randomly arranged fibrous assembly demonstrated the best heat-insulating property; however, considering practical use and the influence of compression, kapok assembly and fibrous assemblies arranged in the form of fiber balls exhibited the most stable and optimum heat-insulating property. The Daryabeigi heat-transfer model that considers fiber contact and scattering effect was used to calculate the heat-insulating properties of the five fibrous assemblies. A similar model was developed by Fanworth, which neglected the fiber and the scattering effect. Comparison of the two models showed that the Daryabeigi model was more accurate in predicting the heat-insulating properties of fibrous assemblies.     

Destruction thermo-oxydante de certains materiaux fibreux cellulosiques et de leurs composants

The investigation of the oxidative thermal destruction of some new cellulose-type fibrous materials, namely poplar down and down of silkweed is described. The latter are characterized by a high content of amorphous components. The components of the fibres, cellulose, holocellulose, hemicelluloses and lignin, separated by extraction, have also been studied. From the experimental data, the compounds isolated from the original material could be classified according to their thermal stabilities. The influence of the molecular structure on the kinetic parameters of the oxidative thermal destruction has also been studied. The activation energies of the single steps of the thermal reaction have been estimated for each compound isolated.     

Investigation of biodegradable composites of poly(3-hydroxybutyrate) ultrathin fibers modified by a complex of iron(III) with tetraphenylporphyrin

Ultrathin fibers based on poly(3-hydroxybutyrate) containing a small concentration of iron(III) complex with tetraphenylporphyrin are obtained by electrospinning. In the absence of the complex, the fibers are characterized by the presence of cylindrical regions with a diameter of 1–3 and spindlelike regions with an average diameter of 7–10 μm. Introduction of the iron(III) complex with tetraphenylporphyrin into the polymer solution leads to the disappearance of spindlelike thickenings on the fibers. Addition of the complex to the polymer matrix results in a sharp rise in crystallinity and slows down the molecular mobility in the amorphous regions of ultrathin fibers. Annealing of the fibers at 140°C involves a sharp increase in the crystallinity of the polymer, while after addition of the complex this characteristic decreases abruptly. The final fibrous materials possess bactericidal properties and should find direct application in the creation of antibacterial and antineoplastic therapeutic systems.     

Functionalization of single layers and nanofibers: a new strategy to produce polymer nanocomposites with optimized properties

Nanocomposites are the emerging materials of the 21st century in view of their possessing design uniqueness without any compromises, certain unusual property combinations that are not found in conventional composites, as well as a wide spectrum of applications. Polymer-based layered compound nanocomposites have special place in view of their best property enhancement. Hence, the objective of this article is to bring new ideas to optimize the design of polymer/layered compounds/fibrous nanocomposites, starting with a brief overview of the preparation, structure, properties and applications. The proposed strategy suggests the use of synthetic and natural layered compounds, taking into account their ability to be exfoliated in the form of single layers, which can be chemically grafted with key molecules. The same procedure can also be applied to fibrous materials. These surface-grafted molecules can carry reactive groups to be bonded to the polymer matrices. Thus adhesion between the reinforcement and the polymer matrix can be achieved. This methodology, which has not been explored systematically in the specialized literature, can be used to produce polymer nanocomposites with low-cost fibrous materials having similarity to expensive carbon nanotubes exhibiting optimized dispersion, interfacial bonding, and attractive physical and other properties.     

Mimicking natural fibrous structures of opals by means of a microemulsion-mediated hydrothermal method

Silica-based nanomaterials are of great interest because of their potential applications in constructing electronic and optoelectronic nanodevices. Especially significant are those that combine the properties of photonic crystal with a fibrous semiconductor structure. Here we report the use of microemulsion droplet systems as a simple and controllable route for the synthesis of 3D opals materials with an unusual fibrous microstructure similar to those that exist in nature. By this method, we demonstrate the creation of very long fibrils of 30-50 nm diameter and more than 20 μm length showing simultaneous short and long wavelength light emissions and band gap values (5.50 and 4.41 eV) comparable to those obtained for silicon-based metal oxide semiconductors.     

