Strong Fibers Research Articles

Chaotically driven sigmoidal maps

We consider skew product dynamical systems [Formula: see text] with a (generalized) baker transformation [Formula: see text] at the base and uniformly bounded increasing [Formula: see text] fibre maps [Formula: see text] with negative Schwarzian derivative. Under a partial hyperbolicity assumption that ensures the existence of strong stable fibres for [Formula: see text], we prove that the presence of these fibres restricts considerably the possible structures of invariant measures — both topologically and measure theoretically, and that this finally allows to provide a “thermodynamic formula” for the Hausdorff dimension of set of those base points over which the dynamics are synchronized, i.e. over which the global attractor consists of just one point.

Manufacturing & characterization of regenerated cellulose/curcumin based sustainable composites fibers spun from environmentally benign solvents

We report a novel manufacturing method for bio renewable regenerated cellulose fibres modified with curcumin, a molecule is known for its medicinal properties. Ionic liquid namely 1-Ethyl 3-Methyl Imidazolium diethyl phosphate (emim DEP) was found to be capable of dissolving cellulose as well as curcumin. Regenerated cellulose/curcumin composites fibres with curcumin concentration ranging from 1 to 10wt% were manufactured using dry jet wet fibres spinning process using three different winding speeds. All the cellulose and curcumin composite fibres showed distinct yellow colour imparted by curcumin. The resultant fibres were characterised using scanning electron microscopy (SEM), infrared spectroscopy, mechanical testing, and X-Ray diffraction studies. Scanning electron microscopy of cellulose/curcumin fibres cross-section did not show curcumin aggregates in cellulose fibres indicating uniform dispersion of curcumin in cellulose matrix. The cellulose chain alignment in cellulose/curcumin composite fibres resulted in tensile strength ranging from 223 to 336MPa and Young’s modulus ranging from 13 to 14.9GPa. The mechanical properties of cellulose/curcumin composite fibres thus obtained are better than some of the commercially available regenerated cellulose viscose fibres. The wide-angle X-ray diffraction analysis of cellulose/curcumin composite fibres showed good alignment of cellulose chains along the fibre axis. Thus, our findings are a major step in manufacturing strong cellulose fibres with a pharmacologically potent drug curcumin which in future could be used for medicinal, cosmetic and food packaging applications.

Molecular Investigation of the Stem Snap Point in Textile Hemp.

Fibre crops are important natural resources, as they sustainably provide bast fibres, an economically-valuable raw material used in the textile and biocomposite sectors. Among fibre crops, textile hemp (Cannabis sativa L.) is appreciated for its long and strong gelatinous bast fibres. The stem of fibre crops is a useful system for cell wall-oriented studies, because it shows a strong tissue polarity with a lignified inner core and a cellulosic hypolignified cortex, as well as a basipetal lignification gradient. Along the stem axis of fibre crops, a specific region, denoted snap point, marks the transition from elongation (above it) to fibre thickening (below it). After empirically determining the snap point by tilting the plant, we divided the stem segment containing it into three non-overlapping consecutive regions measuring 1 cm each, and carried out targeted RT-qPCR on cell wall-related genes separately, in outer and inner tissues. Different gene clusters can be observed, two of which are the major gene groups, i.e., one group with members expressed at higher levels in the inner tissues, and one group whose genes are more expressed in the cortex. The present results provide a molecular validation that the snap point is characterised by a gradient of events associated with the shift from fibre elongation to thickening.

Properties and Structural Anisotropy of Gel-Spun Lignin/Poly(Vinyl Alcohol) Fibers Due to Gel Aging

In contrast to traditional techniques for fiber spinning, the gel-spinning of biobased lignin/poly(vinyl alcohol) (PVA) fibers yields higher mechanical performance. To further improve upon the mechanical properties and molecular anisotropy of gel-spun lignin/PVA fibers, gel-fibers were aged in chilled solvents prior to fiber drawing. Fibers, containing 5% and 30% lignin to PVA, were spun from gel-fibers aged in 25/75 (v/v) water/acetone for up to 30 days at 5 °C. The best values of mechanical performance were obtained from 5% lignin fibers, where the average tensile strength was 1.4 GPa after 1 day of gel aging in water/acetone. After 14 days of aging 5% lignin fiber, the Young’s modulus was 54 GPa, and toughness was 25 J/g. Gel containing 30% lignin yielded high mechanical properties after 30 days of aging; however, some lignin gradually diffused into the aging solvent. The strongest fibers had the highest degrees of crystallinity and molecular anisotropy among PVA and lignin functional groups. Interesti...

Ultrafine high performance polyethylene fibers

Stiff, strong and tough ultrafine polyethylene fibers that rival the best high performance fibers, but with diameters less than one micron, are fabricated for the first time by “gel-electrospinning.” In this process, solution concentration and process temperatures are chosen to induce the formation of gel filaments “in flight,” which are subsequently drawn at high rates as a consequence of the whipping instability. The resulting submicron-diameter fibers exhibited Young’s moduli of 73 ± 13 GPa, yield strengths of 3.5 ± 0.6 GPa, and toughnesses of 1.8 ± 0.3 GPa, on average. Among the smallest fibers examined, one with a diameter of 490 ± 50 nm showed a Young’s modulus of 110 ± 16 GPa, ultimate tensile strength of 6.3 ± 0.9 GPa, and toughness of 2.1 ± 0.3 GPa, a combination of mechanical properties that is unparalleled among polymer fibers to date. The correlation of stiffness, strength and toughness with fiber diameter is attributed to high crystallinity and crystallite orientation, combined with fewer defects and enhanced chain slip associated with small diameter and high specific surface area. Gel-electrospinning improves the prospects for production of such fibers at scale.

Microscopic Characterization and Analysis of Electrospun TiO<sub>2</sub>-PVP and TiO<sub>2</sub>-PVDF Fibers

Titanium dioxide (TiO2) is a suitable material to be used in the field of photocatalytic water treatment. In this research, TiO2 membrane fibers were synthesized using a combination of non-aqueous sol gel method and electrospinning technique. Titanium isopropoxide (TTIP) was used as the precursor for the TiO2 filler of the fibers. Both polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were used as the polymer base to obtain the respective membrane fibers. The effects of weight concentration of TTIP as well as the type and molecular weight of the polymer on the morphology of the fibers were studied. Microscopic characterization using field-emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray (EDX) analysis was performed to obtain the morphology and elemental composition of the fibers. Sub-micron range fibers with a continuous network were generally obtained. Fibers that are subjected to post-electrospinning calcination have a lower fiber diameter. Polymer decomposition is shown to occur during calcination which yielded higher purity TiO2 fibers. The use of higher molecular weight polymers can produce a stronger fibre network for membranes.

Ultra strong pyroprotein fibres with long-range ordering

Silks are protein-based natural structured materials with an unusual combination of high strength and elongation. Their unique microstructural features composed of hard β-sheet crystals aligned within a soft amorphous region lead to the robust properties of silks. Herein we report a large enhancement in the intrinsic properties of silk through the transformation of the basic building blocks into a poly-hexagonal carbon structure by a simple heat treatment with axial stretching. The carbon clusters originating from the β-sheet retain the preferred orientation along the fibre axis, resulting in a long-range-ordered graphitic structure by increasing heat-treatment temperatures and leading improvements in mechanical properties with a maximum strength and modulus up to ∼2.6 and ∼470 GPa, respectively, almost four and thirty times surpassing those of raw silk. Moreover, the formation of sp2 carbon configurations induce a significant change in the electrical properties (e.g. an electrical conductivity up to 4.37 × 103 S cm−1).