Thermochemical characterization of chicken litter and peat as a source for energy recovery

The shortage of raw materials and the environmental problems due to pollution require development of new green technologies utilizing some wastes and transforming them to secondary raw materials. The aim of this work is to study the properties of poultry waste to propose possibilities to minimizing the released emissions and avoiding the risk for human health and the environment. At the same time, two types of low grade peats with different origin are studied as components for the production of soil conditioners. During the studies, we applied the inductively coupled plasma (ICP) and chemical analysis, powder X-ray diffraction, thermal analysis, IR spectroscopy, and scanning electron microscopy for determining the composition, crystal phase, the shape and size of particles, and thermal stability of the investigated samples. The chemical and the phase compositions of the studied samples confirmed that the content of nutrient compounds and of the carbon substances is suitable as an effective secondary raw material for soil conditioners. It is found that the poultry wastes and peat samples have a similar phase and chemical composition and contain an organic mass in the form of carbon components with amorphous, fibrous, and skeleton-like structure, suitable to be combined with other nutrient-containing compounds. During the thermal treatment, the carbon compounds are oxidized releasing heat. Based on that the materials under study are considered as environmentally friendly fuels, releasing relatively low emissions.     

Asbeste

Asbestos minerals are naturally occurring fibrous silicates. From the structural chemistry point of view they belong to two different classes: The group of serpentines, to which the primarily used chrysotil (white asbestos) belongs, consists of curled up layer silicates. On the other hand in the amphiboles (for example blue asbestos (crocidolite)), which belong to the band silicates, the fibrous form is pre-formed in their silicon-oxygen partial structure. The characteristic properties of asbestos (its fibrous form, thermal and chemical inertness, good electric and thermal insulation, spinability…) led to extensive application of the mineral fibers in nearly all fields of engineering and everyday life. Because of the health effects of asbestos dust – fibrogene and cancerogene diseases – the application of asbestos containing products will cease with the end of this century. The search for substitute materials (especially fibers) is currently an area of interest in material sciences.     

Graphene Sheet Orientation of Parent Material Exhibits Dramatic Influence on Graphene Properties

The production of graphene from various sources has garnered much attention in recent years with the development of methods that range from “bottom‐up” to “top‐down” approaches. The top‐down approach often requires thermal treatment to obtain a few‐layered and lowly oxygenated graphene sheets. Herein, we demonstrate the production of graphene through oxidation and thermal‐reduction/exfoliation of two sources of differently orientated graphene sheets: multiwalled carbon nanotubes (MWCNTs) and stacked graphene nanofibers (SGNFs). These two carbon‐nanofiber‐like materials have similar axial (length: 5–9 μm) and lateral dimensions (diameter: about 100 nm). We demonstrate that, whereas SGNFs exfoliate along the lateral plane between adjacent graphene sheets, carbon nanotubes exfoliate along its longitudinal axis and leads to opening of the carbon nanotubes owing to the built‐in strain. Subsequent thermal exfoliation leads to graphene materials that have, despite the fact that their parent materials exhibited similar dimensions, dramatically different proportions and, consequently, materials properties. Graphene that was prepared from MWCNTs exhibited dimensions of about 5000×300 nm, whereas graphene that was prepared from SGNFs exhibited sheets with dimensions of about 50×50 nm. The density of defects and oxygen‐containing groups on these materials are dramatically different, as are the electrochemical properties. We performed morphological, structural, and electrochemical characterization based on TEM, SEM, high‐resolution X‐ray photoelectron spectroscopy, Raman spectroscopy, and cyclic voltammetry (CV) analysis on the stepwise conversion of the target source into the exfoliated graphene. Morphological and structural characterization indicated the successful chemical and thermal treatment of the materials. Our findings have shown that the orientation of the graphene sheets in starting materials has a dramatic influence on their chemical, material, and electrochemical properties.