Novel Approach to Strengthening Ceramic Cathode Contact and Validation in a Generic Stack Test Fixture

The mechanical integrity of cathode contact during routine thermal cycling plays an important role in the performance of solid oxide fuel cells. This is because the final stack firing is typically a few hundred degrees lower than normal sintering temperatures, which led leads to poor solid-state sintering and hence poor cathode contact strength. To improve the contact strength and thermal cycle stability, precious metal such as silver has been used and showed good thermal cycle stability. However, issues of cost as well as long-term volatility remain unacceptable for practical industrial application. In this work, we examined three approaches to strengthening cathode contact by (1) mechanical interlocking with engineered surface, (2) enhanced sintering with sintering aid CuO and Bi2O3, and (3) reinforcement with strong and inert YSZ short fibers. Density was measured and bulk strength was determined with diametral compression tests. Ceramic bilayer couples were joined at elevated temperatures of 850 and 950oC for 2h with candidate LSM20 contact using the three approaches. Uniaxial tensile strength measurements were conducted on joined couples at room temperature. Fracture surface analysis was applied to correlate with strength results. The results showed the largest improvement in contact strength with both engineered cathode surface and sintering aid of Bi2O3. The effect of YSZ short fibers alone resulted in very poor strength due to sintering with rigid inclusion. The strength contribution was minute when combining both sintering aid and YSZ fibers. Finally, candidate cathode contact compositions will be tested on a 2”x2” LSM-based cell in a generic stack fixture to assess its effect on thermal cycle stability as well as stability at 800oC for 500-1000h. Post-mortem optical and electron microscopy will be conducted to assess the microstructure and chemical compatibility of cathode and contact materials.

Introducing biomimetic shear and ion gradients to microfluidic spinning improves silk fiber strength

Silkworm silk is an attractive biopolymer for biomedical applications due to its high mechanical strength and biocompatibility; as a result, there is increasing interest in scalable devices to spin silk and recombinant silk so as to improve and customize their properties for diverse biomedical purposes (Vepari and Kaplan 2007 Prog. Polym. Sci. 32). While artificial spinning of regenerated silk fibroins adds tunability to properties such as degradation rate and surface functionalization, the resulting fibers do not yet approach the mechanical strength of native silkworm silk. These drawbacks reduce the applicability and attractiveness of artificial silk (Kinahan et al 2011 Biomacromolecules 12). Here, we used computational fluid dynamic simulations to incorporate shear in tandem with biomimetic ion gradients by coupling a modular novel glass microfluidic device to our previous co-axial flow device. Fibers spun with this combined apparatus demonstrated a significant increase in mechanical strength compared to fibers spun with the basic apparatus alone, with a three-fold increase in Young’s modulus and extensibility and a twelve-fold increase in toughness. These results thus demonstrate the critical importance of ionic milieu and shear stress in spinning strong fibers from solubilized silk fibroin.

Tensile Behavior of a Substituted Poly(m‐,p‐phenylene) versus Its Parent Counterpart and Synthesis of Related Polyarylenes

In a recent report, a poly(m,p‐phenylene) with acid‐cleavable trialkylsilyl side chains is synthesized by Suzuki polycondensation in a molecular weight of Mw = 300 kDa determined by gel permeation chromatography (GPC). Such a high value suggests this polymer as a potentially attractive material for strong films and fibers both in the presence and absence of the side chains. After confirming these molecular weights by static light scattering, the polymer is processed into thin films for tensile stress measurements. Above the glass transition, thus >180 °C, the material shows an extended plasticity, which is used to obtain elongated samples of draw ratios ranging from 1.5 to 6. The elongated samples show a Young's modulus of up to 5 GPa and a yield strength of 140 MPa. Upon removal of the solubilizing side chains, these values further increase to a Young's modulus of 7.5 GPa in the direction of drawing and a maximum strength of 300 MPa. Motivated by these findings, the scope of this polymer class is broadened by synthesizing two new high molecular weight poly(m,p‐phenylene)s. The structural variation allows to tune the glass transition temperatures between 125 and 240 °C depending on the amount of the meta connected phenylene units. image

Flow-assisted assembly of nanostructured protein microfibers

Some of the most remarkable materials in nature are made from proteins. The properties of these materials are closely connected to the hierarchical assembly of the protein building blocks. In this perspective, amyloid-like protein nanofibrils (PNFs) have emerged as a promising foundation for the synthesis of novel bio-based materials for a variety of applications. Whereas recent advances have revealed the molecular structure of PNFs, the mechanisms associated with fibril-fibril interactions and their assembly into macroscale structures remain largely unexplored. Here, we show that whey PNFs can be assembled into microfibers using a flow-focusing approach and without the addition of plasticizers or cross-linkers. Microfocus small-angle X-ray scattering allows us to monitor the fibril orientation in the microchannel and compare the assembly processes of PNFs of distinct morphologies. We find that the strongest fiber is obtained with a sufficient balance between ordered nanostructure and fibril entanglement. The results provide insights in the behavior of protein nanostructures under laminar flow conditions and their assembly mechanism into hierarchical macroscopic structures.

From lab-scale film preparation to up- scale spinning fibre manufacturing of multiwall carbon nanotube/poly ethylene terephthalate composites

Carbon nanotubes are among the stiffest and strongest fibres known and they are thus considered as ideal fillers for polymeric fibre reinforcement. Carbon nanotube polymer composites have consequently attracted huge academic and industrial interest with thousands of relevant research works being published every year. In current work, we present a quite integrated study of multiwall carbon nanotube (MWCNT)-reinforced poly ethylene terephthalate (PET) composites prepared at laboratory scale along with industrial melt-spun fibres. For an optimum dispersion of the nanomaterial in the polymer matrix, we proceeded to appropriate functionalization of multiwall carbon nanotubes. The morphology of the composites was inspected by scanning electron microscope and transmission electron microscope, while the physical properties, such as crystallinity and orientation, by differential scanning calorimetry, X-ray diffraction and Raman spectroscopy. The addition of well-dispersed carbon nanotubes acts as a nucleation agent increasing the crystallization of poly ethylene terephthalate matrix, however, decreasing the orientation of either films or fibres. Carbon nanotubes /poly ethylene terephthalate polymer composite films present an increment of Young’s modulus and tensile strength to detriment of failure strain; namely, stiffness is accompanied by a less ductile behaviour. With the addition of carbon nanotubes to poly ethylene terephthalate fibres, a decrease in shrinkage and only a slight improvement in dimensional stability was attained; this once more explains the slow growth of their commercial applications since the mechanical properties of these materials still remain a fraction of the expected theoretical values.

Macroscopic assembly of flexible and strong green graphene fibres

The scalable production presented here facilitates flexible, strong and electrically conductive graphene fibres, which have emerged as promising graphene based electronic textiles and sensors.

Computing stable hierarchies of fiber bundles

Stable fiber bundles are important structures for understanding nonautonomous dynamics. These sets have a hierarchical structure ranging from stable to strong stable fibers. First, we compute corresponding structures for linear systems and prove an error estimate. The spectral concept of choice is the Sacker-Sell spectrum that is based on exponential dichotomies. Secondly, we tackle the nonlinear case and propose an algorithm for the numerical approximation of stable hierarchies in nonautonomous difference equations. This method generalizes the contour algorithm for computing stable fibers from [ 38 , 39 ]. It is based on Hadamard's graph transform and approximates fibers of the hierarchy by zero-contours of specific operators. We calculate fiber bundles and illustrate errors involved for several examples, including a nonautonomous Lorenz model.

Natural Pineapple Leaf Fibre Extraction On Josapine And Morris

The pineapple’s leaf plant contains approximately 2.5% to 3.5% of strong white silky fibres. These fibres are useful and can be extracted from the leaves. There are a few ways to extract the fibre such as hand scrapping and by extraction machine. The objective of this research is to study the quality of fibre extraction by using different age of pineapple leaf. Next, the study aims to compare the quality of Josapine and Morris pineapple leaf with tensile test. Fibre yield percentage are calculated to determine which type of pineapple leaf produce high production of dry fibre. The mechanical properties of the fibres are analysed by Tensile Test under American Standard Testing Methods (ASTM C1577-03) and Scanning Electron Microscope (SEM). The result of the fibre yield percentage show the Josapine type on 12 month ages are the highest value fibre yield percentage which is 7.89%. Based on fibre yield percentages, it showed the Josapine type produce better dry fibre production compare to Morris type. Based on mechanical test, it showed Josapine type on 12 months ages are the strongest fibre compare to Morris type since it can withstand on 67.6 N of load.

Superbase ionic liquids for effective cellulose processing from dissolution to carbonisation

Strong cellulose fibres and highly ordered carbon fibres can be produced from solutions in superbase ionic liquids.

Use of Rheological Characteristics of Viscoelastic Polymer Systems to Optimize the Fiber-Spinning Process

The rheological characteristics (complex viscosity, equilibrium relaxation time, equilibrium shear modulus) of a viscoelastic spinning solution obtained in a viscometer and under actual fiber-spinning conditions are examined. It is shown that the optimal regimes for spinning stronger fibers could be predicted by using the spinning-solution rheological characteristics and correlation coefficients obtained in a viscometer.

Multiscale mechanics of the lateral pressure effect on enhancing the load transfer between polymer coated CNTs.

While individual carbon nanotubes (CNTs) are known as one of the strongest fibers ever known, even the strongest fabricated macroscale CNT yarns and fibers are still significantly weaker than individual nanotubes. The loss in mechanical properties is mainly because the deformation mechanism of CNT fibers is highly governed by the weak shear strength corresponding to sliding of nanotubes on each other. Adding polymer coating to the bundles, and twisting the CNT yarns to enhance the intertube interactions are both efficient methods to improve the mechanical properties of macroscale yarns. Here, we perform molecular dynamics (MD) simulations to unravel the unknown deformation mechanism in the intertube polymer chains and also local deformations of the CNTs at the atomistic scale. Our results show that the lateral pressure can have both beneficial and adverse effects on shear strength of polymer coated CNTs, depending on the local deformations at the atomistic scale. In this paper we also introduce a bottom-up bridging strategy between a full atomistic model and a coarse-grained (CG) model. Our trained CG model is capable of incorporating the atomistic scale local deformations of each CNT to the larger scale collect behavior of bundles, which enables the model to accurately predict the effect of lateral pressure on larger CNT bundles and yarns. The developed multiscale CG model is implemented to study the effect of lateral pressure on the shear strength of straight polymer coated CNT yarns, and also the effect of twisting on the pull-out force of bundles in spun CNT yarns.

Sintering and mechanical properties of mechanically milled Inconel 625 superalloy and its composite reinforced by carbon nanotube

Carbon nanotubes showing tensile strength up to 20 GPa and stiffness up to 1000 GPa, are the strongest fibers known to mankind, which has been proved to be an extraordinary filler for light metals such as aluminium and titanium metals and alloys. However, the efficiency of its reinforcement to hard metallic materials such as Nickel-based superalloys are still unknown and under developed in the current powder metallurgy research. This study focuses on the sintering and mechanical properties of carbon nanotube reinforced Inconel 625 superalloy. The carbon nanotube modified Inconel 625 powder was pressed with a polymer binder and sintered to achieve high density. The mechanical properties are measured and compared with non-reinforced counterparts to verify the efficiency of carbon nanotube reinforcement. The mechanism of such reinforcement will be discussed based on the optical image and nano-indentation analysis.

Green recoating of cotton fiber by different starching methods

Natural fiber composites require coupling agents between phases to prevent poor adhesion between lignocellulosic fiber and a polymer matrix, which leads to a material that is not fully biodegradable. This work proposes the use of starch gum as a coupling agent for cotton fibers. The gum formation and fiber coating were characterized based on the starch paste solubility, clarity level according to UV-visible spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, heated optical microscopy, and fiber weight coating. Water-starch solutions were heated at 70 ℃ for 5, 10, and 24 h with two concentrations (3 and 8 wt.%) to obtain six different systems of gelatinized starch and starched fibers. The fibers are coated during the process of gelatinization and then dried and vacuum filtered. The gelatinization occurs at 70 ℃ for bath samples heated for more than 5 h, which exhibits a more branched structure, higher thermal stability, and increased weight coating up to 140 wt.%. The recoating process promoted stronger fiber adhesion, which would make this reinforcement applicable in an industrial-scale process to produce fully biodegradable composites.